Research On Space Charge And Electrical Properties Of SiO₂/POE/PP Nanocomposites

Cable transmission is widely used in power energy transmission.Traditional cross-linked polyethylene insulated cables have disadvantages such as complicated process and non-recyclable.With the increasing attention to environmental protection,the development and research of eco-friendly materials polypropylene has become a hot spot in cable insulation.PP has the advantages of low cost,good heat resistance,plasticization and recyclability.However,due to its poor toughness,it is difficult to process and install,and it is easy to accumulate charge under the action of DC voltage to accelerate aging,which limits its application in the cable industry.Therefore,it is of great practical significance to improve the mechanical and electrical properties of polypropylene by elastomers and inorganic nanofillers.This thesis enhancing the mechanical and electrical properties of PP by adding elastomer POE and nano-Si O₂ into its matrix.Two kinds of Si O₂ with surface treatment and without surface treatment are selected to prepare Si O₂/POE/PP composites with three different nano-contents of 0.5phr,1phr and 3phr,respectively.The microstructure,crystallization properties,mechanical properties,space charge accumulation and dissipation,dielectric constant and loss factor,conductivity current density,and DC breakdown field strength of the composites are thoroughly characterized and analyzed by SEM,PLM,DSC,tensile test,space charge test,dielectric constant and loss factor test,conductivity current test,and DC breakdown field strength test.The results indicate that the mechanical properties of the composite were enhanced by the addition of POE,however,the regularity of the PP matrix was destroyed,The electrical properties of the composite decreased.There was a significant increase in space charge accumulation,dielectric constant and loss factor,as well as an increase in conduction current density.Additionally,compared to PP,the DC breakdown field strength of the composite declined by 11.6%.After the addition of Si O₂,the nanoparticles become dispersed within the matrix,forming a uniform and dense interface.This results in a heterogeneous nucleation effect that promotes improved crystallization regularity of the Si O₂/POE/PP nanocomposites,the space charge accumulation is inhibited,the conduction current density is reduced,and the DC breakdown field strength is greatly improved.When Si O₂ without surface treatment is added,the most significant improvement in electrical properties at a content of 0.5 phr,with an average space charge density of 0.18C·m^-3 after short circuit,and the DC breakdown field strength is increased by 34.3%compared with POE/PP.However,as the nano-doping content increases,the electrical properties gradually decrease.At 3phr,the dispersion of nanoparticles in the matrix becomes worse and agglomeration occurs,which weakens the nano-effect and reduces the electrical properties.When the surface hydrophobic treated Si O₂ is added,the nanoparticles’dispersion within the matrix can be seen to be more uniform,and agglomeration phenomenon improves significantly.The electrical properties are greatly improved at two nano-contents of 0.5phr and 1phr,After short circuit,the average space charge density is 0.14C·m^-3 and 0.11C·m^-3,and the DC breakdown field strength is increased by 38.3%and 43.8%compared with POE/PP.The dielectric constant of Si O₂/POE/PP nanocomposites range between 2.3 and 2.37.Improving the mechanical and electrical properties of polypropylene by using elastomer POE and inorganic nano-filler Si O₂ is an effective means to develop polypropylene cable insulation materials.