Thermoplastic waxy starch films processed by extrusion and pressing: Effect of glycerol and water concentration

Abstract

Thermoplastic starch properties depends of plastification process. The aim of this study was to analyze the effect of concentration of glycerol and water on plastification, glass transition temperature (Tg) and tensile properties of thermoplastic waxy starch (TPWS). Formulations were extruded in the following concentrations of starch/glycerol/water: 70/30/0 (TPWS 0%); 70/25/5 (TPWS 5%); 70/20/10 (TPWS 10%) weight percentage. Crystalline peaks in WAXS diagrams and native grains present in SEM micrographs showed that the TPWS 0% and 5% were not sufficient to promote total plastification of the waxy starch, and TPWS 10% showed the higher starch plastification. Tg measurements by DMTA were 30 ºC to TPWS 0%, 23 ºC to TPWS 5% and 40 ºC to TPWS 10%. These results showed that glycerol and water had effect plasticizer in TPWS 5% and antiplasticizer in TPWS 10%. Mechanical tensile results showed that higher tensile strength was observed in the systems with more effective starch plastification.