Effect of Gamma-Irradiation on Creation and Dynamic of Space Charge in PTFE

Electrical properties of polymers undergo significant changes when exposed to ionizing radiation which may alter insulation reliability in radiative environment. The aim of this work is to investigate the effect of gamma-irradiation on the creation and the dynamic of space charges in PolyTetraFluoroEthylene (PTFE). The 200 μm thick PTFE films were exposed to a
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Co gamma radiation source to different doses 30, 60 and 100 kGy at a constant dose rate. Space charge measurements were achieved by Pulsed Electro-Acoustic method under a field of 40 kV/mm on virgin and irradiated films. Unlike in virgin sample, positive and negative heterocharges were observed in a few minutes after irradiation. The results highlight the creation of pair of charges and the structural modification of the polymer that enhances their mobility. These space charge effects go with a strong increase of the polymer conductivity.