Résumé :
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Dielectric relaxation measurements on poly(ethylene terephthalate) (PET) samples of different microstructures (semicrystalline, amorphous, amorphous oriented), between 80 and 300 K for frequencies ranging from 10(2) to 10(5) Hz have been performed. The data pertaining to the beta relaxation of PET could be fitted to the Cole-Cole (CC) phenomenological equations, from which the relaxation strength, the average activation energies, and the temperature-dependent distribution functions of relaxation times were obtained. On the basis of these results, we discuss briefly the origin of the beta relaxation and the degree of cooperativity of the beta motions.
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