.pvdf / Ptfe Composite Membrane Electret Performance

Many significant progresses have been made in the field of electrets and function dielectric materials over the past few years. For example, electret electric and acoustic transducers are widely used today and advance in electret microsensors spur a expanded development. The investigation of electret phenomena in biological materials provides a new method for human being to understand nature and themselves. Recently, the electret research shows a steady transformation characterized by porous-polymer and hybrid films consisting of porous and solid polymer film, especially for the porous PTFE. The results in the research for porous PTFE electret have been shown that charge storage life is better for a magnitude than FEP, which is the best electret material. Especially, since the piezo- and pyroelectricity are reported in mechanically non-uniform space charge electret and hybrid piezoelectric electret structure made of 'soft' hand 'hard' polymer layer is proposed the piezoelectricity of space charge electret containing porous PTFE have become main study field.In present paper the behavior of injection, storage and decay of charges for the different kind of materials are investigated by means of corona charging, isothermal surface-potential and piezoelectricity modulus decay measurement etc. The effect of aging condition and preparation methods for different materials on the crystal status of PVDF is explained with their XRD analyze figure. PVDF/PTFE compound electret piezoelectricity film was succsessfully prepared by flow casting ,spin coating ,soaking skills and corona charging. With the model of sandwich-structure of spacial charge of electret film,we research the effect of aging and charging condition on the piezoelectricity of PVDF/PTFE film by dynamic measure method of piezoelectricity.By analysing their characteristic electret property,we discuss the engender mechanism of piezoelectricity. The result shows pizoelectricity modulus isthe highest which was prepared by soaking, enough to 81pC/N,this is because of the high content of 3 -PVDF minicrystal in the compound film.