Protein-based materials biodegradable plastics

The over growing environmental pressure caused by the wide spread consumption of petroleum based polymers and plastics has hastened the development of biodegradable and environmentally acceptable materials. Biopolymers derived from various natural resources such as proteins, cellulosics, starch and other polysaccharides are regarded as the alternate materials. Biodegradable polymeric materials derived from renewable sources are the most promising materials because of their easy availability and cost effectiveness. Biodegradable modified polysaccharides have been found to possess varied applications such as salt resistant absorption of water [109]. 

Soy protein-based plastics are another group of biodegradable, environmentally friendly, polymer materials from an abundantly renewable resource [29-31]. There are several types of soybean products that can potentially be utihzed for engineering structural applications [29],... 

Until recently, the ordy uses and apphcations for proteins were in food sciences [55]. The development of studies on non-food uses of agricultiual raw materials initiated an interest in protein-based plastics. A number of proteins of plant origin have received attention for the production of biodegradable polymers. These proteins are com zein, wheat gluten, soy protein, and sunflower protein. 

Soy protein-based green composites are not only applied as an environmental friendly material in the fields of adhesives (Kumar et al. 2002), plastics (Kumar et al. 2011), and textile fibers (Kobayashi et al. 2014), but also as biodegradable membranes (Mamthi et al. 2014). Furthermore, the nutritional and health benefits of soy protein draw attention to the application in the field of biomedical materials (Silva et al. 2014), such as tissue engineering scaffolds (Chien and Shah 2012),... 

Since the 1980s, the number of academic research programmes and industrial research and development projects on protein-based bioplastics have increased exponentially, as a result of the present interest in using some field crops for renewable and biodegradable materials for non-food applications, and also in order to explore the unique specific properties of proteins. The complexity of proteins and the diversity of their different fractions can be tapped to develop materials with original functional features that differ markedly from those of standard synthetic plastic materials. Apart from the previously mentioned proteins. 

Guilbert, S. (2002) Protein-based Bio-Plastics formulation, thermoplastic processing and main applications International Congress Trade Show The Industrial Applications of Bioplastics, 3rd, 4th and 5th February Gunatillake P.A. and Adhikari R. (2003) Biodegradable synthetic polymers for tissue engineering , European Cells and Materials, 5, 1-16. 

Among the different categories of biodegradable plastics obtained from agropolymers, both starch/polyesters blends and microbial biodegradable plastics satisfied the majority of requirements asked by the plastic packaging industries (material qualities, processability, performances, etc.). Other bioplastics based on natural polysaccharides or proteins are mainly interesting for their low cost but their non-reproduetive quality and lower performances are still a handicap. 

Biodegradable plastics based on soy protein were prepared with glycerol as a plasticizer and compounded wi different additives such as polycaprolactone and zinc stearate as well as heat treated at various temperatures after the injection molding process in order to characterize base material strength and the effect of water absorption. The results indicated that the polycaprolactone and, respectively a medium to high heat treatment enhanced the tensile strength and decreased the water absorption significantly. 

The book addresses the most important biopolymer classes like polysaccharides, lignin, proteins and polyhydroxyalkanoates as raw materials for bio-based plastics, as well as materials derived from bio-based monomers like lipids, poly(lactic acid), polyesters, polyamides and polyolefines. Additional chapters on general topics - the market and availability of renewable raw materials, the importance of bio-based content and the issue of biodegradability - will provide important information related to all bio-based polymer classes. 

Proteins are natural, renewable, and biodegradable polymers which have attracted considerable attention in recent years in terms of advances in genetic engineering, eco-friendly materials, and novel composite materials based on renewable sources. This chapter reviews the protein structures, their physicochemical properties, their modification and their application, with particular emphasis on soy protein, zein, wheat protein, and casein. Firstly, it presents an overview of the structure, classification, hydration-dehydration, solubility, denaturation, and new concepts on proteins. Secondly, it concentrates on the physical and chemical properties of the four important kinds of proteins. Thirdly, the potential applications of proteins, including films and sheets, adhesives, plastics, blends, and composites, etc. are discussed. 

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