Correlation between dipolar TSDC and AC dielectric spectroscopy at the PVDF glass transition
✍ Scribed by M. Grimau; E. Laredo; A. Bello; N. Suarez
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 225 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0887-6266
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✦ Synopsis
The a a -mode (associated to the dynamic glass transition) in PVDF-a has been studied by Thermally Stimulated Depolarization Currents (TSDC) and Dielectric Spectroscopy (DS) techniques. The distribution of relaxation parameters, reorientation energies, characteristic temperature, and preexponential factors of the Vogel-Tammann-Fulcher relaxation times have been precisely determined by using the Simulated Annealing Direct Signal Analysis applied to a partially discharged TSDC a a peak. This distribution has been used to predict the variation of the dielectric loss, 1Љ(v, T ), in the temperature and frequency range where the DS measurements were made on the same material. The simulated 1Љ(T, v) for various v, are compared to the experimental values. The width of the peak is always too low, due to the restricted distribution used for the generation of the curves. A relaxation map including the TSDC results is used to determine the relaxation time variation. In the limited frequency range where the AC DS experiments are performed (10 2 °f °10 5 Hz) a master curve is drawn and the exponents of the frequency dependence are found at low and high frequency; also, a fitting to the Havriliak-Negami distribution is successfully performed.