Pressure dependence of the dielectric properties and phase transitions of polyvinylidene fluoride (PVDF) and a copolymer with trifluoroethylene

Abstract

The frequency, temperature, and hydrostatic pressure dependences of the dielectric properties, molecular relaxations, and phase transitions in PVDF and a copolymer with a 30 mol% trifluoroethylene were investigated. The β‐relaxation peak temperature Tβ and the melting temperature Tm of both polymers, and the ferroelectric transition temperature Tc of the copolymer, are strong increasing functions of pressure. The magnitudes of the pressure derivatives of Tβ, Tc, and Tm increase in the order of the “transition” temperatures, i.e., Tβ(P) < Tc(P) < Tm(P). These results can be qualitatively understood in terms of the nature of the molecular motion and/or reorientation processes involved. The results on the copolymer suggest that pressure should induce a ferroelectric‐paraelectric transition in PVDF below Tm, but such a transition was not observed over the limited pressure range of the present experiments. The relaxational dynamic (not static) nature of the melting process in these materials is indicated by the observed dependence of Tm on probe frequency. The frequency (or rate) and strong pressure dependences of Tm of PVDF provide a rational explanation for why it is possible to use this polymer as a piezoelectric shock‐wave gauge to relatively high shock pressures and the accompanying high temperatures.

AC Conductivity and Dielectric Relaxation Behavior of Solution Grown Poly (Vinylidene Fluoride) Films

“…The α c -relaxation is attributed to the rotation of the side groups dipoles or to the local oscillations of the frozen main chain [18]. The α a -relaxation near 260 K has been observed earlier in PVDF whereas the α c -relaxation appears as a kink near 380 K [19]. Similar results have been observed in the present investigations.…”

Mechanical behaviors and molecular deformation mechanisms of polymers under high speed shock compression: A molecular dynamics simulation study

“…Polymeric materials have a wide range of engineering applications [1,2], which stimulate huge interests in academics due to their fantastic mechanical, thermal and electrical properties [3e6]. The material properties of polymers are determined not only by their chemical composition but also by the mutual arrangement of their macromolecule [7,8].…”

Dynamics response of polyethylene polymer nanocomposites to shock wave loading

“…Polymer and polymer‐based composites have been investigated for a wide range of engineering applications including high strain rate condition, for example, shock‐wave loading . In particular, recent experimental and computational studies have demonstrated that polyurea, which falls into the class of elastomeric copolymers, have great potentials for the dispersion/attenuation of the shock waves resulting from the blast and/or ballistic impact loading .…”