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 160 K and the other at 390 K. The results suggested that the low temperature isochronal peak was due to structural motions @-relaxation) whereas the peak at 390 K was not due to a second-order transition process (cc-relaxation).

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Charging and discharging current transients in polypropylene films were measured over a wide range of temperatures and electric fields. Some limited studies of the behaviour of these current transients were also made with different electrode materials and sample thicknesses. The experimental evidence suggests that the absorption current in the temperature range 83-270K may be caused mainly by dipolar processes associated with structural motions. At temperatures above approximately 270K the absorption current may be attributed to a carrier hopping process.

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