Dielectric and thermal properties of irradiated polyetheretherketone

The dielectric and thermal properties of electron-beam-irradiated polyether etherketone (PEEK) have been investigated and the properties of a heat-trea ted specimen studied. Results of the temperature dependence of epsilon (r)' and epsilon (r)" indicated that epsilon (r)' and epsilon (r)" were higher after electron beam irradiation and lower after heat treatment. The tempera ture at which epsilon (r)' begins to increase and that at which the peak of epsilon (r)" appears, rise with both electron beam irradiation and heat tr eatment. Glass transition temperature T, values were calculated from graphs depicting the relationship between logarithmic values of tau (T-m) data an d T-m, through the use of the Williams-Landel-Ferry (WLF) equation. T-g shi fted to higher temperatures with either irradiation or heat treatment. Resu lts suggest that electron beam irradiation causes crosslinking among molecu les via free radicals in the specimen. Consequently, crosslinking among mol ecules via free radicals is thought to occur with heat treatment.