Glass/rubber transitions and heat capacities of binary sugar blends

Abstract

The pairs of sugars glucose–fructose and fructose–sucrose have been comelted and quenched to form binary glasses. Glass-to-rubber transition temperatures T_g and heat capacities of the glasses and the crystalline sugars have been measured by computer-aided differential scanning calorimetry. T_g was found to vary smoothly with glass composition and the (constant pressure) heat capacities C of the glasses and rubbers varied monotonically with T_g. It is suggested that C is a better and experimentally more convenient indicator of T_g and the glassy state than is the inferred viscosity in terms of which T_g is usually defined. The T_g data for mixtures extrapolate smoothly to a T_g of fructose of 286 K which differs substantially from the value (373 K) previously reported. C values for the crystalline sugars agree with literature data.