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Effects of initial crystallization process on piezoelectricity of PVDF-HFP films

Abstract The effects of some important factors in the initial crystallization process of the solution casting method on the piezoelectricity of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films were extensively explored. The experimental results revealed that there is an optimal initial crystallization temperature at around 90°C. The slow cooling speed can moderately enhance the degree of crystallinity. The most important finding was that a bilayer crystalline structure caused by an asymmetrical heating pattern can enhance the formation of packed micro-fibrillar morphologies after drawing. These three points can increase the piezoelectricity of the PVDF-HFP films, indicating the increase of the extended-chain crystals (β-phase).