Preparation and characterization of biodegradable copolyester-starch basedfoams

Regular (25% amylose) and waxy corn starches blended to various ratios with Eastar Bio Copolyester (R) 14766 (EBC) were extruded into loose-fill foams using a twin screw extruder. Included in this study were two types of corn starch, three levels of EBC content, and three levels of starch moisture c ontent. Waxy starch produced foams with greater radial expansions and lower unit and bulk densities than regular starch. Regular starch foams had lowe r water solubility indices (WSIs) than waxy starch foams. Foams made of bot h types of starch possessed similar mechanical properties. No differences w ere observed in compressibilities and spring indices of either waxy or regu lar starch foams. Higher levels of EBC addition resulted in less radial exp ansion and higher unit and bulk densities. Foams made with 10% EBC had high er compressibility than foams containing 25% EBC. Spring indices of single- piece samples and compressibilities and spring indices of bulk samples were not affected by the differences in the level of EBC addition. At 19% and 2 2% of moisture contents, foams had greater radial expansion than at 25% moi sture content. Unit and bulk densities were not affected by variations in m oisture content. At 22% moisture content, a lower WSI of 18.5% was obtained . At 22% moisture content, softer foams were produced. At all three levels of moisture content, no differences were detected in the spring indices. (C ) 2001 Elsevier Science Ltd. All rights reserved.