QUANTITATIVE-ANALYSIS OF PIEZOELECTRICITY IN SIMULTANEOUSLY STRETCHEDAND CORONA-POLED POLYVINYL-CHLORIDE FILMS

Piezoelectric activity in cyclohexane-treated polyvinyl chloride films has been found to increase when processed under simultaneously stretc hed and corona poled (SSCP) conditions. The piezoelectric coefficient d(31) = 7.2 +/- 1.1 pC/N was obtained in these films under optimum pol ing conditions. The main contributor to the improved piezoelectricity has been the increased dipolar polarization. Crystallinity and complia nce have contributed marginally to the former. Thermally stimulated cu rrent (TSC) experiments show that maximum oriented dipole density has been achieved during the SSCP. Dipolar polarization approximate to 10( -2) C/m(2) has been obtained. The TSC and the shrinkage effect involvi ng molecular rotation and/or chain motion are closely related. An appl ication of the extended Mopsik and Broadhurst theory shows that 56% of the measured d(31) is due to the dimensional effect and 44% due to th e local field effect. (C) 1997 American Institute of Physics.