Preparation Of MgO/Polypropylene Insulation Nanocomposites And Study Of Its Properties

High Voltage Direct Current Transmission(HVDC)is one of the most important way to solve large-capacity transmission,while the new flexible HVDC technology with characteristics of high reliability,low cost and convenient operation is the direction of HVDC development.At present,plastic-insulation cable has been widely used in AC transmission system,owing to its advantages of simple construction,stable operation,as well as good resistance of heat and corrosion.However,its application in HVDC systems is still relatively backward.One of the most main reasons is believed to be the accumulation of space charge in polymer insulation when subjected to a SC field,which can accelerate insulation degradation through local field enhancement,ionization and electromechanical energy storage.So it's so important to suppress the space charge in polymer materials under DC high Voltage.Nowadays,only XLPE has been industrialized as polymer insulation of HVDC.But there is a big problem that XLPE,thermosetting resin,can't be recycle.Heavy use of XLPE does not meet the requirement of environment friendly.So it is urgent to find a substitution for XLPE.This paper choose thermoplastic resin PP,because PP possess good electrical performance and better high-temperature resistance,as well as excellent processing performance.At the same time Nano magnesium oxide(MgO)particles are utilized to modify polypropylene to suppress space charge.First of all,we make a series of nano-composites with different MgO content: 0.5wt%,1wt%,2wt%,3wt% and composites with 1wt% MgO showed the best electrical property.Then six different kinds of PP,like block copolymer,random copolymer,homo-PP and isotactic PP,were chosen as basic resin materials.1wt% nano-MgO and 5wt% POE were added to each PP matrix through melt-blending process.Ternary copolymer and isotactic polymer was regarded as optimum candidate for insulating material of DC cable,after comprehensive analysis of the performance of all kinds of PP.What's more,nano-MgO can reduce the space charge in PP effectively.Finally,by modifying the surface of MgO with silane coupling agent,the interface interaction of composites were enhanced,thus further improving the electrical properties.All in all,recyclable thermoplastic PP is a new option for HVDC cable in the furure.