Mechanical properties of starch-based foams as affected by ingredient formulations and foam physical characteristics

Mechanical properties of foams extruded with starch and biodegradable polym ers were correlated with ingredient formulations and physical characteristi cs of the extrudates. The type of polymer had a significant effect on foam compressibility and Young 's modulus. The PLA-starch and EBC-starch foams w ere softer than the Mater-Bi(R)-starch foam. Both regular and waxy corn sta rch-based foams had similar mechanical properties. Spring indices were not affected by the types of polymers and starches. A 25% polymer content resul ted in the softest foams. Foams containing 10% polymers possessed the highe st spring indices. Higher moisture contents increased the compressibilities and spring indices. A moisture content of 22% resulted in the lowest Young 's modulus. The relationships between the compressibilities, Young's moduli and the physical characteristics were described by power law equations. Co mpressibilities and Young's moduli decreased as radial expansion increased, and increased as the unit densities increased. Unit density had little eff ect on spring index. Increasing bulk density significantly increased compre ssibility and Young's modulus. The correlations between spring indices and physical characteristics were low