Study on the high frequency insulation strength of disiloxane modified polyimide film

High frequency power transformer is conducive to the reliable grid connection of distributed energy. Polyimide is commonly used in the cladding insulation of high frequency power transformer, but the surface discharge will lead to insulation failure, so molecular structure modification is adopted. In this paper, 1,3-bis (3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (GAPD) with 1%, 2% and 5% molar content was introduced into polyimide, then we tested the physical and chemical properties and the high-frequency insulation strength along the surface of the modified films. The results show that after adding GAPD, the overall functional group of the material does not change, the intermolecular charge transfer complexation increases, the UV absorption increases, the material does not appear phase separation and the structure is more orderly, and the glass transition temperature increases. The modified films have excellent thermal properties and high breakdown strength. The high frequency insulation strength along the surface is improved, and it increases with the increase of GAPD content. The flashover voltage along the surface has no obvious change, but the electrical life along the surface is 4.77 times of that of pure polyimide. Further analysis shows that the Si-O-Si network is formed in the matrix of the modified film through the bonding and charge transfer complexation. After the destruction of the outer matrix, there will be dispersed flocculent inorganic particles, which can protect the inner matrix and improve the material performance. Combined with UV energy absorption, thermal performance improvement and other factors, it can better improve the high-frequency surface insulation strength of polyimide film, which has potential application value.