Deterioration of Starch-Plastic Composites in the Environment

Abstract

The rate and extent of deterioration of starch-plastic composite and control plastic films were determined for films weathered in landfill, compost, soil, seawater and the strawline of a marsh. Films were placed in the exposure sites during the Spring of 1989 and sampled over a 28 month period. Environmental conditions at each exposure site were determined during each sampling event. Following placement, deterioration of the starch-plastic composite and control plastic films was determined by measuring changes in tensile properties, weight, starch content and morphology.

Results showed that the rate of degradation of the starch-plastic composite films varied when weathered in different environmental settings. Rapid degradation and fragmentation of the films in the strawline of a marsh was primarily attributed to photodegradation. Lesser degradation was measured for films placed in compost, landfill, soil and seawater. Starch loss was measured for starch-plastic composite films in each of the exposure sites. The rate of starch loss decreased with time. With the exception of films in the strawline, the starch-based films did not fragment or lose mass during two years of weathering. Although starch-plastic composite films are designed to deteriorate primarily through the actions of microorganisms, deterioration of these films is a result of the interaction of biological, chemical and physical processes.