Generation, Development and Modification in Natural Fibres

**3**

**1. Introduction**

**Chapter 1**

**Abstract**

Development, Characterization

and Properties of Silk Fibre and

Grafted Silk Fibre Reinforced

*Sareen Sheik and Gundibasappa Karikannar Nagaraja*

The use of natural fibres over synthetic fibres is gaining widespread importance due to its availability; renewability, low density and satisfactory mechanical properties making them an ecological alternative to synthetic fibres. The innumerable properties of silk fibre have made it superior to be used by researchers both in the plastic and biomedical sector. Silk fibre reinforced PVA (polyvinylalcohol) and PVA/PVP (polyvinyl pyrrolidone) films were prepared via solution casting technique. The effect of silk fibre concentration, on the structural, thermal, mechanical, bio-degradable and the morphological properties of the composite films was assessed. The results indicated that the addition of silk fibres improved the thermal, morphological, mechanical and biodegradable properties of the films. The extensive use of silk fibroin in the biomedical field, due to its robust properties has made it a promising material, suitable in tissue engineering applications. Keeping this in view, the current study also focuses on re-tailoring the properties of silk fibres by grafting a natural polysaccharide like chitosan and thereby fabricate composite films of PVA reinforced with this grafted fibre. The films were tested for their potential applications in tissue engineering, by subjecting them to *in vitro* biocompatibility tests. The films were also tested for their antibacterial properties. The results thus obtained indicated that the films were non-toxic in all concentra-

Polymer Composite Films

tions and were found to be suitable for biomaterial applications.

processing, biodegradability and minimum health hazards [2].

**Keywords:** silk fibre, chitosan, grafting, tissue-engineering, biodegradation

With the advent of polymer technology and large scale production of synthetic fibre reinforced composites, natural fibres as reinforcements have gained greater insights due to ecological concerns, accessibility, relatively low cost and biodegradability. This thrust for green products has empowered the mankind to consider these natural fibres, to be an alternative over conventional glass and carbon fibres [1]. Natural fibres are however considered far more superior over synthetic fibres as they are known to possess good relative mechanical properties, flexibility during

#### **Chapter 1**

## Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced Polymer Composite Films

*Sareen Sheik and Gundibasappa Karikannar Nagaraja*

#### **Abstract**

The use of natural fibres over synthetic fibres is gaining widespread importance due to its availability; renewability, low density and satisfactory mechanical properties making them an ecological alternative to synthetic fibres. The innumerable properties of silk fibre have made it superior to be used by researchers both in the plastic and biomedical sector. Silk fibre reinforced PVA (polyvinylalcohol) and PVA/PVP (polyvinyl pyrrolidone) films were prepared via solution casting technique. The effect of silk fibre concentration, on the structural, thermal, mechanical, bio-degradable and the morphological properties of the composite films was assessed. The results indicated that the addition of silk fibres improved the thermal, morphological, mechanical and biodegradable properties of the films. The extensive use of silk fibroin in the biomedical field, due to its robust properties has made it a promising material, suitable in tissue engineering applications. Keeping this in view, the current study also focuses on re-tailoring the properties of silk fibres by grafting a natural polysaccharide like chitosan and thereby fabricate composite films of PVA reinforced with this grafted fibre. The films were tested for their potential applications in tissue engineering, by subjecting them to *in vitro* biocompatibility tests. The films were also tested for their antibacterial properties. The results thus obtained indicated that the films were non-toxic in all concentrations and were found to be suitable for biomaterial applications.

**Keywords:** silk fibre, chitosan, grafting, tissue-engineering, biodegradation

#### **1. Introduction**

With the advent of polymer technology and large scale production of synthetic fibre reinforced composites, natural fibres as reinforcements have gained greater insights due to ecological concerns, accessibility, relatively low cost and biodegradability. This thrust for green products has empowered the mankind to consider these natural fibres, to be an alternative over conventional glass and carbon fibres [1]. Natural fibres are however considered far more superior over synthetic fibres as they are known to possess good relative mechanical properties, flexibility during processing, biodegradability and minimum health hazards [2].

Among the natural fibres, silk, a natural animal fibre is widely used due to its enormous applications. Silk is a strong and filamentous fibre produced by the larva of silkworm, during metamorphosis [3]. Of the many varieties of silk fibres, the best known is the *Bombyx mori*, which is essentially recognized for its strength and lustre [4].

It is structurally made up of a protein called fibroin which is composed of amino acids like glycine, alanine and serine, with a crystallinity in the order of 70–75 and 25–30% amorphous in nature. Besides, polypeptide chains in silk lie close enough to each other, to form a network of hydrogen bonds. As a result, bond formation is enabled with other hydrogen atoms of the polymer matrix resulting in higher thermal stability [3, 5]. The vast properties of silk fibres are mainly due to its high ultimate tensile strength which is about 208.45 MPa, elongation at break: 19.55%, modulus of 6.10 GPa and density of 1.33 g/cm3 [6]. Furthermore, silk also exhibits high softening temperature and decomposes at a higher temperature [3]. Moreover, it is a potential candidate in the field of medical, pharmaceutical and agricultural areas and is also known to possess properties, like microbial resistance, oxygen permeability, biocompatibility, water absorbability [7–9]. Due to these properties, the emphasis lies on the study of silk based fibre reinforced polymer composites.

The surface modification of biomaterials using biomolecules is known to improve blood compatibility [10] or to enhance cell attachment and proliferation [11]. Over the centuries, grafting of silk fibres using vinyl monomers was performed to improve properties of the fibre to make it equally competent over manmade fibres [12, 13]. Although, grafting of vinyl monomers improves the properties of fibres, it however has a major limitation, due to the damaging products released by slow degradation [14]. Therefore, environmental surface modification of fibres was a technique introduced in an attempt to retain the properties of silk by grafting natural polysaccharides such as chitin and chitosan. Chitosan, is a derivative of chitin and is prepared through the deacetylation of chitin. It is a major component present in marine invertebrates such as crustacean shells (shrimps, crabs etc.), exoskeleton of insects and a few fungi [15]. Chitosan and silk fibroin are natural biopolymers that are applied in tissue engineering and biomedical fields. Chitosan has been proposed as a biomaterial for biomedical applications mainly due to its biocompatibility [16, 17]. The properties of chitosan including easy availability, biodegradability, bioactivity and nontoxicity, as well as bio-adhesion and antimicrobial properties are the major reasons for its applications widely considered by researchers [18].

Glycosaminoglycans (GAGs), which are native components of the extracellular matrix (ECM), are known to structurally resemble chitosan, making it one of the promising biomaterials, for cartilage repair [19, 20]. Furthermore, it accelerates wound healing [21, 22] and amends the immune system by macrophage activation [23] to generate cytokines thus, inhibiting infections [24]. In view of this, the grafting of silk fibres using chitosan was adopted for the current study.

The best route to successfully graft chitosan over silk is via acylation as it provides an enhanced surface area for grafting. Chitosan grafting over silk and via acylation has been successfully performed by researchers to enhance the properties of silk in the textile industry [25, 26]. However, the application of grafted silk fibres in the field of tissue engineering remains unexplored. Therefore, the current chapter focuses on the preparation and properties of silk fibre reinforced PVA and PVA/PVP composite films and thereafter study the effect of surface modification of silk fibre by grafting a natural polysaccharide like chitosan and thus explore the potential of these fibre reinforced composites for packaging and biomedical applications respectively.

**5**

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

Silk fibre reinforced PVA (SF-PVA) and PVA/PVP (SF-PVA/PVP) films were prepared as follows. The degummed silk fibres were rinsed with distilled water to remove any impurities/solid dust particles sticking to the fibres. Further, the fibres were dried completely and then incised into small particles and powdered. This powdered silk was used for the preparation of films. Using the solution-casting technique, SF-PVA and SF-PVA/PVP films were prepared by mixing different weights of silk fibre and the polymer. For the blend composites, the weight of PVP was kept constant and the weight of silk fibres and PVA was varied. The solvent used for the preparation of films was double distilled water. The SF-PVA and SF-PVA/PVP solutions were mixed, for about 8 hours at 80°C. Further, to avoid agglomeration of fibres and to enhance its dispersion in the polymer matrix, the solutions were ultra-sonicated. The solutions were finally poured to a petri-dish and

**2. Silk fibre reinforced PVA and PVA/PVP composite films**

subjected to evaporation and final drying in an oven at 50°C [27, 28].

The morphology of the films was observed using field emission scanning electron microscopy (FESEM) [27, 28]. The surface morphology and cross sections depicting thickness of a few selected films is as depicted in **Figure 1**. The thickness of the film corresponds to 27.53 μm. PVA film, without the fibre shows a homogenous and continuous matrix throughout without cracks. Similarly, in case of blend film, the compatibility of both PVA and PVP was clearly observed due to the smooth and homogenous surface resulting from the interaction between the two polymers. In both the cases, when the film is reinforced with 9 wt% silk, the smoothness of the surface is however lost and appears rough. The images depict that the fibres are randomly distributed and embedded well in the matrix indicating proper mixing of fibres. This could possibly be due to the interaction of the polar functional groups of the fibre with that of the matrix. When the fibre concentration is further increased to 15 wt%, the fibres seem to be less adhered to the matrix phase and tend to agglomerate indicating phase discontinuity [29] resulting in loss

Thermogravimetric analysis (TGA) was performed for both SF-PVA and SF-PVA/PVP films as depicted in **Figure 2**. For SF-PVA films, the pristine PVA film exhibited three decomposition steps. The initial decomposition, due to the loss of water from the sample occurred at 80–150°C with a mass loss of 7.6%. The maximum degradation occurred from 250–400°C accompanied by a major weight loss of about 62.1%. This was due to the structural degradation followed by scissions of polymer chains in PVA. Further decomposition occurred from 450°C. This was due to the breakdown of C-C bonds in the polymer backbone. The addition of silk fibre (3–15 wt%) reduced the percentage mass loss (59.7–45.5%) [27]. This decrease in mass loss and the resultant increase in thermal stability is attributed to the higher thermal stability of silk fibres, which on interaction with the polymer matrix act as barriers for better heat insulation and lower

**2.2 Characterization of the composite films**

*2.2.1 Morphological properties*

of film homogeneity.

*2.2.2 Thermal properties*

the rate of degradation of the polymer [30].

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

**2.1 Preparation**

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

#### **2. Silk fibre reinforced PVA and PVA/PVP composite films**

#### **2.1 Preparation**

*Generation, Development and Modifications of Natural Fibers*

19.55%, modulus of 6.10 GPa and density of 1.33 g/cm3

lustre [4].

polymer composites.

researchers [18].

Among the natural fibres, silk, a natural animal fibre is widely used due to its enormous applications. Silk is a strong and filamentous fibre produced by the larva of silkworm, during metamorphosis [3]. Of the many varieties of silk fibres, the best known is the *Bombyx mori*, which is essentially recognized for its strength and

It is structurally made up of a protein called fibroin which is composed of amino acids like glycine, alanine and serine, with a crystallinity in the order of 70–75 and 25–30% amorphous in nature. Besides, polypeptide chains in silk lie close enough to each other, to form a network of hydrogen bonds. As a result, bond formation is enabled with other hydrogen atoms of the polymer matrix resulting in higher thermal stability [3, 5]. The vast properties of silk fibres are mainly due to its high ultimate tensile strength which is about 208.45 MPa, elongation at break:

also exhibits high softening temperature and decomposes at a higher temperature [3]. Moreover, it is a potential candidate in the field of medical, pharmaceutical and agricultural areas and is also known to possess properties, like microbial resistance, oxygen permeability, biocompatibility, water absorbability [7–9]. Due to these properties, the emphasis lies on the study of silk based fibre reinforced

The surface modification of biomaterials using biomolecules is known to improve blood compatibility [10] or to enhance cell attachment and proliferation [11]. Over the centuries, grafting of silk fibres using vinyl monomers was performed to improve properties of the fibre to make it equally competent over manmade fibres [12, 13]. Although, grafting of vinyl monomers improves the properties of fibres, it however has a major limitation, due to the damaging products released by slow degradation [14]. Therefore, environmental surface modification of fibres was a technique introduced in an attempt to retain the properties of silk by grafting natural polysaccharides such as chitin and chitosan. Chitosan, is a derivative of chitin and is prepared through the deacetylation of chitin. It is a major component present in marine invertebrates such as crustacean shells (shrimps, crabs etc.), exoskeleton of insects and a few fungi [15]. Chitosan and silk fibroin are natural biopolymers that are applied in tissue engineering and biomedical fields. Chitosan has been proposed as a biomaterial for biomedical applications mainly due to its biocompatibility [16, 17]. The properties of chitosan including easy availability, biodegradability, bioactivity and nontoxicity, as well as bio-adhesion and antimicrobial properties are the major reasons for its applications widely considered by

Glycosaminoglycans (GAGs), which are native components of the extracellular matrix (ECM), are known to structurally resemble chitosan, making it one of the promising biomaterials, for cartilage repair [19, 20]. Furthermore, it accelerates wound healing [21, 22] and amends the immune system by macrophage activation [23] to generate cytokines thus, inhibiting infections [24]. In view of this, the graft-

The best route to successfully graft chitosan over silk is via acylation as it provides an enhanced surface area for grafting. Chitosan grafting over silk and via acylation has been successfully performed by researchers to enhance the properties of silk in the textile industry [25, 26]. However, the application of grafted silk fibres in the field of tissue engineering remains unexplored. Therefore, the current chapter focuses on the preparation and properties of silk fibre reinforced PVA and PVA/PVP composite films and thereafter study the effect of surface modification of silk fibre by grafting a natural polysaccharide like chitosan and thus explore the potential of these fibre reinforced composites for packaging and biomedical

ing of silk fibres using chitosan was adopted for the current study.

[6]. Furthermore, silk

**4**

applications respectively.

Silk fibre reinforced PVA (SF-PVA) and PVA/PVP (SF-PVA/PVP) films were prepared as follows. The degummed silk fibres were rinsed with distilled water to remove any impurities/solid dust particles sticking to the fibres. Further, the fibres were dried completely and then incised into small particles and powdered. This powdered silk was used for the preparation of films. Using the solution-casting technique, SF-PVA and SF-PVA/PVP films were prepared by mixing different weights of silk fibre and the polymer. For the blend composites, the weight of PVP was kept constant and the weight of silk fibres and PVA was varied. The solvent used for the preparation of films was double distilled water. The SF-PVA and SF-PVA/PVP solutions were mixed, for about 8 hours at 80°C. Further, to avoid agglomeration of fibres and to enhance its dispersion in the polymer matrix, the solutions were ultra-sonicated. The solutions were finally poured to a petri-dish and subjected to evaporation and final drying in an oven at 50°C [27, 28].

#### **2.2 Characterization of the composite films**

#### *2.2.1 Morphological properties*

The morphology of the films was observed using field emission scanning electron microscopy (FESEM) [27, 28]. The surface morphology and cross sections depicting thickness of a few selected films is as depicted in **Figure 1**. The thickness of the film corresponds to 27.53 μm. PVA film, without the fibre shows a homogenous and continuous matrix throughout without cracks. Similarly, in case of blend film, the compatibility of both PVA and PVP was clearly observed due to the smooth and homogenous surface resulting from the interaction between the two polymers. In both the cases, when the film is reinforced with 9 wt% silk, the smoothness of the surface is however lost and appears rough. The images depict that the fibres are randomly distributed and embedded well in the matrix indicating proper mixing of fibres. This could possibly be due to the interaction of the polar functional groups of the fibre with that of the matrix. When the fibre concentration is further increased to 15 wt%, the fibres seem to be less adhered to the matrix phase and tend to agglomerate indicating phase discontinuity [29] resulting in loss of film homogeneity.

#### *2.2.2 Thermal properties*

Thermogravimetric analysis (TGA) was performed for both SF-PVA and SF-PVA/PVP films as depicted in **Figure 2**. For SF-PVA films, the pristine PVA film exhibited three decomposition steps. The initial decomposition, due to the loss of water from the sample occurred at 80–150°C with a mass loss of 7.6%. The maximum degradation occurred from 250–400°C accompanied by a major weight loss of about 62.1%. This was due to the structural degradation followed by scissions of polymer chains in PVA. Further decomposition occurred from 450°C. This was due to the breakdown of C-C bonds in the polymer backbone. The addition of silk fibre (3–15 wt%) reduced the percentage mass loss (59.7–45.5%) [27]. This decrease in mass loss and the resultant increase in thermal stability is attributed to the higher thermal stability of silk fibres, which on interaction with the polymer matrix act as barriers for better heat insulation and lower the rate of degradation of the polymer [30].

#### **Figure 1.**

*FESEM images of SF-PVA and SF-PVA/PVP films.*

**7**

**Table 1.**

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

The TGA of PVA/PVP film (**Figure 2**) and the film composites showed three decomposition steps. For the pure blend, the initial decomposition, with a mass loss of 7.4%, occurred at 70–140°C which was due to the loss of bound water molecules and acetic acid in the polymer [31]. Major degradation, due to the melting and breakdown of the blend segments, occurred between 200 and 365°C followed by a major weight loss of about 42%. Further decomposition and degradation of the sample resulted in a mass loss of 36% which occurred from 370 to 460°C. This was mainly due to the condensation and cyclization of the polyaromatic PVP [32]. With the addition of silk fibres, the percentage weight loss was slightly reduced to 40%, followed by an additional decrease to 36% (15 wt%) with a maximum residual content. It is quite obvious that due to the presence of amide groups, silk is known to possess a higher thermal stability as indicated by its high melting temperature, than PVA. The existence of a strong intermolecular hydrogen bonding interaction between hydroxyl groups of PVA and amide groups of silk in the composites

To further explain, after a thermal analysis, the final residual mass of a composite (char) is a measure of its flame resistance. This residual char, when exposed to a higher temperature can thermally insulate the undecomposed polymer from degrading [28]. The high varying nitrogen content in silk fibres (about 15–18%), has provided the fibre with a self-extinguishing property and hence a higher flame resistance. Therefore, it can thus be concluded that the decrease in mass loss with increasing fibre concentration, is mainly due to the thermal stability and flame

From differential scanning calorimetry (DSC), the melting temperature, glass transition (Tg) and enthalpy values (ΔHm) were assessed and summarized in **Table 1** and depicted in **Figure 3**. The melting temperature values for PVA and SF-PVA films were to a certain extent close to each other. The Tg for pure PVA film observed was 85.89°C [27]. Substantial increase in the Tg and ΔHm values was observed with the addition of silk fibres, as compared to the PVA film. The addition of silk reinforce-

For SF-PVA/PVP films, a single glass transition temperature was observed. The occurrence of a single glass transition temperature (Tg) indicates the miscibility between the two polymers [35]. For the blend films, this endothermic transition appeared at a temperature of 93°C. Glass transition temperature (Tg) was further increased to higher temperatures (97, 101, and 105°C for 3, 9 and 15 wt%

**C) Tm (o**

 85.9 222.7 21.9 62.1 101.9 223.04 23.5 59.7 106.7 221.9 28.7 58.7 93.9 221 29.8 45.5

 93 215 27.4 42 97 217 21.6 41.4 101 219 23.3 40 105 220 28.6 36

**C) ΔHm (J/g) Mass loss (%)**

resulted in an improved thermal stability and mechanical strength.

resistance properties of silk fibres in the composites [33, 34].

ments hinders the chain mobility, thus shifting the Tg [30].

**Silk fibre content (wt%) Tg (o**

*Thermal properties of SF-PVA and SF-PVA/PVP films.*

SF-PVA films

SF-PVA/PVP films

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

**Figure 2.** *TGA curves for SF-PVA and SF-PVA/PVP films.*

#### *Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

The TGA of PVA/PVP film (**Figure 2**) and the film composites showed three decomposition steps. For the pure blend, the initial decomposition, with a mass loss of 7.4%, occurred at 70–140°C which was due to the loss of bound water molecules and acetic acid in the polymer [31]. Major degradation, due to the melting and breakdown of the blend segments, occurred between 200 and 365°C followed by a major weight loss of about 42%. Further decomposition and degradation of the sample resulted in a mass loss of 36% which occurred from 370 to 460°C. This was mainly due to the condensation and cyclization of the polyaromatic PVP [32]. With the addition of silk fibres, the percentage weight loss was slightly reduced to 40%, followed by an additional decrease to 36% (15 wt%) with a maximum residual content. It is quite obvious that due to the presence of amide groups, silk is known to possess a higher thermal stability as indicated by its high melting temperature, than PVA. The existence of a strong intermolecular hydrogen bonding interaction between hydroxyl groups of PVA and amide groups of silk in the composites resulted in an improved thermal stability and mechanical strength.

To further explain, after a thermal analysis, the final residual mass of a composite (char) is a measure of its flame resistance. This residual char, when exposed to a higher temperature can thermally insulate the undecomposed polymer from degrading [28]. The high varying nitrogen content in silk fibres (about 15–18%), has provided the fibre with a self-extinguishing property and hence a higher flame resistance. Therefore, it can thus be concluded that the decrease in mass loss with increasing fibre concentration, is mainly due to the thermal stability and flame resistance properties of silk fibres in the composites [33, 34].

From differential scanning calorimetry (DSC), the melting temperature, glass transition (Tg) and enthalpy values (ΔHm) were assessed and summarized in **Table 1** and depicted in **Figure 3**. The melting temperature values for PVA and SF-PVA films were to a certain extent close to each other. The Tg for pure PVA film observed was 85.89°C [27]. Substantial increase in the Tg and ΔHm values was observed with the addition of silk fibres, as compared to the PVA film. The addition of silk reinforcements hinders the chain mobility, thus shifting the Tg [30].

For SF-PVA/PVP films, a single glass transition temperature was observed. The occurrence of a single glass transition temperature (Tg) indicates the miscibility between the two polymers [35]. For the blend films, this endothermic transition appeared at a temperature of 93°C. Glass transition temperature (Tg) was further increased to higher temperatures (97, 101, and 105°C for 3, 9 and 15 wt%


#### **Table 1.**

*Thermal properties of SF-PVA and SF-PVA/PVP films.*

*Generation, Development and Modifications of Natural Fibers*

**6**

**Figure 2.**

**Figure 1.**

*FESEM images of SF-PVA and SF-PVA/PVP films.*

*TGA curves for SF-PVA and SF-PVA/PVP films.*

**Figure 3.** *DSC curves for SF-PVA and SF-PVA/PVP films.*

respectively) with the increased amounts of silk fibre [28]. This increase in Tg along with the increase in the concentration of silk is due to the interaction of the silk fibre with the PVA/PVP matrix, thus, hindering chain mobility as previously discussed [30].

#### *2.2.3 Mechanical properties*

Tensile strength, Young's modulus and percentage elongation at break of the SF/ PVA films was assessed and illustrated in **Figure 4**. For the SF-PVA film, the tensile strength and Young's modulus values effectively increased up to a fibre concentration of 12 wt% and thereafter decreased. The maximum values recorded for tensile strength and Young's modulus were 41.87 ± 2.08 and 202.08 ± 2.53 MPa respectively [27]. This was probably due to the hydrogen bonding interactions between the PVA and silk fibre that resulted in an increased mechanical property. When the fibre concentration was relatively low (3 wt%), the matrix was not restrained by adequate fibres and thus a remarkably high strain occurred which was confined to a small area in the matrix. This can cause rupturing in the bonds between the matrix and the fibre ensuing in an insufficient mechanical strength [36]. When the fibre concentration was increased, the load was shared between the fibres and the matrix, wherein the maximum load was taken by the fibres by the stress transfer mechanism. At a high fibre concentration, the –NH2 and CO– groups of silk have a tendency to entangle and agglomerate among each other thus failing to interact with PVA [37] and hence a resulting decrease in the mechanical strength. The interfacial adhesion of the fibre and matrix plays a pivotal role in understanding the strength of a composite [36]. Highest percentage elongation at break was seen in PVA film, while the films reinforced with silk fibre, showed lower values due to the decrease in the concentration of PVA. This resulted in a fragile character and less ductile nature of the films.

For the SF-PVA/PVP films, the tensile strength and Young's modulus values increased up to 9 wt%, and subsequently decreased at a fibre concentration of 12 wt%. The maximum values for 9 wt% film, recorded a tensile strength of 30.3 ± 1.58 MPa and Young's modulus of 276.5 ± 4.05 MPa [28].

It is obvious that when a polymer matrix is reinforced with short fibres such as silk, the mechanical keying effects between the polymer chains and the fibre primarily restricts the segmental motion of the polymer matrix. Further, as previously

**9**

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

discussed, the chemical interactions such as hydrogen bonding between the matrix

The trend observed in the percentage elongation at break was similar to that observed in the case of SF-PVA films. This decrease was again ascribed to the

The biodegradability of the film samples was evaluated using the weight loss method [39] and depicted in **Figure 5**. For a period of 8 days, the average weight decrease was 5% and the weight of the films further gradually decreased as the time increased. For SF-PVA/PVP films, for a period of 8 days, the average weight decrease was found to be 12% and as time increased, the weight of the films also gradually decreased. After 64 days the average weight decrease was approximately 36 and 32% for SF-PVA and SF-PVA/PVP respectively. It was observed that, as the percentage of silk fibre increased there is enhancement in the rate of bio-degradation of the films when compared to the pure PVA and blend film without the fibre. As the soil microbes attack, structural deformations in the film composites occurred resulting in the brittleness of the films. Therefore the films became hard and fragile in nature. When this protein based silk fibre, is buried in soil, it tends to undergo degradation

In short fibre reinforced composites; the matrix plays a dynamic role as it provides a cushioning effect to the embedded fibres, although the load is shared by both fibre and matrix. When the concentration of the matrix is decreased, followed by a relatively increase in the concentration of the fibres, the increased load results in more strain resulting in breaking, thus leading to de-bonding between the fibre and matrix [38]. In addition to this, as evident from FESEM analysis (**Figure 1**) the silk fibres were less adhered to the matrix at the surface of the film (15 wt% fibre

and fibre, improves the strength of the composite.

*Mechanical properties of the composite films.*

associated decrease in the concentration of the matrix [28].

concentration) [28].

**Figure 4.**

*2.2.4 Biodegradation by soil burial tests*

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

**Figure 4.**

*Generation, Development and Modifications of Natural Fibers*

respectively) with the increased amounts of silk fibre [28]. This increase in Tg along with the increase in the concentration of silk is due to the interaction of the silk fibre with the PVA/PVP matrix, thus, hindering chain mobility as previously

and the fibre ensuing in an insufficient mechanical strength [36]. When the fibre concentration was increased, the load was shared between the fibres and the matrix, wherein the maximum load was taken by the fibres by the stress transfer mechanism. At a high fibre concentration, the –NH2 and CO– groups of silk have a tendency to entangle and agglomerate among each other thus failing to interact with PVA [37] and hence a resulting decrease in the mechanical strength. The interfacial adhesion of the fibre and matrix plays a pivotal role in understanding the strength of a composite [36]. Highest percentage elongation at break was seen in PVA film, while the films reinforced with silk fibre, showed lower values due to the decrease in the concentration of PVA. This resulted in a fragile character

For the SF-PVA/PVP films, the tensile strength and Young's modulus values increased up to 9 wt%, and subsequently decreased at a fibre concentration of 12 wt%. The maximum values for 9 wt% film, recorded a tensile strength of 30.3 ± 1.58 MPa

It is obvious that when a polymer matrix is reinforced with short fibres such as silk, the mechanical keying effects between the polymer chains and the fibre primarily restricts the segmental motion of the polymer matrix. Further, as previously

Tensile strength, Young's modulus and percentage elongation at break of the SF/ PVA films was assessed and illustrated in **Figure 4**. For the SF-PVA film, the tensile strength and Young's modulus values effectively increased up to a fibre concentration of 12 wt% and thereafter decreased. The maximum values recorded for tensile strength and Young's modulus were 41.87 ± 2.08 and 202.08 ± 2.53 MPa respectively [27]. This was probably due to the hydrogen bonding interactions between the PVA and silk fibre that resulted in an increased mechanical property. When the fibre concentration was relatively low (3 wt%), the matrix was not restrained by adequate fibres and thus a remarkably high strain occurred which was confined to a small area in the matrix. This can cause rupturing in the bonds between the matrix

**8**

discussed [30].

**Figure 3.**

*2.2.3 Mechanical properties*

*DSC curves for SF-PVA and SF-PVA/PVP films.*

and less ductile nature of the films.

and Young's modulus of 276.5 ± 4.05 MPa [28].

discussed, the chemical interactions such as hydrogen bonding between the matrix and fibre, improves the strength of the composite.

In short fibre reinforced composites; the matrix plays a dynamic role as it provides a cushioning effect to the embedded fibres, although the load is shared by both fibre and matrix. When the concentration of the matrix is decreased, followed by a relatively increase in the concentration of the fibres, the increased load results in more strain resulting in breaking, thus leading to de-bonding between the fibre and matrix [38]. In addition to this, as evident from FESEM analysis (**Figure 1**) the silk fibres were less adhered to the matrix at the surface of the film (15 wt% fibre concentration) [28].

The trend observed in the percentage elongation at break was similar to that observed in the case of SF-PVA films. This decrease was again ascribed to the associated decrease in the concentration of the matrix [28].

#### *2.2.4 Biodegradation by soil burial tests*

The biodegradability of the film samples was evaluated using the weight loss method [39] and depicted in **Figure 5**. For a period of 8 days, the average weight decrease was 5% and the weight of the films further gradually decreased as the time increased. For SF-PVA/PVP films, for a period of 8 days, the average weight decrease was found to be 12% and as time increased, the weight of the films also gradually decreased. After 64 days the average weight decrease was approximately 36 and 32% for SF-PVA and SF-PVA/PVP respectively. It was observed that, as the percentage of silk fibre increased there is enhancement in the rate of bio-degradation of the films when compared to the pure PVA and blend film without the fibre. As the soil microbes attack, structural deformations in the film composites occurred resulting in the brittleness of the films. Therefore the films became hard and fragile in nature. When this protein based silk fibre, is buried in soil, it tends to undergo degradation

**Figure 5.** *Graphs depicting soil burial degradation tests for composite films.*

which could be attributed to the penetration of water from the cut edges of the composite films, resulting in loosening of the complex structure and consequently results in the weight loss of the films [40].

## **3. Surface modification of silk by grafting chitosan**

The grafting of chitosan over silk was performed using the optimized procedure with slight modifications, reported by Davarpanah et al. [26, 41]. Briefly, degumming of silk was performed using sodium dodecyl sulphate and sodium carbonate. The material mass to liquor ratio maintained was 1:25. The fibres were further washed with warm and cold distilled water and dried. Acylation of the degummed fibres was performed using succinic anhydride in N,N-dimethyl formamide (DMF). The fibre samples were washed with DMF followed by acetone, to remove unreacted anhydrides. Grafting of chitosan was carried out in acetic acid media followed by drying. In **Figure 6**, the images of the fibres before and after surface modification are shown. Total percentage fibre weight gain was calculated by the difference in weight gain of the acylated and the grafted silk fibre and was found to be 17% [42].

#### **3.1 Preparation of grafted silk fibre reinforced PVA composite films**

Post grafting, the fibres were dried completely and incised into small particles and finely powdered. Fibre reinforced PVA films were prepared by mixing different weight percentages of grafted silk and PVA, followed by the solution-casting technique [42] as described previously under Section 2.1.

**11**

**Figure 7.**

*FESEM images of degummed, acylated and chitosan grafted silk fibres.*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

From scanning electron microscopy the chemically treated and grafted fibres were examined. **Figure 7** depicts the surface of degummed silk fibre and thus appears smooth. The acylated fibres were characterized by a uniform surface with few foreign particles and the roughness of the fibres further increased due to grafting of chitosan,

The surface topography and roughness of the pristine film as well as the fibre reinforced composites was studied using atomic force microscopy (AFM). Atomic force microscopy (AFM) images for PVA and composite film samples are depicted in **Figure 8**. The AFM of PVA film appeared smooth and the surface roughness (RMS) value obtained for PVA film was 86.32 ± 58 nm. For the composite films, AFM revealed the presence of grafted silk fibres randomly scattered along the matrix. The roughness values substantially increased with the addition of the fibres and the films appeared corrugated and irregular. It is apparent that, a fibre, when added to a polymer matrix and later casted to form a film, a repulsive interaction is known to exist between the two phases (matrix + fibre), which eventually results in changes in surface roughness. This is mainly due to the microphase separation and changes in the alignment of the polymer chains [43] that results in changes in the topography.

TGA curves showed three decomposition steps for PVA film as depicted in **Figure 9**. The trend in decomposition observed for PVA was similar to that observed previously. The initial decomposition for PVA occurred at 80–150°C. The

which clearly shows the presence of particles firmly attached on the fibre.

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

*3.2.1 Morphological properties*

*3.2.2 Thermal properties*

**3.2 Characterization and** *in vitro* **biocompatibility studies**

**Figure 6.** *Image depicting degummed, acylated and chitosan grafted silk fibres.*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

#### **3.2 Characterization and** *in vitro* **biocompatibility studies**

#### *3.2.1 Morphological properties*

*Generation, Development and Modifications of Natural Fibers*

results in the weight loss of the films [40].

*Graphs depicting soil burial degradation tests for composite films.*

**Figure 5.**

**3. Surface modification of silk by grafting chitosan**

**3.1 Preparation of grafted silk fibre reinforced PVA composite films**

technique [42] as described previously under Section 2.1.

*Image depicting degummed, acylated and chitosan grafted silk fibres.*

Post grafting, the fibres were dried completely and incised into small particles and finely powdered. Fibre reinforced PVA films were prepared by mixing different weight percentages of grafted silk and PVA, followed by the solution-casting

which could be attributed to the penetration of water from the cut edges of the composite films, resulting in loosening of the complex structure and consequently

The grafting of chitosan over silk was performed using the optimized procedure with slight modifications, reported by Davarpanah et al. [26, 41]. Briefly, degumming of silk was performed using sodium dodecyl sulphate and sodium carbonate. The material mass to liquor ratio maintained was 1:25. The fibres were further washed with warm and cold distilled water and dried. Acylation of the degummed fibres was performed using succinic anhydride in N,N-dimethyl formamide (DMF). The fibre samples were washed with DMF followed by acetone, to remove unreacted anhydrides. Grafting of chitosan was carried out in acetic acid media followed by drying. In **Figure 6**, the images of the fibres before and after surface modification are shown. Total percentage fibre weight gain was calculated by the difference in weight gain of the acylated and the grafted silk fibre and was found to be 17% [42].

**10**

**Figure 6.**

From scanning electron microscopy the chemically treated and grafted fibres were examined. **Figure 7** depicts the surface of degummed silk fibre and thus appears smooth. The acylated fibres were characterized by a uniform surface with few foreign particles and the roughness of the fibres further increased due to grafting of chitosan, which clearly shows the presence of particles firmly attached on the fibre.

The surface topography and roughness of the pristine film as well as the fibre reinforced composites was studied using atomic force microscopy (AFM). Atomic force microscopy (AFM) images for PVA and composite film samples are depicted in **Figure 8**. The AFM of PVA film appeared smooth and the surface roughness (RMS) value obtained for PVA film was 86.32 ± 58 nm. For the composite films, AFM revealed the presence of grafted silk fibres randomly scattered along the matrix. The roughness values substantially increased with the addition of the fibres and the films appeared corrugated and irregular. It is apparent that, a fibre, when added to a polymer matrix and later casted to form a film, a repulsive interaction is known to exist between the two phases (matrix + fibre), which eventually results in changes in surface roughness. This is mainly due to the microphase separation and changes in the alignment of the polymer chains [43] that results in changes in the topography.

#### *3.2.2 Thermal properties*

TGA curves showed three decomposition steps for PVA film as depicted in **Figure 9**. The trend in decomposition observed for PVA was similar to that observed previously. The initial decomposition for PVA occurred at 80–150°C. The

**Figure 7.** *FESEM images of degummed, acylated and chitosan grafted silk fibres.*

**13**

**Figure 10.**

*Graph depicting soil burial degradation test.*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

**C) Tm (o**

 98.8 222.6 22.8 59.4 101.9 222.3 23.5 58 106.7 224.6 26.62 54.9 109.9 224.8 28.9 50

**C) ΔHm (J/g) Mass loss (%)**

The Tg for the PVA film observed was 98.8°C. The grafted silk when added to the matrix, further increased the Tg, and ΔHm values. Thus, the mobility of polymer chains was hindered by further addition of silk; thereafter resulting in a substantial increase in Tg

The prepared film composites turned brittle and lost their flexibility when exposed to soil, after a certain period of time. For a period of 8 days the weight decrease was found to be approximately 8% and as the time increased the percentage decrease in the weight of the samples also increased. After 64 days the weight decrease was approximately 40%. Compared to our previous results as discussed, the trend observed in this study as depicted in **Figure 10**, was that the weight decrease slightly increased due to the incorporation of chitosan grafted silk fibres. Although chitosan is known to be antibacterial in nature, it is however known to be an efficient soil amendment material and shows degradation in soil. This is due to the fact that certain microbes are known to possess an enzyme chitosanase that promotes degradation of chitosan. Berkeley [45] reported that chitosan-hydrolyzing

enzymes (chitosanases) are produced by the genera *Arthrobacter*, *Bacillus*,

*Streptomyces*, *Aspergillus*, and *Penicillium*. Besides, the increased surface roughness with the addition of silk fibres is also known to enhance the rate of biodegradation.

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

**Silk fibre content (wt%) Tg (o**

*Thermal properties of grafted silk fibre composites.*

*3.2.3 Biodegradation by soil burial tests*

values [30, 42].

**Table 2.**

**Figure 8.**

*AFM images of (a) PVA film (b) 3 wt% film (c) 9 wt% film (d) 15 wt% film.*

**Figure 9.** *TGA and DSC curves for grafted fibre reinforced composite films.*

weight loss of about 8% was observed which was due to the loss of bound water

from the sample. The maximum degradation occurred from 250 to 400°C accompanied by a major weight loss of about 59.4%. As previously discussed, this was due to the structural degradation along with the chain scissions in PVA [42]. Further decomposition followed by the decrease in the weight of sample was observed from 450°C. This was due to the breakdown of C–C bonds in the polymer backbone [44].

Incorporation of chitosan onto the silk fibres did not affect its thermal properties. As a result, the higher thermal stability of silk fibre was retained. The higher thermal stability of silk fibres reduced the percentage weight loss to about 58%, followed by further reduction in weight to about 54.9 and 50% for 3, 9 and 15 wt% incorporated grafted fibres respectively [42]. Thus, the hydrogen bonding interaction of PVA, with the functional groups of silk fibre was still observed.

DSC analysis showed a substantial increase in Tg and a slight increase in melting temperatures indicating better thermal stability as depicted in **Table 2** and **Figure 9**.


*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

**Table 2.**

*Generation, Development and Modifications of Natural Fibers*

*AFM images of (a) PVA film (b) 3 wt% film (c) 9 wt% film (d) 15 wt% film.*

*TGA and DSC curves for grafted fibre reinforced composite films.*

weight loss of about 8% was observed which was due to the loss of bound water from the sample. The maximum degradation occurred from 250 to 400°C accompanied by a major weight loss of about 59.4%. As previously discussed, this was due to the structural degradation along with the chain scissions in PVA [42]. Further decomposition followed by the decrease in the weight of sample was observed from 450°C. This was due to the breakdown of C–C bonds in the polymer backbone [44]. Incorporation of chitosan onto the silk fibres did not affect its thermal properties. As a result, the higher thermal stability of silk fibre was retained. The higher thermal stability of silk fibres reduced the percentage weight loss to about 58%, followed by further reduction in weight to about 54.9 and 50% for 3, 9 and 15 wt% incorporated grafted fibres respectively [42]. Thus, the hydrogen bonding interac-

tion of PVA, with the functional groups of silk fibre was still observed.

DSC analysis showed a substantial increase in Tg and a slight increase in melting temperatures indicating better thermal stability as depicted in **Table 2** and **Figure 9**.

**12**

**Figure 8.**

**Figure 9.**

*Thermal properties of grafted silk fibre composites.*

The Tg for the PVA film observed was 98.8°C. The grafted silk when added to the matrix, further increased the Tg, and ΔHm values. Thus, the mobility of polymer chains was hindered by further addition of silk; thereafter resulting in a substantial increase in Tg values [30, 42].

#### *3.2.3 Biodegradation by soil burial tests*

The prepared film composites turned brittle and lost their flexibility when exposed to soil, after a certain period of time. For a period of 8 days the weight decrease was found to be approximately 8% and as the time increased the percentage decrease in the weight of the samples also increased. After 64 days the weight decrease was approximately 40%. Compared to our previous results as discussed, the trend observed in this study as depicted in **Figure 10**, was that the weight decrease slightly increased due to the incorporation of chitosan grafted silk fibres. Although chitosan is known to be antibacterial in nature, it is however known to be an efficient soil amendment material and shows degradation in soil. This is due to the fact that certain microbes are known to possess an enzyme chitosanase that promotes degradation of chitosan. Berkeley [45] reported that chitosan-hydrolyzing enzymes (chitosanases) are produced by the genera *Arthrobacter*, *Bacillus*, *Streptomyces*, *Aspergillus*, and *Penicillium*. Besides, the increased surface roughness with the addition of silk fibres is also known to enhance the rate of biodegradation.

**Figure 10.** *Graph depicting soil burial degradation test.*

Higher surface roughness increases biodegradation by providing more sites for bacterial colonies to settle and proliferate [46].

#### *3.2.4 Antibacterial tests*

*In vitro* antibacterial studies were performed for 2 g negative and 2 g positive bacterial strains. PVA film did not show any activity on all four bacterial strains. The positive control streptomycin showed highest antibacterial activity. **Table 3** shows the zone of inhibition calculated for the films and the activity against the bacterial strains. Due to the lower concentrations of the chitosan grafted silk fibre (3 and 6 wt%), the films showed little or no activity. However as the fibre concentration was increased, the films showed good activity and consequently at 15 wt% concentration, due to a relatively high concentration of chitosan, significant activity was seen against *S. aureus* and *E. coli* the reason being the bacteriostatic as well as bactericidal activity of chitosan towards pathogenic strains of bacteria. It is believed that the polycationic nature of chitosan, due to the positively charged -NH3 + groups of glucosamine, might be a crucial factor contributing to its interaction with the negatively charged surface components of many fungi and bacteria. Consequently, this leads to extensive cell surface alterations, leakage of intracellular substances, and impairment of vital bacterial activities [47–50].

#### *3.2.5 In vitro hemocompatibility*

Hemolysis is a phenomenon that occurs, when the cells swell to the critical bulk and results in the lysis of cell membranes. The resulting broken red blood cells can release adenosine diphosphate, which escalates the assembly of blood platelets, thereby accelerating the formation of clotting and thrombus. It is an additional setback associated with the biocompatibility of material [51]. It is quite obvious that when red blood cells (RBC's) come in contact with water, they tend to hemolyse and when an incompatible material comes in contact with these cells, this problem intensifies. The membrane stability of the RBC's was studied for PVA and film composites, in relation with the standard drug diclofenac sodium [52]. Percentage inhibition of hemolysis for test samples was studied and calculated as follows


**15**

**Figure 11.**

*Bonferroni).*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

A higher percentage inhibition was observed for all composite films in comparison with the pristine PVA film as depicted in **Figure 11**. The highest percentage value obtained was for 15 wt% films (79.0 ± 1.8), which were almost similar to the standard diclofenac (82.5 ± 1.2) [52]. Previous reports suggest that chitosan promoted surface induced hemolysis, which can be ascribed in part to the electrostatic interactions [53, 54]. When the concentration of chitosan was increased to about 100 mg/ml, traces of haemolytic activity was observed and the largest haemolytic activity observed was less than 10%, signifying a wide safety margin suitable for blood contact applications [55]. Thus, on comparing the low hemolytic activity with the high erythrocyte agglutination, it can be seen that, chitosan only induces the surface adhesion of erythrocytes and does not critically damage the cell membrane [56, 57]. The results thus obtained for the films, did not rupture the cell membrane,

The principle underlying the trypan blue dye exclusion assay is that a dead or a dying cell possesses a membrane that happens to be permeable to the dye trypan blue and thus will stain blue. On the contrary, the viability of the cells can be determined as the viable cells are capable of repelling the dye and hence do not stain [58]. **Figure 12** denotes the cultured mouse fibroblast cells growing on PVA and composite films. The cells displayed spindle shaped morphology, rapidly proliferated and grew into small colonies by strongly attaching on the film substrates as compared to the control (Dubecco's Modified Eagle's Medium) and PVA film. It was observed that the composite films of all concentrations supported cell growth and were thus non-toxic. These results when further corroborated with AFM investigations, demonstrated that the enhanced surface roughness of the films provided a larger surface area for the cells to adhere. As a result, cell growth was facilitated when compared to the comparatively smooth pristine film, signifying that surface roughness of the substrate played a huge role in regulating cell

*Graph depicting percentage inhibition of haemolysis. Values expressed as Means ± SD of triplicate* 

*measurements (n = 3). Means with different letters in each column is significantly different (p <0.05, ANOVA,* 

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

subsequently making them hemocompatible.

adhesion and growth [52].

*3.2.6 Cell proliferation studies by trypan blue assay*

Percentage inhibition of haemolysis (%) <sup>=</sup> Control <sup>−</sup> Test sample \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Control <sup>×</sup> <sup>100</sup> (1)

#### **Table 3.**

*Antibacterial activity of composite films reinforced with grafted fibre.*

#### *Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

A higher percentage inhibition was observed for all composite films in comparison with the pristine PVA film as depicted in **Figure 11**. The highest percentage value obtained was for 15 wt% films (79.0 ± 1.8), which were almost similar to the standard diclofenac (82.5 ± 1.2) [52]. Previous reports suggest that chitosan promoted surface induced hemolysis, which can be ascribed in part to the electrostatic interactions [53, 54]. When the concentration of chitosan was increased to about 100 mg/ml, traces of haemolytic activity was observed and the largest haemolytic activity observed was less than 10%, signifying a wide safety margin suitable for blood contact applications [55]. Thus, on comparing the low hemolytic activity with the high erythrocyte agglutination, it can be seen that, chitosan only induces the surface adhesion of erythrocytes and does not critically damage the cell membrane [56, 57]. The results thus obtained for the films, did not rupture the cell membrane, subsequently making them hemocompatible.

#### *3.2.6 Cell proliferation studies by trypan blue assay*

The principle underlying the trypan blue dye exclusion assay is that a dead or a dying cell possesses a membrane that happens to be permeable to the dye trypan blue and thus will stain blue. On the contrary, the viability of the cells can be determined as the viable cells are capable of repelling the dye and hence do not stain [58]. **Figure 12** denotes the cultured mouse fibroblast cells growing on PVA and composite films. The cells displayed spindle shaped morphology, rapidly proliferated and grew into small colonies by strongly attaching on the film substrates as compared to the control (Dubecco's Modified Eagle's Medium) and PVA film. It was observed that the composite films of all concentrations supported cell growth and were thus non-toxic. These results when further corroborated with AFM investigations, demonstrated that the enhanced surface roughness of the films provided a larger surface area for the cells to adhere. As a result, cell growth was facilitated when compared to the comparatively smooth pristine film, signifying that surface roughness of the substrate played a huge role in regulating cell adhesion and growth [52].

#### **Figure 11.**

*Graph depicting percentage inhibition of haemolysis. Values expressed as Means ± SD of triplicate measurements (n = 3). Means with different letters in each column is significantly different (p <0.05, ANOVA, Bonferroni).*

*Generation, Development and Modifications of Natural Fibers*

bacterial colonies to settle and proliferate [46].

and impairment of vital bacterial activities [47–50].

*Antibacterial activity of composite films reinforced with grafted fibre.*

*3.2.5 In vitro hemocompatibility*

**Zone of inhibition (mm)**

*3.2.4 Antibacterial tests*

Higher surface roughness increases biodegradation by providing more sites for

*In vitro* antibacterial studies were performed for 2 g negative and 2 g positive bacterial strains. PVA film did not show any activity on all four bacterial strains. The positive control streptomycin showed highest antibacterial activity. **Table 3** shows the zone of inhibition calculated for the films and the activity against the bacterial strains. Due to the lower concentrations of the chitosan grafted silk fibre (3 and 6 wt%), the films showed little or no activity. However as the fibre concentration was increased, the films showed good activity and consequently at 15 wt% concentration, due to a relatively high concentration of chitosan, significant activity was seen against *S. aureus* and *E. coli* the reason being the bacteriostatic as well as bactericidal activity of chitosan towards pathogenic strains of bacteria. It is believed

that the polycationic nature of chitosan, due to the positively charged -NH3

of glucosamine, might be a crucial factor contributing to its interaction with the negatively charged surface components of many fungi and bacteria. Consequently, this leads to extensive cell surface alterations, leakage of intracellular substances,

Hemolysis is a phenomenon that occurs, when the cells swell to the critical bulk and results in the lysis of cell membranes. The resulting broken red blood cells can release adenosine diphosphate, which escalates the assembly of blood platelets, thereby accelerating the formation of clotting and thrombus. It is an additional setback associated with the biocompatibility of material [51]. It is quite obvious that when red blood cells (RBC's) come in contact with water, they tend to hemolyse and when an incompatible material comes in contact with these cells, this problem intensifies. The membrane stability of the RBC's was studied for PVA and film composites, in relation with the standard drug diclofenac sodium [52]. Percentage inhibition of hemolysis for test samples was studied and calculated as follows

Percentage inhibition of haemolysis (%) <sup>=</sup> Control <sup>−</sup> Test sample \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Control <sup>×</sup> <sup>100</sup> (1)

**Sample films** *S. aureus Bacillus subtilis E. coli K. pneumoniae* Control — — — — 3 wt% 8 ± 1 — — — 6 wt% 8 ± 1 — 11 ± 0.00 — 9 wt% 9.00 ± 0.00 9 ± 0.00 13.66 ± 0.57 9 ± 0.00 12 wt% 12 ± 0.00 12.66 ± 0.57 14.66 ± 1.15 10 ± 0.00 15 wt% 17.33 ± 1.15 13.33 ± 0.57 15.33 ± 1.15 12.66 ± 0.57 Chitosan 22 ± 0.57 19. 33 ± 1.15 21 ± 0.57 22 ± 0.57 Streptomycin 25 ± 1 22. ± 1 28.66 ± 0.57 19.33 ± 0.57

+ groups

**14**

**Table 3.**

**Figure 12.** *Pictomicrographs of attachment of fibroblast cells (Scale bar-500 μm).*

#### *3.2.7 MTT assay*

The mitochondrial activity of cells is measured by a colorimetric assay (MTT assay) that can reduce MTT to a purple coloured product called formazan. The number of viable cells is related to the amount of colour produced. Yellow MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole) is reduced to purple coloured product called formazan in viable cells [59]. This insoluble purple formazan is dissolved using a solvent such as dimethyl sulphoxide (DMSO), so as to form a coloured solution [60]. Solubilization of the cells results in liberation of the purple product, which can be detected using a colorimetric measurement. The resulting purple solution is spectrophotometrically measured [61]. The increase in the absorbance is related to the amount of formazan formed resulting due to rapid proliferation of cells, thus indicating the mitochondrial activity of cells.

The cellular activity on the substrate was studied using cultured mouse astrocytes. The results demonstrated cell viability values higher than 80% for all film samples (**Figure 13**). This enhanced viability is ascribed to the initial time taken by the cells to adapt to the nature of the substrate [62]. Although there was no huge difference in the cell activity of all test samples, highest activity observed was for 3 wt% films (103.25 ± 13.23). The films were thus nontoxic and supported cell growth [52].

#### *3.2.8 Micronucleus cytome assay*

The *in vitro* cytokinesis-blocked micronucleus cytome (CBMN-cytome) assay is a modified CBMN assay which is based on the assessment of micronucleus (MN)

**17**

**Figure 14.**

*Image depicting typical L132 cells.*

chromosome loss.

**Figure 13.**

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

in nucleated cells that have completed only one nuclear division. The MN assay is a simple and rapid method that is perfectly suitable to elicit the biocompatibility of the samples and thus study the genotoxicity of the polymer composite samples. The CBMN cytome assay is not only restricted to micronucleus measurement, but also assists in the assessment of relevant markers like nucleoplasmic bridges (NPBs), nuclear buds (NBUDs), apoptotic and necrotic cells [63]. **Figure 14** reveals the presence of micronucleus, NPBs, NBUDs, and necrotic cells. The MN refer to small nuclei formed from acentric fragments or whole chromosomes, which lag behind and does not get included in either of the daughter nuclei, formed during cell division [64]. Hence, MN provides an indication of both chromosome breakage and

*Cell viability by MTT assay. Results are expressed in percentage survival fraction.*

MN cytome assay as described by Fenech [63], with slight modifications was used in the study. The cells used for the study were cultured normal lung cells

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

**Figure 13.** *Cell viability by MTT assay. Results are expressed in percentage survival fraction.*

in nucleated cells that have completed only one nuclear division. The MN assay is a simple and rapid method that is perfectly suitable to elicit the biocompatibility of the samples and thus study the genotoxicity of the polymer composite samples. The CBMN cytome assay is not only restricted to micronucleus measurement, but also assists in the assessment of relevant markers like nucleoplasmic bridges (NPBs), nuclear buds (NBUDs), apoptotic and necrotic cells [63]. **Figure 14** reveals the presence of micronucleus, NPBs, NBUDs, and necrotic cells. The MN refer to small nuclei formed from acentric fragments or whole chromosomes, which lag behind and does not get included in either of the daughter nuclei, formed during cell division [64]. Hence, MN provides an indication of both chromosome breakage and chromosome loss.

MN cytome assay as described by Fenech [63], with slight modifications was used in the study. The cells used for the study were cultured normal lung cells

**Figure 14.** *Image depicting typical L132 cells.*

*Generation, Development and Modifications of Natural Fibers*

*Pictomicrographs of attachment of fibroblast cells (Scale bar-500 μm).*

The mitochondrial activity of cells is measured by a colorimetric assay (MTT assay) that can reduce MTT to a purple coloured product called formazan. The number of viable cells is related to the amount of colour produced. Yellow MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole) is reduced to purple coloured product called formazan in viable cells [59]. This insoluble purple formazan is dissolved using a solvent such as dimethyl sulphoxide (DMSO), so as to form a coloured solution [60]. Solubilization of the cells results in liberation of the purple product, which can be detected using a colorimetric measurement. The resulting purple solution is spectrophotometrically measured [61]. The increase in the absorbance is related to the amount of formazan formed resulting due to rapid proliferation of cells, thus indicating the mitochondrial activ-

The cellular activity on the substrate was studied using cultured mouse astrocytes. The results demonstrated cell viability values higher than 80% for all film samples (**Figure 13**). This enhanced viability is ascribed to the initial time taken by the cells to adapt to the nature of the substrate [62]. Although there was no huge difference in the cell activity of all test samples, highest activity observed was for 3 wt% films (103.25 ± 13.23). The films were thus nontoxic and supported cell

The *in vitro* cytokinesis-blocked micronucleus cytome (CBMN-cytome) assay is a modified CBMN assay which is based on the assessment of micronucleus (MN)

**16**

*3.2.7 MTT assay*

**Figure 12.**

ity of cells.

growth [52].

*3.2.8 Micronucleus cytome assay*

(L132) cells. Only binucleated cells (BNC) with intact cytoplasm were considered for scoring micronuclei (MNi) by ignoring cells with broken cytoplasm and cells with fused nuclei [65]. No significant difference in the MN yield of micronuclei was observed between the cultures treated with PVA, 3, 9 and 15 wt% silk fibre reinforced films when compared to the negative control, revealing the lack of genotoxic effect. In relation to nuclear division index values, no significant differences were observed between the different composite films and negative control, demonstrating the absence of cytotoxicity.

#### **4. Conclusions**

The surging interest towards silk fibres due to its innumerable properties was the motivation of this study. A comprehensive study on the use of silk fibres as reinforcements, for the development of biocompatible and biodegradable composites was conducted. The composite films were developed by solution casting and the effect of silk fibre concentration on the properties of the composite films was assessed.

Biocomposite films of PVA and PVA/PVP; reinforced with degummed short silk fibres were prepared and showed enhanced properties. The results showed that increasing the fibre concentration, diminished the mechanical properties and the optimum concentration was found to be 12 and 9 wt% respectively. The added short silk fibres, improved the thermal properties of the composite films as confirmed by DSC/TGA. Morphological properties of the film composites indicated a poor fibre matrix adhesion (FESEM) at the fibre concentration of 12 and 15 wt% respectively. The prepared films were found to biodegradable and the biodegradation was aided by the presence of soil microbes.

The properties of silk fibres were re-tailored by grafting a natural polysaccharide like chitosan, thereby fabricating films of PVA, suitable for biomedical applications. Films of PVA reinforced with grafted silk showed improved properties as a result of fibre-matrix interactions and hence prove to be effective to be used as scaffolds for tissue engineering applications. Besides, the composite films also showed enhanced biodegradable characteristics with increasing concentrations of grafted silk fibres. The efficacy of the films to exhibit antimicrobial activity was undoubtedly due to the presence of chitosan on silk. The films were further evaluated for their blood compatibility, cytotoxicity and genotoxicity studies and proved to be nontoxic in almost all concentrations.

#### **Acknowledgements**

The authors are grateful to DST PURSE, Mangalore University for providing the necessary facilities for the characterization of the samples.

#### **Conflict of interest**

The authors of this manuscript declare that they do not hold any conflicts of interest that might have any bearing on research reported in their submitted manuscript.

**19**

**Author details**

Sareen Sheik1,2 and Gundibasappa Karikannar Nagaraja2

\*Address all correspondence to: nagarajagk@gmail.com

provided the original work is properly cited.

1 P.A. College of Engineering and Technology, Mangaluru, India

2 Department of Chemistry, Mangalore University, Mangalagangothri, India

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced…*

*DOI: http://dx.doi.org/10.5772/intechopen.85022*

*Development, Characterization and Properties of Silk Fibre and Grafted Silk Fibre Reinforced… DOI: http://dx.doi.org/10.5772/intechopen.85022*

#### **Author details**

*Generation, Development and Modifications of Natural Fibers*

ing the absence of cytotoxicity.

by the presence of soil microbes.

almost all concentrations.

**Acknowledgements**

**Conflict of interest**

manuscript.

**4. Conclusions**

assessed.

(L132) cells. Only binucleated cells (BNC) with intact cytoplasm were considered for scoring micronuclei (MNi) by ignoring cells with broken cytoplasm and cells with fused nuclei [65]. No significant difference in the MN yield of micronuclei was observed between the cultures treated with PVA, 3, 9 and 15 wt% silk fibre reinforced films when compared to the negative control, revealing the lack of genotoxic effect. In relation to nuclear division index values, no significant differences were observed between the different composite films and negative control, demonstrat-

The surging interest towards silk fibres due to its innumerable properties was the motivation of this study. A comprehensive study on the use of silk fibres as reinforcements, for the development of biocompatible and biodegradable composites was conducted. The composite films were developed by solution casting and the effect of silk fibre concentration on the properties of the composite films was

Biocomposite films of PVA and PVA/PVP; reinforced with degummed short silk fibres were prepared and showed enhanced properties. The results showed that increasing the fibre concentration, diminished the mechanical properties and the optimum concentration was found to be 12 and 9 wt% respectively. The added short silk fibres, improved the thermal properties of the composite films as confirmed by DSC/TGA. Morphological properties of the film composites indicated a poor fibre matrix adhesion (FESEM) at the fibre concentration of 12 and 15 wt% respectively. The prepared films were found to biodegradable and the biodegradation was aided

The properties of silk fibres were re-tailored by grafting a natural polysaccharide like chitosan, thereby fabricating films of PVA, suitable for biomedical applications. Films of PVA reinforced with grafted silk showed improved properties as a result of fibre-matrix interactions and hence prove to be effective to be used as scaffolds for tissue engineering applications. Besides, the composite films also showed enhanced biodegradable characteristics with increasing concentrations of grafted silk fibres. The efficacy of the films to exhibit antimicrobial activity was undoubtedly due to the presence of chitosan on silk. The films were further evaluated for their blood compatibility, cytotoxicity and genotoxicity studies and proved to be nontoxic in

The authors are grateful to DST PURSE, Mangalore University for providing the

The authors of this manuscript declare that they do not hold any conflicts of interest that might have any bearing on research reported in their submitted

necessary facilities for the characterization of the samples.

**18**

Sareen Sheik1,2 and Gundibasappa Karikannar Nagaraja2 \*

1 P.A. College of Engineering and Technology, Mangaluru, India

2 Department of Chemistry, Mangalore University, Mangalagangothri, India

\*Address all correspondence to: nagarajagk@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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app.24064

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10.1177/0021998309345347

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[46] Re GL, Morreale M, Scaffaro R, La Mantia FP. Biodegradation paths of Mater-Bi®/kenaf biodegradable composites. Journal of Applied Polymer Science. 2013;**129**(6):3198-3208. DOI: 10.1002/app.39027

[47] Helander IM, Nurmiaho-Lassila EL, Ahvenainen R, Rhoades J, Roller S. Chitosan disrupts the barrier properties of the outer membrane of gram-negative bacteria. International Journal of Food Microbiology. 2001;**71**(2-3):235-244. DOI: 10.1016/ S0168-1605(01)00609-2

[48] Je JY, Kim SK. Chitosan derivatives killed bacteria by disrupting the outer and inner membrane. Journal of Agricultural and Food Chemistry. 2006;**54**(18):6629- 6633. DOI: 10.1021/jf061310p

[49] Zakrzewska A, Boorsma A, Brul S, Hellingwerf KJ, Klis FM. Transcriptional response of Saccharomyces cerevisiae to the plasma membrane-perturbing compound chitosan. Eukaryotic Cell. 2005;**4**(4):703-715. DOI: 10.1128/ EC.4.4.703-715.2005

[50] Wu T, Zivanovic S, Draughon FA, Conway WS, Sams CE. Physicochemical properties and bioactivity of fungal chitin and chitosan. Journal of Agricultural and Food Chemistry. 2005;**53**(10):3888-3894. DOI: 10.1021/ jf048202s

[51] Singhal JP, Ray AR. Synthesis of blood compatible polyamide block copolymers. Biomaterials. 2002;**23**(4):1139-1145. DOI: 10.1016/ S0142-9612(01)00228-9

[52] Sheik S, Sheik S, Nairy R, Nagaraja GK, Prabhu A, Rekha PD, et al. Study on the morphological and biocompatible properties of chitosan grafted silk fibre reinforced PVA films for tissue engineering applications. International Journal of Biological Macromolecules. 2018;**116**:45-53. DOI: 10.1016/j. ijbiomac.2018.05.019

[53] Hirano S, Zhang M, Nakagawa M, Miyata T. Wet spun chitosan-collagen fibers, their chemical N-modifications, and blood compatibility. Biomaterials. 2000;**21**(10):997-1003. DOI: 10.1016/ S0142-9612(99)00258-6

[54] Amiji MM. Platelet adhesion and activation on an amphoteric chitosan derivative bearing sulfonate groups. Colloids and Surfaces B: Biointerfaces. 1998;**10**(5):263-271. DOI: 10.1016/ S0927-7765(98)00005-8

[55] Wang QZ, Chen XG, Li ZX, Wang S, Liu CS, Meng XH, et al. Preparation and blood coagulation evaluation of chitosan microspheres. Journal of Materials Science: Materials in Medicine. 2008;**19**(3):1371-1377. DOI: 10.1007/s10856-007-3243-y

[56] Jumaa M, Furkert FH, Müller BW. A new lipid emulsion formulation with high antimicrobial efficacy using chitosan. European Journal of Pharmaceutics and Biopharmaceutics. 2002;**53**(1):115-123. DOI: 10.1016/ S0939-6411(01)00191-6

[57] Richardson SW, Kolbe HJ, Duncan R. Potential of low molecular mass chitosan as a DNA delivery system: Biocompatibility, body distribution and ability to complex and protect DNA. International Journal of Pharmaceutics. 1999;**178**(2):231-243. DOI: 10.1016/S0378-5173(98)00378-0

[58] Dankers PY, van Beek DJ, ten Cate AT, Sijbesma RP, Meijer EW. Novel biocompatible supramolecular materials for tissue engineering. Polymeric Materials Science and Engineering. 2003;**88**:52-53

[59] Mosmann T. Rapid colorimetric assay for cellular growth and survival: Application to proliferation and cytotoxicity assays. Journal of Immunological Methods. 1983;**65**(1-2):55-63. DOI: 10.1016/0022-1759(83)90303-4

[60] Altman FP. Tetrazolium salts and formazans. Progress in Histochemistry and Cytochemistry. 1976;**9**(3):III-I51. DOI: 10.1016/S0079-6336(76)80015-0

[61] Denizot F, Lang R. Rapid colorimetric assay for cell growth and survival: Modifications to the tetrazolium dye procedure giving improved sensitivity and reliability. Journal of Immunological Methods. 1986;**89**(2):271-277. DOI: 10.1016/0022-1759(86)90368-6

[62] Gopinathan J, Mano S, Elakkiya V, Pillai MM, Sahanand KS, Rai BD, et al. Biomolecule incorporated polyε-caprolactone nanofibrous scaffolds for enhanced human meniscal cell attachment and proliferation. RSC Advances. 2015;**5**(90):73552-73561. DOI: 10.1039/C5RA14315B

[63] Fenech M. Cytokinesis-block micronucleus cytome assay. Nature Protocols. 2007;**2**(5):1084

[64] Maluf SW, Erdtmann B. Follow-up study of the genetic damage in

lymphocytes of pharmacists and nurses handling antineoplastic drugs evaluated by cytokinesis-block micronuclei analysis and single cell gel electrophoresis assay. Mutation Research, Genetic Toxicology and Environmental Mutagenesis. 2000;**471**(1):21-27. DOI: 10.1016/ S1383-5718(00)00107-8

[65] Heddle JA. A rapid *in vivo* test for chromosomal damage. Mutation Research: Fundamental and Molecular Mechanisms of Mutagenesis. 1973;**18**(2):187-190. DOI: 10.1016/0027-5107(73)90035-3

**25**

and associated by products.

**Chapter 2**

**Abstract**

products.

**1. Introduction**

*Jatinder Singh Dhaliwal*

Natural Fibers: Applications

Fibers derived from bio-based sources such as vegetables and animal origin are termed as natural fibers. This definition includes all natural cellulosic fibers (cotton, jute, sisal, coir, flax, hemp, abaca, ramie, etc.) and protein-based fibers such as wool and silk. There are also man-made cellulose fibers (e.g., viscose rayon and cellulose acetate) that are produced with chemical procedures from pulped wood or other sources (cotton, bamboo). Natural fibers being cost effective and abundantly available yields high potential in various industrial and commercial applications such as in the interior applications of the passenger cars, panels for partition and false ceiling, partition boards, roof tiles, coir fibers in packaging, furniture applications, as insulating materials in low energy houses, geo-textiles for soil protection and erosion control, enhancing barrier properties, composites etc. Due to research and developmental work in modification and treatment methods of natural fibers, utilization of natural fibers has observed a significant growth in various applications. The chapter addresses the potential applications of natural fibers in various commercial sectors for the development of environment-friendly products with an aim to replace synthetic fibers or inorganic fillers with cost-effective and efficient

**Keywords:** natural fibers, polymers, composites, applications, modification

The transition toward a bio-based economy and sustainable developments as a consequence of the Kyoto protocols on greenhouse gas reduction and CO2 neutral production offers high perspectives for natural fiber markets. Changing to a biobased economy requires substitution of common raw materials that are currently largely produced from fossil (petrochemical) or mineral resources, by-products produced from renewable (plant and animal based) resources [1]. The development of a sustainable global economy, which permits improving purchasing power and living standards without exhaustion of resources for future generations, requires a fundamental change in attitude. On ecological grounds products should then be preferred that are based on photosynthetic CO2 fixation [1]. The benefit of those sustainable resources is that they can be regrown within the foreseeable future, without negative side effects on global biodiversity. Therefore, competitive products based on renewable resources need to be developed to have high quality, show excellent technical performance, and harm the environment less than current products based on petrochemical materials [2, 3]. **Table 1** below shows the major natural fiber producers in the world, their potential applications

#### **Chapter 2**

*Generation, Development and Modifications of Natural Fibers*

lymphocytes of pharmacists and nurses handling antineoplastic drugs evaluated by cytokinesis-block micronuclei analysis and single cell gel electrophoresis assay. Mutation Research, Genetic Toxicology and Environmental Mutagenesis. 2000;**471**(1):21-27. DOI: 10.1016/

S1383-5718(00)00107-8

[65] Heddle JA. A rapid *in vivo* test for chromosomal damage. Mutation Research: Fundamental and Molecular Mechanisms of

10.1016/0027-5107(73)90035-3

Mutagenesis. 1973;**18**(2):187-190. DOI:

[57] Richardson SW, Kolbe HJ, Duncan R. Potential of low molecular mass chitosan as a DNA delivery system: Biocompatibility, body distribution and ability to complex and protect DNA. International Journal of Pharmaceutics. 1999;**178**(2):231-243. DOI: 10.1016/S0378-5173(98)00378-0

[58] Dankers PY, van Beek DJ, ten Cate AT, Sijbesma RP, Meijer EW. Novel biocompatible supramolecular materials for tissue engineering. Polymeric Materials Science and Engineering.

[60] Altman FP. Tetrazolium salts and formazans. Progress in Histochemistry and Cytochemistry. 1976;**9**(3):III-I51. DOI: 10.1016/S0079-6336(76)80015-0

[62] Gopinathan J, Mano S, Elakkiya V, Pillai MM, Sahanand KS, Rai BD, et al. Biomolecule incorporated polyε-caprolactone nanofibrous scaffolds for enhanced human meniscal cell attachment and proliferation. RSC Advances. 2015;**5**(90):73552-73561. DOI:

10.1039/C5RA14315B

Protocols. 2007;**2**(5):1084

[63] Fenech M. Cytokinesis-block micronucleus cytome assay. Nature

study of the genetic damage in

[64] Maluf SW, Erdtmann B. Follow-up

[61] Denizot F, Lang R. Rapid colorimetric assay for cell growth and survival: Modifications to the tetrazolium dye procedure giving improved sensitivity and reliability. Journal of Immunological Methods. 1986;**89**(2):271-277. DOI: 10.1016/0022-1759(86)90368-6

2003;**88**:52-53

[59] Mosmann T. Rapid colorimetric assay for cellular growth and survival: Application to proliferation and cytotoxicity assays. Journal of Immunological Methods. 1983;**65**(1-2):55-63. DOI: 10.1016/0022-1759(83)90303-4

**24**

## Natural Fibers: Applications

*Jatinder Singh Dhaliwal*

#### **Abstract**

Fibers derived from bio-based sources such as vegetables and animal origin are termed as natural fibers. This definition includes all natural cellulosic fibers (cotton, jute, sisal, coir, flax, hemp, abaca, ramie, etc.) and protein-based fibers such as wool and silk. There are also man-made cellulose fibers (e.g., viscose rayon and cellulose acetate) that are produced with chemical procedures from pulped wood or other sources (cotton, bamboo). Natural fibers being cost effective and abundantly available yields high potential in various industrial and commercial applications such as in the interior applications of the passenger cars, panels for partition and false ceiling, partition boards, roof tiles, coir fibers in packaging, furniture applications, as insulating materials in low energy houses, geo-textiles for soil protection and erosion control, enhancing barrier properties, composites etc. Due to research and developmental work in modification and treatment methods of natural fibers, utilization of natural fibers has observed a significant growth in various applications. The chapter addresses the potential applications of natural fibers in various commercial sectors for the development of environment-friendly products with an aim to replace synthetic fibers or inorganic fillers with cost-effective and efficient products.

**Keywords:** natural fibers, polymers, composites, applications, modification

#### **1. Introduction**

The transition toward a bio-based economy and sustainable developments as a consequence of the Kyoto protocols on greenhouse gas reduction and CO2 neutral production offers high perspectives for natural fiber markets. Changing to a biobased economy requires substitution of common raw materials that are currently largely produced from fossil (petrochemical) or mineral resources, by-products produced from renewable (plant and animal based) resources [1]. The development of a sustainable global economy, which permits improving purchasing power and living standards without exhaustion of resources for future generations, requires a fundamental change in attitude. On ecological grounds products should then be preferred that are based on photosynthetic CO2 fixation [1]. The benefit of those sustainable resources is that they can be regrown within the foreseeable future, without negative side effects on global biodiversity. Therefore, competitive products based on renewable resources need to be developed to have high quality, show excellent technical performance, and harm the environment less than current products based on petrochemical materials [2, 3]. **Table 1** below shows the major natural fiber producers in the world, their potential applications and associated by products.


#### **Table 1.**

*Natural fiber type, producers and markets [4].*

In 2017, global fiber production exceeded 100 million mt resulting in the largest fiber production volume ever. Global fiber production saw a 10-fold increase from 1950 to 2017 from <10 million mt to over 100 million mt. Synthetic fibers have dominated the fiber market since the mid-1990s when they overtook cotton and became the dominant fiber. With around 65 million mt of synthetic fibers, this fiber category made up approximately 60% of the global fiber production in 2017. Polyester has a market share of around 51% of the total global fiber production. More than 53 million mt of polyester is produced annually. Cotton is the second most important fiber since synthetics took the lead in the mid-1990s [4]. With around 26 million mt, it has a market share of approximately 25% of global fiber production. An increasingly important fiber category is man-made cellulosics (MMCs) with a global production volume of around 6.5 million mt and a market share of around 6–7% in 2017. Wool has a market share of around 1% with a global production volume of a little over one million mt. Other plant-based fibers, including jute, linen, and hemp, together have a market share of about 5%. Silk and down have market shares of less than 1%. The need to decouple growth from resource consumption gets more urgent every year. The significant growth in fiber production results in a significant use of natural resources and a huge production of textile waste. There is a growing awareness of the urgent need for a more responsible use of resources, enabling growth without increased resource consumption.

**27**

yaw control [8–10].

*Natural Fibers: Applications*

lignin [5].

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

overall fiber footprint on the planet [4].

An innovation toward a circular economy and dematerialization can be seen in almost all fiber categories. Accelerating such initiatives will help to reduce the

Natural fibers have three main components lignin, cellulose and hemi-cellulose, percent of each vary with each type of natural fiber. Hemicellulose is strongly tied to cellulose fibrils presumably by hydrogen bonds. Hemicellulose polymers are branched and fully amorphous and have a significantly lower molecular weight than cellulose. Because of its open structure containing many hydroxyl and acetyl groups, hemicellulose is partly soluble in water and hygroscopic. Lignin is amorphous, highly complex, and mainly aromatic polymer of phenyl propane units but had the least water absorption of the natural fiber components. Amorphous lignin matrix helps in the combination of helically arranged cellulose microfibrils, which results in the formation of composite fiber. Lignin plays a very important role in the plant fiber such as water holding capacity, provide protection against biological attacks, and strengthened the stem against wind and gravity forces. Hemicellulose found in the plant fibers is believed to be a compatibilizer between cellulose and

However, the quality of natural fibers is greatly influenced by various factors like the age of the plant, species, growing environment, harvesting, humidity, quality of soil, temperature, and processing steps, and there is a move to reduce the on-field

For centuries different sources like wood, oil, coal and currently materials like coke, natural gas, nuclear materials etc. are used for energy generation. With the significant increase in population, civilization, and industrialization, the consumption of energy has increased many folds. In today's scenario due to this imbalance of ecological system, more ecological awareness and stringent country law and policies have led to the increased interest on renewable and sustainable energy sources. There is a continuous search for sustainable development with minimum pollution and better efficiencies for reduction in energy consumption which have led to the development of wind energy. It is a prominent renewable energy source available to mankind which can be part of the solution of the global energy problem [7]. Currently the wind energy sector is growing, and highly efficient systems capable for converting the kinetic energy of the wind into mechanical or electrical energy are available. Generally the wind turbines consist of three rotor blades that rotate around a horizontal hub and convert the wind energy into mechanical energy and are the key component of the wind turbine. However the design aspect of these wind blades plays a major role in conversion process, the aerodynamic shape, the length of blades,

Based upon the design of orientation of the shaft and rotational axis, wind turbines can be classified into two types (**Figure 1**). A turbine with a shaft mounted horizontally parallel to the ground is known as a horizontal-axis wind turbine (HAWT), and turbine with shaft normal to the ground is called vertical-axis wind turbine (VAWT). Today's leading large-scale turbine manufacturers favor HAWTtype turbines because of attributes like increased rotor control through pitch and

Fiber-reinforced composite materials have been the choice for the commercial production of large-scale wind turbine rotor blades especially glass and carbon

processing to improve consistency and reduce costs [6].

and the material of construction used by the manufacturer.

**2. Applications of natural fibers**

**2.1 Wind turbine blade**

#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

*Generation, Development and Modifications of Natural Fibers*

**Main producers Fiber market By-product**

(hydrophilic absorbents)

Kapok Indonesia Pillow, mattress Seeds, wood Jute India, Bangladesh Hessian, sacking, carpet backing Stalks (sticks)

Ramie China Textile fabric Leaves, stem

Coir India, Sri Lanka Twine, ropes, carpets, brushes, mattress,

Textile fabric: apparel, home furnishing, upholstery, non-wovens, specialty paper, cellulose, medical and hygienic supplies

Textile fabric, composites non-woven, insulation mats, specialist paper

geotextiles, horticultural products

Specialty paper, tea bags Leaves, juice

Twine and ropes Short fiber, juice,

Knitted wear Lamb meat, cheese

Linter, cottonseed,

stalks

Seeds, shives

poles, stem

Copra, water, shell, pith, wood,

fruits, wood

leaves

**Natural fiber**

Cotton China, USA, India, Pakistan

Kenaf China, India,

Flax China, France,

Hemp China

Abaca Philippines,

Sisal Brazil, China,

Wool Australia, China,

*Natural fiber type, producers and markets [4].*

Henequen Mexico

**Table 1.**

Thailand

Ecuador

Tanzania, Kenya

New Zealand

Belgium, Belarus, Ukraine

In 2017, global fiber production exceeded 100 million mt resulting in the largest fiber production volume ever. Global fiber production saw a 10-fold increase from 1950 to 2017 from <10 million mt to over 100 million mt. Synthetic fibers have dominated the fiber market since the mid-1990s when they overtook cotton and became the dominant fiber. With around 65 million mt of synthetic fibers, this fiber category made up approximately 60% of the global fiber production in 2017. Polyester has a market share of around 51% of the total global fiber production. More than 53 million mt of polyester is produced annually. Cotton is the second most important fiber since synthetics took the lead in the mid-1990s [4]. With around 26 million mt, it has a market share of approximately 25% of global fiber production. An increasingly important fiber category is man-made cellulosics (MMCs) with a global production volume of around 6.5 million mt and a market share of around 6–7% in 2017. Wool has a market share of around 1% with a global production volume of a little over one million mt. Other plant-based fibers, including jute, linen, and hemp, together have a market share of about 5%. Silk and down have market shares of less than 1%. The need to decouple growth from resource consumption gets more urgent every year. The significant growth in fiber production results in a significant use of natural resources and a huge production of textile waste. There is a growing awareness of the urgent need for a more responsible use

Silk China, India Fine garments, veils, handkerchiefs Worms, cocoons,

of resources, enabling growth without increased resource consumption.

**26**

An innovation toward a circular economy and dematerialization can be seen in almost all fiber categories. Accelerating such initiatives will help to reduce the overall fiber footprint on the planet [4].

Natural fibers have three main components lignin, cellulose and hemi-cellulose, percent of each vary with each type of natural fiber. Hemicellulose is strongly tied to cellulose fibrils presumably by hydrogen bonds. Hemicellulose polymers are branched and fully amorphous and have a significantly lower molecular weight than cellulose. Because of its open structure containing many hydroxyl and acetyl groups, hemicellulose is partly soluble in water and hygroscopic. Lignin is amorphous, highly complex, and mainly aromatic polymer of phenyl propane units but had the least water absorption of the natural fiber components. Amorphous lignin matrix helps in the combination of helically arranged cellulose microfibrils, which results in the formation of composite fiber. Lignin plays a very important role in the plant fiber such as water holding capacity, provide protection against biological attacks, and strengthened the stem against wind and gravity forces. Hemicellulose found in the plant fibers is believed to be a compatibilizer between cellulose and lignin [5].

However, the quality of natural fibers is greatly influenced by various factors like the age of the plant, species, growing environment, harvesting, humidity, quality of soil, temperature, and processing steps, and there is a move to reduce the on-field processing to improve consistency and reduce costs [6].

#### **2. Applications of natural fibers**

#### **2.1 Wind turbine blade**

For centuries different sources like wood, oil, coal and currently materials like coke, natural gas, nuclear materials etc. are used for energy generation. With the significant increase in population, civilization, and industrialization, the consumption of energy has increased many folds. In today's scenario due to this imbalance of ecological system, more ecological awareness and stringent country law and policies have led to the increased interest on renewable and sustainable energy sources. There is a continuous search for sustainable development with minimum pollution and better efficiencies for reduction in energy consumption which have led to the development of wind energy. It is a prominent renewable energy source available to mankind which can be part of the solution of the global energy problem [7]. Currently the wind energy sector is growing, and highly efficient systems capable for converting the kinetic energy of the wind into mechanical or electrical energy are available. Generally the wind turbines consist of three rotor blades that rotate around a horizontal hub and convert the wind energy into mechanical energy and are the key component of the wind turbine. However the design aspect of these wind blades plays a major role in conversion process, the aerodynamic shape, the length of blades, and the material of construction used by the manufacturer.

Based upon the design of orientation of the shaft and rotational axis, wind turbines can be classified into two types (**Figure 1**). A turbine with a shaft mounted horizontally parallel to the ground is known as a horizontal-axis wind turbine (HAWT), and turbine with shaft normal to the ground is called vertical-axis wind turbine (VAWT). Today's leading large-scale turbine manufacturers favor HAWTtype turbines because of attributes like increased rotor control through pitch and yaw control [8–10].

Fiber-reinforced composite materials have been the choice for the commercial production of large-scale wind turbine rotor blades especially glass and carbon

**Figure 1.** *Alternative configurations of shaft and rotor [8].*

fibers. Carbon fibers are preferred over glass fibers because they provide superior mechanical strength due to their lower density and higher fatigue ratio which extends the life of the blades. The high cost of the carbon fibers which start with the expensive poly-acrylonitrile polymer (PAN) precursor and due to the environmental concerns and stringent laws, these are not considered as first choice since the commercial production of these types of fibers is highly dependent upon petroleum-based resources [11]. Because of these and similar reasons, researchers around the globe have shifted their focus on replacing these man-made fibers with natural fibers. Some of the main requirements for the wind turbine blade are (a) high strength, (b) high fatigue resistance and reliability, (c) low weight, and (d) high stiffness [12].

There is a huge potential to reduce the overall manufacturing cost of the wind turbine blades and replace the man-made fibers with natural fiber-reinforced composite materials. Balsa, flax, hemp, coir, abaca, alpaca, bamboo, and jute fibers have been marketed as potential and prospective substitutes to the traditional composite reinforcements. Lignin which is an aromatic biopolymer and abundantly available and can be sourced from plants and wood can be used as a precursor for production of carbon fibers. Low cost and easy availability can have a saving of 37–49% in the production cost of carbon fibers. However lignin has to be modified so as to be spun, stretched/aligned, and spooled into fibers, and these fibers can also be used in manufacturing of blades. Generally wind turbine blades are made up of array of sandwich panel strips and panels. Because of its light in weight and stiffness relative to density, balsa wood is being studied and used for making wind turbine interior panels and sandwich components [11, 12].

The performance of NFC-based wind turbine blades depend upon the following factors [10]:


**29**

*Natural Fibers: Applications*

procedures [14].

procedures [19–21].

natural and synthetic.

**2.2 Hydrogel production**

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

better performance can be achieved with fibers having higher cellulose content and cellulose microfibrils aligned more in fiber direction. Typical examples are flax, hemp, kenaf, jute, and ramie fibers. The properties of the natural fibers do vary depending upon the chemical structure and composition, growing conditions, treatment procedures, harvesting time, extraction method, and storage

3.Fiber orientation—Orientation of fibers in polymer matrix ultimately governs the performance of the composite material which is best achieved when the fibers are aligned in parallel to the direction of applied load, however it's difficult to achieve in reality. Some alignment can be achieved during injection molding

4.Interference strength—Though the natural fibers are obtained from renewable resources and the composite materials will be environment-friendly, there are certain disadvantages also associated with unmodified or raw natural fibers. Some of the major problems can be high moisture uptake, low thermal stability, poor adhesion, poor mechanicals, etc. However, the majority of these can be overcome by employing suitable treatment/modification

Hydrogels are polymers having a three-dimensional cross-linked hydrophilic structure produced by simple reaction of one or more monomers which renders them capability of absorbing, storing, and releasing water molecules. Hydrogels have been researched considerably over the past decades due to their promising application in various fields. Some of the application areas of hydrogels include the manufacture of personal hygiene products, medical devices, environmental, agricultural, drug delivery systems, pharmaceuticals, biomedical, tissue engineering and regenerative medicines, wound dressing, biosensor, separation of biomolecules

1.Source—Based upon the source, hydrogels can be categorized into two groups:

2.According to the polymeric composition—Preparation method leads to different class of hydrogels. (a) Homopolymeric hydrogels are formed using single monomer. Cross-linking will depend upon the nature of monomer and polymerization technique. (b) Copolymeric hydrogels are formed using two or more monomer species having at least one hydrophilic component. (c) Multipolymer interpenetrating polymeric network (IPN) is formed of two independent cross-linked natural or synthetic polymer components. In semi-IPN hydrogel,

one is cross-linked, while the other component is non-cross-linked.

the hydrogels can be amorphous, semicrystalline, and crystalline.

ing from physical entanglements or interactions [27].

3.Type of cross linking—Based upon the chemical or nature of cross-linking junctions, hydrogels can be classified into two categories. Chemical crosslinked having permanent junctions and hydrogels with physical networks aris-

4.Configuration—Based upon the chemical composition and physical structure,

or cells and barrier materials to regulate biological adhesions, etc. [22–26].

Hydrogels can be classified based upon the following [22]:

process and manual placement of long fibers [15–18].

#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

*Generation, Development and Modifications of Natural Fibers*

*Alternative configurations of shaft and rotor [8].*

(d) high stiffness [12].

**Figure 1.**

factors [10]:

ral fibers [13].

panels and sandwich components [11, 12].

fibers. Carbon fibers are preferred over glass fibers because they provide superior mechanical strength due to their lower density and higher fatigue ratio which extends the life of the blades. The high cost of the carbon fibers which start with the expensive poly-acrylonitrile polymer (PAN) precursor and due to the environmental concerns and stringent laws, these are not considered as first choice since the commercial production of these types of fibers is highly dependent upon petroleum-based resources [11]. Because of these and similar reasons, researchers around the globe have shifted their focus on replacing these man-made fibers with natural fibers. Some of the main requirements for the wind turbine blade are (a) high strength, (b) high fatigue resistance and reliability, (c) low weight, and

There is a huge potential to reduce the overall manufacturing cost of the wind turbine blades and replace the man-made fibers with natural fiber-reinforced composite materials. Balsa, flax, hemp, coir, abaca, alpaca, bamboo, and jute fibers have been marketed as potential and prospective substitutes to the traditional composite reinforcements. Lignin which is an aromatic biopolymer and abundantly available and can be sourced from plants and wood can be used as a precursor for production of carbon fibers. Low cost and easy availability can have a saving of 37–49% in the production cost of carbon fibers. However lignin has to be modified so as to be spun, stretched/aligned, and spooled into fibers, and these fibers can also be used in manufacturing of blades. Generally wind turbine blades are made up of array of sandwich panel strips and panels. Because of its light in weight and stiffness relative to density, balsa wood is being studied and used for making wind turbine interior

The performance of NFC-based wind turbine blades depend upon the following

1.Matrix selection—Matrix plays an important role in fiber-reinforced composites. It acts as a barrier against environment and protects the surface exposed from mechanical abrasion. Most commonly used matrices are polymeric in nature as they hold certain advantages being light in weight and easy to fabricate,

(e.g., polypropylene, polyethylene, nylon, polycarbonate, etc.) and thermoset (e.g., polyurethanes, polyester, epoxy etc.) polymers are being used with natu-

2.Fiber selection—All the plant-based fibers hold cellulose as the major structural component. Choice of the fiber depends upon the country or region and size of the wind turbine blade. It is important to know the availability of the fiber since it varies from country to country. The size of the blade governs the nature of mechanical performance requirements; therefore one particular fiber might not provide adequate strength for a particular size blade. Generally

can be designed to withstand harsh temperatures, etc. Thermoplastic

**28**

better performance can be achieved with fibers having higher cellulose content and cellulose microfibrils aligned more in fiber direction. Typical examples are flax, hemp, kenaf, jute, and ramie fibers. The properties of the natural fibers do vary depending upon the chemical structure and composition, growing conditions, treatment procedures, harvesting time, extraction method, and storage procedures [14].


#### **2.2 Hydrogel production**

Hydrogels are polymers having a three-dimensional cross-linked hydrophilic structure produced by simple reaction of one or more monomers which renders them capability of absorbing, storing, and releasing water molecules. Hydrogels have been researched considerably over the past decades due to their promising application in various fields. Some of the application areas of hydrogels include the manufacture of personal hygiene products, medical devices, environmental, agricultural, drug delivery systems, pharmaceuticals, biomedical, tissue engineering and regenerative medicines, wound dressing, biosensor, separation of biomolecules or cells and barrier materials to regulate biological adhesions, etc. [22–26].

Hydrogels can be classified based upon the following [22]:


#### *2.2.1 Modification methods of natural fibers for hydrogel production*

Lignin, hemicellulose, and cellulose are the major constituents of natural fibers. Lignin which coats or covers the cellulose part shows lower tendency to react with other molecules and poor adhesion with polymer matrix. Therefore the natural fibers most of the time have to undergo through treatment or modifications to improve the reactivity, interaction, and better adhesion with polymer matrix or other molecules [28].

For the hydrogel production, the natural fibers are modified in two stages:


Collectively these steps increase the water absorption and retention capacity throughout with the help of modifying agents and active site generation.

#### *2.2.2 Hydrogel synthesis from plant fibers*

Hydrogel synthesis methods are mass polymerization, solution, and reverse suspension (use of initiator and a crosslinking agent). Generally hydrogel synthesis based upon the plant fibers uses solution polymerization method [28]. **Figure 2** shows general hydrogel preparation process.

**Table 2** shows the different polymerization techniques, method employed, and type of characterization required during hydrogel synthesis. Solution polymerization is typically the preferred method for synthesis.

As reported by [29], during hydrogel synthesis, increase in the fiber content increased the swelling and elastic modulus, whereas Liang et al. showed change in pH, temperature, and salts leads to change in swelling behavior. In acidic environment, hydronium ions interacts with hydroxyl groups of cellulose to form hydrogen

**31**

**Raw material** Modified sugar cane bagasse, sodium hydroxide, acrylic acid

Cross-linker: N,N-methylenebisacrylamide

Initiator: ammonium persulfate and sodium sulfite

Flax fiber (shive) pretreated with NaOH sodium hydroxide, acrylic acid

Reactor set to microwave with condensation System nitrogen as inert gas

Microwave assisted polymerization

Reaction temperature: 22 min

Power of irradiation: 160 W

Concentration of nanocrystals: 1,

Polymerization by free radicals

in solution

3, 5, 6, 7,

and 9.3% weight

Reactor: 50 ml flask with stirring

Nitrogen as inert gas

Temperature: 25°C

Reaction time: 20 hours

Concentration of 1.5% nanofibers

Polymerization

Measurement of rheological and

[34]

compression properties

Swelling ability and kinetics

by free radicals in solution

with the monomer

Reactor: 20 × 60 mm test tubes

Nitrogen as inert gas

Temperature: 40°C

Reaction time: 20 hours

500 ml three-necked reactor

Polymerization in solution

Determination of NPK, release

[35]

ratio (phosphorus), swelling

ability

equipped with reflux

Reaction time: 3 hours

Reaction temperature: 75°C

Cross-linker: N,N-methylenebisacrylamide

Initiator: potassium persulfate

Commercial nanocrystalline cellulose, acrylamide

Cross-linker: N,N-methylenebisacrylamide

Initiator: sodium persulfate and sodium

bisulfite

Chitosan nanofibers, acrylamide

Cross-linker: N, N-methylenebisacrylamide

Initiator: potassium persulfate and sodium bisulfite

Modified sugar cane bagasse

Phosphoric rock acrylic acid partially neutralizing with

NaOH and NH3

Initiator: potassium persulfate

Cross-linker: N,N-methylenebisacrylamide

**Polymerization conditions**

Reactor: beaker of 250 ml

Reaction temperature: 60°C

Reaction time: 3 hours

**Method** Polymerization in solution

Swelling ability Swelling kinetics

 Swelling ability to pH change

Swelling ability in saline solutions (NaCl, CaCl2)

Effect of temperature change on swelling ability

Swelling ability Swelling kinetics

 Swelling ability to pH change

Swelling ability in saline solutions (NaCl, CaCl2, and FelCl3)

 Biodegradability

Rheology of the gelation process

[33]

Swelling ability and kinetics

Measurement of compression

properties

**Type of characterization**

**References**

[31]

*Natural Fibers: Applications*

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

[32]

**Figure 2.** *Schematic for hydrogel preparation [22].*


#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

*Generation, Development and Modifications of Natural Fibers*

other molecules [28].

by alkaline treatment [29].

*2.2.2 Hydrogel synthesis from plant fibers*

shows general hydrogel preparation process.

tion is typically the preferred method for synthesis.

sites of natural fibers of cellulose [30].

*2.2.1 Modification methods of natural fibers for hydrogel production*

5.Physical appearance—It is governed by the polymerization technique used for preparation. Hydrogels can be in form of matrix, films, microsphere, etc.

6.Network electrical charge—On the basis of the presence or absence of electrical charge located on the cross-linked chains, hydrogels are divided into four groups: nonionic, ionic, amphoteric, and zwitterionic (polybetaines) electrolytes.

Lignin, hemicellulose, and cellulose are the major constituents of natural fibers. Lignin which coats or covers the cellulose part shows lower tendency to react with other molecules and poor adhesion with polymer matrix. Therefore the natural fibers most of the time have to undergo through treatment or modifications to improve the reactivity, interaction, and better adhesion with polymer matrix or

For the hydrogel production, the natural fibers are modified in two stages:

• Pretreatment step—It is a very common step even used when NF are used in composite material production also. The main objective of this step is the removal of lignin which is nonreactive toward other molecules and is achieved

• Chemical modification—The step involves insertion of molecules into active

Collectively these steps increase the water absorption and retention capacity

Hydrogel synthesis methods are mass polymerization, solution, and reverse suspension (use of initiator and a crosslinking agent). Generally hydrogel synthesis based upon the plant fibers uses solution polymerization method [28]. **Figure 2**

**Table 2** shows the different polymerization techniques, method employed, and type of characterization required during hydrogel synthesis. Solution polymeriza-

As reported by [29], during hydrogel synthesis, increase in the fiber content increased the swelling and elastic modulus, whereas Liang et al. showed change in pH, temperature, and salts leads to change in swelling behavior. In acidic environment, hydronium ions interacts with hydroxyl groups of cellulose to form hydrogen

throughout with the help of modifying agents and active site generation.

**30**

**Figure 2.**

*Schematic for hydrogel preparation [22].*


**33**

**Raw material** Carboxylated cellulose nanofibers

Carboxymethyl cellulose

Acrylic acid acrylamide

Initiator: ammonium persulfate

Cross-linker: N,N-methylenebisacrylamide

Kapok fiber sodium hydroxide, acrylic acid

Reactor: 250 ml equipped with mechanical agitation

Polymerization in solution

Elastic module Swelling ability Swelling ability to pH change

Swelling kinetics

Swelling ability

[41]

Retention and release capacity

Resistance to compression and

rupture

Swelling ability free and in saline

[42]

solutions

 Swelling ability in saline solutions (NaCl, CaCl2, and AlCl3)

Nitrogen as inert gas

 Reaction temperature: 70°C

Reaction time: 3 hours

Reaction temperature: environment

Not reported

Reaction time: 30 minutes

Cross-linker: N,N-methylenebisacrylamide

Initiator: ammonium persulfate

Polyethylene glycol diacrylate

Chitosan nanofibers

Initiator: ammonium persulfate

Cross-linker: NNNN-tetramethylethylenediamine

Commercial cellulose nanofibers, sodium acrylate poly

Concentration of nanofibers: 0–2%

Photopolymerization

by UV at 365 nm of wavelength

to a power of 100 W

by weight

Reactor: Beaker

Reaction time: 8 minutes

(ethylene glycol) diacrylate

Photoinitiator: 1-phenyl hydroxycyclohexyl

ketone

**Table 2.**

*Some of the reported hydrogel synthesis methods based upon natural fibers.*

**Polymerization conditions**

Three-necked flask with reflux

Reaction time: 2 hours

Reaction temperature: 70°C

Polymerization in solution

Swelling ability Retention and release capacity

Swelling to pH change and saline solutions

Water retention capacity by temperature change

**Method**

**Type of characterization**

**References**

[40]

*Natural Fibers: Applications*

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

[29]


#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

*Generation, Development and Modifications of Natural Fibers*

**32**

**Raw material** Wheat straw pretreated with 1 M HNO3 acrylic acid

neutralized with KOH and dimethyldiallyl ammonium

Initiator: potassium persulfate and ceramic ammonium

chloride acrylamide

nitrate

Cross-linker: N,N-methylenebisacrylamide

Cotton cellulose nanofibers

Chitosan acrylic acid

Initiator: potassium persulfate

Cross-linker: N,N-methylenebisacrylamide

Cotton nanofibers, acrylamide and potassium acrylate

Cross-linker: N,N-methylenebisacrylamide

Initiator: potassium persulfate

Catalyst: N, N, N, N-tetramethyldiamine

**Polymerization conditions**

Three-mouth reactor equipped with

reflux

Reaction time: 5 hours

Reaction temperature: 50°C

Three-mouth reactor with reflux

Polymerization in solution

Swelling in saline solutions and

[37]

to pH change

Reaction time: 2 hours

Reaction temperature:

70°C

Concentration of nanofibers: 1, 5,

Polymerization by free radicals

Swelling ability and kinetics

[37]

Swelling ability in saline

solutions

Water retention capacity

Evaluation of the pH effect on

the swelling ability

in solution

10, and 20% by relative weight to

monomers

Reactor: no report

Nitrogen as inert gas

Temperature: not reported

Reaction time: 15 hours

Crossl-inking concentration: 1–3%

Polymerization by free radicals

Kinetics and speed of swelling

[38]

Swelling ability in saline

solutions and pH change

Mechanical properties (Young's

modulus)

in solution

by weight

Concentration of nanofibers: 5–20%

by weight

Reactor: Three-necked flask

equipped with reflux with n stirring

Reaction temperature: 70°C

Reaction time: 3 hours

Flask with reflux

Polymerization in solution

solutions

Water holding capacity in the

soil

Water retention by temperature

change

Swelling by pH change and saline

[39]

Reaction time: 2 hours

Reaction temperature: 70°C

Pretreated flax fiber waste

Acrylic acid, acrylamide

Initiator: ammonium persulfate

Cross-linker: N,N-methylenebisacrylamide

Cotton nanofibers, cassava starch, and sodium acrylate

Cross-linker: N,N-methylenebisacrylamide

Initiator: potassium persulfate

**Method** Polymerization in solution

**Type of characterization**

Swelling ability and water

[36]

retention

Swelling kinetics, re-swelling

ability

Swelling to pH change and in

saline solutions

**References**

linking forces resulting in increasing chain cross-linking and decreasing absorption capacity, whereas in basic media due to the neutralization of active sites, the swelling ability decreased. A temperature between 0 and 50°C is reported to have positive effect on the swelling ability. Zhong et al. [35] found the inclusion of the phosphoric rock in polymer matrix results into better swelling ability and water release rate.

The effect of use of natural fibers at nanoscale level in the hydrogels also has been studied, and few of the advantages found are the following:


Hydrogels can be tailored and designed as per the requirements and needs for different applications. Natural fibers as part of hydrogels synthesis can provide an eco-friendly alternative and fulfill the potential.

#### **2.3 Automotive application**

Today more than 50% of the vehicles' interior constitutes different polymeric materials. Automotive manufacturers and associations are under tremendous pressure to improve on fuel efficiency and lower emissions. One of the best ways is to reduce the overall weight of the vehicle which can be possible in replacing metal with lightweight composite materials [43]. Automakers have taken initiatives to design and utilize natural renewable resources as part of composite materials, though the use of natural biomaterials like natural fibers in automotive dates back to 1940s when Henry Ford produced the first composite component using hemp fiber. Similarly many other automotive manufacturers started following the same path down the line. Natural fiber-based composites hold great potential especially in automotive industry where studies have reported NFRC can contribute to cost and weight reduction by 20 and 30%, respectively [44]. Natural fiber-reinforced composite materials are generally utilized in interior parts like door panels, dashboard parts, parcel shelves, seat cushions, backrests, cable linings, etc. Applications to exterior are limited due to the high demand of mechanical strength [45–48]. Finished automotive door produced from hemp fiber is shown in **Figure 3**.

**35**

*Natural Fibers: Applications*

fiber composites (**Table 3**).

**Property PP PP+ 30%** 

Density (g/cm3 )

Tensile strength (Mpa)

Tensile modulus (Gpa)

Elongation at break (%)

Izod impact strength (KJ/m2 )

Flexural strength (Mpa)

**Table 3.**

**WP**

*Mechanical properties of filled and unfilled PP and PA6 composites [43].*

**PP+ 30% GF**

**PP+ 30% talc**

0.91 1.04 1.13 1.15 1.14 1.18 1.27 1.27

19 28 65 25 63 83 101 73

1.4 2.3 4.5 2.2 1.4 5.5 6.5 6.5

50 2.5 3.0 5.0 >60 3.0 3.0 6.0

5.0 9.0 9.5 8.0 10 9.0 9.0 9.0

50 78 115 65 95 115 160 115

**PA6 PA6 + 20% curaua**

**PP+ 20% GF**

**PP+ 20% talc**

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

tion of covalent bonds and cross-linking effect [49–53].

The properties of the natural fiber-reinforced composite materials depend upon the interfacial compatibility of the polymer matrix. The inherent characteristics and properties of natural fibers, generally issues like poor adhesion, moisture absorption, poor wet ability, etc., cause lower bonding with the polymer matrix. Therefore, modification or pretreatment of natural fibers is done prior to composite preparation. Several techniques and processes have been studied and reported. Few of them are stretching, calendaring, and production of hybrid yarns which result into change in physical attributes of natural fibers. Corona treatment (electrical discharge) method is another method used which makes surface rough resulting in better adhesion with polymer. The use of oxidizing agents such as sodium/calcium hypochlorite and hydrogen peroxide for removal of dust and oil from natural fibers has been reported. Alkali treatment of natural fibers also have been extensively studied and found to improve wet ability and improve adhesion significantly. Further improvement can be made by the use of grafted polymers like polypropylene/polyethylene-grafted maleic anhydride as compatibilizers and the use of coupling agents. These specialty products facilitate in the introduction and forma-

In a report published by SABIC Innovative Plastics, wood flour and curaua fiber-based composites have been developed. Results are shown in the table below. The company claims that the composites developed are more resistant to fungi growth and have good dimensional stability, lower moisture absorption, and intended mechanical properties as required for the application. **Table 3** shows the comparison of unfilled PP and PA6 with filled natural fibers, glass fibers, and talc at similar loading level. Density advantage can be observed with NFRC as compared to other composite materials. Most of the mechanical properties of PP filled with NFs are almost similar to the talc-filled PP. Glass fiber-filled PP possess advantage in terms of tensile and flexural strength over NFRC and talc-filled PP materials. However, in automotive interior applications, composite materials with mild to high mechanical properties can serve the purpose. Mechanical properties of natural fiber-reinforced polymer composite are comparable to polypropylene talc and glass

**Figure 3.** *Schematic of (a) hemp fiber and (b) automotive part produced using hemp fiber.*

#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

*Generation, Development and Modifications of Natural Fibers*

• Better mechanical strength of hydrogels

• Increase the density of cross-linking points

eco-friendly alternative and fulfill the potential.

**2.3 Automotive application**

• Promotes the formation of porous morphology

*Schematic of (a) hemp fiber and (b) automotive part produced using hemp fiber.*

• Improvement in the swelling ability

release rate.

linking forces resulting in increasing chain cross-linking and decreasing absorption capacity, whereas in basic media due to the neutralization of active sites, the swelling ability decreased. A temperature between 0 and 50°C is reported to have positive effect on the swelling ability. Zhong et al. [35] found the inclusion of the phosphoric rock in polymer matrix results into better swelling ability and water

The effect of use of natural fibers at nanoscale level in the hydrogels also has

Hydrogels can be tailored and designed as per the requirements and needs for different applications. Natural fibers as part of hydrogels synthesis can provide an

Today more than 50% of the vehicles' interior constitutes different polymeric materials. Automotive manufacturers and associations are under tremendous pressure to improve on fuel efficiency and lower emissions. One of the best ways is to reduce the overall weight of the vehicle which can be possible in replacing metal with lightweight composite materials [43]. Automakers have taken initiatives to design and utilize natural renewable resources as part of composite materials, though the use of natural biomaterials like natural fibers in automotive dates back to 1940s when Henry Ford produced the first composite component using hemp fiber. Similarly many other automotive manufacturers started following the same path down the line. Natural fiber-based composites hold great potential especially in automotive industry where studies have reported NFRC can contribute to cost and weight reduction by 20 and 30%, respectively [44]. Natural fiber-reinforced composite materials are generally utilized in interior parts like door panels, dashboard parts, parcel shelves, seat cushions, backrests, cable linings, etc. Applications to exterior are limited due to the high demand of mechanical strength [45–48]. Finished automotive door produced from hemp fiber is shown in **Figure 3**.

been studied, and few of the advantages found are the following:

**34**

**Figure 3.**

The properties of the natural fiber-reinforced composite materials depend upon the interfacial compatibility of the polymer matrix. The inherent characteristics and properties of natural fibers, generally issues like poor adhesion, moisture absorption, poor wet ability, etc., cause lower bonding with the polymer matrix. Therefore, modification or pretreatment of natural fibers is done prior to composite preparation. Several techniques and processes have been studied and reported. Few of them are stretching, calendaring, and production of hybrid yarns which result into change in physical attributes of natural fibers. Corona treatment (electrical discharge) method is another method used which makes surface rough resulting in better adhesion with polymer. The use of oxidizing agents such as sodium/calcium hypochlorite and hydrogen peroxide for removal of dust and oil from natural fibers has been reported. Alkali treatment of natural fibers also have been extensively studied and found to improve wet ability and improve adhesion significantly. Further improvement can be made by the use of grafted polymers like polypropylene/polyethylene-grafted maleic anhydride as compatibilizers and the use of coupling agents. These specialty products facilitate in the introduction and formation of covalent bonds and cross-linking effect [49–53].

In a report published by SABIC Innovative Plastics, wood flour and curaua fiber-based composites have been developed. Results are shown in the table below. The company claims that the composites developed are more resistant to fungi growth and have good dimensional stability, lower moisture absorption, and intended mechanical properties as required for the application. **Table 3** shows the comparison of unfilled PP and PA6 with filled natural fibers, glass fibers, and talc at similar loading level. Density advantage can be observed with NFRC as compared to other composite materials. Most of the mechanical properties of PP filled with NFs are almost similar to the talc-filled PP. Glass fiber-filled PP possess advantage in terms of tensile and flexural strength over NFRC and talc-filled PP materials. However, in automotive interior applications, composite materials with mild to high mechanical properties can serve the purpose. Mechanical properties of natural fiber-reinforced polymer composite are comparable to polypropylene talc and glass fiber composites (**Table 3**).


#### **Table 3.**

*Mechanical properties of filled and unfilled PP and PA6 composites [43].*


#### **Table 4.**

*Applications of natural fibers in automotive industry [54–59].*

Now different regions across globe opt for different natural fibers depending upon their availability and ease of use. European automotive industry prefers flax and hemp, whereas in Asian country India prefers jute and kenaf. Banana fibers are preferred in the Philippines, whereas sisal fibers are used majorly in the USA, Brazil, and South Africa. **Table 4** shows the use of natural fibers in various automotive components.

The use and development of natural fiber-based composite materials in automotive are going on good pace, and in time better composite materials with mechanical performance similar to synthetic fibers will be developed. Continuous development in fiber modification techniques, compounding machines, additives, polymers, etc. will yield a promising future ahead.

#### **2.4 Barrier properties and applications**

Cellulose is the primary component of green plants and is the most abundant organic compound derived from biomass. Due to its characteristic chemical and physical properties, it has been investigated and applied to variety of products and materials for many decades [60, 61]. Cellulose material exists in four different polymorphs [62, 63]:

**37**

**Figure 5.**

*cellulose.*

**Figure 4.**

*fibrils [64, 65].*

*Natural Fibers: Applications*

and II.

shown in **Figure 5**.

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

tion with aqueous sodium hydroxide.

• Type IV—Heat treatment of type III yield type IV.

• Type I—Native cellulose, the form in which cellulose occurs in nature.

• Type II—Regenerated cellulose, formed after recrystallization or merceriza-

• Type III—This type of cellulose is produced by ammonia treatment of types I

Type II is the most stable crystalline form of cellulose*.* The major difference between the type I and type II is the layout of their atoms. Chains in type I are

About 36 individual cellulose molecules collectively form into a larger unit called elementary fibrils. **Figure 4** depicts the details of cellulose fibers and microfibrils. Depending upon the dimensions, functions, and preparation methods, nanocellulose can be subdivided into three main types: (a) microfibrillated cellulose (MFC), (b) nanocrystalline cellulose (NCC), and (c) bacterial nanocellulose (BNC) [64], as

Various petroleum-based materials are widely used for packaging application to prevent food, drinks, cosmetic goods, consumer goods, etc. against physical

*From cellulose sources to cellulose molecules. Details of cellulose fiber structure with emphasis on cellulose* 

*TEM images of (a) microfibrillated cellulose, (b) nanocrystalline cellulose, and (c) bacterial* 

layered in parallel fashion, whereas in type II they are in antiparallel.

#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

*Generation, Development and Modifications of Natural Fibers*

pillars, load floors, etc.

Coconut Seat bottom, back cushions, interior trim, seat

Flax Backseats, covers, rear parcel shelves, other interior

Kenaf/hemp Door panel, rear parcel shelves, interior trims, luxury package shelves, door panels

backseat panels, etc.

*Applications of natural fibers in automotive industry [54–59].*

Wood Carrier for door panels, covered door panels, instrument

Abaca Under floor panel and body panel —

cushioning, seat surfaces/backrests, etc.

Coir Seat covers, doormats, rugs — Cotton Sound proofing, trunk panels, insulation PP/PET

Bast fibers (hemp, flax, jute, sisal, etc.)

Fibrowood recycled

**Natural fibers Component description Polymer matrix**

Carrier for door panel, covered inserts, carrier for hard and soft arm insert, backseat panel, door bolsters, side and back walls, rear deck tray, center console, trunk trim,

Plastic retainer for backseat panel PP

trims, floor trays, pillar panels, central consoles, etc.

Flax/hemp Carrier for covered door panels Epoxy resin Flax/sisal Door linings and panels Thermoset resins

panels, covered inserts and components, covered

Wool Upholstery, seat cover Leather

Wood flour Carrier for door panels, arm rest, and covered inserts PP or polyolefin

Kenaf Door inner panel PP Kenaf/flax Package trays and door panel inserts —

Polypropylene and polyester

Natural rubber

Mat with PP

—

(POE)

Acrylic resin or synthetic fibers

Now different regions across globe opt for different natural fibers depending upon their availability and ease of use. European automotive industry prefers flax and hemp, whereas in Asian country India prefers jute and kenaf. Banana fibers are preferred in the Philippines, whereas sisal fibers are used majorly in the USA, Brazil, and South Africa. **Table 4** shows the use of natural fibers in various automo-

The use and development of natural fiber-based composite materials in automotive are going on good pace, and in time better composite materials with mechanical performance similar to synthetic fibers will be developed. Continuous development in fiber modification techniques, compounding machines, additives, polymers, etc.

Cellulose is the primary component of green plants and is the most abundant organic compound derived from biomass. Due to its characteristic chemical and physical properties, it has been investigated and applied to variety of products and materials for many decades [60, 61]. Cellulose material exists in four different

**36**

tive components.

**Table 4.**

polymorphs [62, 63]:

will yield a promising future ahead.

**2.4 Barrier properties and applications**


Type II is the most stable crystalline form of cellulose*.* The major difference between the type I and type II is the layout of their atoms. Chains in type I are layered in parallel fashion, whereas in type II they are in antiparallel.

About 36 individual cellulose molecules collectively form into a larger unit called elementary fibrils. **Figure 4** depicts the details of cellulose fibers and microfibrils. Depending upon the dimensions, functions, and preparation methods, nanocellulose can be subdivided into three main types: (a) microfibrillated cellulose (MFC), (b) nanocrystalline cellulose (NCC), and (c) bacterial nanocellulose (BNC) [64], as shown in **Figure 5**.

Various petroleum-based materials are widely used for packaging application to prevent food, drinks, cosmetic goods, consumer goods, etc. against physical

#### **Figure 4.**

*From cellulose sources to cellulose molecules. Details of cellulose fiber structure with emphasis on cellulose fibrils [64, 65].*

#### **Figure 5.**

*TEM images of (a) microfibrillated cellulose, (b) nanocrystalline cellulose, and (c) bacterial cellulose.*

#### **Figure 6.**

*Schematic representation of increased diffusion path within nanocellulose film [70].*

and microbiological degradation and deterioration. These polymeric materials provide a layer of barrier against water vapor, oxygen, grease, and microorganisms. Packaging industry is one of the fastest-growing industries in the world. Now with the increased concerns due to the impact of these polymeric and other packaging materials like paper, glass, and metal on environment, materials derived from the renewable resources are strongly advocated. Recent research in more efficient and reliable preparation techniques for cellulose nanofibers and microfibrils synthesis, has attracted significant interest as potential barrier materials in packaging films. Cellulose nanomaterials have large surface area and diameter in range of 2–50 nm. Their ability to form hydrogen bonds results into strong network formation making it difficult for gas or water molecules to pass through it, thus providing excellent barrier properties [66–69].

Microfibrillated cellulose (MFC) films have better gas barrier property than cellulose nanocrystals (CNCs) because of the crystalline and amorphous regions in CNCs. Oxygen transmission rate (OTR) of 25 micron MFC film was found to be competitive with films of similar thickness made from ethylene vinyl alcohol (EVOH) and polyvinylidene fluoride (PVDF). OTR of MFC film was found to be lower than EVOH and PVDF films [71, 72]. **Figure 6** represents the kind of torturous path for permeating molecule because of nanocellulose. As reported, the barrier properties of MFC films can be tuned further. Rodionova et al. [73] in his work showed that oxygen permeability of MFC acetylated and carboxymethylated films can be further reduced. Carboxymethylated films had very low oxygen permeability of 0.009 and 0.0006 cm3 m<sup>−</sup><sup>2</sup> /day kPa-1. Further the oxygen permeability can further be modified by using thermal treatment technique. **Table 5** shows the OTR and WVTR values of commercial polymer films and MFC film.

MFC film have poor water vapor barrier property as compared to PVDF film due to hydrophilic nature of cellulose molecules however it can be improved thereby using different pre and post treatments during production process.

Cellulose nanocrystals have been studied as potential fillers for natural polymers to enhance their barrier properties. Results reported as in Saxena et al. [74] showed that nanocomposite film made by casting aqueous solution containing xylan,


**39**

*2.5.2 Silk fiber applications*

*Natural Fibers: Applications*

m2

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

commercially available polymers.

**2.5 Other applications**

*2.5.1 Composites*

sorbitol, and cellulose nanocrystals had low oxygen permeability of 0.1799 cm3 μm/

 d kPa. As other reports [75, 76] also indicate that cellulose nanocrystals when used in other polymer matrix like PLA and PVOH improved in OTR and WVTR values. Studies based upon the use of microfibrillated and nanocrystals of cellulose in polymeric materials have opened possibilities in films, composites, and coatings to substantially reduce especially the oxygen permeation rate. Microfibrillated cellulose and its nanocrystals have oxygen-barrier efficiency better some of the

There are considerable enhancement and suggestions for the natural fibers that can be implemented in order to enhance their mechanical properties resulting in high strength and structure so that it can be used as fillers and reinforcement agents instead of conventional materials like talc, calcium carbonate, mica, glass fibers, etc. After selecting the appropriate fiber and method of modification for the target application, the polymer matrix properties can be improved. Few of the parameters that effect the composite performance are the (a) orientation of fibers, (b) strength of fibers, (c) physical properties of fibers, (d) interfacial adhesion property of fibers, and many more [77–80]. Natural fiber-reinforced composite materials have shown better properties than pure polymer matrix in many cases. 75.8% of PLA's tensile strength was improved by the introduction of jute fibers. Properties of PP composites were improved by the incorporation of kenaf, cotton, and hemp fibers [77]. Ishagh et al. [81] investigated effects of azodicarbonamide (AZD) and nanoclay (NC) content on the physico-mechanical and foaming properties of HDPE/ wheat straw flour (WSF) composites. With the increase of AZD, the average cell size and density increased, whereas with addition of nanoclay up to 5phr, the cell size and density increased. Idicula et al. [82] investigated thermophysical properties of banana sisal hybrid-reinforced composites. Increase in the thermal conductivity by 43% was observed in fibers which were subjected to mercerization and polystyrene maleic anhydride treatments. Chensong dong et al. [83] reported flexural properties of wheat straw polyester composites. Natural fiber-reinforced composites due to their certain advantages such as high stiffness to weight ratio, lightweight, and biodegradability gave them suitability in different applications in building industries. Sisal fiber reinforced composite have shown good tensile and compression strength making it suitable for wide area of applications, for instance, structural building members, permanent formwork, tanks, facades, long span roofing elements, and pipes strengthening of existing structures [84]. On the other hand, bamboo fiber can be used in structural concrete elements as reinforcement, while sisal fiber and coir fiber composites have been used in roofing components in order to replace asbestos. Natural fiber-reinforced concrete products in construction applications like sheets (both plain and corrugated) and boards are light in weight and are ideal for use in roofing, ceiling, and walling for the construction of low-cost houses.

Silk which is a natural fiber and produced in more than 20 countries finds application in various sectors. Silk proteins are used as special diet for cardiac and diabetic patients due to its low sugar content, easy digestibility, and low cholesterol [83, 84]. The Japan Aerospace Exploration Agency (JAXA) has released a recipe as astronauts' food. Silk biopolymer is used in tissue regeneration for treating burn victims and as

#### **Table 5.**

*Barrier properties of polymers and MFC.*

#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

sorbitol, and cellulose nanocrystals had low oxygen permeability of 0.1799 cm3 μm/ m2 d kPa. As other reports [75, 76] also indicate that cellulose nanocrystals when used in other polymer matrix like PLA and PVOH improved in OTR and WVTR values. Studies based upon the use of microfibrillated and nanocrystals of cellulose in polymeric materials have opened possibilities in films, composites, and coatings to substantially reduce especially the oxygen permeation rate. Microfibrillated cellulose and its nanocrystals have oxygen-barrier efficiency better some of the commercially available polymers.

#### **2.5 Other applications**

#### *2.5.1 Composites*

*Generation, Development and Modifications of Natural Fibers*

barrier properties [66–69].

**Figure 6.**

ity of 0.009 and 0.0006 cm3

*Barrier properties of polymers and MFC.*

and microbiological degradation and deterioration. These polymeric materials provide a layer of barrier against water vapor, oxygen, grease, and microorganisms. Packaging industry is one of the fastest-growing industries in the world. Now with the increased concerns due to the impact of these polymeric and other packaging materials like paper, glass, and metal on environment, materials derived from the renewable resources are strongly advocated. Recent research in more efficient and reliable preparation techniques for cellulose nanofibers and microfibrils synthesis, has attracted significant interest as potential barrier materials in packaging films. Cellulose nanomaterials have large surface area and diameter in range of 2–50 nm. Their ability to form hydrogen bonds results into strong network formation making it difficult for gas or water molecules to pass through it, thus providing excellent

*Schematic representation of increased diffusion path within nanocellulose film [70].*

Microfibrillated cellulose (MFC) films have better gas barrier property than cellulose nanocrystals (CNCs) because of the crystalline and amorphous regions in CNCs. Oxygen transmission rate (OTR) of 25 micron MFC film was found to be competitive with films of similar thickness made from ethylene vinyl alcohol (EVOH) and polyvinylidene fluoride (PVDF). OTR of MFC film was found to be lower than EVOH and PVDF films [71, 72]. **Figure 6** represents the kind of torturous path for permeating molecule because of nanocellulose. As reported, the barrier properties of MFC films can be tuned further. Rodionova et al. [73] in his work showed that oxygen permeability of MFC acetylated and carboxymethylated films can be further reduced. Carboxymethylated films had very low oxygen permeabil-

further be modified by using thermal treatment technique. **Table 5** shows the OTR

MFC film have poor water vapor barrier property as compared to PVDF film due to hydrophilic nature of cellulose molecules however it can be improved thereby

Cellulose nanocrystals have been studied as potential fillers for natural polymers to enhance their barrier properties. Results reported as in Saxena et al. [74] showed that nanocomposite film made by casting aqueous solution containing xylan,

EVOH 24 μm 0.16–1.86 NA [69] MFC 25 μm 0.5–2.347 47–55 [70] PVDF 24 μm 8 0.3 [69]

**/m2**

/day kPa-1. Further the oxygen permeability can

**/d) WVTR (g/m2**

**/d) Sources**

m<sup>−</sup><sup>2</sup>

and WVTR values of commercial polymer films and MFC film.

**Barrier material Thickness OTR (cm3**

using different pre and post treatments during production process.

**38**

**Table 5.**

There are considerable enhancement and suggestions for the natural fibers that can be implemented in order to enhance their mechanical properties resulting in high strength and structure so that it can be used as fillers and reinforcement agents instead of conventional materials like talc, calcium carbonate, mica, glass fibers, etc. After selecting the appropriate fiber and method of modification for the target application, the polymer matrix properties can be improved. Few of the parameters that effect the composite performance are the (a) orientation of fibers, (b) strength of fibers, (c) physical properties of fibers, (d) interfacial adhesion property of fibers, and many more [77–80]. Natural fiber-reinforced composite materials have shown better properties than pure polymer matrix in many cases. 75.8% of PLA's tensile strength was improved by the introduction of jute fibers. Properties of PP composites were improved by the incorporation of kenaf, cotton, and hemp fibers [77]. Ishagh et al. [81] investigated effects of azodicarbonamide (AZD) and nanoclay (NC) content on the physico-mechanical and foaming properties of HDPE/ wheat straw flour (WSF) composites. With the increase of AZD, the average cell size and density increased, whereas with addition of nanoclay up to 5phr, the cell size and density increased. Idicula et al. [82] investigated thermophysical properties of banana sisal hybrid-reinforced composites. Increase in the thermal conductivity by 43% was observed in fibers which were subjected to mercerization and polystyrene maleic anhydride treatments. Chensong dong et al. [83] reported flexural properties of wheat straw polyester composites. Natural fiber-reinforced composites due to their certain advantages such as high stiffness to weight ratio, lightweight, and biodegradability gave them suitability in different applications in building industries. Sisal fiber reinforced composite have shown good tensile and compression strength making it suitable for wide area of applications, for instance, structural building members, permanent formwork, tanks, facades, long span roofing elements, and pipes strengthening of existing structures [84]. On the other hand, bamboo fiber can be used in structural concrete elements as reinforcement, while sisal fiber and coir fiber composites have been used in roofing components in order to replace asbestos. Natural fiber-reinforced concrete products in construction applications like sheets (both plain and corrugated) and boards are light in weight and are ideal for use in roofing, ceiling, and walling for the construction of low-cost houses.

#### *2.5.2 Silk fiber applications*

Silk which is a natural fiber and produced in more than 20 countries finds application in various sectors. Silk proteins are used as special diet for cardiac and diabetic patients due to its low sugar content, easy digestibility, and low cholesterol [83, 84]. The Japan Aerospace Exploration Agency (JAXA) has released a recipe as astronauts' food. Silk biopolymer is used in tissue regeneration for treating burn victims and as

#### *Generation, Development and Modifications of Natural Fibers*

matrix for wound healing. Silk fibroin peptides are used in cosmetics due to their glossy, flexible, elastic powder coating; easy spreading; and good adhesion properties [89, 90]. Silk is reported to be used to fight various health-related diseases like edema, cystitis, impotence, adenosine augmentation therapy, epididymitis, and cancer [91]. Derivatives of silk fibers are reported to be used as nonsteroidal antiinflammatory agents for treating rheumatoid arthritis [85, 86]. Silk fibers are used as surgical sutures and as biodegradable microtubes for repair of blood vessels and as molded inserts for bone, cartilage, and teeth reconstruction [90, 93]. Due to the phenomenal mechanical properties of silk as a biopolymer, it is suitable for biomedical applications.

#### *2.5.3 Natural fiber-reinforced building material*

Various natural fibers have been exploited to be used as reinforcements for building/construction industry. Bamboo due to its lightweight and strength is a very popular construction material. Bamboo-based material has been developed to make eco-friendly roofing product. Other such products such as bamboo mat board (BMB), bamboo mat veneer composites (BMVC), and bamboo mat corrugated sheets (BMCS) have been developed. Sisal fiber-based roofing sheets also have been under development as economical alternative. Rice husk and rice straw are nowadays used to manufacture medium density fiberboards, particle boards, straw bales, cement-bonded boards, etc. Ground nutshell is used for manufacturing building panels, building blocks, chip boards, roofing sheets, particle boards, etc. Cotton stalk fiber is used for making panel, door shutters, roofing sheets, autoclaved cement composite, paper, plastering of walls, etc. Coir fiber is a highly durable fiber used in all types of matrices like fly ash-lime, polymers, bitumen, cement, mud, gypsum, etc. Jute coir composites are seen as cheap and economical alternative to wood for construction industry. Jute coir boards are used for the production of boards which are more resistant than teakwood against rooting under wet and dry conditions with better tensile strength. Jute with rubber, wood, and coir is considered as good alternative to plywood [94].

#### *2.5.4 Geotextiles for soil protection and erosion control*

Soil protection using natural fibers and other bio-based materials includes leaves, straws, and plant residues for the mulching of unprotected soil. Nowadays woven and nonwoven textiles and blankets made from wheat straw, rice straw, long wood shavings, coir, and jute are used as soil protection products. These products are categorized under two subgroups of the rolled control product (RECP) category. These can be open-weave geotextiles made using coir and jute fibers termed as erosion control

**41**

**Author details**

Haryana, India

Jatinder Singh Dhaliwal

*Natural Fibers: Applications*

**3. Summary**

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

devices or sediment retention fiber rolls [95].

and environment with good after-sale service.

meshes (ECM) or nonwoven from natural fibers or synthetic fibers glued or bonded by nets or meshes called as erosion control blankets (ECB) as shown in **Figure 7**. Natural fibers are also commonly used in rolls stuffed with straw or coir fiber bundles held together by nets which further can be used as slope interruption

Natural fibers and the products designed around these materials possess many distinctive advantages: cost-effective, low coefficient of friction, ease of availability, exhibit good thermal and dimensional stability, environmental friendly, etc. Because of these and many more reasons, the popularity of natural fibers is on increase, and a lot of scientific data and research is being done around the globe. However for effective utilization of natural fibers in various potential applications, all the aspects associated with them has to be studied and presented: (a) target application, advantages, and disadvantages of using natural fibers; (b) product design, studies to be carried out on the development of prototype and other engineering software; (c) preparation and fabrication technique, particular technique, or process to be identified which should reduce possibility of failure, etc.; (d) commercial production, should be cost effective and eco-friendly; (e) marketing and sales, product should be marketed to show case its potential benefits toward society

Despite of current prevailing aforementioned issues, several commercial products has been launched by various manufacturers, automotive industry the most active and leading the development of natural fibers based products. Gradually

other sectors related to sports, furniture, medical, etc. are catching up.

Research and Development Center, Indian Oil Corporation Ltd., Faridabad,

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: singhj4@indianoil.in

provided the original work is properly cited.

#### *Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

meshes (ECM) or nonwoven from natural fibers or synthetic fibers glued or bonded by nets or meshes called as erosion control blankets (ECB) as shown in **Figure 7**.

Natural fibers are also commonly used in rolls stuffed with straw or coir fiber bundles held together by nets which further can be used as slope interruption devices or sediment retention fiber rolls [95].

#### **3. Summary**

*Generation, Development and Modifications of Natural Fibers*

*2.5.3 Natural fiber-reinforced building material*

ered as good alternative to plywood [94].

*2.5.4 Geotextiles for soil protection and erosion control*

cal applications.

matrix for wound healing. Silk fibroin peptides are used in cosmetics due to their glossy, flexible, elastic powder coating; easy spreading; and good adhesion properties [89, 90]. Silk is reported to be used to fight various health-related diseases like edema, cystitis, impotence, adenosine augmentation therapy, epididymitis, and cancer [91]. Derivatives of silk fibers are reported to be used as nonsteroidal antiinflammatory agents for treating rheumatoid arthritis [85, 86]. Silk fibers are used as surgical sutures and as biodegradable microtubes for repair of blood vessels and as molded inserts for bone, cartilage, and teeth reconstruction [90, 93]. Due to the phenomenal mechanical properties of silk as a biopolymer, it is suitable for biomedi-

Various natural fibers have been exploited to be used as reinforcements for building/construction industry. Bamboo due to its lightweight and strength is a very popular construction material. Bamboo-based material has been developed to make eco-friendly roofing product. Other such products such as bamboo mat board (BMB), bamboo mat veneer composites (BMVC), and bamboo mat corrugated sheets (BMCS) have been developed. Sisal fiber-based roofing sheets also have been under development as economical alternative. Rice husk and rice straw are nowadays used to manufacture medium density fiberboards, particle boards, straw bales, cement-bonded boards, etc. Ground nutshell is used for manufacturing building panels, building blocks, chip boards, roofing sheets, particle boards, etc. Cotton stalk fiber is used for making panel, door shutters, roofing sheets, autoclaved cement composite, paper, plastering of walls, etc. Coir fiber is a highly durable fiber used in all types of matrices like fly ash-lime, polymers, bitumen, cement, mud, gypsum, etc. Jute coir composites are seen as cheap and economical alternative to wood for construction industry. Jute coir boards are used for the production of boards which are more resistant than teakwood against rooting under wet and dry conditions with better tensile strength. Jute with rubber, wood, and coir is consid-

Soil protection using natural fibers and other bio-based materials includes leaves, straws, and plant residues for the mulching of unprotected soil. Nowadays woven and nonwoven textiles and blankets made from wheat straw, rice straw, long wood shavings, coir, and jute are used as soil protection products. These products are categorized under two subgroups of the rolled control product (RECP) category. These can be open-weave geotextiles made using coir and jute fibers termed as erosion control

*Showing (a) coir fiber-made erosion control mesh and (b) coconut fiber-made erosion control blanket.*

**40**

**Figure 7.**

Natural fibers and the products designed around these materials possess many distinctive advantages: cost-effective, low coefficient of friction, ease of availability, exhibit good thermal and dimensional stability, environmental friendly, etc. Because of these and many more reasons, the popularity of natural fibers is on increase, and a lot of scientific data and research is being done around the globe. However for effective utilization of natural fibers in various potential applications, all the aspects associated with them has to be studied and presented: (a) target application, advantages, and disadvantages of using natural fibers; (b) product design, studies to be carried out on the development of prototype and other engineering software; (c) preparation and fabrication technique, particular technique, or process to be identified which should reduce possibility of failure, etc.; (d) commercial production, should be cost effective and eco-friendly; (e) marketing and sales, product should be marketed to show case its potential benefits toward society and environment with good after-sale service.

Despite of current prevailing aforementioned issues, several commercial products has been launched by various manufacturers, automotive industry the most active and leading the development of natural fibers based products. Gradually other sectors related to sports, furniture, medical, etc. are catching up.

#### **Author details**

Jatinder Singh Dhaliwal Research and Development Center, Indian Oil Corporation Ltd., Faridabad, Haryana, India

\*Address all correspondence to: singhj4@indianoil.in

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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2003;**4**:115-122

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[16] Kang JT, Park SH, Kim SH.

Journal of Composite Materials.

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[18] Sanadi AR, Caulfield DF,

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Co. Ltd.; 2013. pp. 25-39

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[53] Sood M, Dwivedi G. Effect of fiber treatment on flexural properties of natural fiber reinforced composites: A review. Egyptian Journal of Petroleum. 2017

[54] Huda MS, Drzal LT, Ray D, Mohanty AK, Mishra M. Natural-Fiber Composites in the Automotive Sector. In Properties and Performance of Natural-Fibre Composites. Oxford, UK: Woodhead Publishing; 2008

[55] Witayakran S, Smitthipong W, Wangpradid R, Chollakup R, Clouston PL. Natural fiber composites: Review of recent automotive trends. In: Reference Module in Materials Science and Materials Engineering. Amherst, MA, USA: Elsevier Publishing; 2017

[56] Food and Agriculture Organization of the United Nations. Unlocking the Commercial Potential of Natural Fibres. Rome, Italy: Food and Agriculture Organization of the United Nations; 2012

[57] Holbery J, Houston D. Naturalfiber-reinforced polymer composites in automotive applications. Journal of Metals. 2006;**58**:80-86

[58] Ramdhonee A, Jeetah P. Production of wrapping paper from banana fibres. Journal of Environmental Chemical Engineering. 2017

[59] Food and Agriculture Organization of the United Nations. Common fund for commodities. In: Proceedings of the Symposium on Natural Fibres, Rome, Italy. 2008

[60] Azizi Samir AF, Dufresne A. Review of recent research into cellulosic whiskers, their properties and their

application in nanocomposite field. Biomacromolecules. 2005;**6**(2):612-626

[61] Simon J, Muller HP, Koch R, Muller V. Thermoplastic and biodegradable polymers of cellulose. Polymer Degradation and Stability. 1998;**59**:107-115

[62] Aulin C. Novel Oil Resistant Cellulosic Materials (pulp and Paper Technology). Stockholm, Sweden, KTH Chemical Science and Engineering; 2009

[63] Siqueira G, Bras J, Dufresne A. Cellulosic bio nanocomposites: A review of preparation, properties and applications. Polymer. 2010; **2**(4):728-765

[64] Habibi Y, Lucia LA, Rojas OJ. Cellulose nanocrystals: Chemistry, selfassembly, and applications. Chemical Reviews. 2010;**110**(6):3479-3500

[65] Nathalie L, Isabelle D, Alain D, Julien B. Microfibrillated cellulose–Its barrier properties and applications in cellulosic materials: A review. Carbohydrate Polymers. 2012;**90**:735-764

[66] Stelte W, Sanadi AR. Preparation and characterization of cellulose nanofibers from two commercial hardwood and softwood pulps. Industrial and Engineering Chemistry Research. 2009;**48**:11211-11219

[67] Nair SS, Zhu JY, Deng Y, Ragauskas AJ. Hydrogels prepared from cross-linked nanofibrillated cellulose. ACS Sustainable Chemistry & Engineering. 2014;**2**:772-780

[68] Hoeger IC, Nair SS, Ragauskas AJ, Deng Y, Rojas OJ, Zhu JY. Mechanical deconstruction of lignocellulose cell walls and their enzymatic saccharification. Cellulose. 2013;**20**:807-818

[69] Syverud K, Stenius P. Strength and barrier properties of MFC films. Cellulose. 2009;**16**:75-85

[70] Syverud K, Stenius P. Strength and barrier properties of MFC films. Cellulose. 2009;**17**:15-25

[71] Platt D. The Future of Specialty Films: Market Forecasts to 2018. Smithers Pira; 2013

[72] Kumar V, Bollström R, Yang A, Chen Q, Chen G, Salminen P, et al. Comparison of nano- and microfibrillated cellulose films. Cellulose. 2014;**21**(5):3443-3456

[73] Rodionova G, Lenes M, Eriksen O, Gregersen O. Surface chemical modification of microfibrillated cellulose: Improvement of barrier properties for packaging applications. Cellulose. 2011;**18**:127-134

[74] Saxena A, Elder TJ, Kenvin J, Ragauskas AJ. High oxygen nanocomposite barrier films based on xylan and nanocrystalline cellulose. Nano-Micro Letters. 2010;**2**:235-241

[75] Fortunati E, Peltzer M, Armentano I, Torre L, Jimenez A, Kenny JM. Effects of modified cellulose nanocrystals on the barrier and migration of PLA nano-composites. Carbohydrate Polymers. 2012;**90**:948-956

[76] Fortunati E, Peltzer M, Armentano I, Jimenez A, Kenny JM. Combined effects of cellulose nanocrystals and silver nanoparticles on the barrier and migration properties of PLA nano-biocomposites. Journal of Food Engineering. 2013;**118**:117-124

[77] Shalwan A, Yousif BF. In state of art: Mechanical and tribological behaviour of polymeric composites based on natural fibers. Materials and Design. 2013;**48**:14-24

[78] Shinoj S, Visvanathan R, Panigrahi S, Kochubabu M. Oil palm fiber (OPF) and its composites: A review. Industrial Crops and Products. 2011;**33**:7-22

[79] Benezet JC, Stanojlovic-Davidovic A, Bergeret A, Ferry L, Crespy A. Mechanical and physical properties of expanded starch, reinforced by natural fibres. Industrial Crops and Products. 2012;**37**(1):435-440

[80] Kakroodi AR, Cheng S, Sain M, Asiri A. Mechanical, thermal, and morphological properties of nanocomposites based on polyvinyl alcohol and cellulose nanofiber from Aloe vera rind. Journal of Nanomaterials. 2014

[81] Babaei I, Madanipour M, Farsi M, Farajpoor A. Physical and mechanical properties of foamed HDPE/wheat straw flour/nanoclay hybrid composite. Composites Part B: Engineering. 2014;**56**:163-170

[82] Idicula M, Boudenne A, Umadevi L, Ibos L, Candau Y, Thomas S. Thermophysical properties of natural fiber reinforced polyester composites. Composites Science and Technology. 2006;**66**(15):2719-2725

[83] Chensong D, Davies IJ. Flexural properties of wheat straw reinforced polyester composites. American Journal of Materials Science. 2011;**1**(2):71-75

[84] Weyenberg VDI, Ivens J, De Coster DA, Kino B, Baetens E, Verpoest I. Influence of processing and chemical treatment of flax fibres on their composites. Composites Science and Technology. 2003;**63**(9):1241-1246

[85] Ramesh S, Kumar CS, Seshagiri SV, Basha KI, Lakshmi H, Rao CGP, et al. Silk filament its pharmaceutical applications. Indian Silk. 2005;**44**(2):15-19

**47**

*Natural Fibers: Applications*

2008;**17**(1):109-113

Silk. 2007;**45**(12):11-13

and Obstetric Investigation.

2007;**63**(3):155-162

Silk. 2007;**45**(9):5-8

[86] Manohar R. Value addition span of silkworm cocoon-time for utility optimization. International Journal of Industrial Entomology.

[87] Kumaresan P, Sinha RK, Urs SR. Sericin-a versatile by-product. Indian

[88] Federico S, Maja KL, Isabelle G, Godelieve V, Erik V, Dirk DR, et al. Tensile strength and host response towards silk and type 1 polypropylene implants used for augmentation of facial repair in a rat model. Gynecologic

[89] Dandin SB, Kumar SN. Bio-medical uses of silk and its derivatives. Indian

[90] Wang Y, Blasioli DJ, Kim HJ, Kim HS, Kaplan DL. Cartilage tissue engineering with silk scaffolds and human articular chondrocytes. Biomaterials. 2006;**27**(25):4434-4442

[91] Meinel L, Betz O, Fajardo R, Hofmann S, Nazarian A, Cory E, et al.

Silk based biomaterials to heal critical sized femur defects. Bone.

[92] Makaya K, Terada S, Ohgo K, Asakura T. Comparative study of silk fibroin porous scaffolds derived

[93] Sofia S, McCarthy MB, Gronowicz G, Kaplan DL. Functionalized silk-based biomaterials for bone formation. Journal of Biomedical Materials Research.

[94] Pravin VD, Viveka DM. Natural fiber reinforced building materials. Journal of Mechanical and Civil Engineering. 2015;**12**(3):104-107

from salt/water and sucrose/ hexafluoroisopropanol in cartilage formation. Journal of Bioscience and Bioengineering. 2009;**108**(1):68-75

2008;**39**(4):922-931

2001;**54**(1):139-148

*DOI: http://dx.doi.org/10.5772/intechopen.86884*

[95] Jorg M. Industrial Applications of Natural fibers. A John Wiley and Sons Ltd. Publication; 2010. pp. 509-522

*Natural Fibers: Applications DOI: http://dx.doi.org/10.5772/intechopen.86884*

[86] Manohar R. Value addition span of silkworm cocoon-time for utility optimization. International Journal of Industrial Entomology. 2008;**17**(1):109-113

*Generation, Development and Modifications of Natural Fibers*

[78] Shinoj S, Visvanathan R,

[79] Benezet JC, Stanojlovic-Davidovic A, Bergeret A, Ferry L, Crespy A. Mechanical and physical properties of expanded starch,

2011;**33**:7-22

Panigrahi S, Kochubabu M. Oil palm fiber (OPF) and its composites: A review. Industrial Crops and Products.

reinforced by natural fibres. Industrial Crops and Products. 2012;**37**(1):435-440

[80] Kakroodi AR, Cheng S, Sain M, Asiri A. Mechanical, thermal, and morphological properties of

nanocomposites based on polyvinyl alcohol and cellulose nanofiber from Aloe vera rind. Journal of

[81] Babaei I, Madanipour M, Farsi M, Farajpoor A. Physical and mechanical properties of foamed HDPE/wheat straw flour/nanoclay hybrid composite. Composites Part B: Engineering.

Umadevi L, Ibos L, Candau Y, Thomas S. Thermophysical properties of natural fiber reinforced polyester composites. Composites Science and Technology.

[83] Chensong D, Davies IJ. Flexural properties of wheat straw reinforced polyester composites. American Journal of Materials Science. 2011;**1**(2):71-75

[84] Weyenberg VDI, Ivens J, De Coster DA, Kino B, Baetens E, Verpoest I. Influence of processing and chemical treatment of flax fibres on their composites.

Composites Science and Technology.

[85] Ramesh S, Kumar CS, Seshagiri SV, Basha KI, Lakshmi H, Rao CGP, et al. Silk filament its pharmaceutical

Nanomaterials. 2014

2014;**56**:163-170

[82] Idicula M, Boudenne A,

2006;**66**(15):2719-2725

2003;**63**(9):1241-1246

applications. Indian Silk.

2005;**44**(2):15-19

[69] Syverud K, Stenius P. Strength and barrier properties of MFC films.

[70] Syverud K, Stenius P. Strength and barrier properties of MFC films.

[71] Platt D. The Future of Specialty Films: Market Forecasts to 2018.

[72] Kumar V, Bollström R, Yang A, Chen Q, Chen G, Salminen P, et al. Comparison of nano- and microfibrillated cellulose films. Cellulose. 2014;**21**(5):3443-3456

microfibrillated cellulose: Improvement

packaging applications. Cellulose.

[74] Saxena A, Elder TJ, Kenvin J, Ragauskas AJ. High oxygen

[75] Fortunati E, Peltzer M, Armentano I, Torre L, Jimenez A, Kenny JM. Effects of modified cellulose

Carbohydrate Polymers.

[76] Fortunati E, Peltzer M,

Armentano I, Jimenez A, Kenny JM. Combined effects of cellulose

nanocrystals and silver nanoparticles on the barrier and migration properties of PLA nano-biocomposites. Journal of Food Engineering. 2013;**118**:117-124

[77] Shalwan A, Yousif BF. In state of art: Mechanical and tribological behaviour of polymeric composites based on natural fibers. Materials and Design.

2012;**90**:948-956

nanocrystals on the barrier and migration of PLA nano-composites.

nanocomposite barrier films based on xylan and nanocrystalline cellulose. Nano-Micro Letters. 2010;**2**:235-241

[73] Rodionova G, Lenes M, Eriksen O, Gregersen O. Surface chemical modification of

of barrier properties for

2011;**18**:127-134

Cellulose. 2009;**16**:75-85

Cellulose. 2009;**17**:15-25

Smithers Pira; 2013

**46**

2013;**48**:14-24

[87] Kumaresan P, Sinha RK, Urs SR. Sericin-a versatile by-product. Indian Silk. 2007;**45**(12):11-13

[88] Federico S, Maja KL, Isabelle G, Godelieve V, Erik V, Dirk DR, et al. Tensile strength and host response towards silk and type 1 polypropylene implants used for augmentation of facial repair in a rat model. Gynecologic and Obstetric Investigation. 2007;**63**(3):155-162

[89] Dandin SB, Kumar SN. Bio-medical uses of silk and its derivatives. Indian Silk. 2007;**45**(9):5-8

[90] Wang Y, Blasioli DJ, Kim HJ, Kim HS, Kaplan DL. Cartilage tissue engineering with silk scaffolds and human articular chondrocytes. Biomaterials. 2006;**27**(25):4434-4442

[91] Meinel L, Betz O, Fajardo R, Hofmann S, Nazarian A, Cory E, et al. Silk based biomaterials to heal critical sized femur defects. Bone. 2008;**39**(4):922-931

[92] Makaya K, Terada S, Ohgo K, Asakura T. Comparative study of silk fibroin porous scaffolds derived from salt/water and sucrose/ hexafluoroisopropanol in cartilage formation. Journal of Bioscience and Bioengineering. 2009;**108**(1):68-75

[93] Sofia S, McCarthy MB, Gronowicz G, Kaplan DL. Functionalized silk-based biomaterials for bone formation. Journal of Biomedical Materials Research. 2001;**54**(1):139-148

[94] Pravin VD, Viveka DM. Natural fiber reinforced building materials. Journal of Mechanical and Civil Engineering. 2015;**12**(3):104-107

[95] Jorg M. Industrial Applications of Natural fibers. A John Wiley and Sons Ltd. Publication; 2010. pp. 509-522

**49**

**Chapter 3**

*Tayyaba Fatma*

**Abstract**

**1. Introduction**

Surface Modification of

Bast-Based Natural Fibers through

Nowadays, natural products are extremely preferred among the people. These natural products are produced by environment friendly sources. In case of textiles, bast fibers play significant role in producing natural products that are extracted from the stem of various plant and environment friendly in nature. The bast fibers can also improve the livelihood of the poor farmers who are involved in the cultivation of the plants and extraction and processing of the fibers. Therefore, surface modification of established natural fibers (such as hemp, flax, jute, kenaf, urena, nettle, and ramie) and explored natural fibers are momentous area for doing research. And, these modifications can be done through environment friendly methods such as plasma treatment, and utilization of enzymes, bacteria, and fungi.

**Keywords:** natural fibers, surface modification, environment friendly methods,

At global level, 58% of synthetic fibers is used in clothing in which 77% polyester, 9% nylon, 6% acrylic, and 7% cellulosic fibers take place. Hence, the utilization of synthetic fibers is higher as compared to natural fibers. The synthetic fibers are generally made from polymers that have been synthetically produced from chemical compounds, which create lot of air, land, and water pollutions. These synthetic fibers are more harmful for health of the human being as well as environment

To overcome health-related problems and also for environmental safety, people are gradually attracted toward more and more use of natural products in both developed and developing countries. Thus, increasing concerns toward natural products have led to the search for ecological safe, biodegradable, and recyclable characters in their production. Though in case of textiles, production of natural products from natural fibers play a significant role. Natural fibers obtained from natural resources are one of the proficient fibers that replace the synthetic fibers. Numerous natural fibers such as cotton, wool, silk, and jute are used at commercial level and established as the conventional fibers. Apart from these fibers, some other plant-based natural fibers are also used that are introduced as bio-fibers or vegetable fibers.

The utility of vegetable fibers for preparation of textiles started prior to recorded history. Since the dawn of history to present day, the world is being endowed with

physical and mechanical properties of fibers

because these cannot easily degrade after its use.

Environment Friendly Methods

#### **Chapter 3**

## Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods

*Tayyaba Fatma*

#### **Abstract**

Nowadays, natural products are extremely preferred among the people. These natural products are produced by environment friendly sources. In case of textiles, bast fibers play significant role in producing natural products that are extracted from the stem of various plant and environment friendly in nature. The bast fibers can also improve the livelihood of the poor farmers who are involved in the cultivation of the plants and extraction and processing of the fibers. Therefore, surface modification of established natural fibers (such as hemp, flax, jute, kenaf, urena, nettle, and ramie) and explored natural fibers are momentous area for doing research. And, these modifications can be done through environment friendly methods such as plasma treatment, and utilization of enzymes, bacteria, and fungi.

**Keywords:** natural fibers, surface modification, environment friendly methods, physical and mechanical properties of fibers

#### **1. Introduction**

At global level, 58% of synthetic fibers is used in clothing in which 77% polyester, 9% nylon, 6% acrylic, and 7% cellulosic fibers take place. Hence, the utilization of synthetic fibers is higher as compared to natural fibers. The synthetic fibers are generally made from polymers that have been synthetically produced from chemical compounds, which create lot of air, land, and water pollutions. These synthetic fibers are more harmful for health of the human being as well as environment because these cannot easily degrade after its use.

To overcome health-related problems and also for environmental safety, people are gradually attracted toward more and more use of natural products in both developed and developing countries. Thus, increasing concerns toward natural products have led to the search for ecological safe, biodegradable, and recyclable characters in their production. Though in case of textiles, production of natural products from natural fibers play a significant role. Natural fibers obtained from natural resources are one of the proficient fibers that replace the synthetic fibers. Numerous natural fibers such as cotton, wool, silk, and jute are used at commercial level and established as the conventional fibers. Apart from these fibers, some other plant-based natural fibers are also used that are introduced as bio-fibers or vegetable fibers.

The utility of vegetable fibers for preparation of textiles started prior to recorded history. Since the dawn of history to present day, the world is being endowed with

#### *Generation, Development and Modifications of Natural Fibers*

an abundant availability of vegetable fibers such as flax, jute, hemp, ramie, kenaf, urena, nettle, coir, sisal, pineapple, bamboo, and banana.

Globally, cotton is the leading natural fiber which is produced 25 million tons. It is an estimated average production of cotton. Wool and silk fibers are produced around 2.20 and 0.10 million tons per year, respectively. Other vegetable fibers including jute, flax, kenaf, coir, sisal, ramie, hemp, abaca, kapok, and henequen are produced in considerably 4.61 million tons [1, 2]. On the basis of morphological classification, vegetable fibers are categorized into several sub-categories such as bast fibers, leaf fibers, and seed fibers.

#### **2. Bast fibers introduced as a natural fiber**

The bast fibers are usually very long and relatively strong. For this reason, the bast fiber is considered to be the most important fraction of any plant [3].

The bast fibers are referred to as "soft" fibers, which are obtained from the stems of plants. Generally, the stem of fiber-yielding plant consists of bark layer, bast layer, and stem core. The bark layer is the outermost thin skin, that is, cuticle of stem that holds the bast fibers and protects the whole stem. The bast layer occurs between the bark layer and stem core, which is introduced as a fibrous layer of plant. The stem core has two parts, that is, woody tissue (xylem) and pith (**Figure 1**).

The fibrous layers are introduced as forms of primary and secondary fiber layers, which run parallel to the stem of dicotyledonous plants between the nodes. These fiber layers are referred to as bast or phloem or soft fibers, and their bundles vary from stem to stem and in different parts of the stem. There may be as few as 15 bundles to 35 or greater than 35. Each fiber bundle contains 10–40 individual fiber cells that are pointed. The number of cells in the bundle depends on the position of bundle in the stem, which means the largest number being found at the middle of the stem. The size of ultimate fiber cells also varies according to their position in the stem, which means the cells at the bottom of the stem being about three times as thick and longer as those at the top of the stem.

The molecular structure of bast fibers is formed by chains of cellulose molecules and an amorphous matrix of hemicellulose, lignin, pectin, and other substances in a single fiber unit. Therefore, all bast fibers are cellulosic in nature [4, 5]. The large

#### **Figure 1.**

*Microscopic view (cross sectional and longitudinal) of bast fibers. Source: https://textilestudycenter.com/jutefibre-properties-and-end-uses/ [Accessed: 09-02-2019].*

**51**

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods*

2 Gentianales Apocynaceae *Apocynum cannabinum, A. venetum, Chonemorpha* 

7 Malvales Malvaceae *Abutilon angulatum, A. indicum, A. bedfordianum,* 

Moraceae *Artocarpus elastic*

Sterculiaceae *Abroma augusta*

Tiliaceae *Cephalonema polyandrum*

3 Asclepiadaceae *Asclepias syriaca, A. fruticosa* and *A. incarnate*

*macrophylla*

*Calotropis gigantea Cryptostegia grandiflora Marsdenia tenacissima*

Linaceae *Linum angustifolium and L. usitatissimum*

*A. incanum, A. graveolens Adansonia digitata*

*Paritium elatus*

*Pseudabutilon spicatum Sida acuta* and *S. cordifolia Sphaeralcea umbellata*

*Broussonetia papyrifera Cannabis sativa*

*California fremontia Helicteres isora* and *H. viscid*

*Honckenya ficifolia Sparmannia africana*

Urticaceae *Boehmeria cylindrical, B. nivea*, and *B. tenacissima Debregeasia hypoleuca Girardinia palmata Laportea gigas Maoutia puya*

> *Pouzolzia hypoleuca* and *P. viminea Sarcochlamys pulcherrima Touchardia latifolia*

*Urtica dioica, U. urens* and *U. pilulifera Villebrunea integrifolia* and *V. rubescens*

*Lavatera arborea* and *L. maritime Malachra capitata* and *M. radiate Pavonia velutina* and *P. schimperiana*

*Plagianthus betulinus* and *P. pulchellus*

*Thespesia macrophylla* and *T. populnea Urena lobata* and *U. sinuate*

*Ficus benghalensis* and *F. nekbudu*

*Commersonia fraseri* and *C. echinata Dombeya buettneri* and *D. cannabina*

*Sterculia acerifolia, S. diversifolia, S. lurida* and *S. villosa*

*Corchorus acutangulus (syn. fuscus), C. aestuans, C. capsularis, C. hirsutus, C. olitorius,* and *C. siliquosus*

*Grewia occidentalis* and *G. oppositifolia*

*Tilia americana, T. europaea* and *T. japonica Triumfetta cordifolia, T. pentandra (syn neglecta), T. semitriloba, T. bartramia* and *T. rhomboidea*

*Hibiscus abelmoschus, H. cannabinus*, and *H. furcatus*

**S. no. Order Family Botanical name (genus and species)**

4 Geraniales Euphorbiaceae *Euphorbia gregaria and E. gummifera*

1 Asterales Compositae *Eupatorium cannabinum*

5 Laminales Labiatae *Phlomis lychnitis* 6 Loasales Datiscaceae *Datisca cannabina*

*DOI: http://dx.doi.org/10.5772/intechopen.85693*

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods DOI: http://dx.doi.org/10.5772/intechopen.85693*


*Generation, Development and Modifications of Natural Fibers*

bast fibers, leaf fibers, and seed fibers.

**2. Bast fibers introduced as a natural fiber**

thick and longer as those at the top of the stem.

*fibre-properties-and-end-uses/ [Accessed: 09-02-2019].*

urena, nettle, coir, sisal, pineapple, bamboo, and banana.

an abundant availability of vegetable fibers such as flax, jute, hemp, ramie, kenaf,

Globally, cotton is the leading natural fiber which is produced 25 million tons. It is an estimated average production of cotton. Wool and silk fibers are produced around 2.20 and 0.10 million tons per year, respectively. Other vegetable fibers including jute, flax, kenaf, coir, sisal, ramie, hemp, abaca, kapok, and henequen are produced in considerably 4.61 million tons [1, 2]. On the basis of morphological classification, vegetable fibers are categorized into several sub-categories such as

The bast fibers are usually very long and relatively strong. For this reason, the

The bast fibers are referred to as "soft" fibers, which are obtained from the stems

The molecular structure of bast fibers is formed by chains of cellulose molecules and an amorphous matrix of hemicellulose, lignin, pectin, and other substances in a single fiber unit. Therefore, all bast fibers are cellulosic in nature [4, 5]. The large

*Microscopic view (cross sectional and longitudinal) of bast fibers. Source: https://textilestudycenter.com/jute-*

bast fiber is considered to be the most important fraction of any plant [3].

of plants. Generally, the stem of fiber-yielding plant consists of bark layer, bast layer, and stem core. The bark layer is the outermost thin skin, that is, cuticle of stem that holds the bast fibers and protects the whole stem. The bast layer occurs between the bark layer and stem core, which is introduced as a fibrous layer of plant. The stem core has two parts, that is, woody tissue (xylem) and pith (**Figure 1**). The fibrous layers are introduced as forms of primary and secondary fiber layers, which run parallel to the stem of dicotyledonous plants between the nodes. These fiber layers are referred to as bast or phloem or soft fibers, and their bundles vary from stem to stem and in different parts of the stem. There may be as few as 15 bundles to 35 or greater than 35. Each fiber bundle contains 10–40 individual fiber cells that are pointed. The number of cells in the bundle depends on the position of bundle in the stem, which means the largest number being found at the middle of the stem. The size of ultimate fiber cells also varies according to their position in the stem, which means the cells at the bottom of the stem being about three times as

**50**

**Figure 1.**


*Sources: Mauersberger, Herbert R. Mathew's Textile Fibers: Their Physical, Microscopic and Chemical Properties. 6th ed. New York: John Wiley & Sons, Inc. and Landon, Chapman and Hall Limited; 1954.*

#### **Table 1.**

*List of potential plant sources of bast fibers.*

number of plants included in the bast fiber group, which represents in relation to the number that are cultivated and processed on a commercial scale. This group is a very rich potential supply in the field of textiles fibers (**Table 1**).

#### **3. Background information**

The history of bast fibers is not clearly defined. But the several evidences indicate that the bast fibers were used by prehistoric people. The ancient people started their nomadic life by using plant materials for covering and protecting their body, thatched leaf for shelter, and mats for household and other day to day activities. So, the bast fibers were specially cultivated by people to fulfill their needs.

Fragments of linen fabric have been found in excavations at the prehistoric lake regions of Switzerland, which date back to about 10,000 B.C. [6]. The actual samples of woven linen fabric have been recovered from Egyptian tombs dating from 4000 B.C. [7]. The early cultivation of kenaf fiber goes back to 4000 B.C. in West Africa [8]. Ramie has been cultivated for hundreds of years in China, Taiwan and to some extent in Egypt [6]. Hemp is the oldest fiber giving plant, which originated in Southeast Asia and spread to China. The cultivation date of hemp reports back to about 4500 B.C. In 3400 B.C., the skill of spinning and weaving of linen fabric was also well developed in Egypt that indicates the flax was cultivated sometime before that date. According to historical interest, the best known bast fibers include hemp, flax, jute, and ramie and minor fibers are kenaf, urena, and nettle [7].

#### **4. Physico-chemical properties of bast fibers**

To evaluate the quality of natural fibers, the fiber length and fineness are two important dimensions which are considered. The length of fiber must be several

**53**

materials [16–20].

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods*

able to give and recover without significant overall deformation of the textile.

density may be used as an aid in fiber identification [9–12].

way by which the cellulose is built up during plant growth [13].

matter, fats, and waxes [14, 15].

brooms, and wrapping purposes.

attractive for various applications.

The density of a fiber is related to its inherent chemical structure and the packing of the molecular chains within its structure. The density of a fiber will have a noticeable effect on its esthetic appeal and its usefulness in given applications. Fiber

The cross-sectional shape is important in luster, bulk, body, texture, and hand or feel of a fabric. The cross-sectional shape may be round, dog-bone, triangular, lobal, bean-shaped, flat, or straw like. The natural fibers derive their shape from the

The estimation of chemical composition is needed for better understanding regarding the nature of fiber and for making different value-added products. The main constituent of the vegetable fiber cell is cellulose and represented by the general formula C6H10O5. Apart from cellulose, vegetable fibers also contain significant amounts of other chemicals such as hemicellulose, lignin, pectin, resin, mineral

Traditionally, bast fibers were used for making carpets, hessian or burlap, sacks,

Now-a-days, representative of various industries and research institutes are producing range of textile and non-textile products in different fields such as automotive, packaging, horticulture, building, and construction. The bast fibers are suitable in building and construction as a form of geo-textiles, fiber board materials, insulation materials, reinforcement, filler, light-weight concrete, and bricks. High quality thermoplastic and thermosetting composite materials such as door panels, dashboards, seat backs, package trays, headliners and boot liners are produced with the help of bast fibers in automotive. Automotive and aircrafts industries have been actively developing different kinds of natural fibers, mainly on hemp, flax, and sisal and bio-resin systems for their interior components. High specific properties with lower prices of natural fiber composites are making it

The bast fibers are also used to produce non-woven fibers that are applied in various forms and products such as tissues and hygienic products, sorbents in diapers and disposables, insulation mat, filling material in mattresses, and geo-textiles. Biodegradable pots for plants, mulching materials, packing cloth for agriculture products, ship towing ropes, tea bags, currency notes, thermal under wears, stationeries, reusable containers, laboratory equipment, and loudspeakers are also manufactured by bast fibers. Therefore, it may face a renaissance, not only for old industrial products but also for the manufacturing of new type of products in the various fields such as technical textiles, industrial products, paper, and building

Current annual requirement of jute, kenaf, and allied fibers distribute in various sectors such as food grade jute bags, packing materials, family need jute bags, jute

hundred times to the width, which enables fibers to be twisted together to form a yarn or thread. The length of fiber can be infinitely long but it should not be shorter than 6–12 mm (¼–½ inch) because it may not hold together for spinning. The width of the fiber can vary between considerable limits. The natural fibers vary in

In addition, the fiber must be strong and flexible. Strength is needed to enable the spinning and weaving processes and to provide strength in the final cloth. Flexibility gives draping to a textile due to its unique characteristics. Many experts consider a single fiber strength of 5.0 g/D to be necessary for a fiber suitable in most textile applications, although certain fibers with strengths as low as 1.0 g/D have been found suitable for few applications. The elasticity is an important because the individual fibers in textiles are often subjected to sudden stresses, and the textile must be

*DOI: http://dx.doi.org/10.5772/intechopen.85693*

fineness from place to place on an individual fiber.

#### *Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods DOI: http://dx.doi.org/10.5772/intechopen.85693*

hundred times to the width, which enables fibers to be twisted together to form a yarn or thread. The length of fiber can be infinitely long but it should not be shorter than 6–12 mm (¼–½ inch) because it may not hold together for spinning. The width of the fiber can vary between considerable limits. The natural fibers vary in fineness from place to place on an individual fiber.

In addition, the fiber must be strong and flexible. Strength is needed to enable the spinning and weaving processes and to provide strength in the final cloth. Flexibility gives draping to a textile due to its unique characteristics. Many experts consider a single fiber strength of 5.0 g/D to be necessary for a fiber suitable in most textile applications, although certain fibers with strengths as low as 1.0 g/D have been found suitable for few applications. The elasticity is an important because the individual fibers in textiles are often subjected to sudden stresses, and the textile must be able to give and recover without significant overall deformation of the textile.

The density of a fiber is related to its inherent chemical structure and the packing of the molecular chains within its structure. The density of a fiber will have a noticeable effect on its esthetic appeal and its usefulness in given applications. Fiber density may be used as an aid in fiber identification [9–12].

The cross-sectional shape is important in luster, bulk, body, texture, and hand or feel of a fabric. The cross-sectional shape may be round, dog-bone, triangular, lobal, bean-shaped, flat, or straw like. The natural fibers derive their shape from the way by which the cellulose is built up during plant growth [13].

The estimation of chemical composition is needed for better understanding regarding the nature of fiber and for making different value-added products. The main constituent of the vegetable fiber cell is cellulose and represented by the general formula C6H10O5. Apart from cellulose, vegetable fibers also contain significant amounts of other chemicals such as hemicellulose, lignin, pectin, resin, mineral matter, fats, and waxes [14, 15].

Traditionally, bast fibers were used for making carpets, hessian or burlap, sacks, brooms, and wrapping purposes.

Now-a-days, representative of various industries and research institutes are producing range of textile and non-textile products in different fields such as automotive, packaging, horticulture, building, and construction. The bast fibers are suitable in building and construction as a form of geo-textiles, fiber board materials, insulation materials, reinforcement, filler, light-weight concrete, and bricks. High quality thermoplastic and thermosetting composite materials such as door panels, dashboards, seat backs, package trays, headliners and boot liners are produced with the help of bast fibers in automotive. Automotive and aircrafts industries have been actively developing different kinds of natural fibers, mainly on hemp, flax, and sisal and bio-resin systems for their interior components. High specific properties with lower prices of natural fiber composites are making it attractive for various applications.

The bast fibers are also used to produce non-woven fibers that are applied in various forms and products such as tissues and hygienic products, sorbents in diapers and disposables, insulation mat, filling material in mattresses, and geo-textiles. Biodegradable pots for plants, mulching materials, packing cloth for agriculture products, ship towing ropes, tea bags, currency notes, thermal under wears, stationeries, reusable containers, laboratory equipment, and loudspeakers are also manufactured by bast fibers. Therefore, it may face a renaissance, not only for old industrial products but also for the manufacturing of new type of products in the various fields such as technical textiles, industrial products, paper, and building materials [16–20].

Current annual requirement of jute, kenaf, and allied fibers distribute in various sectors such as food grade jute bags, packing materials, family need jute bags, jute

*Generation, Development and Modifications of Natural Fibers*

**S. no. Order Family Botanical name (genus and species)** 8 Myrtales Onagraceae *Epilobium angustifolium* and *E. hirsutum*

9 Polygalales Polygalaceae *Securidaca longipedunculata* 10 Rosales Leguminosae *Acacia leucophloea*

Lecythidaceae *Couratari tauari*

*Bauhinia racemosa* and *B. vahli*

*Crotalaria juncea (syn. tenuifolia)*

*Cytisus scoparius*

*Sesbania exaltata Lonchocarpus sericeus Spartium junceum Vigna sinensis Wisteria floribunda*

*Dirca palustris Lagetta lintearia*

*Brachystegia spicaeformis* and *B. tamarindoides*

*Pueraria thunbergiana* and *P. phaseoloides*

*Daphnopsis guacacoa* and *D. occidentalis*

number of plants included in the bast fiber group, which represents in relation to the number that are cultivated and processed on a commercial scale. This group is a

*Sources: Mauersberger, Herbert R. Mathew's Textile Fibers: Their Physical, Microscopic and Chemical Properties.* 

12 Thymelaeales Thymelaeaceae *Aquilaria agallocha* and *A. malaccensis*

The history of bast fibers is not clearly defined. But the several evidences indicate that the bast fibers were used by prehistoric people. The ancient people started their nomadic life by using plant materials for covering and protecting their body, thatched leaf for shelter, and mats for household and other day to day activities. So,

Fragments of linen fabric have been found in excavations at the prehistoric lake regions of Switzerland, which date back to about 10,000 B.C. [6]. The actual samples of woven linen fabric have been recovered from Egyptian tombs dating from 4000 B.C. [7]. The early cultivation of kenaf fiber goes back to 4000 B.C. in West Africa [8]. Ramie has been cultivated for hundreds of years in China, Taiwan and to some extent in Egypt [6]. Hemp is the oldest fiber giving plant, which originated in Southeast Asia and spread to China. The cultivation date of hemp reports back to about 4500 B.C. In 3400 B.C., the skill of spinning and weaving of linen fabric was also well developed in Egypt that indicates the flax was cultivated sometime before that date. According to historical interest, the best known bast fibers include hemp,

To evaluate the quality of natural fibers, the fiber length and fineness are two important dimensions which are considered. The length of fiber must be several

very rich potential supply in the field of textiles fibers (**Table 1**).

*6th ed. New York: John Wiley & Sons, Inc. and Landon, Chapman and Hall Limited; 1954.*

11 Sapindales Anacardiaceae *Rhus typhina*

the bast fibers were specially cultivated by people to fulfill their needs.

flax, jute, and ramie and minor fibers are kenaf, urena, and nettle [7].

**4. Physico-chemical properties of bast fibers**

**3. Background information**

*List of potential plant sources of bast fibers.*

**Table 1.**

**52**

geo-textiles, and automobiles. It provides work for more than 12 million of farmers, 1 million of industrial workers, and 0.6 million of jute artisans in more than 18 countries from Asia and Africa directly or indirectly.

The bast fibers have played a significant role for both consumer and manufacturer. Through dyes and finishes, the manufacturer can enhance the appeal and functionality of bast fibers, which ultimately increases the demand and sale of their end products. The bast fibers are also an important for consumers in term of wide range of value-added natural products. Apart from this, bast fibers can improve livelihood of the poor farmers who are involved in the cultivation of the plants, extraction, and processing of the fibers, which play a very important part for their economic life [21].

#### **5. Advantages and drawbacks of bast fibers**

The bast fibers have various properties such as comparable specific strength, heat, electrical, and sound insulating properties, good moisture absorbency, air permeability, comfort, low density, low energy requirement, lower pollutant emission, wide availability, better reactivity, and biodegradability. All these properties of the bast fibers are strongly influenced with various factors such as chemical composition, internal fiber structure, micro-fibril angle, and cell dimensions. These factors differ from plant to plant as well as from different parts of a plant. The properties of the bast fibers (cellulosic fibers) also depend on their type of cellulose, because each type of cellulose has its own crystalline organization. Due to their properties, the bast fibers cover a wide range of application from apparel and household fabrics to industrial materials.

One of the most important properties of bast fibers is their eco-friendly nature. Bast fibers are more environment-friendly in term of production and disposal of their products. So, we can say that the bast fibers have been introduced as an emerging "green" economy.

Few drawbacks of bast fibers are also available such as high moisture absorption, poor dimension stability, low thermal stability, low hygroscopicity, low surface energy, and rough structure along with high impurities content in bast fibers. Despite the drawbacks of bast fibers, they have been successfully used in certain applications in the field of insulation, composite, and geotextiles. But these drawbacks inhibit the growth of its applications [22].

However, to increase their applications and achieve better interface of bast fibers, the appropriate environment friendly surface modification methods can be utilize instead of physical and chemical methods for surface modification [1, 23–25].

#### **6. Environment friendly methods for surface modification**

Surface modification may be defined as the treatment to modify the surface of materials using physical, chemical, and biological methods for improving their properties [26].

By keeping the point in mind, world has also turned its attention to renewable and sustainable resources or environmental sustainability. Therefore, environment friendly methods for surface modification of bast fibers can be utilized. These methods introduced as green surface methods indicate to environment friendly processes, which are as follows:

**55**

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods*

Plasma treatment is introduced as a novel dry technique that significantly decreases toxic pollutant in the environment. This technique is suitable to modify the chemical structure along with topography of the surface of the bast fibers. Basically, plasma is a type of ionized gas consisting of electrons (0–10 eV), ions (10–30 eV), photons, atoms, and molecules and is called as the fourth state of matter. Free electrons, photons, and ion clouds begin to be formed, and some atoms continue to remain neutral and the mixture of atoms, ions, and electrons form the plasma. Two different types of plasma are available for industrial purposes:

i.Thermal plasma: formed direct or alternating current or radio-frequency

The basic function of plasma is to exploit surface of a material by using different type gases. After treatment, reactive free radicals and groups are produced, surface energy is increased or decreased and surface crosslinking are introduced [27–29]. There are two types of interactions which are present on the surface of fibers in the

i.Application of non-polymerizing gases such as helium, oxygen, air, and nitrogen, which creates chain scission on the surface that results in surface

ii.Application of polymerizing gases and precursors such as fluorocarbons, hydrocarbons, and silicon containing monomers, which creates plasma-

In the mechanism of plasma treatment, energetic particles and photons generate on the surface of fibers and interact strongly with other substrates by using freeradicals, though various types of changes occur like changes in physical and chemical properties along with changes in the chemical structure of polymers. These changes become due to cleaning, ablation or etching, cross-linking, and grafting modification of surface chemical structure. All these processes, alone or in syner-

Bacterial cellulose (unlike from the plant cellulose) is natural renewable polymer, synthesized from the bacteria in appropriate culture medium. Certain bacteria which belong to the genera such as *Acetobacter, Agrobacterium, Alcaligenes, Pseudomonas, Rhizobium*, *or Sarcina* are used for treatment of plant cellulosic materials. And, the most efficient bacteria for production of bacterial cellulose are *Acetobacter xylinum.* After treatment, the bacterial cellulose is endowed with unique properties such as high crystallinity index, high tensile strength, good chemical stability, and high water-holding capacity. Due to these properties, it is emerging as

a biomaterial that has superior structural aspect to the plant cellulose.

ii.Cold or non-equilibrium plasma: specified by an electron temperature

(RF) or microwave sources at high pressure.

higher than the ion temperature.

etching, cleaning, or activation.

induced polymerization or grafting.

gistic combination, improve the functionality of fibers [27].

*DOI: http://dx.doi.org/10.5772/intechopen.85693*

**6.1 Plasma treatment**

case of plasma treatment.

*6.1.1 Mechanism*

**6.2 Treatment with bacteria**

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods DOI: http://dx.doi.org/10.5772/intechopen.85693*

#### **6.1 Plasma treatment**

*Generation, Development and Modifications of Natural Fibers*

countries from Asia and Africa directly or indirectly.

**5. Advantages and drawbacks of bast fibers**

household fabrics to industrial materials.

backs inhibit the growth of its applications [22].

economic life [21].

ing "green" economy.

[1, 23–25].

properties [26].

processes, which are as follows:

geo-textiles, and automobiles. It provides work for more than 12 million of farmers, 1 million of industrial workers, and 0.6 million of jute artisans in more than 18

The bast fibers have played a significant role for both consumer and manufacturer. Through dyes and finishes, the manufacturer can enhance the appeal and functionality of bast fibers, which ultimately increases the demand and sale of their end products. The bast fibers are also an important for consumers in term of wide range of value-added natural products. Apart from this, bast fibers can improve livelihood of the poor farmers who are involved in the cultivation of the plants, extraction, and processing of the fibers, which play a very important part for their

The bast fibers have various properties such as comparable specific strength, heat, electrical, and sound insulating properties, good moisture absorbency, air permeability, comfort, low density, low energy requirement, lower pollutant emission, wide availability, better reactivity, and biodegradability. All these properties of the bast fibers are strongly influenced with various factors such as chemical composition, internal fiber structure, micro-fibril angle, and cell dimensions. These factors differ from plant to plant as well as from different parts of a plant. The properties of the bast fibers (cellulosic fibers) also depend on their type of cellulose, because each type of cellulose has its own crystalline organization. Due to their properties, the bast fibers cover a wide range of application from apparel and

One of the most important properties of bast fibers is their eco-friendly nature. Bast fibers are more environment-friendly in term of production and disposal of their products. So, we can say that the bast fibers have been introduced as an emerg-

Few drawbacks of bast fibers are also available such as high moisture absorption,

poor dimension stability, low thermal stability, low hygroscopicity, low surface energy, and rough structure along with high impurities content in bast fibers. Despite the drawbacks of bast fibers, they have been successfully used in certain applications in the field of insulation, composite, and geotextiles. But these draw-

However, to increase their applications and achieve better interface of bast fibers, the appropriate environment friendly surface modification methods can be

Surface modification may be defined as the treatment to modify the surface of materials using physical, chemical, and biological methods for improving their

By keeping the point in mind, world has also turned its attention to renewable and sustainable resources or environmental sustainability. Therefore, environment friendly methods for surface modification of bast fibers can be utilized. These methods introduced as green surface methods indicate to environment friendly

utilize instead of physical and chemical methods for surface modification

**6. Environment friendly methods for surface modification**

**54**

Plasma treatment is introduced as a novel dry technique that significantly decreases toxic pollutant in the environment. This technique is suitable to modify the chemical structure along with topography of the surface of the bast fibers.

Basically, plasma is a type of ionized gas consisting of electrons (0–10 eV), ions (10–30 eV), photons, atoms, and molecules and is called as the fourth state of matter. Free electrons, photons, and ion clouds begin to be formed, and some atoms continue to remain neutral and the mixture of atoms, ions, and electrons form the plasma. Two different types of plasma are available for industrial purposes:


The basic function of plasma is to exploit surface of a material by using different type gases. After treatment, reactive free radicals and groups are produced, surface energy is increased or decreased and surface crosslinking are introduced [27–29]. There are two types of interactions which are present on the surface of fibers in the case of plasma treatment.


#### *6.1.1 Mechanism*

In the mechanism of plasma treatment, energetic particles and photons generate on the surface of fibers and interact strongly with other substrates by using freeradicals, though various types of changes occur like changes in physical and chemical properties along with changes in the chemical structure of polymers. These changes become due to cleaning, ablation or etching, cross-linking, and grafting modification of surface chemical structure. All these processes, alone or in synergistic combination, improve the functionality of fibers [27].

#### **6.2 Treatment with bacteria**

Bacterial cellulose (unlike from the plant cellulose) is natural renewable polymer, synthesized from the bacteria in appropriate culture medium. Certain bacteria which belong to the genera such as *Acetobacter, Agrobacterium, Alcaligenes, Pseudomonas, Rhizobium*, *or Sarcina* are used for treatment of plant cellulosic materials. And, the most efficient bacteria for production of bacterial cellulose are *Acetobacter xylinum.* After treatment, the bacterial cellulose is endowed with unique properties such as high crystallinity index, high tensile strength, good chemical stability, and high water-holding capacity. Due to these properties, it is emerging as a biomaterial that has superior structural aspect to the plant cellulose.

#### *6.2.1 Mechanism*

In the optimum culture medium, the bacteria produces about 50–80 cellulose microfibrils ranging from 3.0 to 3.5 mm thickness, which are free from lignin, hemicellulose, and other substances [30].

#### **6.3 Treatment with nanocellulose**

Nanocellulose is defined as nanosized cellulose fibril that is a light solid substance obtained from plant resources. It is a pseudo-plastic in nature and also available as a fluids or gels form in standard conditions. The cross dimensions of nanocellulose are starting from 5 to 20 nm, and the longitudinal dimension ranges from a few tens of nanometers to several microns.

The specific properties of nanocellulose are light weight, high strength, and transparency. Hence, this nanocellulose is applicable in a wide variety of areas. Nanocellulose is commonly produced from wood pulp of any plant sources by using mechanical shearing methods such as pulverisette and cryo-crushing or combination of chemical and mechanical method.

#### *6.3.1 Mechanism*

Application of nanocellulosic is performed on the surface of bast fibers for enhancing their properties [31, 32].

#### **6.4 Fungal treatment**

This treatment ultimately increases the interfacial adhesion between fiber and matrix. Fungal treatment is done by the sterilization of bast fibers at 121.8°C for 15 min. Subsequently, the fibers treated with incubated culture of fungi for 2 weeks at 27.8°C. And then, the fibers were washed and dried. The species of fungi used were *Phanerochaete sordida* (D2B), *Pycnoporus* species (Pyc), and *Schizophyllum commune* (*S. com*) of the basidiomycetes group, *Ophiostoma floccosum* (F13) of the ascomycetes group, and *Absidia* (B101), a zygomycete. Fungal treatment gave higher crystallinity index as compared to the untreated fibers. Fungi treatment can provide low cost, highly efficient, and environmentally friendly alternatives to surface treatment of bast fibers.

#### *6.4.1 Mechanism*

Fungal treatment causes the formation of holes (pits) on the surface of fibers, which creates roughness on the surface of fibers by removing the lignin content and increasing the solubility of hemicellulose content.

#### **6.5 Enzymatic treatment**

Bio-grafting through enzymes is a comparatively novel modification method that includes grafting of organic molecules onto bast fibers. The purpose of biografting is to enhance the performance of bast fibers by improving the properties such as strength and stiffness, hydrophobicity, assistance to moisture, and microbial attack. Various enzymes such as *laccases, lipases*, and *peroxidases* are used surface functionalization of bast fibers.

**57**

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods*

The enzymes can oxidize in extensive range of natural polymers and generate reactive species such as phenoxy radicals, thereby increasing the reactivity of

The molecular and morphological structure of bast fibers (before and after

1.SEM analysis: the SEM constitutes one of the oldest and most widely used instruments for surface analysis. It provides a three-dimensional visual image,

and thus, the quantitative analysis is relatively straight forward [33].

2.FTIR analysis: it is another technique to examine the nature of molecular

Lot of researches may be conducted at various levels such as production and extraction of plasma, bacterial cellulose, nanocellulose, fungi, and enzymes from natural resources, way of application on the surface of bast fibers and other related

Development of new bio-composite materials with added functional properties such as in active and smart packaging system has created further scope for expansion of materials technology. Much research is expected for such biodegradable nano-composite materials to replace or reduce the use of the existing petro-based products. Another new approach is GM modification toward higher productivity,

better quality, and higher application areas of natural bast fiber [35].

It can be concluded that these environment friendly methods are green approaches for modifying the surface of bast fibers. Through these methods, drawback of bast fibers can be improved and also the demand for application of bast fiber at commercial level can be increased. So, we can say that it is green concept-based approach toward sustainability of natural resources as a form of

chains, crystallinity as a form of high crystallinity index, and their correlations

*DOI: http://dx.doi.org/10.5772/intechopen.85693*

treatment) is analyzed by using the following:

*6.5.1 Mechanism*

polymers [2].

**7. Analysis of bast fibers**

with various bonds [34].

fibers, and defining its end products.

**8. Future prospective**

**9. Conclusion**

surface modified bast fibers.

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods DOI: http://dx.doi.org/10.5772/intechopen.85693*

#### *6.5.1 Mechanism*

*Generation, Development and Modifications of Natural Fibers*

hemicellulose, and other substances [30].

from a few tens of nanometers to several microns.

tion of chemical and mechanical method.

enhancing their properties [31, 32].

surface treatment of bast fibers.

**6.5 Enzymatic treatment**

increasing the solubility of hemicellulose content.

surface functionalization of bast fibers.

*6.4.1 Mechanism*

**6.3 Treatment with nanocellulose**

In the optimum culture medium, the bacteria produces about 50–80 cellulose microfibrils ranging from 3.0 to 3.5 mm thickness, which are free from lignin,

Nanocellulose is defined as nanosized cellulose fibril that is a light solid substance obtained from plant resources. It is a pseudo-plastic in nature and also available as a fluids or gels form in standard conditions. The cross dimensions of nanocellulose are starting from 5 to 20 nm, and the longitudinal dimension ranges

The specific properties of nanocellulose are light weight, high strength, and transparency. Hence, this nanocellulose is applicable in a wide variety of areas. Nanocellulose is commonly produced from wood pulp of any plant sources by using mechanical shearing methods such as pulverisette and cryo-crushing or combina-

Application of nanocellulosic is performed on the surface of bast fibers for

This treatment ultimately increases the interfacial adhesion between fiber and matrix. Fungal treatment is done by the sterilization of bast fibers at 121.8°C for 15 min. Subsequently, the fibers treated with incubated culture of fungi for 2 weeks at 27.8°C. And then, the fibers were washed and dried. The species of fungi used were *Phanerochaete sordida* (D2B), *Pycnoporus* species (Pyc), and *Schizophyllum commune* (*S. com*) of the basidiomycetes group, *Ophiostoma floccosum* (F13) of the ascomycetes group, and *Absidia* (B101), a zygomycete. Fungal treatment gave higher crystallinity index as compared to the untreated fibers. Fungi treatment can provide low cost, highly efficient, and environmentally friendly alternatives to

Fungal treatment causes the formation of holes (pits) on the surface of fibers, which creates roughness on the surface of fibers by removing the lignin content and

Bio-grafting through enzymes is a comparatively novel modification method

that includes grafting of organic molecules onto bast fibers. The purpose of biografting is to enhance the performance of bast fibers by improving the properties such as strength and stiffness, hydrophobicity, assistance to moisture, and microbial attack. Various enzymes such as *laccases, lipases*, and *peroxidases* are used

*6.2.1 Mechanism*

*6.3.1 Mechanism*

**6.4 Fungal treatment**

**56**

The enzymes can oxidize in extensive range of natural polymers and generate reactive species such as phenoxy radicals, thereby increasing the reactivity of polymers [2].

#### **7. Analysis of bast fibers**

The molecular and morphological structure of bast fibers (before and after treatment) is analyzed by using the following:


#### **8. Future prospective**

Lot of researches may be conducted at various levels such as production and extraction of plasma, bacterial cellulose, nanocellulose, fungi, and enzymes from natural resources, way of application on the surface of bast fibers and other related fibers, and defining its end products.

Development of new bio-composite materials with added functional properties such as in active and smart packaging system has created further scope for expansion of materials technology. Much research is expected for such biodegradable nano-composite materials to replace or reduce the use of the existing petro-based products. Another new approach is GM modification toward higher productivity, better quality, and higher application areas of natural bast fiber [35].

#### **9. Conclusion**

It can be concluded that these environment friendly methods are green approaches for modifying the surface of bast fibers. Through these methods, drawback of bast fibers can be improved and also the demand for application of bast fiber at commercial level can be increased. So, we can say that it is green concept-based approach toward sustainability of natural resources as a form of surface modified bast fibers.

*Generation, Development and Modifications of Natural Fibers*

#### **Author details**

Tayyaba Fatma Department of Clothing and Textiles, College of Home Science, G.B.P.U.A. and T., Pantnagar, Uttarakhand, India

\*Address all correspondence to: tfansari.ct@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**59**

Inc.; 1982

International; 2010

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods*

2002

Limited; 2005

Limited; 1969

1963. p. 9

1999;**42**:467-473

Journal. 2010;**4**:93-101

[18] Mitra BC. Commercial Fibre Crops and their Utilisation. New Delhi: Directorate of Information and Publication of Agriculture; 2008

[9] Angappan P, Gopalakrishnan R. Textile Testing. Komarapalayam: S.S.M. Institute of Textile Technology;

[10] Cook JG. Handbook of Textiles Fibers: Natural Fibres. Cambridge England: Woodhead Publishing

[11] Labarthe J. Textiles: Origins to Usage. London: The Macmillian Company & Collier Macmillian

[12] Needles HL. Textile Fibers, Dyes, Finishes, and Processes. Park Ridge, New Jersey, U.S.A.: Noyes Publication; 1986

[13] Hollen N, Saddler J. Textiles. 3rd ed. London: The Macmillan Company/ Collier Macmillan Limited; 1968

[14] Kirby RH. Vegetable Fibres: Botany, Cultivation and Utilization. Londaon: Leonard Hill [Books] Limited and New York, Interscience Publishers, Inc.;

[15] Pan NC, Day A, Mahalanabis KK. Chemical composition of jute and its estimation. Man-Made Textiles in India.

D. Unconventional fibre plants: A source of sustainable livelihood. International Journal of Science Technology & Management. 2011;**2**(1):27-35

[17] Marques G, Rencoret J, Gutiérrez A, del Río JC. Evaluation of the chemical composition of different non-Woody Plant Fibres used for pulp and paper manufacturing. The Open Agriculture

[16] Kholiya R, Goel A, Kholiya

*DOI: http://dx.doi.org/10.5772/intechopen.85693*

reviews\_on\_perception\_of\_sustainable\_ green\_consumption\_practices\_and\_its\_ impact\_on\_greener\_lifestyles [Accessed:

(Government of India) on other Natural Fibres: Section VI [Internet]. Available from: http://texmin.nic.in/policy/ Fibre\_Policy\_Sub\_%20Groups\_Report\_ dir\_mg\_d\_20100608\_6.pdf [Accessed:

[3] Tahir PM, Ahmad AB, Saiful A, Sayeed OA, Ahmad Z. Review of bast fibre retting. BioResources.

[2] India. Ministry of Textiles

[1] Gopalakrishnan D. Reviews on Perception of Sustainable Green Consumption Practicesand it's Impact on Greener Lifestyles [Internet]. Available from: http:// www.academia.edu/34432113/

**References**

06-02-2019]

03-07-2015]

2011;**6**(4):5260-5281

[4] Klaus F, Breuer Ulf.

Multifunctionality of Polymer Composites: Challenges and New Solution. William Andrew Applied Science [Internet]. 2015. Available from: https://www.sciencedirect.com/science/ article/pii/B9780323264341000040?via %3Dihub [Assessed: 01-02-2019]

[5] NIIR Board of Consultants & Engineers. Natural Fibres: Handbook with Cultivation & Uses. Delhi: National Institute of Industrial Research; 2006

[6] Joseph ML. Introductory Textile Science. 5th ed. New York: Holt, Rinehart and Winston; 1986

[7] Tortora PG. Understanding Textiles. New York: Macmillan Publishing Co.

[8] Chen JY, Liu F. Bast Fibres: From plants to products. In: Singh BP, editor. Industrial Crops and Uses. UK: CAB

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods DOI: http://dx.doi.org/10.5772/intechopen.85693*

#### **References**

*Generation, Development and Modifications of Natural Fibers*

**58**

**Author details**

Tayyaba Fatma

Pantnagar, Uttarakhand, India

provided the original work is properly cited.

\*Address all correspondence to: tfansari.ct@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Department of Clothing and Textiles, College of Home Science, G.B.P.U.A. and T.,

[1] Gopalakrishnan D. Reviews on Perception of Sustainable Green Consumption Practicesand it's Impact on Greener Lifestyles [Internet]. Available from: http:// www.academia.edu/34432113/ reviews\_on\_perception\_of\_sustainable\_ green\_consumption\_practices\_and\_its\_ impact\_on\_greener\_lifestyles [Accessed: 06-02-2019]

[2] India. Ministry of Textiles (Government of India) on other Natural Fibres: Section VI [Internet]. Available from: http://texmin.nic.in/policy/ Fibre\_Policy\_Sub\_%20Groups\_Report\_ dir\_mg\_d\_20100608\_6.pdf [Accessed: 03-07-2015]

[3] Tahir PM, Ahmad AB, Saiful A, Sayeed OA, Ahmad Z. Review of bast fibre retting. BioResources. 2011;**6**(4):5260-5281

[4] Klaus F, Breuer Ulf. Multifunctionality of Polymer Composites: Challenges and New Solution. William Andrew Applied Science [Internet]. 2015. Available from: https://www.sciencedirect.com/science/ article/pii/B9780323264341000040?via %3Dihub [Assessed: 01-02-2019]

[5] NIIR Board of Consultants & Engineers. Natural Fibres: Handbook with Cultivation & Uses. Delhi: National Institute of Industrial Research; 2006

[6] Joseph ML. Introductory Textile Science. 5th ed. New York: Holt, Rinehart and Winston; 1986

[7] Tortora PG. Understanding Textiles. New York: Macmillan Publishing Co. Inc.; 1982

[8] Chen JY, Liu F. Bast Fibres: From plants to products. In: Singh BP, editor. Industrial Crops and Uses. UK: CAB International; 2010

[9] Angappan P, Gopalakrishnan R. Textile Testing. Komarapalayam: S.S.M. Institute of Textile Technology; 2002

[10] Cook JG. Handbook of Textiles Fibers: Natural Fibres. Cambridge England: Woodhead Publishing Limited; 2005

[11] Labarthe J. Textiles: Origins to Usage. London: The Macmillian Company & Collier Macmillian Limited; 1969

[12] Needles HL. Textile Fibers, Dyes, Finishes, and Processes. Park Ridge, New Jersey, U.S.A.: Noyes Publication; 1986

[13] Hollen N, Saddler J. Textiles. 3rd ed. London: The Macmillan Company/ Collier Macmillan Limited; 1968

[14] Kirby RH. Vegetable Fibres: Botany, Cultivation and Utilization. Londaon: Leonard Hill [Books] Limited and New York, Interscience Publishers, Inc.; 1963. p. 9

[15] Pan NC, Day A, Mahalanabis KK. Chemical composition of jute and its estimation. Man-Made Textiles in India. 1999;**42**:467-473

[16] Kholiya R, Goel A, Kholiya D. Unconventional fibre plants: A source of sustainable livelihood. International Journal of Science Technology & Management. 2011;**2**(1):27-35

[17] Marques G, Rencoret J, Gutiérrez A, del Río JC. Evaluation of the chemical composition of different non-Woody Plant Fibres used for pulp and paper manufacturing. The Open Agriculture Journal. 2010;**4**:93-101

[18] Mitra BC. Commercial Fibre Crops and their Utilisation. New Delhi: Directorate of Information and Publication of Agriculture; 2008

[19] Mohanty AK, Misra M, Drzal LT. Surface modifications of natural fibres and performance of resulting biocomposites: An overview. Composite Interfaces. 2001;**8**(5):313-343

[20] Sanjay MR, Arpitha GR, Naik LL, Gopalakrishna K, Yogesha B. Applications of natural Fibres and its composites: An overview. Natural Resources. 2016;**7**:108-114. DOI: 10.4236/nr.2016.73011. [Assessed: 01-02-2019]

[21] International Jute Study Group. Report on World Jute & Kenaf Statistics: At a Glance (Jute, Kenaf other Bast and Hard Fibres: Farm to Fashion). Dhaka, Bangladesh [Internet]. 2012. Available from: http://jute.org/IJSG%20 Publications/Jute%20&%20kenaf%20 Stat%20at%20a%20glance\_ijsg.pdf [Accessed: 13-07-2015]

[22] Sadrmanesh V, Chen Y. Bast fibres: Structure, processing, properties, and applications. International Materials Reviews. 2019;**64**(7):381-406. DOI: 10.1080/09506608.2018.1501171

[23] Kalia S, Vashishta S. Surface modification of sisal fibres (*Agave sisalana*) using bacterial cellulose and methyl methacrylate. Journal of Polymers and the Environment. 2012;**20**:142-152

[24] Kalia S, Thakur K, Celli A, Kiechel MA, Schauer CL. Surface medication of plant fibres using environment friendly methods for their application in polymer composites, textile industry and antimicrobial activities: A review. Journal of Environmental Chemical Engineering. 2013;**1**:97-112

[25] Khoshnava SM, Rostami R, Ismai M, Valipour A. The using fungi treatment as green and environmentally process for surface modification of natural Fibres. Applied Mechanics and Materials. 2014;**554**:116-122

[26] Khan A, Bhawani SA, Asiri AM, Khan I. Thermoset Composites: Preparation, Properties and Applications. Material Research Forum LLC: Millersville, PA; 2018

[27] Senthilkumar P. Surface modification of bast fibres by plasma treatment. Chemical Fibres International. 2017;**67**(2):94-95

[28] Shanmugasundaram OL. Application of plasma in textile industries. Textile Asia. 2006;**38**(5):44

[29] Zille A, Oliveira FR, Souto AP. Plasma treatment in textile industry. Plasma Processes and Polymers. 2014;**12**(2)

[30] Lustri Wilton R, de Oliveira Barud HG, da Silva Barud H, Peres Maristele FS, Junkal G, Agniezka T, et al. Microbial Cellulose—Biosynthesis Mechanisms and Medical Applications [Internet]. 2015. Available from: https://www.intechopen.com/ books/cellulose-fundamentalaspects-and-current-trends/ microbial-cellulose-biosynthesismechanisms-and-medical-applications [Accessed: 09-12-2015]

[31] Halib N, Perrone F, Cemazar M, Dapas B, Farra R, Abrami M, et al. Potential applications of Nanocellulosecontaining materials in the biomedical field. Materials. 2017;**10**:977

[32] Jawaid M, Salit MS, Alothman OY. Green Biocomposites: Design and Applications. Green Energy and Technology [Internet]. 2017. Available from: https://books.google.co.in/book s?id=e6gbDgAAQBAJ&pg=PA280&lp g=PA280&dq=future+scope+of+envir onment+friendly+surface+modificatio n+method+for+bast+fibres&source=b l&ots=N8e5s0pJH2&sig=ACfU3U2jqM V0KQhMo9cK\_3I4XOqGBl2C7w&hl=e n&sa=X&ved=2ahUKEwjD7tX3p6fgA hWJso8KHdVCn8Q6AEwCnoECAcQA Q#v=onepage&q=future%20scope%20

**61**

*Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods*

*DOI: http://dx.doi.org/10.5772/intechopen.85693*

of%20environment%20friendly%20 surface%20modification%20 method%20for%20bast%20

fibres&f=false [Assessed: 01-02-2019]

Chemical Testing of Textiles. Woodhead Publishing in Textiles; 2005. pp. 6-7, 14

[34] Bakar NA, Sultan MTH, Azni ME, Hazwan MH, Ariffin AH. Extraction and surface characterization of novel bast fibers extracted from the *Pennisetum purpureum* plant for composite application. Materials Today: Proceedings. 2018;**5**(10).

[33] Ugbolue SC. Fiber and yarn identification. In: Fan Q, editor.

(Part 2):21926-21935

dsj.64.7323

[35] Mitra BC. Contemporary environment friendly composite materials: Biocomposites and green Co. Defence Science Journal. 2014;**64**(3):244-261. DOI: 10.14429/ *Surface Modification of Bast-Based Natural Fibers through Environment Friendly Methods DOI: http://dx.doi.org/10.5772/intechopen.85693*

of%20environment%20friendly%20 surface%20modification%20 method%20for%20bast%20 fibres&f=false [Assessed: 01-02-2019]

*Generation, Development and Modifications of Natural Fibers*

[26] Khan A, Bhawani SA, Asiri AM, Khan I. Thermoset Composites: Preparation, Properties and

Applications. Material Research Forum

LLC: Millersville, PA; 2018

[27] Senthilkumar P. Surface modification of bast fibres by plasma treatment. Chemical Fibres International. 2017;**67**(2):94-95

[28] Shanmugasundaram OL. Application of plasma in textile industries. Textile Asia. 2006;**38**(5):44

2014;**12**(2)

[29] Zille A, Oliveira FR, Souto AP. Plasma treatment in textile industry. Plasma Processes and Polymers.

[30] Lustri Wilton R, de Oliveira Barud HG, da Silva Barud H, Peres Maristele FS, Junkal G, Agniezka T, et al. Microbial Cellulose—Biosynthesis Mechanisms and Medical Applications [Internet]. 2015. Available from: https://www.intechopen.com/ books/cellulose-fundamentalaspects-and-current-trends/ microbial-cellulose-biosynthesismechanisms-and-medical-applications

[Accessed: 09-12-2015]

field. Materials. 2017;**10**:977

[31] Halib N, Perrone F, Cemazar M, Dapas B, Farra R, Abrami M, et al. Potential applications of Nanocellulosecontaining materials in the biomedical

[32] Jawaid M, Salit MS, Alothman OY. Green Biocomposites: Design and Applications. Green Energy and Technology [Internet]. 2017. Available from: https://books.google.co.in/book s?id=e6gbDgAAQBAJ&pg=PA280&lp g=PA280&dq=future+scope+of+envir onment+friendly+surface+modificatio n+method+for+bast+fibres&source=b l&ots=N8e5s0pJH2&sig=ACfU3U2jqM V0KQhMo9cK\_3I4XOqGBl2C7w&hl=e n&sa=X&ved=2ahUKEwjD7tX3p6fgA hWJso8KHdVCn8Q6AEwCnoECAcQA Q#v=onepage&q=future%20scope%20

[19] Mohanty AK, Misra M, Drzal LT. Surface modifications of natural fibres and performance of resulting biocomposites: An overview. Composite

[20] Sanjay MR, Arpitha GR, Naik LL,

[21] International Jute Study Group. Report on World Jute & Kenaf Statistics: At a Glance (Jute, Kenaf other Bast and Hard Fibres: Farm to Fashion). Dhaka, Bangladesh [Internet]. 2012. Available from: http://jute.org/IJSG%20 Publications/Jute%20&%20kenaf%20 Stat%20at%20a%20glance\_ijsg.pdf

[22] Sadrmanesh V, Chen Y. Bast fibres: Structure, processing, properties, and applications. International Materials Reviews. 2019;**64**(7):381-406. DOI: 10.1080/09506608.2018.1501171

[23] Kalia S, Vashishta S. Surface modification of sisal fibres (*Agave sisalana*) using bacterial cellulose and methyl methacrylate. Journal of Polymers and the Environment.

[24] Kalia S, Thakur K, Celli A, Kiechel MA, Schauer CL. Surface medication of plant fibres using environment friendly methods for their application in polymer composites, textile industry and antimicrobial activities: A review. Journal of Environmental Chemical

[25] Khoshnava SM, Rostami R, Ismai M, Valipour A. The using fungi

treatment as green and environmentally process for surface modification of natural Fibres. Applied Mechanics and

Engineering. 2013;**1**:97-112

Materials. 2014;**554**:116-122

2012;**20**:142-152

[Accessed: 13-07-2015]

Interfaces. 2001;**8**(5):313-343

Gopalakrishna K, Yogesha B. Applications of natural Fibres and its composites: An overview. Natural Resources. 2016;**7**:108-114. DOI: 10.4236/nr.2016.73011. [Assessed:

01-02-2019]

**60**

[33] Ugbolue SC. Fiber and yarn identification. In: Fan Q, editor. Chemical Testing of Textiles. Woodhead Publishing in Textiles; 2005. pp. 6-7, 14

[34] Bakar NA, Sultan MTH, Azni ME, Hazwan MH, Ariffin AH. Extraction and surface characterization of novel bast fibers extracted from the *Pennisetum purpureum* plant for composite application. Materials Today: Proceedings. 2018;**5**(10). (Part 2):21926-21935

[35] Mitra BC. Contemporary environment friendly composite materials: Biocomposites and green Co. Defence Science Journal. 2014;**64**(3):244-261. DOI: 10.14429/ dsj.64.7323

**63**

**Chapter 4**

**Abstract**

bioeconomy

**1. Introduction**

*Petronela Nechita*

Use of Recycled Cellulose Fibers

Bioeconomy Applications

biodegradable pots available on the import market.

to Obtain Sustainable Products for

Knowing the negative impact of plastic materials from agriculture sources on the environmental pollution, in this chapter, some of research activities carried on the utilization of secondary cellulose fibers (from recovered papers and boards) and other lignocellulosic materials on obtaining of sustainable composite materials are presented. The aim was to obtain the (bio)composite materials with applications in manufacturing processes of biodegradable nutritive pots used in the production of vegetable seedlings. The tests were developed on a pilot plant designed to obtain the pots from a mixture of secondary cellulose fibers, red peat, and other additives. These materials were characterized in terms of biodegradability and growth and development of tomatoes and lettuce seedlings. For all the compositional versions studied, the specific indicators of seedlings growth and development have recorded values that allow a normal growth of plants similar to the use of plastic pots or

**Keywords:** biodegradable nutritive pots, cellulose fibers, peat, recovered papers, seedling, biodegradable potential, biodegradable rate, wet strength, dry strength,

In the most technological processes, current trends are geared toward the identification of alternative solutions for the rational use of raw materials by replacing the petroleum-based materials with negative environmental impact with those from renewable resources, biocompatibles, and highly recyclables in order to obtain

The negative impact on the environment of plastic pots used in agriculture has convinced many consumers that this is an unsustainable practice and has determined them to explore and identify the "green" alternatives to obtain the new materials, biodegradable, eventually recyclable and based on renewable resources

Nowadays, the plastic pots, containers, and trays are widely used in industrial greenhouse and private farms. In 2002, there were 1.678 billion pounds of plastics

After their utilization, these are dumped in landfills where they are very slowly degraded. The total flow of agricultural plastic waste reaches ca. 400,000 tonnes per year, and plastic pots and trays constitute about 16,000 tonnes

sustainable products according to the circular economy concept.

with low pollution for soils and plants [1, 2].

used in the agricultural sector [3].

#### **Chapter 4**

## Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications

*Petronela Nechita*

#### **Abstract**

Knowing the negative impact of plastic materials from agriculture sources on the environmental pollution, in this chapter, some of research activities carried on the utilization of secondary cellulose fibers (from recovered papers and boards) and other lignocellulosic materials on obtaining of sustainable composite materials are presented. The aim was to obtain the (bio)composite materials with applications in manufacturing processes of biodegradable nutritive pots used in the production of vegetable seedlings. The tests were developed on a pilot plant designed to obtain the pots from a mixture of secondary cellulose fibers, red peat, and other additives. These materials were characterized in terms of biodegradability and growth and development of tomatoes and lettuce seedlings. For all the compositional versions studied, the specific indicators of seedlings growth and development have recorded values that allow a normal growth of plants similar to the use of plastic pots or biodegradable pots available on the import market.

**Keywords:** biodegradable nutritive pots, cellulose fibers, peat, recovered papers, seedling, biodegradable potential, biodegradable rate, wet strength, dry strength, bioeconomy

#### **1. Introduction**

In the most technological processes, current trends are geared toward the identification of alternative solutions for the rational use of raw materials by replacing the petroleum-based materials with negative environmental impact with those from renewable resources, biocompatibles, and highly recyclables in order to obtain sustainable products according to the circular economy concept.

The negative impact on the environment of plastic pots used in agriculture has convinced many consumers that this is an unsustainable practice and has determined them to explore and identify the "green" alternatives to obtain the new materials, biodegradable, eventually recyclable and based on renewable resources with low pollution for soils and plants [1, 2].

Nowadays, the plastic pots, containers, and trays are widely used in industrial greenhouse and private farms. In 2002, there were 1.678 billion pounds of plastics used in the agricultural sector [3].

After their utilization, these are dumped in landfills where they are very slowly degraded. The total flow of agricultural plastic waste reaches ca. 400,000 tonnes per year, and plastic pots and trays constitute about 16,000 tonnes

(www.greenfacts.org). In this respect, the biodegradable pots represent a good alternative to plastic materials [4].

Generally, the plastic pots are light, cheap, and durable, and their walls are relatively impermeable. The last feature contributes to reducing the water consumption by the plants cultivated in such pots. Nevertheless, the salts and nutritive elements in their walls are not concentrated, and the recycling of the used plastic pots is still an unsolved problem [5].

Recently, alternative containers based on natural raw materials, impregnated with various components, such as slow-releasing fertilizers, fungicides, insecticides, and plant growth regulators that are released during plant growth, are gaining entry to the market and could enhance the efficiency of the production system. Industry and researchers are continuously working together to develop and fine-tune sustainable alternative containers to suit emerging grower and customer requirements [6, 7].

The researches in the field of biodegradable pots are focused into groups:


The researches in the field of biodegradable plastic materials are very intense and generally are economically stimulated to become alternatives to nondegradable materials [8]. Nevertheless, biocontainers are considerably more expensive and their cost ranges from 10 to 40%, which is more than their plastic counterparts [9]. Furthermore, these are only partially degradable and their degradation products do not exhibit the ecological safety [10, 11, 12].

In particular case of seedling biodegradable pots, it is required that beside the lack of toxicity, their degradation products should have nutritive properties for plants and contribute to soil quality improvement [13].

In this context, when the reuse and recycling are the first options in the concerns of sustainable management of production processes, cellulose fibers (primary and secondary) are considered to be the raw materials with great availability between the existing vegetal and renewable resources, presenting the important advantages compared with synthetic, inorganic, or mineral fibers.

The use of cellulose fibers has been explosive over the last decades, being directed both to the production of paper products (paper and cardboard) but, more and more as auxiliaries in many economical fields, such as: obtaining of (bio) composite materials with applicability in the construction materials industry, automobiles, aeronautics, electronics, agriculture, etc., medicine, pharmaceutical applications, or the food industry.

Considerable progress has been reported in the development of nano or microfibrilated cellulose with large-scale applications in medicine (cardiovascular implants, prostheses, etc.), and also in the field of biorefinery, the concept and basic process of the future of the cellulose and paper industry, which provides integrated solutions for the complex exploitation of plant biomass for energy production and the extraction of chemicals based on "green chemistry" concept.

*The biodegradable pots based on cellulose fibers* are composite materials obtained from mixtures of cellulose fibers and peat on wire or vacuum dewatering process using specials molds [14].

The main drawback of these materials is their low strength, especially wet strength. However, the researches in this field are focused on increasing the dry and wet strength without affecting their biodegradation capacity [15, 16].

**65**

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

This chapter highlights the use of cellulose fibers in composite materials with application in agriculture to obtain the biodegradable nutritive pots for seedling

**2. Utilization of cellulose fibers to obtain the biodegradable nutritive** 

(bio)composite materials or (bio)chemicals as alternative to petroleum-based

The cellulose is the most available polymer in nature that can be converted into

Among the biodegradable and nutritive pots, the pots based on peat and cellulose fibers are most widely used. They can be either embedded into soil together with plants or digested [18, 19]. The advantages of using the nutritive pots in the seedling manufacturing process are based on the fact that, comparing with existing plastic pots, these are biodegradable, have good water and air permeability and high ability of plant roots to penetrate the pot walls. Furthermore, these types of pots do not generate the waste after use and their degradation products are adequately fertilizers that contribute to soil bioremediation [20]. In their walls, the nutritional and biostimulative elements can be incorporated. These have an important role for improving

• increasing the work productivity in the seedling production by elimination of collecting, selection, storage, cleaning and sterilization stages that exist for the

• reducing the costs for seedlings production—due to the fact that these are

• improving the seedling quality—the walls of biodegradable pots have incorporated all the nutritive elements necessary for growing of plant roots (i.e. cellulose fibers, peat, protective and stimulative additives) and allow water retention and air penetration; these are very important parameters to ensure

• reducing the duration of seedling production with about 14–21 days comparing with existing conditions, which contribute to obtain a better production

• obtaining 100% biodegradable fully organic products (cellulose fibers, peat,

• eliminating recycling and waste management totally—at soil contact, these pots

The applications of nutritive and biodegradable pots in seedling manufacturing are varied, starting with vegetables and flowers, medicinal plants, ornamental

The nutritive biodegradable pots belong to new generation of transplantation

• resilient support of seedling for a variable period depending on the cultivated plant;

shrubs, or various forest species until the production of vine cuttings [21].

**pots with applications in the seedlings production**

The other advantages are presented as follows:

planted in soil together with biodegradable pots;

are converted in humus that improves the soil fertility.

media being designed to fulfill the following functions:

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

manufacturing.

products [17].

the plant prophylaxis.

plastic pots;

the oxygen flow;

efficiency;

etc.);

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*

This chapter highlights the use of cellulose fibers in composite materials with application in agriculture to obtain the biodegradable nutritive pots for seedling manufacturing.

#### **2. Utilization of cellulose fibers to obtain the biodegradable nutritive pots with applications in the seedlings production**

The cellulose is the most available polymer in nature that can be converted into (bio)composite materials or (bio)chemicals as alternative to petroleum-based products [17].

Among the biodegradable and nutritive pots, the pots based on peat and cellulose fibers are most widely used. They can be either embedded into soil together with plants or digested [18, 19]. The advantages of using the nutritive pots in the seedling manufacturing process are based on the fact that, comparing with existing plastic pots, these are biodegradable, have good water and air permeability and high ability of plant roots to penetrate the pot walls. Furthermore, these types of pots do not generate the waste after use and their degradation products are adequately fertilizers that contribute to soil bioremediation [20]. In their walls, the nutritional and biostimulative elements can be incorporated. These have an important role for improving the plant prophylaxis.

The other advantages are presented as follows:


The applications of nutritive and biodegradable pots in seedling manufacturing are varied, starting with vegetables and flowers, medicinal plants, ornamental shrubs, or various forest species until the production of vine cuttings [21].

The nutritive biodegradable pots belong to new generation of transplantation media being designed to fulfill the following functions:

• resilient support of seedling for a variable period depending on the cultivated plant;

*Generation, Development and Modifications of Natural Fibers*

alternative to plastic materials [4].

• biodegradable plastic pots; and

not exhibit the ecological safety [10, 11, 12].

applications, or the food industry.

using specials molds [14].

plants and contribute to soil quality improvement [13].

compared with synthetic, inorganic, or mineral fibers.

an unsolved problem [5].

requirements [6, 7].

• cellulose fibers pots

(www.greenfacts.org). In this respect, the biodegradable pots represent a good

Generally, the plastic pots are light, cheap, and durable, and their walls are relatively impermeable. The last feature contributes to reducing the water consumption by the plants cultivated in such pots. Nevertheless, the salts and nutritive elements in their walls are not concentrated, and the recycling of the used plastic pots is still

Recently, alternative containers based on natural raw materials, impregnated with various components, such as slow-releasing fertilizers, fungicides, insecticides, and plant growth regulators that are released during plant growth, are gaining entry to the market and could enhance the efficiency of the production system. Industry and researchers are continuously working together to develop and fine-tune sustainable alternative containers to suit emerging grower and customer

The researches in the field of biodegradable pots are focused into groups:

The researches in the field of biodegradable plastic materials are very intense and generally are economically stimulated to become alternatives to nondegradable materials [8]. Nevertheless, biocontainers are considerably more expensive and their cost ranges from 10 to 40%, which is more than their plastic counterparts [9]. Furthermore, these are only partially degradable and their degradation products do

In particular case of seedling biodegradable pots, it is required that beside the lack of toxicity, their degradation products should have nutritive properties for

In this context, when the reuse and recycling are the first options in the concerns of sustainable management of production processes, cellulose fibers (primary and secondary) are considered to be the raw materials with great availability between the existing vegetal and renewable resources, presenting the important advantages

The use of cellulose fibers has been explosive over the last decades, being directed both to the production of paper products (paper and cardboard) but, more and more as auxiliaries in many economical fields, such as: obtaining of (bio) composite materials with applicability in the construction materials industry, automobiles, aeronautics, electronics, agriculture, etc., medicine, pharmaceutical

Considerable progress has been reported in the development of nano or microfibrilated cellulose with large-scale applications in medicine (cardiovascular implants, prostheses, etc.), and also in the field of biorefinery, the concept and basic process of the future of the cellulose and paper industry, which provides integrated solutions for the complex exploitation of plant biomass for energy production and the extraction of chemicals based on "green chemistry"

*The biodegradable pots based on cellulose fibers* are composite materials obtained from mixtures of cellulose fibers and peat on wire or vacuum dewatering process

The main drawback of these materials is their low strength, especially wet strength. However, the researches in this field are focused on increasing the dry and

wet strength without affecting their biodegradation capacity [15, 16].

**64**

concept.


Therefore, obtaining biodegradable nutritive pots is based on the principles of sustainable development, considering the entire life cycle of the product [22]:


As a result of these aspects and in the context of integration of the horticultural production with other industrial fields (i.e., processing and recycling of cellulosic fibers), the experimental programs were managed to obtain the biodegradable nutritive supports (pots) based on peat and secondary cellulose fibers. These pots were tested with promising results for obtaining tomatoes and lettuce seedlings [23].

#### **2.1 The composition of biodegradable nutritive pots**

The properties of composite structure are highly influenced by the distribution and interactions between raw materials during wet forming and fibrous network consolidation by pressing and drying.

The mechanical strength properties are most important for a composite structure because indifferently by their use, this must meet specific characteristics such as shape, stiffness, and strength.

The fibrous materials are the main raw material for the biodegradable nutritive pots, having a decisive role to obtain the composite structure with adequate strength properties without compromising their biodegradability.

In this context, the most used fibrous materials are: kraft pulp for achieving the structure strength; secondary cellulose fibers from different types of recycled papers as fine material for forming and reinforcing the structure; peat consisting of vegetal materials, including wood fibers, in different stages of degradation, which gives the structure porosity, absorption, and water retention capacity as well as the nutritional properties.

Therefore, the characteristics of composite material may vary depending on the levels and properties of the fibrous raw materials.

After the analysis of the sources of fibrous materials based on their utilization in the composition of biodegradable and nutritive pots, for our experimental program, the following fibrous components have been identified: secondary cellulose fibers (from recycling of corrugated board boxes) and surface peats.

**67**

**Figure 1.**

*composite material (23°C and 50% RH).*

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

biostimulators during germination and plant growing;

the dry and wet strength of nutritive biodegradable pots.

• a product with a proper strength of the support for a variable period depending

• a high content of biologically active material, which releases the nutrients and

• a pot with permeable structure for water and oxygen and penetrable by the plant roots, which is completely degradated over a life cycle of plants transplanted in soil.

A content over 80% peat has as a result decreased the dewatering rate as well as

Regarding the cellulose fiber quality, it is recommended to have a high content of long fiber fraction that ensures a better bonding capacity and reinforcement of the

The physical-mechanical properties that are important for seedling pots are bursting and tensile strength (bursting index and breaking length). These properties are recommended to be evaluated in dry and wet state [24]. Another important property is the structure porosity that is determined by air permeability measurement. All these characteristics of composite material were tested on hand sheets (400 g/m2

obtained in the laboratory by Rapid-Köthen method with different percent of fibrous components (peat and cellulose fibers). The values of dry and wet strength of laboratory hand sheets with different contents of peat are presented in the **Figures 1** and **2**. It is important to mention that the optimization of these strength parameters is very difficult to obtain only from fibrous composition, because some requirements on resistance indexes are somewhat in opposite; for example, to obtain the composite material as pot shape, high resistance indexes (both for tensile and bursting strength) are necessary; during seedling manufacturing, a high wet strength for composite materials is necessary; after soil transplantation of seedling and pot, a lower bursting strength as

the plant roots to easily penetrate the composite material structure is necessary.

The tensile and bursting strength in dry state are influenced by total interfiber bonding energy and fiber length. Therefore, at high grammage, it is difficult to

*The influence of peat content on dry breaking length and dry bursting index for the laboratory hand sheets of* 

)

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

on the cultivated plant;

pot structure.

Based on the laboratory tests performed on the choice of the ratio between fibrous components, a value of 70/30 peat/secondary cellulose fiber ratio was identified as optimal.

This ratio allows obtaining:

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*


A content over 80% peat has as a result decreased the dewatering rate as well as the dry and wet strength of nutritive biodegradable pots.

Regarding the cellulose fiber quality, it is recommended to have a high content of long fiber fraction that ensures a better bonding capacity and reinforcement of the pot structure.

The physical-mechanical properties that are important for seedling pots are bursting and tensile strength (bursting index and breaking length). These properties are recommended to be evaluated in dry and wet state [24]. Another important property is the structure porosity that is determined by air permeability measurement. All these characteristics of composite material were tested on hand sheets (400 g/m2 ) obtained in the laboratory by Rapid-Köthen method with different percent of fibrous components (peat and cellulose fibers). The values of dry and wet strength of laboratory hand sheets with different contents of peat are presented in the **Figures 1** and **2**.

It is important to mention that the optimization of these strength parameters is very difficult to obtain only from fibrous composition, because some requirements on resistance indexes are somewhat in opposite; for example, to obtain the composite material as pot shape, high resistance indexes (both for tensile and bursting strength) are necessary; during seedling manufacturing, a high wet strength for composite materials is necessary; after soil transplantation of seedling and pot, a lower bursting strength as the plant roots to easily penetrate the composite material structure is necessary.

The tensile and bursting strength in dry state are influenced by total interfiber bonding energy and fiber length. Therefore, at high grammage, it is difficult to

#### **Figure 1.**

*The influence of peat content on dry breaking length and dry bursting index for the laboratory hand sheets of composite material (23°C and 50% RH).*

*Generation, Development and Modifications of Natural Fibers*

able, and can to contribute to soil bioremediation.

natural polymers, biodegradables, and nontoxic;

**2.1 The composition of biodegradable nutritive pots**

properties without compromising their biodegradability.

levels and properties of the fibrous raw materials.

(from recycling of corrugated board boxes) and surface peats.

consolidation by pressing and drying.

as shape, stiffness, and strength.

nutritional properties.

identified as optimal.

This ratio allows obtaining:

germination and seedling growth;

lulose fibers, lignocellulosic waste);

good soil fertilizers.

• biologically active material that releases nutrients and biostimulators during

• support with a structure that is totally degradated during a life cycle of plants transplanted in soil, and the degradation products must be nontoxic for soil, biodegrad-

Therefore, obtaining biodegradable nutritive pots is based on the principles of

• utilization of natural raw materials, renewables and recyclables (recycled cel-

• using of additives for strength properties of composite structures, based on

• all of these additives ensure the adequate level of nutrients for plants growth and their the degradation products of the nutritive and biodegradable pots are

As a result of these aspects and in the context of integration of the horticultural production with other industrial fields (i.e., processing and recycling of cellulosic fibers), the experimental programs were managed to obtain the biodegradable nutritive supports (pots) based on peat and secondary cellulose fibers. These pots were tested with promising results for obtaining tomatoes and lettuce seedlings [23].

The properties of composite structure are highly influenced by the distribution and interactions between raw materials during wet forming and fibrous network

The mechanical strength properties are most important for a composite structure because indifferently by their use, this must meet specific characteristics such

The fibrous materials are the main raw material for the biodegradable nutritive pots, having a decisive role to obtain the composite structure with adequate strength

In this context, the most used fibrous materials are: kraft pulp for achieving the structure strength; secondary cellulose fibers from different types of recycled papers as fine material for forming and reinforcing the structure; peat consisting of vegetal materials, including wood fibers, in different stages of degradation, which gives the structure porosity, absorption, and water retention capacity as well as the

Therefore, the characteristics of composite material may vary depending on the

After the analysis of the sources of fibrous materials based on their utilization in the composition of biodegradable and nutritive pots, for our experimental program, the following fibrous components have been identified: secondary cellulose fibers

Based on the laboratory tests performed on the choice of the ratio between fibrous components, a value of 70/30 peat/secondary cellulose fiber ratio was

sustainable development, considering the entire life cycle of the product [22]:

**66**

#### **Figure 2.**

*The influence of peat content on wet breaking length and wet bursting index for laboratory hand sheets of composite material.*

obtain a fibrous structure with better breaking length than bursting strength. In this context, the solution is to exploit the fact that long and rigid peat fibers reduce the interfiber bonding energy. This will have a higher impact on the bursting strength that is more influenced by the fibers length (**Figures 1** and **2**).

The wet strength retention of fibrous composite structures (percent of fraction from dry strength that remains when the structure is saturated with water) is obtained by introducing, in the composite structure, the specific additives that protect the interfiber bonds by blocking the access of water when this is wetted for different durations. The wet strength retention (%) can be at different levels (10–40%), and mechanical wet strength of the composite structure is directly influenced by dry strength and level of wet strength retention [25].

Aiming to obtain the appropriate wet strength retention of composite structure, a polyamide-polyamine-epichlorohydrin (Kymene 611) resin was used in the fibrous composition. This additive has a high efficiency for improving wet strength and a good degradation capacity. Furthermore, this resin, in accordance with environmental safety, is being used in the composition of tissue papers or cellulosic food packaging.

*Breaking length and wet strength retention*: At different contents of Kymene 611, the dry breaking length increases linearly with resin content (approx. 150 m/1%). The optimum content of resin for 40% value of wet strength retention is between 4 and 6% (**Figure 3**).

Based on these experiments, the content of Kymene resin was considered as optimum at 6%, when the wet strength retention level is over 35%.

*Bursting index and wet strength retention*: Dry bursting strength increases linearly with the content of Kymene (approx.10%/1%) (**Figure 4**).

Unlike the wet strength retention reported as breaking length that starts to decrease at 4% Kymene content, the wet strength retention reported as bursting strength starts to decrease at 6% Kymene content.

The dry bursting index for the tested samples has a maximum value for 6% Kymene content. The wet tensile and bursting strength of the composite material are directly influenced by their values in dry state as well as by wet strength retention level.

**69**

**Figure 4.**

**Figure 3.**

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

The dosage of resin for wet strength can be a means for retention of the components control, contributing also to increase of the additive efficiency as nutrient intake.

*Bursting index and wet strength retention at different contents of Kymene 611.*

*Breaking length and wet strength retention at different contents of polyamide-polyamine-epichlorohydrin resin.*

**2.2 The influence of fibrous composition and additive content on the structure** 

Generally, the porosity is an important property that characterizes the structure of fibrous composites. This property influences the other characteristics of

**of nutritive biodegradable pots**

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*

**Figure 3.**

*Generation, Development and Modifications of Natural Fibers*

obtain a fibrous structure with better breaking length than bursting strength. In this context, the solution is to exploit the fact that long and rigid peat fibers reduce the interfiber bonding energy. This will have a higher impact on the bursting strength that is more influenced by the fibers length (**Figures 1** and **2**).

*The influence of peat content on wet breaking length and wet bursting index for laboratory hand sheets of* 

The wet strength retention of fibrous composite structures (percent of fraction from dry strength that remains when the structure is saturated with water) is obtained by introducing, in the composite structure, the specific additives that protect the interfiber bonds by blocking the access of water when this is wetted for different durations. The wet strength retention (%) can be at different levels (10–40%), and mechanical wet strength of the composite structure is directly influ-

Aiming to obtain the appropriate wet strength retention of composite structure,

*Breaking length and wet strength retention*: At different contents of Kymene 611, the dry breaking length increases linearly with resin content (approx. 150 m/1%). The optimum content of resin for 40% value of wet strength retention is between 4

Based on these experiments, the content of Kymene resin was considered as

Unlike the wet strength retention reported as breaking length that starts to decrease at 4% Kymene content, the wet strength retention reported as bursting

The dry bursting index for the tested samples has a maximum value for 6% Kymene content. The wet tensile and bursting strength of the composite material are directly influenced by their values in dry state as well as by wet strength retention level.

*Bursting index and wet strength retention*: Dry bursting strength increases linearly

optimum at 6%, when the wet strength retention level is over 35%.

with the content of Kymene (approx.10%/1%) (**Figure 4**).

strength starts to decrease at 6% Kymene content.

a polyamide-polyamine-epichlorohydrin (Kymene 611) resin was used in the fibrous composition. This additive has a high efficiency for improving wet strength and a good degradation capacity. Furthermore, this resin, in accordance with environmental safety, is being used in the composition of tissue papers or cellulosic

enced by dry strength and level of wet strength retention [25].

**68**

food packaging.

**Figure 2.**

*composite material.*

and 6% (**Figure 3**).

*Breaking length and wet strength retention at different contents of polyamide-polyamine-epichlorohydrin resin.*

**Figure 4.**

*Bursting index and wet strength retention at different contents of Kymene 611.*

The dosage of resin for wet strength can be a means for retention of the components control, contributing also to increase of the additive efficiency as nutrient intake.

#### **2.2 The influence of fibrous composition and additive content on the structure of nutritive biodegradable pots**

Generally, the porosity is an important property that characterizes the structure of fibrous composites. This property influences the other characteristics of

composites such as air permeability, liquids filtering, and water absorption. The porosity of composite structure was evaluated by air permeability measurement, which means the air volume that passes through a sample with known surface, under given time and pressure. The moisture content at equilibrium was evaluated beside air permeability.

The increasing peat content as a result has increased the porosity of the composite structure, evaluated by air permeability. Due to the high capacity of water retention of peat, the composite structure exhibits an increased moisture content (**Figure 5**).

The permeability of the composite structure is mainly influenced by the peat content. A lower influence is obtained with the increase of the resin content, also (**Figure 6**).

**Figure 5.** *The influence of peat content on air permeability and equilibrium moisture of composite structures.*

**71**

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

**2.3 The level of nutrients in composition of biodegradable nutritive pots**

ground), keeping the proportion of peat in the range of 50–70%.

• zinc sulfate and copper sulfate for zinc and copper release;

problems during the formation process of their fibrous structure.

pots were dried in a laboratory oven at 105°C temperature [26].

**Table 1** and their preparing stages in **Figure 7**.

• potassium nitrate for the release of potassium;

to obtain an optimal ratio of nutritive elements (N, P, K).

posite material structure are:

microelements;

mineral salts.

**3.1 Materials preparation**

A high content of peat in the composition of biodegradable pots involves an ideal medium for development of seedling roots, while providing a nutritional reserve. This fibrous component allows circulation of air and water ensuring the oxygen flow. The peat cannot be a permanent source of nutrients for a long time. In this respect, the ways of retaining nitrogen from urea or ammonium phosphates, phosphorus from potassium or ammonium phosphate, potassium and microelements such as molybdenum, boron, manganese, copper, and zinc, were analyzed.

For an additional contribution of mineral salts and nutrients in the composition of biodegradable pots, it was established that a part of the peat to be replaced with a mixture of waste from grape processing (skins and bunches of grapes, dried and

All of these additives were introduced in the mass of composite materials aiming

The chemical and natural auxiliaries identified to be introduced into the com-

• urea and dibasic ammonium phosphate—for nitrogen and phosphorus release;

• mixture of waste from grape processing (peelings and bunches) for additional

The nutritional properties of biodegradable composites are improved by incorporating bioactive substances in their structure (walls). Furthermore, a peat content of about 50–70% contributes to accelerating biodegradation rate of composite pots. A content of 70% peat in the composite structure facilitates the accessibility of seedling roots toward nutritive elements within the optimum range of pH. Exceeding the proportion of peat in the composition of the nutritive pots (over 70%) raises high

**3. Experimental program for obtaining the biodegradable nutritive pots**

In our experiments, three compositional versions (M1, M2, and M3) of biodegradable nutritive pots dedicated to produce seedling material were obtained using the formation and dewatering system through die molding. The obtained nutritive

The composition of those three versions of nutritive pots is presented in the

After separation of coarse materials, the peat was dried at 105°C and defibrated using a homogenization device (Lhomargy type) for 4–5 min at 2000 rpm. Recycled

• borax and ammonium molybdate—for release of boron and molybdenum

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

**Figure 6.** *The effect of resin content on the air permeability.*

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*

#### **2.3 The level of nutrients in composition of biodegradable nutritive pots**

A high content of peat in the composition of biodegradable pots involves an ideal medium for development of seedling roots, while providing a nutritional reserve. This fibrous component allows circulation of air and water ensuring the oxygen flow. The peat cannot be a permanent source of nutrients for a long time. In this respect, the ways of retaining nitrogen from urea or ammonium phosphates, phosphorus from potassium or ammonium phosphate, potassium and microelements such as molybdenum, boron, manganese, copper, and zinc, were analyzed.

For an additional contribution of mineral salts and nutrients in the composition of biodegradable pots, it was established that a part of the peat to be replaced with a mixture of waste from grape processing (skins and bunches of grapes, dried and ground), keeping the proportion of peat in the range of 50–70%.

All of these additives were introduced in the mass of composite materials aiming to obtain an optimal ratio of nutritive elements (N, P, K).

The chemical and natural auxiliaries identified to be introduced into the composite material structure are:


The nutritional properties of biodegradable composites are improved by incorporating bioactive substances in their structure (walls). Furthermore, a peat content of about 50–70% contributes to accelerating biodegradation rate of composite pots. A content of 70% peat in the composite structure facilitates the accessibility of seedling roots toward nutritive elements within the optimum range of pH. Exceeding the proportion of peat in the composition of the nutritive pots (over 70%) raises high problems during the formation process of their fibrous structure.

#### **3. Experimental program for obtaining the biodegradable nutritive pots**

In our experiments, three compositional versions (M1, M2, and M3) of biodegradable nutritive pots dedicated to produce seedling material were obtained using the formation and dewatering system through die molding. The obtained nutritive pots were dried in a laboratory oven at 105°C temperature [26].

#### **3.1 Materials preparation**

The composition of those three versions of nutritive pots is presented in the **Table 1** and their preparing stages in **Figure 7**.

After separation of coarse materials, the peat was dried at 105°C and defibrated using a homogenization device (Lhomargy type) for 4–5 min at 2000 rpm. Recycled

*Generation, Development and Modifications of Natural Fibers*

beside air permeability.

(**Figure 5**).

**Figure 5.**

composites such as air permeability, liquids filtering, and water absorption. The porosity of composite structure was evaluated by air permeability measurement, which means the air volume that passes through a sample with known surface, under given time and pressure. The moisture content at equilibrium was evaluated

The increasing peat content as a result has increased the porosity of the composite structure, evaluated by air permeability. Due to the high capacity of water retention of peat, the composite structure exhibits an increased moisture content

The permeability of the composite structure is mainly influenced by the peat content. A lower influence is obtained with the increase of the resin content, also (**Figure 6**).

*The influence of peat content on air permeability and equilibrium moisture of composite structures.*

**70**

**Figure 6.**

*The effect of resin content on the air permeability.*

#### *Generation, Development and Modifications of Natural Fibers*


**Table 1.**

*The compositional versions of nutritive pots obtained in the experimental program.*

#### **Figure 7.**

*The stages of fibrous material preparing.*

papers from corrugated board boxes were defibrated in a laboratory Hollander until 35–40°SR. The fibrous components (peat and cellulose fibres) are mixed using a homogenizer where the Kymene 611 resin is added. The consistency of the fibrous mixture is adjusted at 0.8–1.0%.

#### **3.2 Formation and dewatering of biodegradable nutritive pots**

Fibrous suspension corresponding to each compositional version was transferred to a laboratory pilot plant where the die molding and dewatering of biodegradable nutritive pots took place as is described in **Figure 8**.

For each compositional version, about 150 pieces of nutritive pots have been obtained, and technical parameters during formation and dewatering processes are presented in the **Table 2**.

All composite structures have an adequate wet strength and fibrous network integrity (after formation and dewatering). This allowed manual take-up of nutritive pots and their introduction into drying equipment, where free-air drying was carried out.

**73**

**3.3 Drying of nutritive pots**

*Formation and dewatering of biodegradable nutritive pots [27].*

**biodegradable pots**

(**Figure 9**).

**Figure 8.**

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

The nutritive pots were dried at 105°C for 60–80 min in a laboratory oven

The mechanical strength properties were measured using a specific device for strength evaluation, whose construction was developed to simulate the specific shape and individual stresses to which biodegradable nutritive pots are subjected [27].

**3.4 Assessment of mechanical strength properties of nutritive** 

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*

**Figure 8.**

*Generation, Development and Modifications of Natural Fibers*

*The compositional versions of nutritive pots obtained in the experimental program.*

**Materials M1 (%) M2 (%) M3 (%)** Peat 70 55 70 Waste from grapes processing — 15 — Secondary cellulose fibers 30 30 30 Wet strength resin (Kymene 611) 6 6 6 Chemical additives 2 2 —

papers from corrugated board boxes were defibrated in a laboratory Hollander until 35–40°SR. The fibrous components (peat and cellulose fibres) are mixed using a homogenizer where the Kymene 611 resin is added. The consistency of the fibrous

Fibrous suspension corresponding to each compositional version was transferred to a laboratory pilot plant where the die molding and dewatering of biode-

For each compositional version, about 150 pieces of nutritive pots have been obtained, and technical parameters during formation and dewatering processes are

All composite structures have an adequate wet strength and fibrous network integrity (after formation and dewatering). This allowed manual take-up of nutritive pots and their introduction into drying equipment, where free-air drying was

**3.2 Formation and dewatering of biodegradable nutritive pots**

gradable nutritive pots took place as is described in **Figure 8**.

**72**

carried out.

**Figure 7.**

**Table 1.**

mixture is adjusted at 0.8–1.0%.

*The stages of fibrous material preparing.*

presented in the **Table 2**.

*Formation and dewatering of biodegradable nutritive pots [27].*

#### **3.3 Drying of nutritive pots**

The nutritive pots were dried at 105°C for 60–80 min in a laboratory oven (**Figure 9**).

#### **3.4 Assessment of mechanical strength properties of nutritive biodegradable pots**

The mechanical strength properties were measured using a specific device for strength evaluation, whose construction was developed to simulate the specific shape and individual stresses to which biodegradable nutritive pots are subjected [27].

#### *Generation, Development and Modifications of Natural Fibers*


#### **Table 2.**

*Technical parameters during formation and dewatering of nutritive biodegradable pots.*

**Figure 9.** *Drying of biodegradable nutritive pots.*

#### **Figure 10.**

*Dry strength of biodegradable nutritive pots.*

Strength tests were carried out both on samples conditioned in the standard atmosphere (23°C, moisture 50% RH) and wetted by immersion in water at 23°C for 15 minutes.

**75**

process.

**Figure 11.**

**manufacturing process**

*Wet strength of biodegradable nutritive pots.*

(*Lycopersicon esculentum*) seedlings [27].

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

In **Figures 10** and **11**, the results obtained after the strength tests of those three

As it can be observed, the M3 version exhibits the best strength properties, both in dry and wet state. Values obtained for the M3 pots were of two and three times higher than those registered for the M1 and M2 versions. It seems that in case of the M1 version, the nutrient charge as salts affected resin retention and crosslinking, as it is known that resin adsorption on fibers decreases significantly, at the same time, increasing the valence of metallic ions and their stock concentration [28, 29, 30]. In case of the M2 version, the charge of residue from grape processing breaks the continuity of the fibrous network and introduces fine and colloidal anionically charged material. Nevertheless, in both cases (M1 and M2), the obtained strength exceeds the strength requirement for handling and transport in the seedling manufacturing

To assess the biodegradability of nutritive pots, the cellulosic degradation rate was determinated [31, 32]. Based on this evaluation method, the nutritive pot samples (dried at 105°C) were incubated in a nutritive substrate commonly used for producing seedlings. During incubation, the nutritive pots were introduced in a previously weighed synthetic bag, in order to totally recover the fibrous material contained in it. During the entire experimenting period (141 days), the effective substrate moisture was maintained in the range of 60–65% relative humidity, and temperature in the range of 24–28°C. The biodegradation rate (degradation degree)

The *capability to create a favorable environment for developing a typical microflora for soil and culture substrates* was evaluated by microflora respiration intensity, having in view that microflora are involved in cellulosic material degradation [33]. The experiments were carried out on both experimental nutritive pots and the current process for the production of lettuce (*Lactuca sativa,* var. Capitata) and tomatoes

Analyzing the obtained results (**Figure 12**), it is observed that during the experimental program, the pots from M1 version showed the lowest biodegradation

versions of biodegradable nutritive pots are presented.

**3.5 Assessment of nutritive pots biodegradability during seedling** 

was calculated as weight loss of initial and after soil incubation of pots.

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*

**Figure 11.** *Wet strength of biodegradable nutritive pots.*

*Generation, Development and Modifications of Natural Fibers*

Consistency of fibrous material, % 1.2–1.4 1.2–1.4 0.9–1.1

Time of die formation, s 12–15 15–16 15–17 Dewatering time, s 60 60 60 Consistency of white water, % 0.0397 0.0351 0.0320 Ash content of white water, % 41.43 30.34 21.72 Number of nutritive pots 150 pcs. 150 pcs. 150 pcs.

*Technical parameters during formation and dewatering of nutritive biodegradable pots.*

**Parameter Value Observations**

Formation consistency, % 22–24 22–24 22–24 After die formation Weight of wet pot, g 32–34 34–36 24–28 After die formation Weight of dry pot, g 7.5–8.0 8.0–9.0 6.5–7.5 After drying at 105°C

**M1 M2 M3**

**74**

**Table 2.**

**Figure 9.**

*Drying of biodegradable nutritive pots.*

for 15 minutes.

*Dry strength of biodegradable nutritive pots.*

**Figure 10.**

Strength tests were carried out both on samples conditioned in the standard atmosphere (23°C, moisture 50% RH) and wetted by immersion in water at 23°C

In **Figures 10** and **11**, the results obtained after the strength tests of those three versions of biodegradable nutritive pots are presented.

As it can be observed, the M3 version exhibits the best strength properties, both in dry and wet state. Values obtained for the M3 pots were of two and three times higher than those registered for the M1 and M2 versions. It seems that in case of the M1 version, the nutrient charge as salts affected resin retention and crosslinking, as it is known that resin adsorption on fibers decreases significantly, at the same time, increasing the valence of metallic ions and their stock concentration [28, 29, 30]. In case of the M2 version, the charge of residue from grape processing breaks the continuity of the fibrous network and introduces fine and colloidal anionically charged material. Nevertheless, in both cases (M1 and M2), the obtained strength exceeds the strength requirement for handling and transport in the seedling manufacturing process.

#### **3.5 Assessment of nutritive pots biodegradability during seedling manufacturing process**

To assess the biodegradability of nutritive pots, the cellulosic degradation rate was determinated [31, 32]. Based on this evaluation method, the nutritive pot samples (dried at 105°C) were incubated in a nutritive substrate commonly used for producing seedlings. During incubation, the nutritive pots were introduced in a previously weighed synthetic bag, in order to totally recover the fibrous material contained in it. During the entire experimenting period (141 days), the effective substrate moisture was maintained in the range of 60–65% relative humidity, and temperature in the range of 24–28°C. The biodegradation rate (degradation degree) was calculated as weight loss of initial and after soil incubation of pots.

The *capability to create a favorable environment for developing a typical microflora for soil and culture substrates* was evaluated by microflora respiration intensity, having in view that microflora are involved in cellulosic material degradation [33]. The experiments were carried out on both experimental nutritive pots and the current process for the production of lettuce (*Lactuca sativa,* var. Capitata) and tomatoes (*Lycopersicon esculentum*) seedlings [27].

Analyzing the obtained results (**Figure 12**), it is observed that during the experimental program, the pots from M1 version showed the lowest biodegradation

#### **Figure 12.** *Biodegradation potential of nutritive biodegradable pots [27].*


#### **Table 3.**

*The biodegradability of nutritive pots with cultivated seedling.*

potential; though at the first analysis time (after 34 days), the M3 version pots showed a higher degradation rate (28.76%) than the M1 and M2 pots. In the last analysis period (after 141 days), the biodegradation potential was the highest for the M2 version pots (44.19%); this behavior can be explained by the fact that the pots obtained with this composition contained a lower amount of fibrous material (85%) compared with the M1 and M3 pots; in the composition of these pots, the waste from grape processing acts as a filler, increasing the distance between fibers and reducing bonding forces in the fibrous network. The obtained results are correlated with the wet strength of the M2 version pots, also.

Regarding the effective biodegradation rate measured during seedlings manufacturing process (tomatoes—*Lycopersicon esculentum* and lettuce—*Lactuca sativa*), the obtained results showed that all of three tested versions of pots behaved differently according to the seedling type (**Table 3**). Therefore, in case of tomatoes seedlings (after 51 days), the M1 pots exhibited the highest biodegradation rate (16.48%) and the M2 version showed the lowest rate (15.35%). When the lettuce seedlings are produced, the highest biodegradation rate was obtained in M2 (13.65%) and the lowest in M1 (12.39%).

The reason is that tomatoes naturally have a stronger root system than lettuce, though the latter develops its roots faster. As a result, the rhizosphere effect is more intense for tomatoes, and biodegradation conditions are modified both in the culture substrate and in the pots.

Analyzing the average daily biodegradation rate, it is noticed that this is more intense when pots are not planted with seedling compared to seedling production

**77**

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

**Plant/roots ratio**

*Comparative morphological characteristics of seedlings planted in biodegradable pots with different* 

**Tomatoes** M1 20.3 18.1 1.12 6.6 0.32 10.0 M2 14.2 23.8 0.60 5.4 0.38 7.0 M3 14.0 16.8 0.83 4.6 0.32 8.4 Jiffy pot 24.8 21.8 1.13 7.2 0.29 10.2 **Lettuce** M1 5.3 9.6 0.55 6.6 1.24 9.6 M2 5.0 9.8 0.51 6.2 1.24 8.6 M3 4.6 7.4 0.62 6.4 1.39 8.8 Jiffy pot 5.1 5.1 1.00 7.0 1.37 9.5

**Number of leaves**

**Leaves frequency (no./plant height)** **Roots volume (cm3 )**

when the pots benefit by rhizosphere effect of seedling. In these circumstances, there are differences between the two types of tested seedlings. Therefore, the daily biodegradation rate of lettuce seedling is with 0.02–0.08% higher than tomatoes seedling. This is based on the existence of an initial rate of roots growth which is

*Tomatoes and lettuce plants obtained using the experimental nutritive biodegradable pots.*

From the results presented in the **Table 4** and **Figure 13** regarding the growth and development of lettuce and tomatoes seedlings, it can be observed that for all the studied versions, the growth indicators have values that allow the framing within the favorable limits according to the data from specialty literature. The mass indicators show accumulations that have allowed normal growth. The experiences have shown that for both the lettuce and tomatoes, the type of pots used for seedling and transplanting strongly influences the number of leaves and roots volume. By visual appreciation, it has been found that the good development of the seedlings is also related to the good penetration of the roots through the walls of the pots, even if their effective biodegradation was quite small. This aspect is mainly related to the mechanical properties of the nutritive pots, especially the penetration resistance. It is also observed that the morphological properties of the plants raised in the experimentally pots are comparable to those of the plants developed in

more intense in lettuce than tomatoes.

currently existing Jiffy pots.

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

**Length of roots (cm)**

**plant (cm)**

**Pot version Height of** 

**Table 4.**

*compositions.*

**Figure 13.**

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*


#### **Table 4.**

*Generation, Development and Modifications of Natural Fibers*

*Biodegradation potential of nutritive biodegradable pots [27].*

*The biodegradability of nutritive pots with cultivated seedling.*

potential; though at the first analysis time (after 34 days), the M3 version pots showed a higher degradation rate (28.76%) than the M1 and M2 pots. In the last analysis period (after 141 days), the biodegradation potential was the highest for the M2 version pots (44.19%); this behavior can be explained by the fact that the pots obtained with this composition contained a lower amount of fibrous material (85%) compared with the M1 and M3 pots; in the composition of these pots, the waste from grape processing acts as a filler, increasing the distance between fibers and reducing bonding forces in the fibrous network. The obtained results are cor-

**Pot version Effective biodegradation rate (%) Daily biodegradation rate (%)**

M1 16.484 12.391 0.32 0.34 M2 15.351 13.657 0.30 0.38 M3 16.312 13.008 0.32 0.36

**Tomatoes Lettuce Tomatoes Lettuce**

Regarding the effective biodegradation rate measured during seedlings manufacturing process (tomatoes—*Lycopersicon esculentum* and lettuce—*Lactuca sativa*), the obtained results showed that all of three tested versions of pots behaved differently according to the seedling type (**Table 3**). Therefore, in case of tomatoes seedlings (after 51 days), the M1 pots exhibited the highest biodegradation rate (16.48%) and the M2 version showed the lowest rate (15.35%). When the lettuce seedlings are produced, the highest biodegradation rate was obtained in M2

The reason is that tomatoes naturally have a stronger root system than lettuce, though the latter develops its roots faster. As a result, the rhizosphere effect is more intense for tomatoes, and biodegradation conditions are modified both in the

Analyzing the average daily biodegradation rate, it is noticed that this is more intense when pots are not planted with seedling compared to seedling production

related with the wet strength of the M2 version pots, also.

(13.65%) and the lowest in M1 (12.39%).

culture substrate and in the pots.

**76**

**Figure 12.**

**Table 3.**

*Comparative morphological characteristics of seedlings planted in biodegradable pots with different compositions.*

**Figure 13.**

*Tomatoes and lettuce plants obtained using the experimental nutritive biodegradable pots.*

when the pots benefit by rhizosphere effect of seedling. In these circumstances, there are differences between the two types of tested seedlings. Therefore, the daily biodegradation rate of lettuce seedling is with 0.02–0.08% higher than tomatoes seedling. This is based on the existence of an initial rate of roots growth which is more intense in lettuce than tomatoes.

From the results presented in the **Table 4** and **Figure 13** regarding the growth and development of lettuce and tomatoes seedlings, it can be observed that for all the studied versions, the growth indicators have values that allow the framing within the favorable limits according to the data from specialty literature. The mass indicators show accumulations that have allowed normal growth. The experiences have shown that for both the lettuce and tomatoes, the type of pots used for seedling and transplanting strongly influences the number of leaves and roots volume. By visual appreciation, it has been found that the good development of the seedlings is also related to the good penetration of the roots through the walls of the pots, even if their effective biodegradation was quite small. This aspect is mainly related to the mechanical properties of the nutritive pots, especially the penetration resistance. It is also observed that the morphological properties of the plants raised in the experimentally pots are comparable to those of the plants developed in currently existing Jiffy pots.

#### **4. Conclusions**

In our experimental programs, three compositional versions of biodegradable nutritive pots based on 50 and 70% peat, 30% recycled cellulose fibers, and organic and mineral nutritive materials between 0 and 2% were tested; these biodegradable nutritive pots were tested on production of lettuce and tomatoes seedlings.

The results on mechanical strengths (wet and dry) demonstrated the importance of fibrous composition and chemistry relative to the formation and integrity of biodegradable nutritive pots for the seedling production process.

The additional nutrients (mineral or organic) stimulate the pulp degradation; therefore, the pots containing both chemical (for nutrient contribution) and natural (waste from grape processing) additives—M2 version—showed the highest biodegradation potential.

For all the studied versions of pots, the specific indicators of plant growth have values that allow them to be framed within the limits of favorability, ensuring a normal growth of plants.

The obtained results are promising and the biodegradable nutritive pots based on lignocellulosic materials can be used in the seedlings manufacturing process; based on their composition, these products can be considered a good reserve of organic materials for soil. These materials are nontoxic and biodegradable, according to the provisions of European Directives, concerning reduction of environmental pollution with plastics from agricultural sources. Furthermore, it represents a real opportunity to stimulate transition towards a circular economy.

#### **5. Future recommendations**

The experiments will be continued with testing of biodegradable pots on other types of seedling as well as for optimization of wet strength additives content aiming to ensure an adequate biodegradation according with the duration of seedling development.

#### **Acknowledgements**

The author thanks for support of Research and Consultancy Centre for Environmental and Agriculture "Lunca" from Dunărea de Jos University of Galaţi, Romania.

**79**

**Author details**

Petronela Nechita

provided the original work is properly cited.

"Dunărea de Jos" University of Galați, Romania

\*Address all correspondence to: petronela.nechita@ugal.ro

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Department of Environmental, Applied Engineering and Agriculture,

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications*

*DOI: http://dx.doi.org/10.5772/intechopen.86092*

#### **Conflict of interests**

The author declares no potential conflicts of interest with respect to the research, authorship, and/or publication of this chapter.

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*

#### **Author details**

*Generation, Development and Modifications of Natural Fibers*

In our experimental programs, three compositional versions of biodegradable nutritive pots based on 50 and 70% peat, 30% recycled cellulose fibers, and organic and mineral nutritive materials between 0 and 2% were tested; these biodegradable

The results on mechanical strengths (wet and dry) demonstrated the importance of fibrous composition and chemistry relative to the formation and integrity

The additional nutrients (mineral or organic) stimulate the pulp degradation;

For all the studied versions of pots, the specific indicators of plant growth have values that allow them to be framed within the limits of favorability, ensuring a

The obtained results are promising and the biodegradable nutritive pots based on lignocellulosic materials can be used in the seedlings manufacturing process; based on their composition, these products can be considered a good reserve of organic materials for soil. These materials are nontoxic and biodegradable, according to the provisions of European Directives, concerning reduction of environmental pollution with plastics from agricultural sources. Furthermore, it represents a

The experiments will be continued with testing of biodegradable pots on other types of seedling as well as for optimization of wet strength additives content aiming to ensure an adequate biodegradation according with the duration of seedling

The author thanks for support of Research and Consultancy Centre for Environmental and Agriculture "Lunca" from Dunărea de Jos University of Galaţi,

The author declares no potential conflicts of interest with respect to the

research, authorship, and/or publication of this chapter.

nutritive pots were tested on production of lettuce and tomatoes seedlings.

therefore, the pots containing both chemical (for nutrient contribution) and natural (waste from grape processing) additives—M2 version—showed the highest

of biodegradable nutritive pots for the seedling production process.

real opportunity to stimulate transition towards a circular economy.

**4. Conclusions**

biodegradation potential.

normal growth of plants.

**5. Future recommendations**

development.

Romania.

**Acknowledgements**

**Conflict of interests**

**78**

Petronela Nechita Department of Environmental, Applied Engineering and Agriculture, "Dunărea de Jos" University of Galați, Romania

\*Address all correspondence to: petronela.nechita@ugal.ro

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[3] Levitan L, Barros A. Recycling agricultural plastics in New York state. In: A Research Report Prepared for the Environmental Risk Analysis Program. Ithaca, New York: Cornell University; 2003

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[5] Welleman JCC. Fytocell, an increasingly popular substrate. Acta Horticulturae (ISHS). 2005;**697**:195-198

[6] Evans MR, Taylor M, Kuehny J. Physical properties of biocontainers for greenhouse crops production. HortTechnology. 2010;**20**(3):549-555

[7] Nambuthiri S, Schnelle R, Fulcher A, Geneve R, Koeser A, Verlinden S, et al. Alternative containers for a sustainable greenhouse and nursery crop production. Agriculture & Natural Resources. 2013;**1**(11)

[8] Seiichiro I, Hongkang Z. Products Based on Corn Gluten Meal and Other Agro Byproducts, World Conference and Exhibition on Oilseed and Vegetable Oil Utilization. Istanbul, Turkey; 2006

[9] Robinson T. Containers evolve to satisfy industry, retailer, and consumer needs. GMPro. 2008;**28**(1):35-40

[10] Environment Australia. Biodegradable Plastics – Developments and Environmental Impacts, Ref: 3111- 01/ October 2002, Prepared by NOLAN-ITU Pty Ltd in Association with ExcelPlas Australia; 2002. pp. 37-40

[11] Yue C, Hall CR, Behe BK, Campbell BL, Dennis JH, Lopez RG. Are consumers willing to pay more for biodegradable containers than for plastic ones? Evidence for hypothetical conjoint analysis and nonhypothetical experimental auctions. Journal of Agricultural and Applied Economics. 2010;**42**(4):757-772

[12] Camberato D, Lopez R. Biocontainers for Long-Term Crops. Greenhouse Grower; 2010. Available from: https://www.greenhousegrower. com/production/pots-trays/ biocontainers-for-long-term-crops/

[13] Abaecherli A, Popa VI. Lignin in crop cultivations and bioremediation. Environmental Engineering and Management Journal. 2005;**4**(3): 273-292. DOI: 10.30638/eemj.2005.030

[14] United States Patent, No. 6,490,827 B2. 2002

[15] Kirchhoff MM. Promoting sustainability through green chemistry. Conservation and Recycling, Resources. 2005;**44**:237-243

[16] Bobu E. Improving the effectiveness of papermaking chemicals by controlling the aggregation mechanisms. In: PIRA International Conferenece- Scientific and Technical Advances in Wet End Chemistry. 2004; 1-12 May, Nice, France

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[26] Nechita P, Bobu E, Ciolacu F, Dobrin E, Biocomposites from renewable resources – biodegradable nutritive support for containerized seedling manufacturing. 2009; National Research Programme, BIOSUN project -

Contract no. 51-090, stage 3

2010;**5**(2):1102-1113

1989;**2**:155-163

[27] Nechita et al. Biodegradable pots for planting. BioResources.

[29] Roberts JC. Wet-strength

com/la/book/9780751402360

[31] Ştefanic G. Probleme de agrofitotehnie teoretică şi aplicată. 1999;**XXVIII**(Supplement):45-50

[32] Bourtoom T. Plasticizer effect on the properties of biodegradable blend film from rice starch.Chitosan. Songklanakarin Journal of Science and Technology. 2008;**30**(Suppl. l):149-155

[33] Szegi J. Cellulose Decomposition and Soil Fertility. Budapest: Akademiai

Kiado; 1988. pp. 65-68

[28] Ampulski RS, Neal CW. The effect of inorganic ions on the adsorption and ion exchange of Kymene 557H by bleached northern softwood Kraft pulp. Nordic Pulp & Paper Research Journal.

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[30] Yoon SH. Adsorption kinetics of polyamide-epichlorohydrin on cellulosic fibres suspended in aqueous solution. Journal of Industrial and Engineering Chemistry. 2006;**12**(6):877-881

2003;**18**:91-100

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[19] Verhoeven JTA, Setter TL. Agricultural use of wetlands:

of Botany. 2010;**105**:155-163

Opportunities and limitations. Annals

[20] Ingram DL, Nambuthiri S. Using plantable containers for selected groundcover plant production. Hortscience. 2012;**47**(9). (Supplement) SR–ASHS Annual Meeting—February 3-6, 2012

[21] Maljanen M, Sigurdsson BD, Guðmundsson J, Óskarsson H, Huttunen JT, Martikainen PJ.

Greenhouse gas balances of managed peatlands in the Nordic countries, present knowledge and gaps. Biogeosciences. 2010;**7**:2711-2738

[22] Evans MR, Taylor M, Kuehny J. Physical properties of biocontainers for greenhousec rops production. HortTechnology. 2010;**20**:549-555

[23] Wang X, Fernandez T, Cregg B, Fulcher A, Geneve R, Niu G, et al. Performance of alternative containers and plant growth and water use of *Euonymus fortune*. Hortscience.

[24] Taylor M, Evans M, Kuehny J. The beef on biocontainers: Strenght, water use, biodegradability and greenhouse performance. OFA Bulletin. 2010;3:923

[25] Orliac O, Rouilly A, Silvestre F, Rigal L. Effects of various plasticizers

2012;**47**(9):S2.(Abstr.)

2010;**7**:2711-2738

*Use of Recycled Cellulose Fibers to Obtain Sustainable Products for Bioeconomy Applications DOI: http://dx.doi.org/10.5772/intechopen.86092*

[17] Zhu S, Wu Y, Cheng Q , Yu Z, Wang C, Jen S, et al. Dissolution of cellulose with ionic liquids and its application: A minireview. Green Chemistry. 2006;**8**:325

[18] Maljanen M, Sigurdsson BD, Guðmundsson J, Skarsson H, Huttunen JT, Martikainen P. Greenhouse gas balances of managed peatlands in the Nordic countries ñ present knowledge and gaps. Biogeosciences. 2010;**7**:2711-2738

[19] Verhoeven JTA, Setter TL. Agricultural use of wetlands: Opportunities and limitations. Annals of Botany. 2010;**105**:155-163

[20] Ingram DL, Nambuthiri S. Using plantable containers for selected groundcover plant production. Hortscience. 2012;**47**(9). (Supplement) SR–ASHS Annual Meeting—February 3-6, 2012

[21] Maljanen M, Sigurdsson BD, Guðmundsson J, Óskarsson H, Huttunen JT, Martikainen PJ. Greenhouse gas balances of managed peatlands in the Nordic countries, present knowledge and gaps. Biogeosciences. 2010;**7**:2711-2738

[22] Evans MR, Taylor M, Kuehny J. Physical properties of biocontainers for greenhousec rops production. HortTechnology. 2010;**20**:549-555

[23] Wang X, Fernandez T, Cregg B, Fulcher A, Geneve R, Niu G, et al. Performance of alternative containers and plant growth and water use of *Euonymus fortune*. Hortscience. 2012;**47**(9):S2.(Abstr.)

[24] Taylor M, Evans M, Kuehny J. The beef on biocontainers: Strenght, water use, biodegradability and greenhouse performance. OFA Bulletin. 2010;3:923

[25] Orliac O, Rouilly A, Silvestre F, Rigal L. Effects of various plasticizers on the mechanical properties, water resistance and aging of thermomoulded films made from sunflower proteins. Industrial Crops and Products. 2003;**18**:91-100

[26] Nechita P, Bobu E, Ciolacu F, Dobrin E, Biocomposites from renewable resources – biodegradable nutritive support for containerized seedling manufacturing. 2009; National Research Programme, BIOSUN project - Contract no. 51-090, stage 3

[27] Nechita et al. Biodegradable pots for planting. BioResources. 2010;**5**(2):1102-1113

[28] Ampulski RS, Neal CW. The effect of inorganic ions on the adsorption and ion exchange of Kymene 557H by bleached northern softwood Kraft pulp. Nordic Pulp & Paper Research Journal. 1989;**2**:155-163

[29] Roberts JC. Wet-strength additives. In: Roberts JC, editor. Paper Chemistry. 2nd ed. Blackie Academic & Professional; 1996. pp. 104-107. Available from: https://www.springer. com/la/book/9780751402360

[30] Yoon SH. Adsorption kinetics of polyamide-epichlorohydrin on cellulosic fibres suspended in aqueous solution. Journal of Industrial and Engineering Chemistry. 2006;**12**(6):877-881

[31] Ştefanic G. Probleme de agrofitotehnie teoretică şi aplicată. 1999;**XXVIII**(Supplement):45-50

[32] Bourtoom T. Plasticizer effect on the properties of biodegradable blend film from rice starch.Chitosan. Songklanakarin Journal of Science and Technology. 2008;**30**(Suppl. l):149-155

[33] Szegi J. Cellulose Decomposition and Soil Fertility. Budapest: Akademiai Kiado; 1988. pp. 65-68

**80**

*Generation, Development and Modifications of Natural Fibers*

[9] Robinson T. Containers evolve to satisfy industry, retailer, and consumer needs. GMPro. 2008;**28**(1):35-40

Biodegradable Plastics – Developments and Environmental Impacts, Ref: 3111- 01/ October 2002, Prepared by NOLAN-

[11] Yue C, Hall CR, Behe BK, Campbell

[10] Environment Australia.

ITU Pty Ltd in Association with ExcelPlas Australia; 2002. pp. 37-40

BL, Dennis JH, Lopez RG. Are consumers willing to pay more for biodegradable containers than for plastic ones? Evidence for hypothetical conjoint analysis and nonhypothetical experimental auctions. Journal of Agricultural and Applied Economics.

2010;**42**(4):757-772

B2. 2002

2005;**44**:237-243

[12] Camberato D, Lopez R.

com/production/pots-trays/

Biocontainers for Long-Term Crops. Greenhouse Grower; 2010. Available from: https://www.greenhousegrower.

biocontainers-for-long-term-crops/

[13] Abaecherli A, Popa VI. Lignin in crop cultivations and bioremediation. Environmental Engineering and Management Journal. 2005;**4**(3): 273-292. DOI: 10.30638/eemj.2005.030

[14] United States Patent, No. 6,490,827

sustainability through green chemistry. Conservation and Recycling, Resources.

effectiveness of papermaking chemicals

[15] Kirchhoff MM. Promoting

[16] Bobu E. Improving the

1-12 May, Nice, France

by controlling the aggregation mechanisms. In: PIRA International Conferenece- Scientific and Technical Advances in Wet End Chemistry. 2004;

[1] Carrión C, Abad M, Maquieira A, Puchades R, Fornes F, Noguera V. Leaching of composts from agricultural wastes to prepare nursery potting media. Acta Horticulturae (ISHS).

[2] Hurley S. Postconsumer Agricultural Plastic Report. California Integrated Waste Management Board; Published by California Environmental Protection

[3] Levitan L, Barros A. Recycling agricultural plastics in New York state. In: A Research Report Prepared for the Environmental Risk Analysis Program. Ithaca, New York: Cornell University;

[4] Treinytea J, Grazulevicienea V, Bridziuviene D, Svediene J. Properties and behaviour of starch and rapeseed cake based composites in horticultural applications. Estonian Journal of Ecology. 2014;**63**(1):15-27. DOI: 10.3176/

[5] Welleman JCC. Fytocell, an increasingly popular substrate. Acta Horticulturae (ISHS). 2005;**697**:195-198

[6] Evans MR, Taylor M, Kuehny J. Physical properties of biocontainers for greenhouse crops production. HortTechnology. 2010;**20**(3):549-555

Resources. 2013;**1**(11)

[7] Nambuthiri S, Schnelle R, Fulcher A, Geneve R, Koeser A, Verlinden S, et al. Alternative containers for a sustainable greenhouse and nursery crop production. Agriculture & Natural

[8] Seiichiro I, Hongkang Z. Products Based on Corn Gluten Meal and Other Agro Byproducts, World Conference and Exhibition on Oilseed and Vegetable Oil Utilization. Istanbul, Turkey; 2006

**References**

2005;**697**:117-112

Agency; 2008

eco.2014.1.02

2003

**83**

Section 2

Non-Woven Fabrics

Technology

Section 2
