Phase transitions during stretching of poly(vinylidene fluoride)

The effect of temperature and deformation rate on the structure of drawn poly(vinylidene fluoride) samples was investigated by means of wide angle X-ray scattering. It was shown that drawing in the range of 50 and 145 degrees C results in transition of non-polar alpha phase into polar beta crystallites. The analysis of the reflection from the planes (111) and (201) of the beta phase indicates that the content and orientation of beta crystallites are affected by the temperature of drawing. The highest content of well oriented beta crystallites was achieved during drawing at 87 degrees C. This temperature is close to the above temperature of alpha(c) transition/relaxation and corresponds with the temperature of deformation applied in industrial processes in the formation of piezoelectric poly(vinylidene fluoride) (PVDF) films. (C) 1998 Elsevier Science Ltd. All rights reserved.