聚酰亚胺/二氧化钛纳米复合薄膜制备与耐电晕性

采用原位聚合法制备不同TiO₂组分聚酰亚胺(PI)/纳米TiO₂复合薄膜, 薄膜厚度50μm。 测试结果表明, TiO₂呈球状颗粒, 直径约为100 nm, 聚酰亚胺呈片状, 尺寸约为2μm×1μm。随着TiO₂含量的增加, 复合薄膜介电常数和介电损耗增大, 击穿场强先增加后降低; 在40 kV/mm电场强度下, 复合薄膜耐电晕老化寿命增加, 纯PI薄膜寿命为3 h, 20wt%TiO₂含量薄膜寿命达到25 h; TiO₂颗粒耐电晕能力强, 与聚合物形成界面相, 改变材料陷阱能级, 有利于空间电荷的扩散和热量的传输, 在薄膜表面形成放电阻挡层, 降低局部放电对薄膜内部的侵蚀, 显著提高薄膜耐电晕老化寿命。

Preparation and Corona Resistant of Polyimide/TiO2 Nanocomposite Films

The polyimide (PI)/TiO₂ composite films with different component were prepared by in-situ dispersion polymerization. Thickness of the obtained films is about 50μm. The characterization results show that diameter of spherical TiO₂ in the films is about 100 nm and the size of the lamellar polyimide is about 2μm×1μm. With the increase of the TiO₂ content, electrical breakdown strength increases firstly and then decreases, while the values of permittivity, dielectric loss, corona resistant lifetime increase. Under the electric field of 40 kV/mm, corona resistant lifetime of pure PI is about 3 h, while the lifetime of composite film with 20wt% TiO₂ is about 25 h. TiO₂ has a high performance in corona resistance forming interphase with polymer and changing the trapping levels of material, facilitating diffusion of space charge and transmission of heat in material. A large of TiO₂ particles can form discharge blocking layer on the surface of films and reduce internal erosion by partial discharge. Therefore, the corona resistant ability of nanocomposite films is significantly improved.