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Selected Functional Properties of Extruded Starch Acetate and Natural Fibers Foams

¹University of Nebraska Industrial Agricultural Products Center, 208 L.W. Chase Hall, Lincoln, NE 68583-0730. ²Banner Pharmacaps, Inc., High Point, NC 27265. ³Corresponding author. Phone: 402-472-1634. Fax: 402-472-6338. E-mail: mhanna1@unl.edu

Response surface methodology was employed to study the functional properties of starch acetate foams blended with 0, 7.5, and 15% wood, oat, and cellulose fibers. The blends were extruded with 14, 17, and 20% ethanol as a blowing agent, using a twin-screw extruder with 160°C barrel temperature and 225 rpm screw speed. Physical characteristics of the extrudates including radial expansion ratio, unit density, and bulk density; and mechanical properties including unit spring index and bulk spring index were determined. Scanning electron micrographs were taken to observe foam cell textures. Higher fiber content resulted in lower radial expansion. Ethanol content had a positive effect on foam expansion. Higher expansion was obtained in starch acetate-cellulose foams because better starch acetate-fiber matrix was formed. Mechanical properties increased with higher fiber and ethanol contents. Micrographs showed that uniform cell structures were associated with better mechanical properties.