Influence of heating on dielectric relaxation phenomena of electron beam irradiated PEEK

Dielectric properties of non-irradiated specimen and specimens irradiated with electron beams were studied. In the temperature dependence of epsilon (r)' and epsilon (r)", the temperature at which epsilon (r)' begins to increase and an absorption of E-r" appears shifted to higher temperatures with exposure dose, and the maximum absorption (epsilon (m)") was larger for the irradiated specimens. For the same specimens, epsilon (r)' and epsilon (r)" values were smaller in measurements taken the second time than in those taken the first time under the same temperature conditions. Further study revealed that epsilon (r)' and epsilon (r)" values tend to decrease over time for irradiated specimens, while those for non-irradiated specimens remained constant at the same values as noted the second time and with later measurements. A similar trend was observed for frequency dependence of epsilon (r)' and epsilon (r)" data for measurements conducted five times with the same specimens.