Biodegradation of Thermoplastic Starch and its Blends with Poly(lactic acid) and Polyethylene: Influence of Morphology

The room temperature mineralization of thermoplastic starch (TPS) with a high glycerol content and its blends with low-density polyethylene (LDPE) and polylactic acid (PLA) are examined under controlled degradation conditions. These results are correlated with the morphologies and continuity behavior of the various blend systems. It is found that thermoplastic starch degrades more rapidly than native starch. Lowering the glycerol content in the TPS has virtually no effect on its biodegradation behavior. The only contribution to biodegradation of the TPS blend is from the TPS component. Blending TPS with LDPE and PLA in a co-continuous morphology at a 50/50 composition provides a significant increase in TPS surface area, which increases the biodegradation rate for the blends as compared to pure TPS. The results indicate a close relationship between morphology, phase continuity, and biodegradation behavior.