1 Inorganic electret material
Silica is an inorganic electret material that has been studied extensively, especially after chemical surface treatment, high stability electrets can be prepared. Barium titanate (BaTiO3), lead zirconate titanate (PZT), zinc oxide (ZnO), tantalum oxide (Ta2O5), aluminum oxide (A12O3), titanium oxide (TiO2) and other oxides, as well as silicon nitride (Si3N4), etc. Both are inorganic electret materials that have been studied. Huang Zhiqiang et al. modified silica by ion doping to improve its positive charge electret performance and storage stability, thereby obtaining the desired positive electret material. He used the fusion process to mix A12O3 with a mass fraction of 0.2 and PbO with a mass fraction of 0.4 into the amorphous SiO2 film electret. Experiments such as positive corona charging at high temperature and constant gate voltage and isothermal charge attenuation show that the SiO2 film modified by Al3+ and Pb2+ ion doping has good positive electret performance, and its positive charge storage stability is high after 210 d At 95%. In addition, B3+, Zn2+ doping can also be used to modify the SiO2 film electret.
Among natural minerals, there are also polar materials, and among them, tourmaline has a strong polarity of self-generating polarity, and its polarization vector will not be affected by the external electric field. In 1993, a Japanese scholar Teru Taro Nakamura published a report on the properties of tourmaline. Many scholars became interested in this and developed a tourmaline electret fiber. Takahashi et al. added fine tourmaline powder to synthetic fibers and made this fiber into a non-woven fabric, which was then used as an air filter material. Studies have shown that after adding tourmaline, the filter material not only improves the filtration efficiency of dust, but also can sterilize and purify the air.
2 Organic electret materials
Highly insulating fluoropolymers represented by fluorocarbon polymers, such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (PFA), polyperfluoroethylene propylene (Teflon-FEP), soluble polyethylene (PFA) ), polyvinylidene fluoride (PVDF), etc. are all organic electret materials with excellent performance. There are many reports on electrets in this area. Reinhard et al. discussed the higher piezoelectric performance and charge storage capacity of PTFE nanomaterials than conventional PTFE, and it still maintains better charge stability at 300 hours. Xia Zhongfu et al. used grid-controlled constant voltage corona charging at room temperature and high temperature to explore the charge storage stability of both positive and negative electrets formed by a porous polytetrafluoroethylene film. Polypropylene is a typical non-polar, hydrophobic polymer, and its high resistivity is also a good electret material, usually used as an electret filter material. G. M. Sessler et al. analyzed the good piezoelectricity and charge storage capacity of the porous polypropylene film after charging. Zhao Huijuan et al. used low-temperature plasma to treat the polypropylene film surface to improve the electret performance of the polypropylene film. Bozena et al. studied the properties of high-voltage corona discharge electret polypropylene fabric. The study showed that fine and soft curled fibers and fabrics with higher surface density have good electret effects, and their filtration efficiency and moisture resistance are better. . However, the charge storage performance of organic electret materials is worse than that of inorganic electret materials, especially in high temperature or humid environment, the charge is easily attenuated, which affects the service life of the product. In order to improve the charge storage capacity of organic electret materials, many scholars combine mineral electrets with organic materials. For example, the composite of polyvinylidene fluoride and ceramic barium titanate or lead zirconate titanate (PVDF /BaTiO3, PVDF /PZT), the composite of PVDF and piezoelectric rubber, have all been research results and development applications.key words：electret masterbatch factoryChina electret masterbatch factory
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