A review on completely biodegradable composites developed using soy-based matrices

Considerable efforts have been made to develop biocomposites that can replace the non-biodegradable synthetic polymer-based composites. Most often, composites are made using either the matrix or reinforcement derived from renewable resources, but are still referred to as biocomposites. However, the biodegradability of such composites, especially those containing synthetic polymers as matrices, is questionable. Attempts have also been made to develop completely biodegradable composites that contain both the matrix and reinforcement from renewable and biodegradable sources. Composites containing biopolymers as matrix have shown to have good tensile and flexural properties but typically fail to have adequate resistance to moisture leading to poor performance at high humidity or aqueous conditions. Among the various biopolymer matrices used, soy-based matrices are extensively studied due to the abundant and low cost availability of coproducts. Soy proteins, soy concentrate, soy flour and soy oil obtained as coproducts of soybean processing have been studied as possible matrices for composites in their native form and also after chemical and physical modifications. Although extensively studied, information on composites containing soy-based matrices is incoherent and the suitability of the composites developed for practical applications is not clear. This review provides an overview of the literature available on composites developed using thermoplastic soy-based resins, properties of such composites and their limitations and future potential.