Research On DC Dielectric And Thermal Aging Properties Of Crosslinked Polyethylene Grafted With Antioxidant

Under the action of high-voltage DC electric field,the space charge inside cross-linked polyethylene(XLPE)has always been an important factor restricting the use of high-voltage DC cables.The space charge will cause distortion of the electric field in XLPE,partial discharge and even breakdown,which will seriously affect the cable life.At present,nanoparticle modification is a method widely studied by scholars at home and abroad,but the problems of nanoparticle modification XLPE have been affected by the problem of easy agglomeration and moisture.Therefore,it is very important to study the modification of XLPE with polar groups to solve the space charge problem inside XLPE.In this paper,AMD with a double bond is introduced into low density polyethylene(LDPE)materials.Dicumyl peroxide(DCP)is used as a crosslinking agent and a graft initiator at the same time.During the LDPE crosslinking process,AMD molecules Grafted on XLPE molecular chains,different mass parts of AMD grafted modified XLPE insulating materials were prepared.The effects of AMD grafting modification on the degree of cross-linking,DC dielectric properties and anti-aging properties of XLPE insulating materials were studied.Infrared spectroscopy tests show that AMD molecules have been successfully grafted onto XLPE molecular chains.Gel extraction experiments and thermal extension experiments show that AMD graft modification has no significant effect on the degree of cross-linking of XLPE materials.Compared with pure XLPE,AMD-grafted XLPE insulation material has a stronger ability to suppress the accumulation of space charge,lower the conductivity and slightly increase the characteristic breakdown field strength.The results of the thermal stimulation current test show that after AMD grafting modification,deep traps in the material can be increased,freely moving charges in the material are restrained,and freely moving carriers can be reduced.The carriers sink into the surface of the sample to form a uniform and densely distributed charge lattice,which further prevents the further injection of carriers,reduces the accumulation of space charges in the material,and improves the space charge suppression capability.The oxidation induction period and tensile test results show that AMD grafted modified materials have strong oxidation resistance,which is close to the oxidation resistance of XLPE insulation materials with the addition of antioxidants 4020 and 300.AMD grafted modification XLPE still has good mechanical properties after heat aging treatment.And the mechanical properties of the material are basically consistent with other commonly used antioxidants due to the aging time.Therefore,the DC dielectric properties of AMD-grafted XLPE materials have been significantly improved,and they have stronger anti-aging properties.