PIEZOELECTRICITY OF CORONA-POLED POLY(VINYLIDENE FLUORIDE)

The 100-μm thick films of poly(vinylidene fluoride) (PVDF) were stretched four times their original lengths at 80°C and heat treated at 140°C for 30min under the condition of fixed length. Arrays of needle electrodes were placed 5-mm above and below the film. The d.c. voltage 12 kV applied between the electrodes produced corona discharge in the air gap and polarized the film. The piezoelectric constant d31 was about 12pC/N, independent of poling temperature. When the process of heat-treatment at 140°C was omitted, the piezoelectric constant attained a maximum at the poling temperature 80°C and the stabilized value of d31 was about 20pC/N. When the corona poling and stretching were performed simultaneously, the piezoelectric constant became the highest at the poling temperature 50°C and the stabilized value of d31 reached 40pC/N. © 1979, The Society of Polymer Science, Japan. All rights reserved.