Primary Piezoelectric Relaxation in a Copolymer of Ã\x9f-Hydroxybutyrate and Ã\x9f-Hydroxyvalerate

Oriented films of a copolymer of 75 mol% ß-hydroxybutyrate and 25 mol% ß-hydroxyvalerate obtained from microoganisms showed intrinsic shear piezoelectricity. The complex piezoelectric factor e = e\´-ie" elastic constant c = c\´ ± ic", and dielectric permittivity ¿= ¿\´ -i¿" were dynamically determined at 0.8 to 100 Hz and from -150 to 100 ° C. The relaxational behavior of these quantities was observed around the glass transition temperature. Assuming time-temperature equiv alence, master curves for these three parameters were composed. The temperature variation of the shift factor fitted well with the WLF equation. The theory of spherical dispersion model, in which piezoelectric crystalline spheres are dispersed in a relaxing amorphous medium, was applied satisfactorily to explain the piezoelectric relaxation.