High surface-charge stability of porous polytetrafluoroethylene electret films at room and elevated temperatures

Porous polytetrafluoroethylene films were positively or negatively corona-c harged at room or elevated temperatures and their charge-storage behaviour was investigated by means of isothermal surface-potential and thermally sti mulated discharge-current measurements. In addition, electron micrographs o f the sample morphology were taken and the influence of high humidities on the surface-charge decay was investigated. For comparison, nominally non-po rous polytetrafluoroethylene films were studied in the same manner. It was found that porosity may lead to significantly enhanced surface-charge stabi lity for both polarities if the relative humidity is not too high. Further investigations are under way in order to better understand this behaviour a nd to employ it for electret applications.