Temperature dependence of dynamic mechanical properties of mixed polymer systems

The temperature dependence of the viscous component E2(1/T) of the dynamic modulus is reported for a homologous series of butadiene–styrene copolymers incorporated at various levels in styrene homopolymer. By the use of a vibrating reed technique based on resonance tuning, the frequency of the applied deformation was maintained essentially constant throughout the temperature range which included the glass transitions of the copolymers. It is shown that, when E2(1/T) for such mixed polymer systems is plotted against reciprocal absolute temperature, the area under the peak corresponding to a given copolymer affords a direct measure of the quantity of the copolymer present. Further, the temperature of maximum E2(1/T) is related to the mole fraction of bound styrene in the copolymer, and the shape of the peak is related to the statistical sequence lengths of styrene and butadiene in the copolymer.