**Abstract**

Foamed polymers are future materials, considered "green materials" due to their properties with very low consumption of raw materials; they can be used to ameliorate appearance of structures besides contributing for thermal and acoustic insulation. Nevertheless, waste disposal has generated about 20–30% of total of solid volume in landfills besides prejudicing flora and fauna by uncontrolled disposal. The development of biodegradable polymers aims to solve this problem, considering that in 2012, bio-plastics market was evaluated in 1.4 million tons produced and in 2017 attained 6.2 million tons. Biodegradable polymers as poly(lactic acid) (PLA) and poly(butylene adipate-*co*-terephthalate) (PBAT) are thermoplastics which can be processed using the most conventional polymer processing methods. PLA is high in strength and modulus but brittle, while PBAT is flexible and tough. In order to reduce interfacial tension exhibited by PLA/PBAT blends, it was used as compatibilizing agent 5 phr of PLA previously gamma-radiated at 150 kGy. Ionizing radiation induces compatibilization by free radicals, improving the dispersion and adhesion of blend phases, without using chemical additives and at room temperature. As a reinforcement agent, calcium carbonate from avian eggshell waste was used, at 10 ph of micro particles, 125 μm. Admixtures were further processed in a singlescrew extruder, using CO2 as physical blowing agent (PBA). Property investigations were performed by DSC, TGA, XRD, SEM, FTIR, and mechanical essays.

**Keywords:** PBAT/PLA foams, eggshells, PBA, gamma radiation, compatibilization

#### **1. Introduction**

Natural polymers, biopolymers, and synthetic polymers based on annually renewable resources are the basis for the twenty-first-century portfolio of sustainable, eco-efficient plastics. The interest on these polymers is considerable, due to a decrease of world resources in oil; in addition, there is a concern to limit the plastics' contribution to waste disposal. The degree of concern has been [1–8] raised along with the development in urbanization. The development of biodegradable polymers generally catches the attention of researchers due to environmental problems associated with the disposal of petroleum-based polymers.

The depletion of petroleum resource led to considerable research efforts on the development of biodegradable polymeric materials. Biodegradable polymers offer a great variety of advantages to environmental conservation; based on their nonharmful effects, they can be classified into two major categories: natural polymers and synthetic polymers; polymers obtained basically from renewable sources are a new generation of material capable to significantly reduce the environmental impact in order to achieve certain technical requirements besides being fully biodegradable. In addition, natural polymer-based materials offer a feasible alternative to the traditional polymeric materials when recycling of synthetic polymer is not cost-effective or technically impossible [9–15].

Poly(butylene adipate-*co*-terephthalate) (PBAT) is an aliphatic-aromatic random co-polyester, fully biodegradable, and prepared from 1,4–butanediol, adipic acid, and terephthalic acid: a synthetic polymer based on fossil resources, 100% biodegradable, with high elongation at break, and very flexible [16]. PBAT is an elastomeric polymer intended to improve mechanical properties; it can be used in several applications, such as, packaging materials, hygiene products, biomedical fields, and industrial composting, among others [17–21]; nevertheless, PBAT has poor thermal and mechanical properties, which can be overcome through the addition of fillers; in addition, it is a versatile polymer that allows the manufacturing from films up to shaped devices, and it can be used in food and dairy industries as well in hygiene packing [22, 23].

Polylactide or poly(lactic acid) (PLA) is the front-runner in the emerging bioplastics market with the best availability and the most attractive cost structure: PLA is a linear, aliphatic thermoplastic polyester, used for different applications ranging from medical to packaging, resorbable, and biodegradable under industrial composting conditions [24]. Therefore, its rheological properties, especially its shear viscosity, have important effects on thermal processes. Despite all its advantages, some properties of PLA such as inherent brittleness, low toughness, slow crystallization, poor melt strength, narrow processing window, and low thermal stability, besides high cost, pose considerable scientific challenges that limit their large-scale applications (film blowing, injection molding, and foaming) [25–27].

So, combining the high toughness of PBAT and the relatively low price of PLA can result in a novel blend. PLA was blended with PBAT flexible polymer, considering its high toughness and biodegradability. Poly(lactic acid) (PLA) and poly(butylene adipate-*co*-terephthalate) (PBAT), both biodegradable aliphatic polyesters, semicrystalline, and thermoplastic, can be processed by conventional methods. Their resulting blends provide interesting materials for industrial and hygiene packaging applications, due to their increased ductility in function of PBAT content.

PLA and PBAT binary blends exhibited improved properties concerned with higher elongation at break but lower tensile strength and modulus than pure PLA. Therefore, the addition of filler to PLA/PBAT blends led to a modulus approaching that of pure PLA.

In this paper bio-calcium carbonate from avian egg shells was used. Daily, tons of chicken eggshells are discarded, generating commercially devalued waste from restaurants, food industry, and homes. Currently, egg production throughout the world is 65.5 million metric tons per year, with Asia as a key contributor to global egg output growth [28]. The eggshell is rich in calcium carbonate, a natural bioceramic composite with a unique chemical composition of high inorganic (95% of calcium carbonate in the form of calcite) and 5% of organic (type X collagen,

**141**

*Study of Bio-Based Foams Prepared from PBAT/PLA Reinforced with Bio-Calcium Carbonate…*

sulfated polysaccharides) components; this eggshell characteristic structure combined with substantial availability makes eggshells a potential source of bio-fillers

Unfortunately, PLA/PBAT blends filled with calcium carbonate (CaCO3) have poor mechanical properties due to the poor interfacial adhesion. Many polymers are immiscible and form heterogeneous systems when blended. In order to cope with this problem, irradiation was used to improve the compatibility between immiscible polymers in a blend. In comparison with other methods of compatibilization based on the reactivity of functional groups grafted on the polymer backbone, the changes are not limited to the interface. Irradiation leads to changes not only in the interphase but also in the bulk of both polymers (chain scission, crosslinking, etc.). Therefore, it is very difficult to determine whether macroscopic properties change due to the compatibilizing effect of irradiation or due to modification of the polymers in bulk. A great number of authors working on irradiated immiscible polymer blends claim in their articles to have increased the compatibility between the two polymers just considering mechanical properties. Compatibilization is essential in order to decrease interfacial tension exhibited by PLA/PBAT blends: herein it was used as compatibilizing agent of PLA previously gamma-radiated at 150 kGy,

ionizing radiation in replacing chemical compatibilizing agents for thermoplastic

Foam technology has been developing since 1930, using blowing agents in polymer processing. Polymer foams consist of two phases: a polymeric matrix and entrapped, well-dispersed cells generated by blowing agents. Foams have several advantages: low density, insulating capability, energy absorption, etc. These make foams a desired product in many applications such as packaging, floating materials, paddings, shields for reducing noise, shoes, etc. Foam density varies across a wide

to near thousands kg/m3

as a physical blowing agent (PBA): it has a regular solubility and is considered as an eco-friendly gas. A PBA is capable to produce a cellular structure via foaming process, and it is typically applied when blown material is in liquid stage. Cellular structure in a matrix reduces density, increasing thermal and acoustic insulation

The proposal of the present work is the development of biodegradable foams from PBAT/PLA blends, reinforced with bio-calcium carbonate from avian eggshells, 125 μm particle size, compatibilized with PLA gamma-radiated at 150 kGy, and further assessed for DSC, TGA, XRD, SEM, FTIR, and mechanical essays.

PLA and PBAT polymers, with main characteristics described in **Table 1**. Both PLA and PBAT were dried at 70°C for 12 h before processing. PLA, irradiated in a Cobalt-60 source, 150 kGy, 10.5 kGY h<sup>−</sup><sup>1</sup>

multipurpose reactor, in CTR/IPEN, Instituto de Pesquisas Energéticas e Nucleares,

Calcium carbonate (CaCO3) from avian eggshells: white chicken eggshells were subjected to a thorough cleaning using tap water for removing of internal membranes. Afterward, clean eggshells were kept for 4 h in a 100°C water bath

Carbon dioxide (CO2): physical blowing agent, selected according to good diffu-

. Güven and collaborators have proposed the use of

[39]. Carbon dioxide was used

dose ratio, at

*DOI: http://dx.doi.org/10.5772/intechopen.85462*

air environment, 10.5 kGy h<sup>−</sup><sup>1</sup>

range from several kg/m3

**2. Experimental section**

sion in PLA foaming [42].

[40, 41].

**2.1 Materials**

São Paulo.

materials with enhanced properties [30–38].

that can be efficiently used for polymer composites [29].

#### *Study of Bio-Based Foams Prepared from PBAT/PLA Reinforced with Bio-Calcium Carbonate… DOI: http://dx.doi.org/10.5772/intechopen.85462*

sulfated polysaccharides) components; this eggshell characteristic structure combined with substantial availability makes eggshells a potential source of bio-fillers that can be efficiently used for polymer composites [29].

Unfortunately, PLA/PBAT blends filled with calcium carbonate (CaCO3) have poor mechanical properties due to the poor interfacial adhesion. Many polymers are immiscible and form heterogeneous systems when blended. In order to cope with this problem, irradiation was used to improve the compatibility between immiscible polymers in a blend. In comparison with other methods of compatibilization based on the reactivity of functional groups grafted on the polymer backbone, the changes are not limited to the interface. Irradiation leads to changes not only in the interphase but also in the bulk of both polymers (chain scission, crosslinking, etc.). Therefore, it is very difficult to determine whether macroscopic properties change due to the compatibilizing effect of irradiation or due to modification of the polymers in bulk. A great number of authors working on irradiated immiscible polymer blends claim in their articles to have increased the compatibility between the two polymers just considering mechanical properties. Compatibilization is essential in order to decrease interfacial tension exhibited by PLA/PBAT blends: herein it was used as compatibilizing agent of PLA previously gamma-radiated at 150 kGy, air environment, 10.5 kGy h<sup>−</sup><sup>1</sup> . Güven and collaborators have proposed the use of ionizing radiation in replacing chemical compatibilizing agents for thermoplastic materials with enhanced properties [30–38].

Foam technology has been developing since 1930, using blowing agents in polymer processing. Polymer foams consist of two phases: a polymeric matrix and entrapped, well-dispersed cells generated by blowing agents. Foams have several advantages: low density, insulating capability, energy absorption, etc. These make foams a desired product in many applications such as packaging, floating materials, paddings, shields for reducing noise, shoes, etc. Foam density varies across a wide range from several kg/m3 to near thousands kg/m3 [39]. Carbon dioxide was used as a physical blowing agent (PBA): it has a regular solubility and is considered as an eco-friendly gas. A PBA is capable to produce a cellular structure via foaming process, and it is typically applied when blown material is in liquid stage. Cellular structure in a matrix reduces density, increasing thermal and acoustic insulation [40, 41].

The proposal of the present work is the development of biodegradable foams from PBAT/PLA blends, reinforced with bio-calcium carbonate from avian eggshells, 125 μm particle size, compatibilized with PLA gamma-radiated at 150 kGy, and further assessed for DSC, TGA, XRD, SEM, FTIR, and mechanical essays.
