Effect of an External Electric Field on the Crystallization Behavior of Poly(Vinylidene Fluoride)

The effect of electric field strength upon the rate of overall crystallization, crystal morphology, and crystal modifications was investigated by studying the melt-crystallization of poly(vinylidene fluoride) in the presence of an external dc electric field of 0~0.09 MV/cm. With increase in the exectric field strength. the temperature at which tar electro-active polar ${\gamma}$-crystal begins to form decreased and the ${\gamma}$-crystal content increased with reduction in the content of the electro-inactive $\alpha$-crystal. The transition of $\alpha$-crystal to ${\gamma}$-crystal was found to be suppressed by the electric field in the course of the isothermal melt-crystallization. The electric field did not have a significant effect on the rate of overall crystallization at 150~ 154 $^{\circ}C$ where only $\alpha$-crystal was formed. However, the rate of crystallization was reduced by the electric field at slightly higher temperatures (ca. 156-158$^{\circ}C$) where a mixture of $\alpha$- and ${\gamma}$-crystals was formed, whereas the electric field increased the rate of crystallization at 160-162 $^{\circ}C$ where ${\gamma}$-crystal was preferentially formed.

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