Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 8, 1995
Publication Date: N/A
Interpretive Summary: There is considerable demand for environmentally friendly biodegradable plastic items such as cups, plates and packaging. Currently, such items are made from non-degradable, petroleum based materials which accumulate in landfills. Cornstarch can be processed into plastic-like articles but these have poor resistance to water. This paper describes a rapid method for preparing starch acetate, a chemically modified starch having much improved water resistance. It was shown that addition of a small amount of water to the starch acetate made the mixture flowable at high temperatures commonly used in plastic processing equipment. This allowed preparation of extruded, water-resistant foams. These findings could lead to increased utilization of cornstarch in biodegradable products and stimulate further research in industry and academia.
Technical Abstract: Starch acetates having degree of substitution (D.S.) 1.5, 2.0 and 2.5 were prepared by 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 (Tg) of dry starch acetates (165-185 deg C) were lowered to 95-35 deg C in the presence of excess moisture. Extrusion of D.S. 2.5 starch acetate containing 15% moisture at 150 deg 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.