The phase diagram and morphology of blends of poly(vinylidene fluoride) and poly(ethyl acrylate)

Abstract

The phase diagram and crystallization behaviour of the polymer blend system consisting of poly(vinylidene fluoride) (PVF 2) and poly(ethyl acrylate) (PEA) have been examined. The melt exhibits phase separation upon heating to 10°C–50°C above the melting point of the PVF 2, depending on the composition. The cloud point and equilibrium melting point curve (for α-PVF 2) intersect at about 180°C and a composition of 50% (by weight) PVF 2. The polymer-polymer interaction parameter, χ, was calculated from the equilibrium melting point depression data and found to be −0.16 (at 170°C). Spherulite growth rate data have been measured as a function of composition and temperature. Assuming regime II crystallization a value of the product of the surface free energies of the α-PVF 2 crystals was calculated to be 4.4 × 10 −4J 2m −4. In blends crystallized from the one phase melt the texture of spherulites becomes more open and the spherulite extinction ring spacing (due to lamaller twist) becomes larger with increasing crystallization temperature. In addition the ring spacing increases with PEA content at constant crystallization temperature.