Thermally stimulated depolarisation currents (TSDC) in Townsend breakdown charged polypropylene foils

A study of thermally stimulated depolarisation currents (TSDC) with air-gap arrangement has been made in commercial polypropylene (PP). The study was made with positively and negatively Townsend breakdown charged samples with fields ranging from 2 to 10 kV/cm. The thermograms were characterized by a single peak centred at 393°K. The total charge under the peak as well as the peak current was found to increase nonlinearly with polarizing field, tending to saturate at higher forming fields. The samples charged at negative forming fields were found to decay slowly indicating that negative carriers are more stably trapped in PP.