Dielectric and other physical/chemical changes induced by ionizing radiation in poly(ether ether ketone) (PEEK) and poly(ethersulphone) (PES) films

There has been an increasing commercial and industrial demand for advanced polymeric materials capable of being utilised in harsh environments as electrical insulation. Aromatic polymers have proved to be chemically and mechanically stable in such a situation. They have been identified for use in the presence of ionizing radiation but little information is available as to their dielectric properties under such conditions. In this study poly(ether sulphone) (PES) and poly(ether ether ketone) (PEEK), typical aromatic polymers, were irradiated to different dose levels using both a gamma ray source and a high energy electron source. Possible chemical and structural changes were examined using the techniques of differential scanning calorimeter (DSC), UV-Visible absorption spectroscopy and photo induced phosphorescence for irradiated films. Electrical changes induced by the radiation were studied using thermally stimulated discharge current (TSDC) measurements. The low frequency dielectric response was derived from the measurement of transient currents (TC)