Functional properties of polylactic acid starch-based loose-fill packaging foams

In this study, attempts were made to improve the characteristics of starch-based plastic foams by blending starch with polylactic acid (PLA), a biodegradable polymer made from renewable sources. Formulations of the foams (types of starch, ratio of starch to polymer, and moisture content) were optimized. Physical and mechanical properties of the foams, including expansion, unit density, bulk density, water solubility index (WSI), spring index, and compressibility on both single piece and bulk samples were determined. The addition of the PLA polymer to regular (25% amylose) and waxy corn starches significantly improved the physical and mechanical properties of the extruded foams. Foams made from waxy starch had better radial expansions, higher WSI, higher compressibilities, and lower spring indices than those of regular starch foams. Both regular and waxy starches produced foams with similar unit and bulk densities, bulk compressibilities, and bulk spring indices. Increasing PLA polymer contents increased the radial expansions and spring indices and significantly reduced the unit and bulk densities and bulk compressibilities. Changing the PLA content had no significant effect on WSI, compressibilities, and bulk spring indices. Increasing the moisture content adversely affected foam characteristics. The formulation containing waxy starch, 40% PLA, and 19% moisture produced a loose fill foam with the best physical characteristics and mechanical properties.