BIODEGRADABLE BLENDS OF CELLULOSE-ACETATE AND STARCH - PRODUCTION ANDPROPERTIES

Blends of cellulose acetate (2.5 degree of substitution) and starch we re melt processed and evaluated for mechanical properties, biodegradab ility during composting, and marine and soil toxicity. Formulations co ntaining, on a weight basis, 57% cellulose acetate (CA), 25% corn star ch (St) and 19% propylene glycol (PG) had mechanical propertiessimilar to polystyrene. Increasing plasticizer or starch content lowered tens ile strength. Simulated municipal composting of cellulose acetate alon e showed losses of 2-3 and 90% dry weight after 30 and 90 days, respec tively. CA/St/PG blends in both soil burial and composting experiments indicate that propylene glycol and starch are degraded first. Extende d incubations are required to detect losses from cellulose acetate. Ma rine toxicity tests using polychaete worms and mussels showed no toxic ity of cellulose acetate or starch. High doses had an adverse effect d ue 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, buttern ut squash, and plum tomatoes. The results indicate that CA/St blends h ave acceptable properties for injection-molded applications and are bi odegradable and nontoxic.