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 ε_r\´ and ε_r", the temperature at which ε_r\´ begins to increase and an absorption of ε_r" appears shifted to higher temperatures with exposure dose, and the maximum absorption (ε_m") was larger for the irradiated specimens. For the same specimens, ε_r\´ and ε_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 ε_r\´ and ε_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 ε_r\´ and ε_r" data for measurements conducted five times with the same specimens