BIODEGRADABLE BLENDS OF CELLULOSE-ACETATE AND STARCH - PRODUCTION AND PROPERTIES

Blends of cellulose acetate (2.5 degree of substitution) and starch were melt processed and evaluated for mechanical properties, biodegradability during composting, and marine and soil toxicity. Formulations containing, on a weight basis, 57% cellulose acetate (CA), 25% corn starch (St) and 19% propylene glycol (PG) had mechanical propertiessimilar to polystyrene. Increasing plasticizer or starch content lowered tensile strength. Simulated municipal composting of cellulose acetate alone showed losses of 2-3 and 90% dry weight after 30 and 90 days, respectively. CA/St/PG blends in both soil burial and composting experiments indicate that propylene glycol and starch are degraded first. Extended incubations are required to detect losses from cellulose acetate. Marine toxicity tests using polychaete worms and mussels showed no toxicity of cellulose acetate or starch. High doses had an adverse effect due to oxygen depletion in the marine water due to rapid biodegradation of the polymers. Preliminary plant toxicity tests of the CA/St blends showed no negative impact on growth and yield for sweet corn, butternut squash, and plum tomatoes. The results indicate that CA/St blends have acceptable properties for injection-molded applications and are biodegradable and nontoxic.