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为了研究方波条件下纳米Al2O3对PI膜介电性能的影响,将粒径为60 nm的Al2O3纳米粒子作为无机填料添加到PI基体中,制作了掺杂量质量分数为1%,2%,5%,7%,10%的PI薄膜。测量了PI/Al2O3薄膜耐电晕性能和介电温度谱以及介电频谱,并用SEM镜观察了放电前后PI/Al2O3薄膜微观形貌。研究结果表明:Al2O3纳米粒子的掺入提高了复合薄膜的耐电晕性能;PI/Al2O3复合薄膜的相对介电常数(εr)与介质损耗正切(tanδ)值随着Al2O3含量升高而升高,其tanδ值随着频率的增加先减小后增大,在200 Hz处有最小值。在同一频率下,PI/Al2O3薄膜εr和tanδ表现出对温度的依赖性,tanδ在70℃与170℃附近出现两个峰值;且随着Al2O3含量的增高,tanδ介电峰向高温方向移动。PI基体中高分子链缠结在纳米粒子周围,纳米粒子所引入的界面以及在聚合物中表现的“钉扎效应”是影响PI/Al2O3复合薄膜介电性能的主要原因。
In order to study the influence of nano-Al2O3 on the dielectric properties of PI films under the condition of square wave, Al 2 O 3 nano-particles with particle size of 60 nm were added into PI matrix as inorganic fillers. The doping amount of 1%, 2% 5%, 7%, 10% PI film. The corona resistance, dielectric temperature and dielectric spectra of PI / Al2O3 films were measured. The microstructures of PI / Al2O3 films before and after discharge were observed by SEM. The results show that the incorporation of Al2O3 nanoparticles improves the corona resistance of the composite films. The relative permittivity (εr) and dielectric loss tangent (tanδ) of PI / Al2O3 composite films increase with the increase of Al2O3 content , The value of tanδ firstly decreases and then increases with the increase of frequency, and has the lowest value at 200 Hz. At the same frequency, the εr and tanδ of PI / Al2O3 films show the temperature dependence. The tanδ peaks at 70 ℃ and 170 ℃, and the peak of tanδ shifts to higher temperature with the increase of Al2O3 content. The main reason for the dielectric properties of PI / Al2O3 composite films is that the polymer chains in the PI matrix are entangled around the nanoparticles, the interfaces introduced by the nanoparticles and the “pinning effect” exhibited in the polymer.