On the interpretation of the TSDC results in the study of the alpha-relaxation of amorphous polymers

The alpha-relaxation around the glass transition of poly(vinyl acetate) (PVAc) is investigated by combining several dielectric techniques, namely frequency and time domain dielectric spectroscopies, as well as thermally stimulated depolarization current (TSDC). The results obtained by means of both the isothermal methods and the TSDC technique are interpreted on the basis of a Kohlrausch-Williams-Watts functional form of the time decay function. Both isothermal and TSDC measurements show that the dynamics of the alpha-relaxation in the glassy state has a non-Debye character which is similar to the one observed in the supercooled melt. From the comparison between the obtained results, a new way of analysis and interpretation of the TSDC results in the alpha-relaxation range is proposed. Moreover, from a set of TSDC spectra obtained at different heating rates, both beta(T) and tau(T) are calculated in the whole temperature range covered by TSDC, i.e. below and across the glass transition. Copyright (C) 1996 Elsevier Science Ltd.