Effect of controlled solvent evaporation on the electroactive phase content of P (VDF-HFP) films

Abstract

Poly (vinylidene fluoride)-based dielectric materials have attracted much attention in the field of high power density electric energy storage due to their ferroelectric properties, high dielectric breakdown strength and superior processability. However, it is a key challenge how to obtaining high content electroactive phases with ferroelectric and piezoelectric properties in PVDF. Up till now, researchers have prepared PVDF films with high content of electroactive phase via irradiation with high-energy electron-beam or γ-ray radiations and pressing-and-folding process. In this paper, P(VDF-HFP) films were prepared by controlled solvent evaporation method at different ambient temperature. The results showed that the morphologiy of the film showed insignificant changes with the increase of ambient temperature. Total contents of β and γ phases were nearly 100 % in the PVDF films prepared at ambient temperature below 110 °C. The microcrystals in P(VDF-HFP) was more and more perfect with the increase of the ambient temperature under the condition of controlled solvent evaporation. The films prepared at 70 °C showed a dielectric constant of 12.76 under the test condition of 100 Hz with the remnant polarization of 0.54 μC/cm2. All of these results demonstrated that the formation of the electroactive phase of P(VDF-HFP) thin films was related to the evaporation process and evaporate rate of the solvent.