?Antiplasticization? in starch-glycerol films?

Abstract

Calorimetric, mechanical, and thermomechanical properties have been measured on starch films with various glycerol/water contents. For calorimetric measurements, a continuous decrease in Tg was observed as glycerol increases from 0 to 25%. Mechanical properties exhibit a minimum of elongation at break for glycerol content ∼ 12%. In slightly hydrated starch films not containing another plasticizer, a β relaxation is detected by DMTA around −68°C. This relaxation is modified by the presence of glycerol, the α relaxation of which appears in the same temperature range. Results are discussed comparing with the well-known antiplasticization effect in synthetic polymers such as PVC and PC. The combination of the plasticizer α mode and the polymer β mode is considered. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1047–1053, 1997