IMPROVED PIEZOELECTRICITY IN SOLVENT-CAST PVC FILMS

The piezoelectric coefficient of solvent cast polyvinyl chloride (PVC) films processed under simultaneous stretching and corona poling (SSCP ) conditions has been enhanced by similar to 4x (d(31) approximate to 5.3 +/- 0.35 pC/N) as compared to the maximum value (0.5 to 1.3 pC/N) reported in the literature [1,5]. The optimized values of d(31) are co mpared for SSCP, stretched and corona poled (STCP), and unstretched an d poled films. An efficient dipolar orientation can be achieved by the SSCP method, leading to the highest piezoelectric coefficient. It was shown that d(31) decayed to similar to 70% of its original value afte r 14 months for both SSCP and STCP films. X-ray experiments reveal tha t the (110) and (210) reflections are considerably reduced in SSCP fil ms as compared to STCP films. The orientation of (200) planes parallel to the film surface is preferred in the SSCP films. The crystallinity was found to increase with stretching in SSCP films. Young's modulus for the unstretched, STCP and SSCP films was measured.