A study of thermally stimulated discharge and transient currents in PES

This paper characterises the dielectric properties of a widely used new amorphous polymer PES (polyethersulphone) by means of TSDC (thermally stimulated discharge currents) and TC (transient discharge currents). These measurements were undertaken over a range of electric fields unlike a previous study carried out at a fixed voltage of 1 kV. The results of TSDC measurements on virgin PES and material gamma irradiated to 0.5 MGy under vacuum and dry nitrogen are compared. The TSDC peaks for PES were observed to shift slightly to higher temperatures on increasing the polarising field from 8/spl times/10/sup 6/ to 8/spl times/10/sup 7/ V/m. Transient discharge currents excited by polarisation voltages in the range of 200 V to 1.8 kV were measured in air over the temperature range 30 to 90/spl deg/C. From this data the imaginary part of the relative permittivities in the low frequency region were derived. The mechanisms of dipole polarisation, charge storage and charge decay processes which give rise to the TSDC peaks and the dielectric behavior are discussed.