Dielectric relaxation of acrylonitrile-butadiene copolymers as a function of frequency, temperature and applied pressure

Abstract

Molecular motion in three acrylonitrile–butadiene copolymers has been studied using dielectric technique over a wide range of frequency, temperature and applied hydrostatic pressure. Two relaxation processes were observed for the 18 % and 27 % acrylonitrile copolymers, and one well defined α process was observed for the 40 % acrylonitrile copolymer. The detailed results are discussed in relation to the observation of multiple glass transitions in these systems, and it is shown that the motion of acrylonitrile groups is the origin of the higher glass transition temperature in these systems. The results for the 40 % acrylonitrile copolymer are considered in terms of the dipole moment correlation function.