Dielectric materials can be used in radiative environment that is why it is of major importance to determine their properties modifications with time. In this paper we focus our attention on PolyTetraFluoroEthylene (PTFE) films submitted to gamma radiations. We investigate the FTIR spectra and show that after exposure to Co 60 the crystallinity of the material is increasing. This result is confirmed by Differential Scanning Calorimetry (DSC) analysis. Some space charge distribution profiles obtained by the Pulse Electro Acoustic (PEA) method show that the irradiation favours the drift of injected charges toward the bulk. Obviously the dose of radiation must be carefully chosen in order to be able to perform electrical measurements. Indeed, we observed that if the radiation dose is too high the sample becomes fragile and most of the characterisation tools cannot be used.
In this work, we focus our attention on data obtained from Pulse Electro Acoustic (PEA) measurements on PTFE films before and after irradiation with a 60 Co gamma radiation source. At first, samples are just polarized to determine the effect of the gamma irradiation on the charge transport in the bulk. In a second stage, these films have been exposed to a mono-energetic electron beam. The aim is to study the effect of gamma radiation on charge storage in the bulk.
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 60 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.
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