Effect of Blending with Polysulfone on Thermally Stimulated Discharge Behavior of Polyvinylidenefluoride Films

Thermally stimulated depolarization current (TSDC) have been undertaken on solution grown foil samples of polyvinylidenefluoride (PVDF)-polysulfone (PSF) blends as a function of the polarizing temperature, applied field, and polysulfone weight percentage in the blend. The TSDC thermograms of pure PVDF and PSF shows two peaks whereas the blend composition of the two polymers shows a single peak at around 170–190°C. The magnitude of the TSDC peak current increases and the peak current position shifted toward the lower temperature side as the polysulfone weight percentage in the blends was increased. The peak temperature of blend samples is higher than the dipolar peak (β peak) of PVDF samples and does not vary with change in polarizing field. This indicates that this peak may be due to dipoles. At the same time, the peak shifts towards higher temperatures with increase in polarizing temperature, which shows the behavior of space charge peak. This contradiction may be explained on the basis of induced dipoles. It seems that the charge originating from the bulk of the samples gets trapped in the deeper traps during polarization, and thus form induced dipoles. Afterward these induced dipoles get aligned in the polarizing field. It can be explained on the basis that either the dipolar peak gets covered by the space charge peak, or its contribution to the total polarization is very small.