Dielectric and thermal properties of irradiated polyetheretherketone

The dielectric and thermal properties of electron-beam-irradiated polyetheretherketone (PEEK) have been investigated and the properties of a heat-treated 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 temperature 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 treatment. Glass transition temperature T, values were calculated from graphs depicting the relationship between logarithmic values of tau (T-m) data and T-m, through the use of the Williams-Landel-Ferry (WLF) equation. T-g shifted to higher temperatures with either irradiation or heat treatment. Results suggest that electron beam irradiation causes crosslinking among molecules via free radicals in the specimen. Consequently, crosslinking among molecules via free radicals is thought to occur with heat treatment.