Thermally Stimulated Discharge Current study of PMMA : PVP blends

Thermally stimulated discharge current (TSDC) method was used to study the dielectric relaxation phenomena in pure Polymethyl methacrylate (PMMA), Polyvinyl pyrrolidone (PVP) and their blends films of approximately 50 μm in thickness, measured at 60 o C as a function of poling fields (50, 70, 90, and 110 kV/cm) and weight ratios (100:0, 95:05, 90:10, 85:15, 80:20 and 0:100). The relaxation processes for PMMA and PVP shows two peaks observed at around 90 ± 5 and 150 ± 5 o C but in the blend samples the first peak disappears and only one peak can be seen at higher temperature range 155 ± 10 o C. The first peak is α-peak which is due to micro-Brownian motion of the main chain segments and the higher temperature ρ-peak is due to space charge near the electrodes. It was found that the order of current increases with increase in weight percent of PVP in PMMA and the main reason is the formation of phase between PVP and PMMA. A decrease in activation energy observed with the increase in polarizing fields and weight % composition. This suggests that peak is not due to a discrete level having a single relaxation but is a complex one having distributed activation energies.