Biodegradable plastic composites from corn gluten meal

BACKGROUND: Utilisation of naturally occurring polymers as substitutes for non-biodegradable synthetic polymers derived from non-renewable resources is a key component of sustainable polymer technology. The aim of this study was to make thermoformable, biodegradable plastics from protein-rich corn gluten meal (CGM) in combination with a synthetic biodegradable polyester. RESULTS: CGM plasticised with 1,2-propylene glycol was blended at 150 degrees C with Skygreen SG100 aliphatic polyester and wood fibre, and injection moulded to give composites with tensile strength and water resistance superior to those of the protein component of CGM. Experimental design software was used to generate composite formulations with the limits (component, proportion as wt%) plasticised CGM (A), 10-80; Skygreen SG100 (B), 10-85; wood fibre (C), 0-10. Composites with A:B:C = 10:80:10 and A:B:C = 15:85:0 showed a glass transition at -20 degrees C associated with the SG100 component; composites with more than 15 wt% CGM showed an additional glass transition for the plasticised CGM component. SG100 imparted water resistance and tensile strength, while CGM and wood fibre increased tensile modulus. CONCLUSION: The low-cost industrial by-product CGM, derived from an abundant renewable resource, can be incorporated into SG100 to give readily biodegradable, thermoformable materials. Composites with up to 30 wt% CGM have moderately high tensile strength, elongation at break and water resistance. (C) 2007 Society of Chemical Industry