Charge storage and transport in oriented and non-oriented polytetrafluoroethylene films

The charge storage and transport in oriented and non-oriented polytetrafluoroethylene (PTFE) films, charged by the corona method at room temperature, were investigated by isothermal decay and thermally stimulated discharge (TSD) techniques. The crystallinity of the PTFE films was determined by differential scanning calorimetry (DSC). The results obtained from isothermal decay of the surface potential and the spectra of the TSD charge and current indicate that the thermal stability of both positive and negative charges in oriented PTFE films is significantly better than that of non-oriented PTFE films. This is probably due to the higher crystallinity in oriented PTFE films. The transport of the de-trapped positive charges in oriented PTFE films, which occurred due to thermal excitation, can be explained by a model that takes thermal ion emission into consideration.