Abstract
Starch acetates having degrees of substitution (DS) 1.5, 2.0 and 2.5 were prepared by the reaction of high-amylose cornstarch with acetic anhydride and aqueous sodium hydroxide. Differential scanning calorimetry studies revealed that water was an effective plasticizer for the starch acetates. Glass transition temperatures ( T g) of dry starch acetates (165–185 °C) were lowered to 35–95 °C in the presence of excess moisture. Extrusion of DS 2.5 starch acetate containing 15% moisture at 150 °C gave an expanded, water-resistant foam. The foam had a higher bulk density, higher compressive strength and lower resiliency than polystyrene foam. Little degradation of the starch acetate occurred during extrusion. Possible uses for starch acetate foam include seedling containers, soil drainage aids and food packaging/serving.
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