Influence of heat treatment temperature after the pressure expansion on the electromechanical properties of cellular polypropylene electret

The influence of heat treatment temperature after the pressure expansion on the electromechanical properties of cellular polypropylene (PP) electret is studied. The results point out that over the temperature range form RT to the melting temperature of the sample, the thickness of the sample after pressure expansion increases with the heat treatment temperature. Compared to that mentioned above, obviously different influence of heat treatment temperature on the electromechanical properties of cellular PP is observed. The elastic modulus and electromechanical coupling factor of cellular PP electret reach minimum and maximum at 90℃ heat treatment temperature, respectively. As a result, the piezoelectric d 33 coefficient reaches its maximum of 377pC/N. Further, with the increase of heat treatment temperature, the resonance frequency of cellular PP could be regulated from about 794 to 371kHz.