聚四氟乙烯和氟化乙丙烯共聚物复合膜的压电性

以多孔PTFE膜为骨架，而以致密（非多孔）FEP膜为储电介质层的孔洞结构复合压电驻极体膜的制备方法.利用正压电效应，测量了复合膜的准静态压电系数d₃₃；研究了压电系数的热稳定性和复合膜中空间电荷的动态特性；并通过介电谐振谱的分析，比较了这类复合膜的准静态和动态压电系数.结果表明：FEP和PTFE复合膜压电驻极体的准静态压电系数d₃₃可以达到300 pC/N.经90℃老化20 h 后的d₃₃仍保持在初 关键词： 压电驻极体 压电性 多孔聚四氟乙烯 致密氟化乙丙烯共聚物

Piezoelectricity of laminated polymer films made of nonporous fluoroethylene and porous polytetrafluoroethylene layers

The piezoelectrets made of porous polytetrafluoroethylene （PTFE） films and nonporous fluoroethylenepropylene （FEP） films are prepared by using a hot-pressing method. The quasi-static piezoelectric d₃₃-coefficients of such piezoelectret films are measured. The thermal stability of d₃₃-coefficients and dynamic characteristics of charges in the piezoelectret films are investigated. The dynamic d₃₃-coefficients are obtained by analyzing the dielectric resonance spectra of the piezoelectret films. The results show that the piezoelectric d₃₃-coefficients up to 300 pC/N are achieved for the laminated PTFE/FEP films. The d₃₃ value retains 40% of the initial value when the sample was annealed at the temperature of 90℃ for 20 h. Pre-ageing is an effective way to further improve the thermal stability of d₃₃-coefficients. The dominant drift path of the detrapped charges in the shallow traps is most likely along the surface of the PTFE fibers, while charge drift through the solid layer of FEP is possibly prevailing for the charges in the deeper traps. The d₃₃ value determined from the dielectric resonance spectrum is smaller than the quasi-static d₃₃ value, which is mainly due to the enhanced Young's modulus with the increase of frequency.