On the nature of absorption currents in polyethyleneterephthalate (PET)

Transient charge and discharge currents in oriented PET films (Melinex) were measured over a wide range of temperature and electrical stresses. Some limited studies of the nature of these current transients were also made by varying parameters such as electrode material and the sample thickness. Isochronal characteristics (i.e. current/temperature plots at constant times) constructed from these data seemed to reveal two broad peaks, one centred at approximately 160K and the other at 390K. The results suggested that the low temperature isochronal peak was due to structural motions ( beta -relaxation) whereas the peak at 390K was not due to a second-order transition process ( alpha -relaxation).