纳米SiO2分散性对SiO2/LDPE纳米复合材料直流介电性能的影响

SiO₂/低密度聚乙烯(LDPE)复合材料的介电性能与纳米SiO₂在LDPE基体中的分散性密切相关。为研究室温下拉伸处理对纳米SiO₂颗粒在LDPE基体中分散性的作用机制，本文选取7 nm粒径的疏水型纳米SiO₂与LDPE熔融共混制备SiO₂/LDPE纳米复合材料。将制备好的纳米复合材料经过三次拉伸处理，利用SEM、DSC表征纳米粒子的分散性及复合材料的结晶度，利用热刺激电流法(TSC)测试分析复合材料的陷阱能级和陷阱密度。通过对纳米复合材料的空间电荷，电导电流，直流击穿强度进行实验测试，研究了拉伸对纳米粒子分散性的影响及其所导致的直流介电性能的改变。结果表明室温下拉伸有助于纳米粒子的分散，使纳米SiO₂粒子的团聚尺寸从200 nm左右缩减到100 nm左右；但拉伸会破坏LDPE的结晶结构，劣化其性能；通过掺杂纳米SiO₂引入深陷阱能级可以改善LDPE的直流介电性能。经过拉伸的SiO₂/LDPE的空间电荷积累得到...

Influence of nano-SiO2 dispersion on the direct current dielectric properties of SiO2/LDPE nanocomposite

The dielectric properties of SiO₂/low-density polyethylene (LDPE) composites are closely related to the dispersion of nano-SiO₂ in LDPE matrix. In order to study the mechanism of tensile treatment on the dispersion of nano-silica particles in the LDPE matrix at room temperature, a hydrophobic nano-SiO₂ with a particle size of 7 nm was selected to be fused and blended with LDPE to prepare SiO₂/LDPE nanocomposites. The prepared nanocomposites were stretched three times, and the dispersion of nanoparticles and the crystallinity of the composites were characterized by SEM and DSC, the trap energy levels and trap densities of the composites were analyzed by thermally stimulated galvanometry (TSC). The effects of stretching on the dispersion of nanoparticles and the resulting changes in direct current dielectric properties were investigated by experimentally testing the space charge, electrical conductivity, and direct current breakdown strength of the nanocomposites. The results show that stretching at room temperature helps the dispersion of nanoparticles and reduce the agglomeration size of nano-SiO₂ particles from about 200 nm to about 100 nm. However, stretching will destroy the crystal structure of LDPE and deteriorate its properties; The DC dielectric properties of LDPE can be improved by introducing deep trap levels by doping nano-SiO₂.The space charge accumulation of the stretched SiO₂/LDPE is suppressed, and the mechanism of conducting current is changed. By fitting the conductance current data, it is found that the conductance of the stretched SiO₂/LDPE is dominated by ion hopping conductance, and its hopping distance is reduced to about 1.98 nm. Compared with LDPE, the DC breakdown field strength of SiO₂/LDPE is improved by about 43%, The main reason for the decrease of the breakdown strength of SiO₂/LDPE after stretching at room temperature is the structural defects of the LDPE matrix caused by the stretching process.