Thermally stimulated discharge currents in polyvinyl butyral films

Abstract

The persistent electrical polarisation in polyvinyl butyral was investigated by measuring the thermally stimulated discharge (TSD) current at different polarising fields, temperatures and heating rates. A peak was observed at about 331K which has the characteristics of a dipolar relaxation process. Thermal sampling technique showed that the relaxation is distributed. Differential thermal analysis gave a second-order transition at about 334K. Because of the good correlation between both thermal techniques it is concluded that the TSD peak is associated with the glass transition of the polymer, and therefore it involves the motion of large parts (sequences of 20-50 carbon atoms) of the polymer chains.