DIELECTRIC-RELAXATION PHENOMENA IN PEEK

Molecular movements in poly(ether-ether-ketone) have been investigated by thermally stimulated currents (TSC). The TSC spectra have been ana lyzed as a function of crystallinity. Around -80 degrees C, two sub-mo des are observed: the lower temperature sub-mode has been attributed t o localized cooperative movements in the crystallizable amorphous phas e; and the upper temperature sub-mode has been located in the crystall ine phase. The magnitude of the corresponding compensation line increa ses with the ratio of crystallinity. Around the glass transition tempe rature (145 degrees C), the existence of two sub-modes has been shown: the lower temperature sub-mode has been attributed to the dielectric manifestation of the glass transition and the cooperative movements ha ve been assigned to the ''true amorphous region'' of PEEK; the upper t emperature sub-mode is dependant upon crystallinity. Regardless of the preceding sub-mode, the activation enthalpies of the constituting ele mentary processes are practically constant. This sub-mode has been att ributed to the ''rigid amorphous region'', constrained by the crystall ites.