含氟基团对聚酰亚胺耐电晕及介电性能的影响

Effect of fluorine-containing groups on the corona resistance and dielectric properties of polyimide

电气设备的高频化趋势对绝缘材料的耐电晕老化性能及介电性能提出了更高的要求。因此,提高绝缘材料的绝缘性能对高频电力系统的发展至关重要。本文以2,2’-双(三氟甲基)-4,4’-二氨基苯基醚(6FODA)、4,4’-二氨基二苯醚(ODA)、均苯四甲酸二酐(PMDA)为反应单体,设计制备了嵌段共聚型含氟聚酰亚胺(FPI)三层薄膜,并重点研究了材料的耐电晕性能和介电性能。结果表明:不同含氟量嵌段共聚型FPI三层薄膜的耐电晕寿命均高于纯聚酰亚胺(PI)三层薄膜,且随着含氟量的增加,薄膜耐电晕寿命相应增大。当ODA与6FODA摩尔比为1∶9时三层薄膜的耐电晕寿命在常温(20℃)、80 kV/mm下最高可达4.0 h,是纯PI三层薄膜(1.4 h)的2.86倍。随着含氟量的增加,FPI三层薄膜的介电常数呈现先减后增趋势,ODA与6FODA摩尔比为1∶1时三层薄膜的介电常数在1 MHz时最低可降至2.26,介电损耗与电导率呈现先增后减趋势。介电强度随着含氟量的增加有所下降,但均高于纯PI三层薄膜,ODA与6FODA摩尔比为9∶1时,三层薄膜的介电强度高达434 kV/mm。

The increasing use of electrical equipment at high frequencies poses greater demands on the corona aging resistance and dielectric properties of insulating materials.Therefore,it is crucial to enhance the insulation properties of insulating materials for the development of high-frequency power systems.In this study,we utilized 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether(6FODA),4,4'-diaminodiphenyl ether(ODA),and 1,2,4,5-benzenetetracarboxylic anhydride(PMDA)as reactive monomers to design and synthesize block copolymerized fluoro-polyimide(FPI)three-layer films.The focus was primarily on assessing the corona-resistant and dielectric properties of these materials.Results reveal that the corona-resistant life of the block copolymerized FPI three-layer films,with varying amounts of fluorine,is higher when compared to the pure polyimide(PI)three-layer films.Furthermore,the corona-resistant life of the films increase with an increase in fluorine content.When the molar ratio of ODA to 6FODA is 1:9,the corona resistance life of the three-layer film can reach up to 4.0 h at room tem-perature(20°C)and 80 kV/mm,which is 2.86 times higher than that of the pure PI three-layer film(1.4 h).Moreover,with the increase of fluorine content,the dielectric constant of FPI three-layer film shows a trend of decreasing and then increasing,and the dielectric constant of the three-layer film when the molar ratio of ODA and 6FODA is 1:1 can be reduced to as low as 2.26 at 1 MHz,and the dielectric loss and conductivity show a trend of increasing and then decreasing.The dielectric strength decreases with the increase of fluorine content,but they are all higher than that of the pure PI three-layer film,and the dielectric strength of the three-layer film is as high as 434 kV/mm when the molar ratio of ODA to 6FODA is 9:1.