Physical, Mechanical, and Macromolecular Properties of Starch Acetate during Extrusion Foaming Transformation

Due to the transformation of starch acetate during extrusion, the functional properties of extruded starch acetate-based foams were significantly affected by the extrusion process parameters. To obtain the optimum functional properties as packaging materials, it was necessary to analyze the functional proprieties of extruded starch acetate foams based on the morphological properties after extrusion transformation. Corn starch acetate with degree of substitution (DS) of 2.30 and potato starch acetate with DS of 1.09 were extruded with 10, 15, and 20% ethanol in a twin screw extruder using screw speeds of 110, 130, and 150 rpm and barrel temperatures of 130, 150, and 170 C. A response surface design was applied to analyze the effects of ethanol content, screw speed, and barrel temperature on the physical properties (radial expansion ratio, unit and bulk densities, and water absorption index), mechanical properties (unit and bulk spring indices and compressibility), and macromolecular properties (scanning electron micrographs) of the extruded starch acetate foams. Ethanol content, barrel temperature, and screw speed had significant effects on the functional properties of extruded starch acetate foams. Because of the differences in molecular structure degradation in the corn and potato starch acetates, the functional properties of extruded corn starch acetate foams were higher than those of extruded potato starch foams. This was substantiated with significant macromolecular structural differences.