Induced Internal Bubble Shapes Affected Piezoelectric Behaviors of PVDF Films

摘要

In this research, the effect of induced internal bubble shapes on dielectric behavior and piezoelectric properties in polyvinylidene fluoride (PVDF) was studied. The bubbles were created inside PVDF films by thermal phase inversion and AZDC blowing agent techniques. Subsequently, PVDF films with internal bubble were stretched to change the spherical to ellipsoidal. The dielectric constant and the loss tangent of porous PVDF films were measured as a function of frequency range, 1 kHz-10 MHz, at room temperature by an impedance/gain-phase analyzer in different % porosities, sizes, structures, and shapes of bubbles. It was found that at high frequency the ellipsoid bubble shape showed more promising data, including a higher dielectric constant, less relaxation with frequency, and lower dielectric loss than spherical shaped. Also, the measured dielectric constant is fitted well with the Yamada model indicating 0-3 connectivity of PVDF/air bubble composites. Moreover, the ellipsoid shape can enhance the piezoelectric properties higher than those of spherical shape in PVDF films. Consequently, the PVDF with internal bubbles can be proposed as another candidate to use instead of ceramic-filled PVDF in lightweight piezoelectric applications.