Surface conductivity of irradiated polymers in humid environment

The authors report results of an investigation of hydration isotherms and surface conductivity of PEEK (polyetheretherketone) as a function of relative humidity. Gamma irradiation of samples with radiation dose not exceeding 6 Mrad was performed both in air and in nitrogen. Typical behavior of surface currents at varying hydration for three different voltages are shown for the untreated PEEK film. The presence of water molecules on the polymer surfacer gives rise to surface conduction, the absorption behavior being naturally dependent on the surface characteristics of the material. Hydration isotherms of untreated and gamma-irradiated PEEK are shown from which it may be observed that there is a significant increase in the absorption of water after such treatment. It is suggested that the excess water absorption with irradiation occurs in the bulk of the polymer, the surface conductivity remaining, however, independent of the bulk effect. >