Ferroelectric polarization in stretched piezo- and pyroelectric poly(vinylidene fluoride-hexafluoropropylene) copolymer films

Abstract

After suitable preparation, films of poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] show strong piezo- and pyroelectric effects. We investigated the polarization buildup in stretched P(VDF-HFP) copolymer films, cast from a dimethylsulfoxide/acetone solution. The films were poled under varying or constant electric fields. We observed a hysteresis of the polarization as a function of the electric field during poling of the stretched P(VDF-HFP) copolymer films with varying electric fields. From the hysteresis curve, a polarization of 24 mC/m2, and a coercive field of 100 MV/m were determined. The polarization values are lower than those of PVDF films cast from solution and stretched under the same conditions. It seems that HFP comonomer leads to a decrease in the amount of switchable dipoles. Nevertheless, the P(VDF-HFP) copolymer is very attractive because of its high piezo- and pyroelectric coefficients as well as its better chemical and thermal stability and its predicted longer lifetime. A rather uniform polarization across the whole sample thickness was found in spatially resolved measurements of the piezo- and pyroelectric properties. For comparison with PVDF and for structural information, we also report and discuss infrared transmission as well as dielectric response.

Advances in Dielectric Elastomers for Actuators and Artificial Muscles

“…Bulky side groups can be introduced though the formation of copolymers containing PVDF, TrFE, and either chloride containing monomers such as cholorofluoroethylene (CFE) [102,105] and chlorotrifluoroethylene (CTFE) [106,107] or hexafluoropropylene (HFP). [108][109][110] The actuation mechanism is essentially the same as for ferroelectric polymers; a transition between paraelectric and ferroelectric phases is induced by the application of a high electric field as represented in Figure 4. Recent work by Bao et al [111] has shown that P(VDF-TrFE) synthesized via reductive dechlorination from P(VDF-CTFE) exhibits ferroelectric relaxor behavior at high temperature (%100 8C) with a melting point near 200 8C.…”

Fluoropolymer and aluminum piezoelectric reactives

“…The investigation of these composites has been performed to determine if they represent piezoelectric reactives. Fluorel™ FC-2175 (chemically equivalent to Viton™), a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), was chosen to be used because it exhibits ferroelectric properties without the need of poling or stretching of the material [3]. Dyneon TM THV220A, a terpolymer of tetrafluoroethylene (TrFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF) was also used due to its potential to store energy [4].…”

Characterization, performance and optimization of PVDF as a piezoelectric film for advanced space mirror concepts.

“…The sample should be monitored for contaminants as the charges may get injected into the material at high electric and thermal fields [29]. Both constant and varying electric fields can be applied to the sample during electrode poling [30,31]. A constant electric field is held on the sample from 10-30 minutes up to 2 hours [32][33][34].…”