Biocomposites from Renewable Resources

Keywords

Biocomposite • Renewable resource • Agricultural byproduct • Matrix • Rein­forcement • Synthetic biopolymer • Protein • Matrix

The term “biocomposites” has been widely used to denote composites that are made using either the matrix or reinforcement or both from renewable resources that are biodegradable. Conventionally, biocomposites were developed using natural cellu­lose fibers such as jute and flax as reinforcement to replace glass fibers with polypropylene, polyethylene, epoxy, and other synthetic polymer-based matrices. The advent of biopolyesters such as poly(lactic acid) and poly(hydroxy alkoanates) led to a quantum jump in the research on developing biocomposites using both the matrix and reinforcement from renewable resources. In addition, efforts were made to utilize agricultural by-products such as corn stover, wheat straw, and coir fibers as reinforcement resulting in inexpensive and renewable composites. However, biopolyesters such as poly(lactic acid) are considerably more expensive and also do not have the performance properties comparable to that of the traditional synthetic polymers such as polypropylene and polyethylene. Therefore, resins/matrices have also been developed from agricultural byproducts. For instance, soy proteins and wheat gluten have been used as matrix in their native form and also after various chemical modifications.

There is an infinite amount of literature on biocomposites and it is not feasible to provide an exhaustive review of available literature in one part. Several authorita­tive books on biocomposites have been published. The focus of this part is to provide an overview of the possible sources and properties of biocomposites developed using renewable resources that have been covered in the previous parts. Particular emphasis has been on completely biodegradable composites but some examples of composites containing either the matrix or reinforcement obtained for renewable resources have also been included for illustrative purposes. In some cases, the reinforcing fibers have been derived from renewable and biodegradable agricultural residues but have been combined with traditional syn­thetic polymers. Similarly, composites have been developed by directly blending agricultural residues such as corn stover or wheat straw into synthetic polymer or protein-based matrices that have been derived from renewable resources. Such literature has also been reviewed. Overall, the purpose of this part is to provide an overview of the composites developed from agricultural by-products and coproducts and the properties and potential applications of such composites.

Although efforts have been made to divide the part into clear and distinct chapters, some overlap is inevitable. For instance, lignocellulosic fibers have been used as reinforcement with both synthetic polymers and biodegradable polymers as matrix. Therefore, some of the reinforcement and matrix materials have been covered in multiple chapters but the literature reported has not been duplicated.