β Phase Optimization of Solvent Cast PVDF as a Function of the Processing Method and Additive Content

Abstract

A semicrystalline polymer with high piezo-, pyro-, and ferroelectric characteristics, poly(vinylidene fluoride) (PVDF) offers exciting possibilities in various applications. The semicrystalline structure of PVDF is composed of several phases including α, β, θ, γ, and ε phases. β phase polymorphs of PVDF exhibit the highest piezoelectric properties, which can be enhanced through different processing methods. This study aims to investigate the β phase transformation of PVDF through different processes/treatment methods and the processing of a PVDF polymer composite containing 0.2 wt % multiwalled carbon nanotubes and/or 20 wt % modified/unmodified barium titanate. The effects of annealing, uniaxial stretching, rolling, atmospheric plasma treatment, UV treatment, and their combinations were investigated. The transformation of α to β phase was determined by Fourier transform infrared spectrometer, X-ray diffractometer and differential scanning calorimeter. The most remarkable β phase transformation of PVDF films was obtained by stretching following solvent casting and hot pressing. It was observed that various process combinations, as well as the incorporation of additives, influence the β phase content of PVDF. Alongside studying β phase content of PVDF, the investigation extends to analyzing the tan δ and elastic and loss modulus values of rolled PVDF polymer composite films.