Abstract: A poly(vinylidene fluoride) (PVDF) film was prepared by a solventcasting method, and its crystalline structures after a isothermally crystallizing treatment was characterized by Fouriertransform infrared spectroscopy and Xray powder diffraction. The effect of melting temperature on the isothermal crystallization behavior of this film was investigated by a cycling meltcrystallization technique. The results indicated that, after the isothermally crystallizing treatment, only αphase crystals were formed in the film, and its equilibrium melting point of PVDF is around 197 ℃. The effect of melting temperature on the isothermal crystallization behavior of the film was not significant above the equilibrium melting point. However, when the melting temperature was lower than the equilibrium melting point, the number of spherulites increased with an increase of melting temperature, but its size decreased.

Key words: poly(vinylidene fluoride), equilibrium melting point, isothermal crystallization, melting temperature