Quasi-static and dynamic piezoelectric d33 coefficients of irradiation cross-linked polypropylene ferroelectrets

Abstract

Irradiation cross-linked polypropylene (IXPP) foams show high piezoelectric activity after proper hot-pressing treatment and corona charging. Quasi-static piezoelectric d33 coefficients around 400 pC/N were measured by means of the direct piezoelectric effect. Dynamic values of the inverse piezoelectric d33 coefficients, determined from the dielectric resonance spectra at 220 kHz, is about 68% of the quasi-static d33 values. The difference between the quasi-static and the dynamic values of d33 is probably due to the enhancement of Young’s modulus of IXPP with increasing frequency. The piezoelectric d33 coefficients are slightly dependent on the applied pressure in the range up to 50 kPa. The d33-values decrease by 70% when the samples are exposed to 90 °C for 1 day; and a pre-aging treatment improves the thermal stability of the d33 coefficients.