Preparation and characterization of starch-based composite foams

Abstract

Starch-based composite foams were prepared by baking a mixture of starch and a synthetic biodegradable polymer (i.e., poly (vinyl alcohol), poly (lactic acid), and poly (e-caprolactone) in a hot mold. This process can be used to prepare a thin walled object, such as a plate. Scanning electron micrographs of the cross-sectional view of the foams showed that the cellular size is very dense in the outer layer and less dense in the inner layer. The effects of relative humidity, storage time, the presence of synthetic biodegradable polymers, and the presence of plasticizers (i.e., glycerol, urea, and ammonium chloride) on tensile and flexural properties were investigated. For all formulations, the amount of relative humidity which gave the maximum value of the ultimate strength of the foams was 42%, while the storage time which gave the maximum value of the ultimate strength of the foams was 2 days (only tested for a fixed relative humidity of 42%). Addition of the synthetic biodegradable polymers improved the ultimate strength and the elongation at break of the foams. Increasing the plasticizer contents increased the elongation at break at the expense of the ultimate strength. Water absorption and biodegradability of the foams were also studied. Increasing the synthetic biodegradable polymer contents increased the water resistivity of the foams. Enzymatic degradation tests showed that the foams were degraded by enzyme α-amylase.