Structural revolution of PVDF crystallized on nanocarbon surface on a gradient temperature stage and its dielectric properties

Poly (vinylidene fluoride) (PVDF) has been widely concerned because of its various transformations of crystal phase as well as its special dielectric, piezoelectric, and other electrical properties. In this paper, the temperature gradient (T-gradient) was constructed for studying the temperature dependence of crystallization behavior of PVDF and the heterogenous nucleation effect of multiwall carbon nanotubes (MWCNT) and graphene nano-platelets (GN). The aggregate structure, the change content of PVDF conformation, and the influence of heterogenous nucleating agent on the crystallization behavior of PVDF formed at different crystallization temperature (Tc) were investigated through three different dimensions by using FTIR for surface, WAXD/SAXS for bulk and AFM for cross-section respectively. The results showed that the low temperature and heterogenous nucleating agent were both conductive to the formation of γ phase of PVDF. The content of γ phase reached to 77% when Tc was lower than 61 ℃, and the proportion of γ (021) peak increases from 1.7–7.0% when PVDF crystallized at Tc =117 ℃ induced by MWCNT-rich. And the high density of nucleus and low Tc lead to the lower lamellar thickness and lower crystallite size. Higher content and lower crystallite size of γ phase leads to higher dielectric constant. The dielectric constant of sample crystallized at 61 ℃ which was induced by GN was significantly increased up to 6.2 which can lay a foundation for its future application in the field of dielectric.