APPLICATION OF A PROBABILITY MODEL FOR RELAXATION TO THE DIELECTRIC ALPHA-RELAXATION AND BETA-RELAXATION OF AMORPHOUS POLYETHYLENE TEREPHTHALATE

A probability model (PM) developed recently, which is an alternative t o the conventional Havriliak-Negami (HN) dispersion function for polym er systems, is applied for the first time to the study of the dielectr ic alpha- and beta-relaxation of amorphous polyethylene terephthalate (PET). It has been found that the temperature dependence of the maxima of the imaginary part of the dielectric function and of the half-widt h of the distribution in the PM of the alpha-relaxation exhibit Vogel- Fulcher-type temperature behaviour; the temperature dependence of the maxima of the imaginary part of the dielectric function of the beta at ion is proportional to the ratio of the gauche content to the trans co ntent of the ethylene glycol linkages in PET. Finally, the mechanisms of the alpha- and beta-relaxation are elucidated concisely.