Characteristics of biodegradable Mater-Bi (R)-starch based foams as affected by ingredient formulations

Expanded polystyrene (EPS) foams are widely used to provide protection to m erchandise during shipping and handling. The disposal of EPS foams, however , causes pollution to the environment. Starch based loose fill packaging fo ams are commercially available to replace the EPS foams. Starch foams disso lve readily in water, and do not possess satisfactory physical and mechanic al properties. To improve the functional properties and water resistance of starch foams, regular (25% amylose) and waxy corn starches blended with Ma ter-Bi-(R) ZF03U (MBI) were extruded into loose-fill packaging foams using a co-rotating twin screw extruder. MBI contents of 10, 25 and 40% and starc h moisture contents of 19, 22 and 25% (d.b.) were used. Waxy starch produce d foam with greater radial expansion and lower unit and bulk densities than regular starch. Higher levels of MBI reduced radial expansion and increase d unit and bulk densities. Foam made with regular starch had a lower water solubility index than foam made with waxy starch. The addition of MBI impro ved the water solubility. Higher starch moisture contents increased foam wa ter solubility indices. Foams made from both types of starch possessed acce ptable mechanical properties. Regular starch produced more rigid foams than the waxy starch as indicated by the higher compressibility values based on both single-piece and bulk samples. Moisture content affected the compress ibilities. Higher moisture contents produced more rigid foams. The spring i ndices of bulk samples were excellent ( > 95%) fur all MBI contents. (C) 20 01 Elsevier Science B.V. All rights reserved.