Mechanical and Physical Properties of Poly(Vinylidene Fluoride) at High Pressures and Temperatures

摘要

Stress-strain behavior in tension and compression at various pressures, Pressure-Volume-Temperature (PVT) relations, and the pressure dependency of transitional behavior, by dielectric technique, of Phase I and Phase II poly(vinylidene fluoride) (PVDF) have been determined. The result obtained are used in analyzing the complex behavior of piezoelectric and pyroelectric properties of the material at high pressures and temperatures. The Young's modulus (E) of Phase II PVDF Increases, at room temperature, monotonically but nonlinearly, with increasing pressure as long as the amorphous material is in the rubbery state. It then takes a step-jump at Pg (5 Kbars) and continues to increase with pressure. However, the yield strentgh in both tension and compression is observed to be linear functions of pressure. PVT measurements clearly show the glass transition temperature (Tg) at -50C and the crystal transition (Tc) at 22C at atmospheric pressure. The Tg of both unoriented and oriented Phase I PVDF increase, in most part, linearly with increasing pressure except at low pressures where the increase is parabolic.