Structural revolution of PVDF crystallized on MWCNT film on a gradient temperature stage and its dielectric properties

Abstract

Poly(vinylidene fluoride) (PVDF) has been widely studied because of its various crystal phase transformations as well as its special dielectric, piezoelectric, and other electrical properties. In this study, a temperature gradient (T-gradient) was constructed for studying the temperature dependence of the crystallization behavior of PVDF and the heterogeneous nucleation effect of multiwall carbon nanotubes (MWCNTs). The nanoscale structure of PVDF was investigated through three different dimensions using FTIR for the surface, WAXD/SAXS for the bulk and AFM for the cross-section. The results showed that low temperature and a heterogeneous nucleating agent were both conducive to the formation of the γ phase of PVDF. The distance of MWCNT nucleation effect is about 15 μm, and it is more significant in 0–5 μm. The content of the γ phase reached 77% when T_c was lower than 61 °C. The higher content and lower crystallite size of the γ phase lead to a higher dielectric constant, which can lay a foundation for its future application in the field of dielectrics.