SIMULTANEOUS STRETCHING AND CORONA POLING OF PVDF FILMS

Simultaneous stretching and corona poling (SSCP) of polyvinylidene fluoride (PVDF) films at elevated temperatures in batch mode greatly enhanced the piezo- and pyroelectric constants. When poled under optimum conditions, a piezoelectric constant d31 approximately 60 pC N-1 and a pyroelectric constant p approximately 6 nC cm-2 K-1 at 30-degrees-C were obtained. Both these values are about twice the best values found by us, and other workers, for films that were first stretched and then corona poled. The time stability of d31 at all temperatures was also greatly improved by SSCP. We postulate that there is a greater contribution of whole beta crystallite rotation in these SSCP films. X-rays show that they have enhanced beta phase over those that are first stretched and then poled.