Effect Of Compatibilizer LDPE-g-MAH On Space Charge Characteristics In MgO-doped Polyethylene Composite Films

Nanoparticle-doping polymer materials have become the mainstream method to improve the space charge accumulation of wire and cable insulation materials.However,agglomeration and other phenomena greatly affect the use of nanocomposites.Therefore,this paper uses low density polyethylene(LDPE)as the matrix material,choose different content of compatibilizer(LDPE-g-MAH)to modify the matrix material,and then doped with MgO nano particles.This paper studied the effect of compatibility on the space charge properties and other properties of nano composite material by different testing method,discussed the relationship between the microstructure and the macroscopic properties of the material,and provide a theoretical reference for the research and engineering application of cable insulation material.The experimental principles are expounded in this paper,including the compatibility principle of polymer blends,the interface theory of polymer composites and the principle of polymer space charge,which provide a theoretical basis for subsequent experiments.Three samples of pure LDPE,MgO/LDPE and MgO/LDPE-g-MAH/LDPE films were prepared by melt blending.Scanning electron microscopy(SEM)showed that the MgO/LDPE composites were dispersed uniformly,but there are still agglomeration phenomena.The compatibility of MgO/LDPE-g-MAH/LDPE films modified by compatibilizer was good,and the dispersion of MgO particles was more homogeneous,almost no agglomeration phenomena.The space charge characteristics of polyethylene doped with nanoparticle modified by different compatibilizer content under pressure and short circuit were characterized by PEA.The test results show that the MgO/LDPE composite with mass fraction of 1wt%can suppress the accumulation of space charge compared with pure LDPE film.However,due to the agglomeration of nanoparticles,there is a space charge pack with positive and negative charge alternating inside MgO/LDPE composite.The MgO/LDPE-g-MAH/LDPE film modified by compatibilizer can effectively suppress space charge.The content of 10wt%compatibilizer is the most significant.It can reduce the generation of space charge packet,and the space charge density of materials decreases from 6.79C/m~3 to 0.35C/m~3.The effects of compatibilizer on the dielectric properties and trap characteristics of MgO/LDPE thin films were studied by broadband dielectric spectroscopy and PSD method.The experimental results show that the dielectric constant of MgO/LDPE-g-MAH/LDPE thin films is smaller than that of unmodified ones,but the dielectric constant of MgO/LDPE-g-MAH/LDPE thin films is higher than that of pure LDPE films.The PSD experimental results show that the deep trap density of MgO/LDPE composite increases compared with pure LDPE,and the density of shallow traps decreases,which is consistent with the phenomenon of space charge pack inside the composites.The trap energy level distribution of MgO/LDPE-g-MAH/LDPE films is about 5.18~5.91 eV,and the peak area of the10wt%compatibilizer is the least,indicating that 10wt%compatibilizer can make the trap density of nanocomposites reduce greatly.