Functional properties of extruded foam composites of starch acetate and corn cob fiber

Abstract

With increasing concerns about environmental protection and garbage handling, natural renewable materials such as starch, cellulose and other natural fibers become more and more popular in packaging materials manufacturing. In this study, physical and mechanical properties of extruded foam composites, prepared from starch acetate and cellulose/corn cob, were evaluated. A split-plot experimental design was used to compare selected functional properties of foams produced from starch acetate blended with ground corncobs, compared to blending with cellulose, and with different ethanol contents. Extrusions were conducted in a twin-screw extruder with 160 °C barrel temperature and 225 rpm screw speed. Physical properties of extrudates were measured including radial expansion ratio, unit density, bulk density, and water absorption index. Mechanical properties including unit spring index, bulk spring index, and compression strength were measured. Scanning electron microscopy was used to compare the macromolecular structures of the two types of starch acetate blends. Blending with corncobs significantly hindered radial expansion of starch acetate foams, whereas cellulose did not affect expansion significantly. Higher compression strength was obtained with higher corncob content. Although ethanol penetration assisted in the formation of a starch acetate–fiber matrix, corncob blends produced inferior linkages and cell development in the foams than foams produced with cellulose blends.