| Power cables are common in everyday life,but they are important electrical equipment and an integral part of power transmission systems.With the continuous development of technology and cities,renewable energy is continuously being developed,and the demand for power cables in power grid systems is also increasing.Low-density polyethylene has entered the field of vision due to its outstanding insulation properties.At the same time,it is easy to process and has good ductility,and has emerged in the field of cable insulation.In order to meet the needs of the growing scientific and technological development,engineering has put forward higher and higher requirements for the performance of polyethylene and cross-linked polyethylene materials for cable insulation.The effect of long-term high field strength will degrade some properties of polyethylene,and even cause insulation failure due to aging.In order to obtain a material that is more excellent in electric aging resistance,the base material can be modified.Nanoparticles are widely used in the doping modification of polymers due to their peculiar effects.In this paper,the electrical aging properties of polyethylene based on nanometer MMT and SiO2 are studied in depth.For this reason,the microstructure of composites is characterized by X-ray diffraction,polarized light microscopy and differential scanning calorimetry.Experiments were carried out on conductivity and dielectric spectrum.Polyethylene-based nanocomposites were prepared by melt blending method.The performance of electric aging experiments on samples was carried out by alternating current electric field.Through research,it is found that electrical aging will affect the crystallinity and crystal structure of materials to some extent.Basically,the crystallinity decreases with the aging time;in the initial stage of electric aging,the breakdown field strength of the material shows a small increase;with the further increase of the electric aging time,the breakdown field strength decreases,but the nanometer The introduction of filler can delay the trend of this decline;electrical aging will increase the electrical conductivity of the material to varying degrees,especially in the high electric field test,the electrical conductivity of MMT/LDPE is significantly higher than SiO2/LDPE;It causes the increase of dielectric constant and dielectric loss;as the aging time increases,the grain size in the composite material gradually becomes smaller.When the aging time reaches a certain value,the macromolecular chain scission occurs in the material,and the amorphous region expands.A large number of low-density areas appear,and secondary aggregation of small spherulites occurs.The addition of nanofillers has a very significant inhibitory effect on the aging of polyethylene materials. |
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