The Research And Development Of Shielding Materials With Graphene Used In Power Cable

The requirement of middle and high crosslinked polyethylene(XLPE)cable is increasing in the past years with the upgrade of our country's electric power transmission and distribution system.Currently,the semiconductive shielding layer of crosslinked XLPE cable is mainly manufactured by adding about 15wt%-50wt%conductive carbon black with other additional agents into the ethylene/vinyl acetate copolymer(EVA)matrix.However,adding amount of carbon black not only reduces the extrusion processing performance and mechanical property of shielding material but also roughen the surface of the shielding material,which may result in the electrical stress concentrations that can lead to insulation damage.The main purpose of this research is to reduce the amount of conductive filler in the shielding layer by using graphene,a kind of carbon filler with a better electrical,mechanical propertiesto replace some parts of CB.At first,EVA/15%CB-1.5%GNS composite material was manufactured after the ratio of two kinds of fillers was comfirmed.But a big problem was that although the thermal,electrical properties of composite material were very well,the mechanical property decreased significantly.According to that,we optimized the procession by adding the lubricant,crosslinking agent,antioxidant,and determined the suitable processing conditions to improve the mechanical properties of composite materials.Eventually,the best retio and processing conditions of 15wt%CB,5wt%GNS,3wt%stearamide,3wt%DCP,0.75wt%of antioxidant 300,RPM to 65 RPM,10 min mixing time was confirmed.The thermal,electrical properties of composite material which got through thisprocess can reach tothe requirement of industry standard of shielding material.The volume resistivity of composite has been reduced at 97.1?·cm,the tensile strength and elongation at break have been improved at 513.7%and 15.5MPa respectively.Because of the low dispersibility and combination capacity between graphene and EVA matrix,the modified reduced graphene oxide(MrGO)was prepared successfully in order to enhance the compatibility between graphene and EVA matrix through grafting KH570 on the surface of graphene.The content of MrGO and CB in EVA matrix was confirmed by testing the electrical and mechanical properties of composite material.The result shows that although the electrical property of MrGO is not as so good as ordinary graphene,the compatibility between MrGO and EVA matrixis has been improved.The mechanical property of EVA/10%CB-6%MrGO composite material is better than the mechanical property of EVA/15%CB-1.5%GNS composite material.The EVA/10%CB-6%MrGO exhibits the great mechanical property that the tensile strength and elongation at break have achieved at 13.8MPa and 554.1%,up from 90.1%and 215.5%respectively based on EVA/15%CB-1.5%GNS.