ANTIPLASTICIZATION IN STARCH-GLYCEROL FILMS

Calorimetric, mechanical, and thermomechanical properties have been me asured on starch films with various glycerol/water contents. For calor imetric measurements, a continuous decrease in T-g was observed as gly cerol increases from 0 to 25%. Mechanical properties exhibit a minimum of elongation at break for glycerol content similar to 12%. In slight ly hydrated starch films not containing another plasticizer, a beta re laxation is detected by DMTA around -68 degrees C. This relaxation is modified by the presence of glycerol, the alpha relaxation of which ap pears in the same temperature range. Results are discussed comparing w ith the well-known antiplasticization effect in synthetic polymers suc h as PVC and PC. The combination of the plasticizer alpha mode and the polymer beta mode is considered. (C) 1997 John Wiley & Sons, Inc.