Study On Piezoelectric Property Of Novel PVDF-based Fluoropolymers

Electret is an unique kind of dielectric materials which can retain the remnant polarization permanently after polarized in electric field and trap the charge on both sides of films. These materials that have attracted considerable attention in area of physics, chemistry, biology and military owing to supply of a stable electric field have similar behavior as permanent magnet which still holds positive and negative charge separately on surfaces when split into half. PVDF of a excellent polymer electret in which quantities of C-F dipoles result in high polarization must be employed to mechanical extension and an externally applied field to exhibit piezoelectric property. As a result of complex process, P(VDF-co-TrFE) has been concerned by researchers, which is similar as PVDF with corrosion resistance, climate ageing resistance and solvent resistance and possesses as excellent ferroelectric and piezoelectric property as extended and polarized PVDF only applied in simple procedure. The main research content and conclusions are abstracted as follow:1.P(VDF-co-TrFE)(80/20 mol%) is synthesized from commercial P(VDF-co-CTFE)(80/20 mol%) by hydrogenation process. P(VDF-co-TrFE) films are analyzed structure by XRD, FTIR and DSC, electric property by ferroelectric and dielectric tester and piezoelectric property by d33 tester. The most appropriate annealed temperature is explored that the best annealed temperature is set between Tc and Tm. P(VDF-TrFE)(80/20 mol%) only crystallizes into ? phase by XRD and FTIR, and possesses more homogeneous ferroelectric crystalline by DSC. After annealed, at an electric field of 300MV/m, the maximum and remnant polarization rise to 11.21 ?C/cm2 and 7.22 ?C/cm2, coercive field declines to 56 MV/m, ?r rises to 12.5 at 100 Hz and d33 rises to 25 pC/N.2.P(VDF-co-TrFE)(65/35 mol%) synthesized by hydrogenation process is annealed between Tm and Tc followed by conclusion of P(VDF-co-TrFE)(80/20 mol%). Analysis exhibits that both crystallinity and electric property are significantly lower than P(VDF-co-TrFE)(80/20 mol%) and d33 is 13 pC/N.3.Piezoelectric property of PVF is inferior to P(VDF-co-TrFE) whose repeat unit is(CH2-CHF). Although at an electric field of 300 MV/m, the maximum polarization, remnant polarization and d33 are 10 ?C/cm2, 5 ?C/cm2 and 11 pC/N, after annealed, curie transition temperature of PVF is detected at 168 ? which is much higher than PVDF-based polymer. It would attract particular interest in the applications for the high stability at elevated temperature.