Piezoelectricity of single-layer and multi-layer cellular polypropylene film electret

The piezoelectricity of a pressure-treated cellular PP(commercially available,trade name PQ50) film electret was studied by measurement of direct-piezoelectric and inverse-piezoelectric coefficient d_(33).The sample expanded with optimal parameters has a quasi-static piezoelectric coefficient d_(33) of up to 600pC/N,which is about 40 times higher than that of PVDF.While the hybrid multi-layer system by properly combining single-layer cellular PP film electret shows a quasi-static piezoelectric coefficient d_(33) as large as 2010pC/N,which is around 3 times of that of well-known PZT ceramics.The results are theoretically and technically helpful for promoting the application of cellular PP film electret.