Transitions in semicrystalline polymers. I. poly(vinyl Fluoride) and poly(vinylidene fluoride)

Abstract

The relaxation phenomena of two semicrystalline polymers, poly(vinyl fluoride) and poly(vinylidene fluoride) were studied by a dilaitometric technique in the temperature range from—30°C to 200°C. The premelting (Tα_c), upper [T_g(U)] and lower glass [T_g(L)] transitions are observed for both polymers, as well as a transition in PVF₂ which is sensitive to thermal history. Comparison of our results with previous work, in most cases at higher frequencies, as well as thermal treatment of PVF₂ allow us to make assignments and calculate activation energies for the relaxations. Certain characteristic quantities are given, namely, T < T_g(L)/T_g(L), T_g(L)/T_m, and Tα_c/T_m, as well as αΔ_g and ΔαT_g.