Dielectric relaxation measurements of poly(vinyl acetate) in glassy state in the frequency range 10−6–106 Hz

Abstract

Dielectric relaxation measurements covering a wide frequency range extending from 10−6 to 106 Hz were made on poly(vinyl acetate) with conventional glass transition temperature Tg of 31 °C at temperatures between 26.85 and 84.77 °C. It was found that temperature dependence of frequency of the maximum dielectric loss below Tg cannot be described by the Williams–Landel–Ferry equation which gives a complete explanation to the dependence in the temperature range sufficiently higher than Tg, but by a simple expression of Arrhenius type with activation energy 138 kcal/mol. It was also found that distribution of the relaxation times changes abruptly in the vicinity of Tg. Potential barrier height for the chain motion has a distribution to some extent below Tg.