Xing Zhaoliang, Zhang Chong, Xue Naifan, Li Zhihui, Li Fei, Wan Xiangnan, Guo Shaowei, Hao Jianhong
State Key Laboratory of Advanced Power Transmission Technology, Global Energy Interconnection Research Institute Co., Ltd., Beijing 102209, China.
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.
Polymers (Basel). 2021 Dec 31;14(1):146. doi: 10.3390/polym14010146.
High-frequency power transformers are conducive to the reliable grid connection of distributed energy sources. Polyimide is often used for the coating insulation of high-frequency power transformers. However, creeping discharge will cause insulation failure, therefore, it is necessary to use disiloxane for the purpose of modifying the molecular structure of polyimide. This paper not only introduces 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (GAPD) with a molar content of 1%, 2%, and 5% to polyimide, but also tests both the physical and chemical properties of the modified film and the high frequency creeping dielectric strength. The results show that after adding GAPD, the overall functional groups of the material do not change, at the same time the transfer complexation of intermolecular charge and the absorption of ultraviolet light increase. There is no phase separation of the material and the structure is more regular and ordered, moreover the crystallinity increases. The overall dielectric constant and the dielectric loss tangent value show different trends, which means that the former value increases, while the latter value decreases. In addition, the resistivity of the surface and the volume increase, which is the same as the glass transition temperature. The mechanical properties are excellent, and the strength of bulk breakdown is mounting. The insulation strength of the high frequency creeping surface has been improved, which will increase with larger contents of GAPD. Among them, the relative change of the creeping flashover voltage is not obvious, and the creeping discharge life of G5 is 4.77 times that of G0. Further analysis shows that the silicon-oxygen chain links of the modified film forms a uniformly dispersed Si-O-Si network in the matrix through chemical bonds and charge transfer complexation. Once the outer matrix is destroyed, it will produce dispersed flocculent inorganic particles which have the role of protecting the inner material and improving the performance of the material. Combined with the ultraviolet light energy absorption, the increase of deep traps, the reduction of dielectric loss, and the improvement of thermodynamic performance, can better improve the high-frequency creeping insulation strength of polyimide film and its potential application value.
高频电力变压器有利于分布式能源的可靠并网。聚酰亚胺常用于高频电力变压器的涂层绝缘。然而，沿面放电会导致绝缘失效，因此，有必要使用二硅氧烷来改性聚酰亚胺的分子结构。本文不仅将摩尔含量为1%、2%和5%的1,3-双（3-氨基丙基）-1,1,3,3-四甲基二硅氧烷（GAPD）引入聚酰亚胺中，还对改性薄膜的物理和化学性能以及高频沿面介电强度进行了测试。结果表明，添加GAPD后，材料的整体官能团不变，同时分子间电荷的转移络合和紫外光吸收增加。材料没有相分离，结构更加规则有序，结晶度增加。整体介电常数和介电损耗正切值呈现不同趋势，即前者值增加，而后者值减小。此外，表面和体积电阻率增加，玻璃化转变温度也一样。力学性能优异，体击穿强度不断提高。高频沿面的绝缘强度得到了改善，且随着GAPD含量的增加而提高。其中，沿面闪络电压的相对变化不明显，G5的沿面放电寿命是G0的4.77倍。进一步分析表明，改性薄膜的硅氧链节通过化学键和电荷转移络合在基体中形成均匀分散的Si-O-Si网络。一旦外部基体被破坏，就会产生分散的絮状无机颗粒，这些颗粒具有保护内部材料和改善材料性能的作用。结合紫外光能量吸收、深陷阱增加、介电损耗降低以及热力学性能的改善，可以更好地提高聚酰亚胺薄膜的高频沿面绝缘强度及其潜在应用价值。
