The Investigation of /spl alpha//spl rArr//spl beta/ phase transition in poly(vinylidene fluoride) (PVDF)

The phase transition from the non-polar /spl alpha/-phase to the polar /spl beta/-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous for being a non-destructive technique. Films of a-PVDF were subjected to stretching under controlled rates and at 80 /spl deg/C, the transition to /spl beta/-PVDF being monitored by the decrease in the Raman band at 794 cm/sup -1/ characteristic of the /spl alpha/-phase, with the concomitant increase in the 839 cm/sup -1/ band characteristic of the /spl beta/-phase. Poling with negative corona discharge was found to affect the a-PVDF morphology improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, viz, X-ray diffraction and infrared spectroscopy.