EFFECT OF CRYSTALLIZATION, POLING AND AGING CONDITIONS ON THE FIR, DIELECTRIC AND PYROELECTRIC PROPERTIES OF HOT-PRESSED PVDF AND P(VDF TFE)-(0.98/0.02)/

We studied the influence of hot-pressing temperature as well as poling and ageing conditions on the amount of polar phase of hot-pressed PVD F and P(VDF/TFE)-(0.98/0.02) foil. FIR transmission spectra of hot-pre ssed homopolymer and copolymer films were measured in the 30-450 cm(-1 ) range as a function of hot-pressing temperature T-hp and poling temp erature T-p. The FIR studies show that homopolymer and copolymer consi st of both polar and nonpolar modifications of PVDF. The content of th e polar phase tends to decrease with T-hp and increase after poling. T he FIR spectra of our samples exhibit a strong absorption peak near 10 0 cm(-1) absent in the biaxially oriented Solef samples, which is beli eved to be due to the amorphous phase in our samples. Four thermally s timulated current (TSC) maxima are attributed to the relaxation in the amorphous region (similar to 40 degrees C), to the dipolar relaxation in the nonpolar (similar to 60 degrees C) and polar (similar to 80 de grees C) phase, and the space charge relaxation (dependent on the poli ng temperature). The pyroelectric co efficient of the homopolymer and copolymer thermoelectret foil prepared by hot-pressing is of the same order as that of the PVDF thermoelectret foil produced by Solvay and c an be influenced by the hot-pressing conditions. The dielectric respon se of the hot-pressed PVDF-type foils can be described by the Kohlraus ch-Williams-Watts function and is characteristic of a heterogeneous sy stem.