Effects of glycerin and glycerol monostearate on performance of thermoplastic starch

The effects of glycerin and glycerol monostearate (GMS) on a variety of properties of anhydrous wheat starch are explored by means of DSC, TGA, as well as mechanical, rheological and moisture sorption assessment. It is found that, as glycerin content (GC) increases, both melting point and degradation temperature decrease, and the range of the processing window extends. Melt viscosity of the glycerin-plasticized starch depends on shear rate following power law, exponentially on GC, and on temperature in Arrhenius type. Increasing GC leads to a linear increment of the equilibrium moisture sorption, which, however, can be depressed significantly by incorporating a small amount of GMS. Moreover, the presence of 2% GMS in the formulations can efficiently reduce the melt viscosity and enhance its temperature sensitivity while has insignificant effect on the non-Newtonian behaviour and mechanical properties. (C) 2001 Kluwer Academic Publishers.