Study On Dielectric Performances Of Fumed-silica/Polyethylene Nanocomposites

In order to study the modification effects and mechanism of nano-particles with different structures in nano-dielectrics on the electrical insulation performances of composites,SiO₂/low-density polyethylene with different doping concentrations were prepared by doping two different types of SiO₂ nanoparticles in polyethylene.（LDPE）nanocomposites.The microscopic morphology and dispersion of SiO₂ in LDPE were characterized by scanning electron microscopy.The effect of nanodoping on the crystallinity of LDPE was analyzed by differential scanning calorimetry.Through the analysis of DC conductance,space charge distribution and DC breakdown characteristics,the modification mechanism of insulation properties of nanocomposites was studied.In this paper,nano-fumed silica was selected as a dopant to prepare different types of nanocomposites,Preparation of different types of nanocomposites.The relationship between the microstructure and macroscopic dielectric properties of composites doped with hydrophilic and hydrophobic nano-silica in polyethylene was investigated.Nano-silica has a significant enhancement of the interfacial effect in the nano-dielectric due to its special structure and large specific surface area,resulting in an increase in the dielectric properties of the composites.In this paper,nanocomposites with different doping concentrations were prepared.Under SEM,the nanoparticles were uniformly dispersed in the composites,and the agglomeration phenomenon was obvious with the increase of nano-doping concentration.The composite was effectively filled with nano-SiO₂ to change the crystallinity of LDPE.Hydrophobic SiO₂ is more effective than hydrophilic SiO₂ to improve the crystallinity of the matrix polyethylene.The infrared transmission test shows that the hydrophilic group and the hydrophobic composite medium carry different polar groups.The SEM test of the composite material shows that the dispersion of the nanoparticles in the 1wt%hydrophobic SiO₂/LDPE composite is better,and the crystallinity of the LDPE is maximized by heterogeneous nucleation.Compared with pure polyethylene,the conductance of nano-SiO₂ polyethylene composites is significantly reduced.Heterogeneous nucleation of SiO₂ nanoparticles increases the crystallinity of LDPE,reduces carrier mobility,increases the number of traps,and increases the probability of charge traps capturing carriers;The-CH₃symmetric group on the surface of hydrophobic SiO₂ nanoparticles significantly increases the dispersion of the nanoparticles in the composite.More effective enhancement of interface effects,suppression of space charge accumulation and increase of electric breakdown field strength.It is proved that the special nanostructure in nano-dielectrics can significantly improve the dielectric properties of polyethylene.Comparing the SiO₂ nanometer particle size,it is found that the nanoparticle with small primary particle size has better improvement effect on the composite material than the nano particle with large primary particle diameter.