Mechanical stability and biodegradability balance of wood fiber reinforced soybean protein composites

In this article, a series of green composites were fabricated using thermal-acid modified soybean protein and wood flour in the presence of various crosslinkers, including glyoxal, polyisocyanate, glyoxal-polyisocyanate combination, epoxy latex, and modified polyamide. The mechanical stabilities (mechanical properties and water resistance) of the wood fiber reinforced soybean protein composites were evaluated. Moreover, the biodegradation behaviors of the composites under 16 weeks of natural soil burial conditions were systematically investigated in terms of weight loss, tensile strength loss, and surface morphology change. The mechanical stabilities improvement mechanism and natural soil burial degradation characteristics of the composites were proposed, revealing the balance of mechanical stability and biodegradability of wood fiber reinforced soybean protein composites can be achieved via tailoring protein-crosslinker-protein and protein-crosslinker-wood chemical linkages to proper chemical crosslinking efficiency. Among the five evaluated crosslinkers, modified polyamide prepared composites exhibited the best mechanical stability with dry state tensile strength of 32.77 MPa and accelerated aging tensile strength of 19.61 MPa, and an acceptable biodegradation rate with a weight loss of 29.28% after degradation for 16 weeks. Overall, this study provides a promising way to prepare soybean protein-based biocomposites for short-term disposal or long-term duration applications. POLYM. COMPOS., 40:1228–1238, 2019.