Submitted to: Journal of Environmental Polymer Degradation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 1996
Publication Date: N/A
Interpretive Summary: Starch is one of the most abundant and low cost (about 10 cents/lb) polymers available. The use of cornstarch as a raw material for developing biodegradable plastic products has created new and expanded markets for this commodity. A major problem which impedes the use of starch in plastic formulations is its poor physical and water resistance properties. In order to obtain commercially acceptable starch products, starch must be modified or blended with other materials to improve its physical properties and to minimize its water sensitivity. This report describes the use of a chemical (hexamethoxymethylmelamine) to product crosslinked starch-polyvinyl alcohol films with greatly improved physical and water resistance properties. This report provides knowledge useful for starch-based plastic manufacturers on how to enhance starch compatibility with other natural and synthetic polymers and to design starch-based composite materials with controlled biodegradability.
Starch-PVOH cast films were prepared with and without crosslinking agent (hexamethoxymethylmelamine) in the absence of plasticizer. Moisture absorption in films without crosslinking agent at low relative humidity was similar to that of PVOH and increased as the relative humidity increased. Films with crosslinking agent showed moisture absorption linearly proportional to the relative humidity. Significant improvement in resistance to water disintegration for crosslinked starch-PVOH films was observed. While tensile strength decreased and increased relative humidity, crosslinking significantly improved the tensile strength. Increased PVOH content improved elongation of films even when the relative humidity was 80% or higher. Biodegradation studies revealed that the degradation rate was negatively correlated with PVOH content in films and crosslinking generated more converged degradation curves.