**3. Chemical modification of bamboo**

**Chemical constituents Percentage** Cellulose 73.83 Hemicellulose 12.49 Lignin 10.15 Aqueous Extract 3.16 Pectin 0.37

**2. Chemical composition of bamboo**

28 Bamboo - Current and Future Prospects

growth habits. Apart from its socio-economical utilisation, bamboo has many environmental benefits [7]. It has some ecological functions on soil erosion control, water conservation, land rehabilitation, carbon sequestration, etc. In China, bamboo forests are recognised as a massive carbon sink in the global cycles of carbon. They have high potentials in carbon fixation, and this is due to the prediction that the carbon stocks in bamboo stands based on previous data

Some studies have revealed bamboo to produce higher biomass yield than other lignocelluloses crops with a growth rate ranging from 30 to 60 cm/day and height of about 36 m in growing season [28]. The aboveground biomass of bamboo in the Philippines was first reported as 146.8 Mg ha−1 year−1 (Suzuki and Jacalne [119]). Nath et al. [29] reported that the total aboveground standing biomass of bamboo in northeast India was 42.98 Mg ha−1 year−1. Hong et al. [30], when comparing the annual biomass yield between bamboo and *Miscanthus*

Cellulose, hemicelluloses and lignin are the three major chemical compositions of bamboo, and they are closely associated in a complex structure [31]. They contribute about 90% of the total bamboo mass. The minor components are pigments, tannins, protein, fat, pectin and ash. Others include resins, waxes and inorganic salts. These constituents play an important role in physiological activity of bamboo, and they are found in cell cavity or special organelles [15]. The chemical composition of bamboo is known to be similar to that of wood, but bamboo has

Li et al. [33] in their studies reported the chemical composition of bamboo fibre as shown in **Table 4**. Usually, there is variation in the chemical composition of bamboo depending on their age. Notably, cellulose content decreases with increase in age of bamboo. Different authors have investigated different species and bamboo parts. They include bamboo (Kumamoto, Japan) with cellulose content of 47%, hemicelluloses 23% and lignin 28% [9]; bamboo with cellulose 43%, hemicelluloses 15% and lignin 26% [34]; bamboo (Dendrocalamus sp.) with cellulose 47%, hemicelluloses 16% and lignin 18% [35]; bamboo with cellulose 44%, hemicelluloses 30% and lignin 26% [36]; Moso bamboo (*Phyllostachys pubescens* Mazel), with cellulose 46%,

.

for 2050 may get to 1017.64 Tg C [26] or reach 1138.8 Tg C [27].

species, reported that of bamboo to range from 5.9 to 49.5 Mg ha−1 year−1

a higher content of minor components compared with wood [32].

**Table 4.** Chemical composition of bamboo fibre [33].

Many research and technical works have been carried out on the chemical modification of bamboo fibres to improve their properties for specialised applications [43–46]. Chemical modification methods include alkali hydrolysis, acid hydrolysis, coupling, etc.

Alkali hydrolysis is a conventional technique. It is a chemical processing raw cellulose fibre to delignify and to remove the amorphous regions. It creates a rough fibre surface, activates hydroxyl groups and improves the fibre tensile strength. This process involves the initial use of an alkali solution (NaOH) to remove not only the cellulosic components but also the noncellulosic components such as hemicellulose, lignin and pectin inside the plant fibre [1]. The alkali-treated fibres are then passed through multi-phase bleaching. Most of the manufacturers use this process as it requires not only a little time to yield the bamboo fibres but also less economic means mainly when compared with mechanical methods. Kumar et al. [47] in their study, soaked bamboo strips in 4% NaOH for 72 h to extract the fibre. This method removed 38–42% of the polysaccharides and lignin from the bamboo chips. The obtained pulp was cooled, filtered and washed, and then further treated with glacial acetic acid. Sodium chlorite was occasionally used to bleach the fibre to white. The treated pulp was called bleached bamboo fibre. The problem with this method was that fibre bundles with diameters of 100 ± 10.4 μm were also formed during the extraction; therefore, the parameters were chosen to optimise separation of bamboo fibre by using a minimum amount of NaOH [48].

In an exciting study, Kumar et al. [49] reported that the characteristic properties of mercerised bamboo fibres used for the preparation of bamboo fibre-reinforced epoxy composites made the bio composites cost useful for dielectric applications. In another interesting study reported by Kumar and Kumar [50], alkali treatment of bamboo fibre further increased the tensile and flexural strength of bamboo-epoxy nanocomposites by 60 and 42%, respectively, as compared to pure composites.

Many researchers have worked on the physical, mechanical and thermal behaviour (weathering behaviour, % water uptake, % thickness swelling and thermal stability), morphology properties and impact test of bamboo fibres reinforced novolac resin composites prepared using mercerised bamboo fibres. They reported that the modification improved various features such as fine structure, impact strength, wetting ability, interfacial strength, mechanical properties, weathering and thermal properties of the composites [51–53]. The effect of acrylic acidgrafted bamboo rayon on the antibacterial activity of acrylic acid-grafted bamboo rayon silver nanoparticles has been reported [54]. Bamboo rayon-copper nanoparticle composite fabric was also prepared using acrylic acid-grafted bamboo rayon revealed antibacterial activity against both Gram-positive and Gram-negative bacteria, which was durable until 50 washings [55].

Liu et al. [64] developed and reported an efficient and eco-friendly technology for the improvement of interfacial adhesion of bamboo fibre-Unsaturated polyester (UPE) composites. A soybean oil-based monomer, acrylated epoxidised soybean oil (AESO) monomer was grafted onto the surface of bamboo fibre using 1,6-diisocyanatohexane (DIH) as a linker, and the attached C=C bonds participated in the crosslinking of UPE resins, thus forming chemical connections between the bamboo fibres and the UPE matrix. This resulted in significant improvements in both the static and dynamic mechanical properties of the composites by the improved interfacial adhesion. In addition, it significantly prevented the penetration and movement of water in

Bamboo, Its Chemical Modification and Products http://dx.doi.org/10.5772/intechopen.76359 31

the composites and resulted in reduced water uptake rates and diffusion coefficients.

cial adhesion between bamboo fibre and poly-(butylene succinate) [66].

exhibiting best overall properties [67].

Bamboo fibres could also be modified by atom transfer radical polymerisation (ATRP) technique. ATRP is a technique, which could allow the incorporation of polymers with predetermined molecular weight onto the surfaces of particles, fibres or membranes. It has been extensively studied for graft copolymerization of vinyl monomers onto fibres in a living/ controllable way [65]. This method has made the incorporation of poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) onto the surfaces of bamboo fibres to improve interfa-

Lu et al. [67] carried out a comparative study on the effect of alkali soaking, silane coupling agent and maleic anhydride grafting on the mechanical properties of cellulose/poly(l-lactic acid) composites. They reported that the modifications improved the mechanical properties of the cellulose/poly(l-lactic acid) composites by improving the interfacial adhesion of the cellulose fibre and the matrix. NaOH solution pre-treatment of cellulose provided the composites with the highest stiffness, KH560 modification resulted in best ductility. Maleic anhydride grafting onto poly(l-lactic acid) balanced the improvements of stiffness and ductility,

Silanes are recognised as efficient coupling agents that are used extensively in composites and adhesive formulations. Silane coupling agents have a hydrophilic structure with different groups attached to the silicon atoms that can act as a bridge; one end is interacting with the matrix and the other end reacting with the hydrophilic fibres [64]. The silane coupling treatment has been found to significantly improve the impact fatigue strength of the composites [66]. A functional silane was employed as a coupling agent to enhance the interfacial adhesion between bamboo fibre and polylactic acid [68]. The silane-treated bamboo fibre-reinforced polylactic acid composite showed excellent mechanical and thermal properties compared with the properties of polylactic acid composite containing delignified BF. It was thought that effective surface treatment from the silane coupling agent-improved adhesion between the polylactic acid matrix and the bamboo fibre. In another study, Kushwaha and Kumar [69] investigated the effect of silanes on the mechanical properties of bamboo fibre-epoxy composites. They prepared two sets of bamboo-epoxy composites, one with silane treatment bamboo mats and the other with silane treatment mercerised bamboo mats. The mechanical properties (tensile strength, elastic modulus, flexural strength and flexural modulus) observed that silane treatment improved the tensile and flexural strength, but the addition of silane treatment mercerised bamboo leads to significant reduction of the strength. Similarly, Kumar and Kumar [50] in their work confirmed that the alkali and silane treatments with nano-clay filler

improved the dielectric and mechanical properties of bamboo-epoxy composites.

In another study, the effects of alkaline and acetylating agents on the morphology of bamboo fibre-polypropylene were reported [56]. Their mechanical, thermal, rheological property, morphology and miscibility properties were extensively studied. The comparison of alkaline and acetylating treatments showed that the mechanical properties of bamboo fibre-polypropylene composites were improved and adhesion between bamboo fibre and polypropylene matrix was enhanced.

An HNO<sup>3</sup> -KClO<sup>3</sup> method has also been used to extract fibre from bamboo samples. Before the addition of KClO<sup>3</sup> , dry raw bamboo strands were immersed in a diluted nitric acid solution [57, 58]. After treating for 24 h at 50°C, the obtained bamboo fibre suspension was cooled then dialysed against distilled water to remove low molecular weight compounds. The slurry was then freeze-dried to obtain dry bamboo fibre.

He et al. [59] suggested a complicated method for obtaining bamboo fibre. Crude fibre bundles of bamboo, obtained by drawing bamboo chips roasted at 150°C for 30 min, were first immersed in water at 60°C for 24 h, and then air-dried before removing impurities further by repeated rolling. Subsequently, the fibre bundles were heated with 0.5% NaOH (w/v), 2% sodium sulphite, 2% sodium silicate and 2% sodium polyphosphate solutions for about 60 min at 100°C. The liquor-to-bamboo ratio was 20:1. After being washed with hot water, the fibres were treated with 0.04% xylanase and 0.5% DTPA (diethylene triamine pentaacetic acid) at 70°C for 60 min at a pH of 6.5. The fibres obtained were then heated for about 60 min at 100°C, except using 0.7% NaOH. In the bleaching step, the bamboo fibre was placed in a polyethylene bag with 4% H2 O2 , 0.2% NaOH and 0.5% sodium silicate for 50 min. The liquor ratio was 20, and the pH was maintained at 10.5. After treatment with 0.5% sulphuric acid solution for 10 min and then being emulsified for 5 days, refined bamboo fibre was obtained.

Maleic anhydride treatment has been reported to improve the mechanical (Modulus of elasticity and flexural modulus) as well as water-resistant properties (water uptake) of bamboo-epoxy composites [60]. The same trend in the properties of permanganate- and benzoylation-treated bamboo fibre polyester composites was observed [61]. In another study, the preparation of short bamboo fibre-reinforced polypropylene composites with various loadings percentages of chemically modified bamboo fibres was reported [62]. Maleic anhydride-grafted polypropylene was chosen, supported as a compatibiliser to improve adhesion between fibre and matrix.

Acrylonitrile treatment of bamboo fibre has been reported to improve the tensile, flexural and water absorption properties of acrylonitrile-treated bamboo fibre composites [49].

Anwar et al. [63] evaluated the effect of pressing time on physical and mechanical properties of phenolic-impregnated bamboo strips. The treatment of bamboo strips with low molecular weight phenol formaldehyde (LMwPF) resin followed by pressing at 140°C improved the dimensional stability and strength properties of the strips. The treatment improved water absorption, thickness swelling and linear expansion perpendicular to grain after 24 h of cold water soaking [63].

Liu et al. [64] developed and reported an efficient and eco-friendly technology for the improvement of interfacial adhesion of bamboo fibre-Unsaturated polyester (UPE) composites. A soybean oil-based monomer, acrylated epoxidised soybean oil (AESO) monomer was grafted onto the surface of bamboo fibre using 1,6-diisocyanatohexane (DIH) as a linker, and the attached C=C bonds participated in the crosslinking of UPE resins, thus forming chemical connections between the bamboo fibres and the UPE matrix. This resulted in significant improvements in both the static and dynamic mechanical properties of the composites by the improved interfacial adhesion. In addition, it significantly prevented the penetration and movement of water in the composites and resulted in reduced water uptake rates and diffusion coefficients.

nanoparticles has been reported [54]. Bamboo rayon-copper nanoparticle composite fabric was also prepared using acrylic acid-grafted bamboo rayon revealed antibacterial activity against both Gram-positive and Gram-negative bacteria, which was durable until 50 washings [55].

In another study, the effects of alkaline and acetylating agents on the morphology of bamboo fibre-polypropylene were reported [56]. Their mechanical, thermal, rheological property, morphology and miscibility properties were extensively studied. The comparison of alkaline and acetylating treatments showed that the mechanical properties of bamboo fibre-polypropylene composites were improved and adhesion between bamboo fibre and polypropylene matrix

[57, 58]. After treating for 24 h at 50°C, the obtained bamboo fibre suspension was cooled then dialysed against distilled water to remove low molecular weight compounds. The slurry was

He et al. [59] suggested a complicated method for obtaining bamboo fibre. Crude fibre bundles of bamboo, obtained by drawing bamboo chips roasted at 150°C for 30 min, were first immersed in water at 60°C for 24 h, and then air-dried before removing impurities further by repeated rolling. Subsequently, the fibre bundles were heated with 0.5% NaOH (w/v), 2% sodium sulphite, 2% sodium silicate and 2% sodium polyphosphate solutions for about 60 min at 100°C. The liquor-to-bamboo ratio was 20:1. After being washed with hot water, the fibres were treated with 0.04% xylanase and 0.5% DTPA (diethylene triamine pentaacetic acid) at 70°C for 60 min at a pH of 6.5. The fibres obtained were then heated for about 60 min at 100°C, except using 0.7% NaOH. In the bleaching step, the bamboo fibre was placed in a

ratio was 20, and the pH was maintained at 10.5. After treatment with 0.5% sulphuric acid solution for 10 min and then being emulsified for 5 days, refined bamboo fibre was obtained.

Maleic anhydride treatment has been reported to improve the mechanical (Modulus of elasticity and flexural modulus) as well as water-resistant properties (water uptake) of bamboo-epoxy composites [60]. The same trend in the properties of permanganate- and benzoylation-treated bamboo fibre polyester composites was observed [61]. In another study, the preparation of short bamboo fibre-reinforced polypropylene composites with various loadings percentages of chemically modified bamboo fibres was reported [62]. Maleic anhydride-grafted polypropylene was chosen, supported as a compatibiliser to improve adhesion between fibre and matrix.

Acrylonitrile treatment of bamboo fibre has been reported to improve the tensile, flexural and

Anwar et al. [63] evaluated the effect of pressing time on physical and mechanical properties of phenolic-impregnated bamboo strips. The treatment of bamboo strips with low molecular weight phenol formaldehyde (LMwPF) resin followed by pressing at 140°C improved the dimensional stability and strength properties of the strips. The treatment improved water absorption, thickness swelling and linear expansion perpendicular to grain after 24 h of cold

water absorption properties of acrylonitrile-treated bamboo fibre composites [49].

method has also been used to extract fibre from bamboo samples. Before the

, dry raw bamboo strands were immersed in a diluted nitric acid solution

, 0.2% NaOH and 0.5% sodium silicate for 50 min. The liquor

was enhanced.

addition of KClO<sup>3</sup>


30 Bamboo - Current and Future Prospects

polyethylene bag with 4% H2

water soaking [63].

then freeze-dried to obtain dry bamboo fibre.

O2

An HNO<sup>3</sup>

Bamboo fibres could also be modified by atom transfer radical polymerisation (ATRP) technique. ATRP is a technique, which could allow the incorporation of polymers with predetermined molecular weight onto the surfaces of particles, fibres or membranes. It has been extensively studied for graft copolymerization of vinyl monomers onto fibres in a living/ controllable way [65]. This method has made the incorporation of poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) onto the surfaces of bamboo fibres to improve interfacial adhesion between bamboo fibre and poly-(butylene succinate) [66].

Lu et al. [67] carried out a comparative study on the effect of alkali soaking, silane coupling agent and maleic anhydride grafting on the mechanical properties of cellulose/poly(l-lactic acid) composites. They reported that the modifications improved the mechanical properties of the cellulose/poly(l-lactic acid) composites by improving the interfacial adhesion of the cellulose fibre and the matrix. NaOH solution pre-treatment of cellulose provided the composites with the highest stiffness, KH560 modification resulted in best ductility. Maleic anhydride grafting onto poly(l-lactic acid) balanced the improvements of stiffness and ductility, exhibiting best overall properties [67].

Silanes are recognised as efficient coupling agents that are used extensively in composites and adhesive formulations. Silane coupling agents have a hydrophilic structure with different groups attached to the silicon atoms that can act as a bridge; one end is interacting with the matrix and the other end reacting with the hydrophilic fibres [64]. The silane coupling treatment has been found to significantly improve the impact fatigue strength of the composites [66]. A functional silane was employed as a coupling agent to enhance the interfacial adhesion between bamboo fibre and polylactic acid [68]. The silane-treated bamboo fibre-reinforced polylactic acid composite showed excellent mechanical and thermal properties compared with the properties of polylactic acid composite containing delignified BF. It was thought that effective surface treatment from the silane coupling agent-improved adhesion between the polylactic acid matrix and the bamboo fibre. In another study, Kushwaha and Kumar [69] investigated the effect of silanes on the mechanical properties of bamboo fibre-epoxy composites. They prepared two sets of bamboo-epoxy composites, one with silane treatment bamboo mats and the other with silane treatment mercerised bamboo mats. The mechanical properties (tensile strength, elastic modulus, flexural strength and flexural modulus) observed that silane treatment improved the tensile and flexural strength, but the addition of silane treatment mercerised bamboo leads to significant reduction of the strength. Similarly, Kumar and Kumar [50] in their work confirmed that the alkali and silane treatments with nano-clay filler improved the dielectric and mechanical properties of bamboo-epoxy composites.

Lee and Wang [70] used lysine-based diisocyanate (LDI) as a coupling agent for polylactic acid/bamboo fibre and poly(butylenes succinate)/bamboo fibre composites which improved their tensile and water resistance properties. Two novel bifunctional monomers, namely isocyanatoethyl-methacrylate and N-methylol acrylamide, have been used as the coupling agents to strength the interface of bamboo fibre/unsaturated polyester composites [71, 72].

of bamboo fibres as reinforcement in composite materials has been immensely amplified with high-tech revolution in recent years. This is as a response to the increasing demand for developing materials that are biodegradable, sustainable and recyclable [15]. Apart from the above, several other applications exist, though on a relatively small scale. For instance, there are some situations where bamboo is used as poles for aerial antenna, electrification, rafters, fishing traps, yam stakes, etc. Ladapo et al. [75] further reported that the current uses of bamboo in

Bamboo, Its Chemical Modification and Products http://dx.doi.org/10.5772/intechopen.76359 33

Besides its role as a raw material for consumer products, bamboo has enormous prospects for industrial utilisation and as industrial raw material. Industrial application of bamboo is in the

Bamboo is a good source of food particularly the shoot. It is a delicacy in Asia. In India, young and tender bamboo shoots are used as a seasonal vegetable in both rural and urban areas [78]. It has been reported to include natural products, such as potassium, carbohydrates, dietary fibres, vitamins and other active materials, which are used for traditional food in many countries [79] and further conversion of these carbohydrates, give rise to other products like xylitol. Figures of nutrient contents of *Bambusa vulgaris* show it to contain crude protein (10.1 g), crude fibre (21.7 g), ether extract (2.5 g), ash (21.3 g), phosphorous (86 mg), iron (13.4 mg),

Tea made from the bamboo leaf is rich in silica, which is important in bone and other rigid tissue health. Silica improves bone health, strengthens hair and nails, improves dental health and make the skin more elastic and healthy [80]. Bamboo leaf tea is a low-calorie health food, which is rich in protein and fibre, but free of caffeine. As many cups as possible can be taken as bamboo tea stimulates metabolism without side effects [3]. The common species of bamboo

Bamboo charcoal can be used in different industries including chemical, pharmaceutical and energy production industries (**Table 5**). Recent studies have shown that bamboo species are also a good source of quality activated carbon, which can find application in medicine, foods, chemical and metallurgical industries. Activated bamboo charcoal has found application in cleaning the environment, absorbing excess moisture and producing medicines [81]. Bamboo charcoal is generally used by goldsmith and in gardening to prevent moisture avail-

Bamboo charcoals are multi-functional materials pyrolysed from bamboo under anaerobic conditions. During this pyrolytic process, bamboo is converted to stable charcoal. It serves as a substitute for wood charcoal or mineral coal and has been reported to possess absorption capacity which is six times that of wood charcoal of the same weight [3, 14]. Hence, it is a suitable absorbent. Studies have also revealed their uses as absorbent for dyes [82–85], heavy metal [86, 87], organic pollutants [88] and other substances [89, 90]. Other applications include for purification of waters, soils and sediments contaminated by PAHs; for environmental protection and archi-

Nigeria represent only a fraction of economic activities in the country.

vitamin B1 (0.1 mg), vitamins B2 (2.54 mg) and carotene (12.3 mg)/100 g).

areas highlighted below:

**4.1. Bamboo human food products**

for this purpose are given in **Table 5**.

able to plants particularly in Japan [78].

tectural decorations [91] and as conductor and fuel [14].

**4.2. Bamboo charcoal**

A recently reported work reported an improved interfacial strength between poly(vinyl chloride) (PVC) and bamboo flour in PVC/bamboo flour composites using novel coupling agents [73]. One pot synthesis generated the coupling agents. The increased content of the coupling agents used increased the morphological and mechanical properties of composites. The result revealed that coupling agent enhanced the affinity between fibre and polyvinyl matrix by lowering down the interfacial tension. SEM studies carried out showed a better dispersion of fibre into the PVC matrix due to an increased amount of coupling agents used. The enhancement in mechanical properties was also an indication of strong bonding between matrix and bamboo fibre [73].

Dilute acid pre-treatment of bamboo shoots shell fibre (BSSF) and bamboo stem and leaf (BSL) have been investigated for xylose and glucose yields [42]. Pre-treatment of bamboo (*Dendrocalamus asper*) with dilute sulphuric acid before enzymatic hydrolysis process to produce fermentable sugars has also been investigated [38]. Dilute phosphoric acid pre-treatment of bamboo was also studied for producing dissolving pulp for textile utilisation [74].

Recently in another study, a solvent (concentrated phosphoric acid) and organic solvent (95% ethanol)-based lignocellulose fractionation (COSLIF) methods have been developed to pretreat bamboo [34].
