Influence of di-functional versus multi-functional chain extenders on the foamability of a potato starch-based biopolymer.

This study examines the effectiveness of di-functional versus multi-functional glycidyl ether chain extenders (CE) for improving the foamability of a commercial blend of hydrolyzed potato starch and polylactic acid, Solanyl® 30R (Solanyl Biopolymers Inc.). The blend was reactively modified in bulk using CEs at concentrations ranging from 0.5-2.5 wt% within a twin-screw extruder operating at 170°C and 150 RPM. Thermal and rheological analysis of the modified blends found that only one multi-functional polymeric CE was effective for altering the molecular structure of the blend while both significantly improved the foamability of the material. The two di-functional CEs did not produce detectable changes in melt elasticity for the blend but again had a notable influence on improved foamability. Foamability was evaluated based on improvements to the material that increased foam stability (i.e. higher cell densities and smaller bubbles), and the results in this study suggested that these CEs influenced bubble expansion in ways other than simply causing rheological change. [ABSTRACT FROM AUTHOR]