General properties of secondary relaxations in polymers as determined by the thermally stimulated current method

Abstract

Abstract The method of thermally stimulated current (TSC) has been used to study the low‐temperature dielectric β relaxations of several polymers including especially poly(vinyl chloride), poly(vinyl acetate), polyamide 6, 6,6,poly( t ‐butyl acrylate), poly(methyl methacrylate), poly(ethyl methacrylate), poly(phenyl methacrylate), and poly( t ‐butyl methacrylate). The distribution characteristics of the relaxation processes have been determined from the corresponding TSC peaks by a fractional polarization technique which consists of applying the electric field in several discrete steps during a slow cooling. Several common features have been found in all the polymers investigated: the β peaks are characterized by a distribution of relaxation times resulting from a distribution in activation energy and this distribution is quasisymmetrical and continuous. These facts are in agreement with the hypothesis of a relaxation involving local motions of small polar groups undergoing various interactions with the environment. Some discrepancy remains, however, between our calculated values of the mean activation energy and those obtained from the dielectric loss.