Samples containing the three crystalline phases of poly(vinylidene fluoride), ␣, ␤, and ␥, have been obtained under distinct crystallization conditions. Samples containing exclusively unoriented ␤ phase have been obtained by crystallization from dimethylformamide (DMF) solution at 60°C. Oriented ␤ phase has been obtained by uniaxial drawing, at 80°C, of an originally ␣ phase sample. Samples containing exclusively ␣ phase have been obtained by melting and posterior cooling at room temperature. Samples containing both ␣ and ␥ phases have been obtained by melt crystallization at 164°C for 16 and 36 h. Presence of the crystalline phases in each sample were confirmed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXD), polarized light optical microscopy (PLOM), and scanning electron microscopy (SEM). Infrared absorption bands identifying unequivocally the presence of ␤ and ␥ phases in a sample are presented. It is shown that solution crystallization at T Ͻ 70°C always results in the ␤ phase, regardless of the solvent used. Melt temperatures of the respective phases have also been determined.

The effect of temperature on the crystallization of α, β, and γ phases of PVDF from dimethylacetamide (DMA) solution was studied. Variation in the crystallinity content of these three phases was obtained as a function of temperature using infrared spectroscopy, differential scanning calorimetry (DSC) and x‐ray diffraction techniques. Such variation is related to the dependence of the crystallization rate of each phase with temperature, and allowed a better understanding of some results found in the literature about the crystallization and interconversion of these phases. Micrographs of samples present morphologies that corroborate with the proposed explanations. © 1994 John Wiley & Sons, Inc.

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