Research On The Preparation And Performance Of MgO/Polyolefin Nano Composite Material

In recent years, requirements of HVDC cable are increasingly high indomestic with the rapid development of the HDVC technology in power systems.We have made great progress in MgO/polyolefin nanomaterials as a DCtransmission cable, which has well application and potantial developmentprospect. But the analysis reports in connection with how to prepare high qualitynano MgO and improve the dielectric properties of the nano-polyethylenecomposite material are rarely.This paper focus on the influencing factors on the MgO/polyolefinnanomaterials properties of microwave assisted preparation of Mg（OH）₂,preparation of nano-MgO and the type and amount of mPE, and the effects ofhumidity on the properties of nanocomposits were investigated.The craft of microwave assisted preparation of Mg（OH）₂was investigatedby using orthogonal experimental program, the range analysis and Multi-factorline regression method were used in dealing with experimental results, the nanoMgO calcined was tested and characterizd by the SEM（scanning electronmicroscope） and XRD（X-ray diffraction）. Contrasting the nano MgO made bydirect precipation method and homogeneous precipation, the results reveal thatthe nano MgO prepared by microwave assisted reunion was not obvious, and hada uniform particle size, high purity and grain size of12.76nm when the molarratio of Magnesium nitrate hexahydrate and ammonium bicarbonate is1:4, thereaction temperature is80℃, the rection time is50min. The mechanical stretch,volume resistivity, DC breakdown field strength, space charge, DSC and SEMtesting and characterization methods were used to analyse the effects on thenano-materials properties of the preparation of nano MgO, the type and dosage ofEVA and the dosage of mPE. The results reveals that nano particles reached adispersion of nanoscale in polyethylene matrix, the crystallization, mechanical and electrical properties of the nanomaterials had a large extent improved, andthe properties of nanomaterials was especially improved in the capability ofsuppressing space charge when the nano MgO materials had a mass percentage ofEVA （The mass percentage of VA is14） was9wt%. The space charge density incathode droped to1.0C/m3and0.5C/m3in anode. The nano-materials have afurther promotion in suppressing space charge when the mPE is added to LDPE.There are about0.5C/m3in cathode but almost no charge injections in anodewhen the mass percentage of mPE is6wt%.MgO/polyolefin nano-materials have an obvious water absorption which thewater absorption rate reached0.08%. The ability of nano-materials insuppressing space charge and electrical treeing decreased after moistureabsorption. The space charge density in anode increases2.1C/m3and also0.5C/m3in cathode.