Wheat gluten (WG) is the protein extracted from wheat flour and normally manufactured as an industrial by-product. WG is found to possess reasonable mechanical properties when processed into biodegradable plastic and thus has the potential to substitute some petroleum-based non-degradable plastics and composites matrix. Nevertheless, application of WG biodegradable plastics is restricted by two major disadvantages: brittleness and high water absorption. Brittleness causes WG materials to fail at strains as low as 1%, and high water absorption softens WG when exposed to water. In the current study, anhydride functionalized macromolecular cross-linkers are developed to construct a new intermolecular network structure that is able to efficiently blunt crack propagation to improve WG mechanical performance. Rubbery cross-linkers, such as polyethyl acrylate-co-maleic anhydride (PEA-MA), blunt crack propagation and have strong energy damping capabilities, leading to a large improvement in mechanical properties. Meanwhile, the network structure restricts WG from swelling to reduce the high water absorption. Characterization techniques, such as FTIR, DSC, TGA, SE-HPLC, DMA, NMR, and mechanical testing are performed to determine the new molecular structure, energy damping and performance of the WG. Among all the blends, WG/PEA-MA achieves so far the highest mechanical properties in the field, with strength, strain, and toughness improved by 110%, 255%, 880%, respectively, and water absorption ratio is greatly reduced from 115% to 50%. WG/PEA-MA blend has mechanical performance better than polystyrene, therefore making it promising for applications such as non-degradable plastics and composite matrices.
