CORROSION EFFECTS OF NUCLEAR TRACKS IN POLYMERS

Usually ion tracks are studied ex-situ, i.e. after removal of the ion- irradiated sample from the evacuated irradiation vessel. The exposure to ambient air leads to degradation effects which are frequently negle cted and consequently have been studied rarely. They have never been e xplained consistently. In this work we compile and discuss them in the frame of today's general understanding of ion tracks in polymers. It appears that some pristine polymers such as polyethylene are covered b y a surface layer which is badly permeable for gaseous contaminants. I on irradiation leads to destruction of this protective layer so that o xygen and moisture from the ambient air can easily penetrate through t he ion tracks, and eventually even into the surrounding pristine mater ial. Moisture absorption along the tracks gives rise to some faint con ductivity. Oxygen uptake adds new trapping centers to the existing one s along the tracks, so that on one hand an increased dopant uptake cap ability is recorded, and on the other hand oxygen-sensitive mobile dop ants are immobilized along the ion tracks. Photooxidation processes co ntribute to the fading of the optical blackening of irradiated polymer s.