Preparation and properties of PVDF-based casting films dominated by melt pulsating elongational flow

In this study a melt conveying device dominated by pulsating elongational flow for inducing β-phase formation in PVDF was developed. The structure and working principles of the new device were introduced in detail. Focusing on flow-induced crystallization, the structure and properties of PVDF/poly (methyl methacrylate) (PMMA)/tetraphenyl phosphonium chloride (TPPC) films under the pulsating elongational flow were prepared and investigated. 2D-WAXD results demonstrated that this flow promotes the orientation of molecular chains within PVDF/PMMA/TPPC along the extrusion direction. 1D-WAXD and FTIR results confirmed enhanced interactions between both PMMA-PVDF and TPPC-PVDF, promoting increased formation of β-phase. When TPPC content is 1 wt.%, β-phase content reached 83.2%. Piezoelectric tests indicated the films exhibited a piezoelectric coefficient of approximately 22.6 pC/N, generating an open-circuit voltage of 2.64 V and a short-circuit current of 340 nA under an applied pressure of 79.1 kPa. Consequently, pulsating elongational processing enables scalable manufacturing of high-performance PVDF-based piezoelectric films.