Pressure dependence of dielectric properties of chlorinated polyethylene vulcanizate. II. Free volume and configurational entropy theories

Abstract

AbstractThe P–V–T relation and the heat capacity of a chlorinated polyethylene vulcanizate were measured. Several tests on the validity of thermodynamic treatments of the α relaxation process and the glass‐transition temperature were performed by using dielectric properties. From a study using excess variables, it was shown that the entropy theories represented by the equations of Goldstein and Adam–Gibbs' were slightly better than the free volume theory represented by Doolittle's equation. However the study provided no distinction between the two entropy theories. Some tests were also performed on the pressure dependence of the glass‐transition temperature, dTg/dP, and on H*V/H*V where H*V is the isochoric activation enthalpy and H*P is the isobaric activation enthalpy. Here, too, the entropy theories were better than the free volume theory. Goldstein's expression gave values of both dTg/dP and H*V/H*P closest to those from the dielectric experiments. The Adam–Gibbs' equation gave a temperature dependence for dTg/dP and H*V/H*P most similar to those from the experiments.