TEMPERATURE-DEPENDENT RELAXATION OF THE CRYSTAL AMORPHOUS INTERPHASE IN POLY(ETHER ETHER KETONE)

The temperature dependence of molecular mobility in the amorphous phase of poly(ether ether ketone), PEEK, was characterized by the dielectric relaxation intensity, DELTA-epsilon = epsilon(g) - epsilon-infinity, at temperatures above the glass transition to determine the contribution that the crystal/amorphous interphase material makes to the relaxation process. Relaxation intensity is shown to be structure sensitive above T(g). For amorphous PEEK, DELTA-epsilon initially decreases as temperature increases, then shows the opposite trend as the material crystallizes above T(g). For all semicrystalline PEEK, DELTA-epsilon increases with temperature. The ratio of semicrystalline intensity to amorphous intensity determines the total fraction of dipoles which are already relaxed at a given temperature. Results indicate that the rigid amorphous phase in PEEK is not rigid at all temperatures but relaxes between the glass transition of the mobile amorphous phase and the melting point of the crystalline phase. The amount of crystal/amorphous interphase material joining the relaxation process increases as the temperature increases.