Polyvinylidene fluoride/magnetite nanocomposites: Dielectric and thermal response

Nanocomposites of poly (vinylidene fluoride), PVDF, and magnetite (Fe3O4) nanoparticles were prepared using the twin screw compounding method and the effect of filler concentration (5-15 wt%) on the thermal stability, dielectric properties and dielectric strength were investigated. It was observed that the dynamic characteristics of crystalline a c -relaxation peak remain almost constant for the composites studied; while the activation energy plots almost coincide indicating that the time scale of this relaxation process is independent of the Fe3O4 filler loading. Ferrite particles alter Maxwell-Wagner-Sillars (MWS) mechanism behaviour. In the isochronal diagrams of electric modulus dielectric function, at the lower ferrite concentration 5 wt% and the lowest frequency 0.1 Hz, two contributions to MWS process were clearly detected. For ferrite concentrations higher than 5 wt%, it seems that the contribution of amorphous-crystalline interfaces to the MWS relaxation drastically decreases and their effect is the broadening of the MWS peak at higher temperatures, while the effect of Fe3O4-PVDF matrix interfaces dominate in the formation of MWS relaxation. Herein, the nanocomposites dielectric strength performance was investigated by means of switching impulse high voltage stressing and AC (50 Hz) high voltage; from the results the nanocomposites demonstrated high levels of dielectrics strength accompanied with stable performance.