Study of dielectric relaxation processes of PET by Dynamic Dielectric and ThermoStimulated spectroscopies

During the last decades, the frequency range of investigation of dielectric materials has been extended by many order of magnitude in the high frequency side. Actually, the reasonable accessible frequency range of dynamic dielectric spectrometers is about [10^-2 - 10⁹ Hz]. However, the main problem occurring in polymer relaxation analysis is the overlapping of relaxation modes when the frequency of measurement is increased, each being associated with a typical kind of motion. The purpose of the investigation reported in this paper is to enlarge the accessible range of dielectric studies of amorphous polymers like amorphous PET, taken as model polymer. For this aim, two dielectric techniques have been used : Dielectric Spectroscopy (DS) and Thermally Stimulated Currents (TSC). This paper presents a comparison of both techniques on results obtained on the secondary (β) and main (α) relaxation regions