Influence of the crystalline phase on the molecular mobility of PVDF

Abstract

AbstractDielectric relaxation and pyrocurrent of PVDF were studied by thermostimulated current spectroscopy. The transition spectrum of the material was investigated by differential scanning calorimetry. Two well‐resolved relaxation peaks have been observed in the temperature range [−100–100°C]. The molecular mechanisms of these phenomena have been discussed, based on a comparative study of α‐PVDF. and β‐PVDF. The β relaxation mode is located at −41°C in α‐PVDF and is slightly shifted toward higher temperatures in the stretched material. This mode has been ascribed to the dielectric manifestation of the glass transition (Tg) of PVDF. It is comprised of two components corresponding to the free and constrained amorphous phases, respectively, in the order of increasing temperatures. The αc transition/relaxation has been associated with molecular motions in the crystalline/amorphous interphase. At higher temperatures, a compensation phenomenon corresponding to cooperative movements liberated at the Curie transition has been observed in β‐PVDF. © 1993 John Wiley & Sons, Inc.