Effects Of Crosslinking Auxiliary Agent On Mechanical Physical Properties And DC Electrical Properties Of UV-XLPE

UV-XLPE is a newly-produced XLPE insulated power cable manufacturing technology.Generally,the high-intensity ultraviolet light source is used to irradiate and cross-link the molten transparent polyethylene material.Compared with the traditional peroxide cross-linking method,the UV crosslinking method has the advantages of fast cross-linking speed,energy saving,environmental protection and relatively excellent DC dielectric properties.In the UV crosslinking method,a crosslinking agent with a polar group can form a bridge bond between polyethylene molecular chains during the cross-linking reaction,and is connected to the macromolecular chain,so it is reasonable to believe that there are bound to be differences in the properties of UV-crosslinked polyethylene using different types of crosslinking agents.In view of the lack of research on the influence of different crosslinking auxiliaries on the DC dielectric properties of UV-crosslinked polyethylene,this paper uses linear low density polyethylene?LLDPE?as the basic resin and benzophenone?BP?as the photoinitiator.Using TMPTMA?trimethylolpropane trimethacrylate?,TAIC?triallyl isocyanurate?,and PDM?N,N'-m-phenylene bismaleimide?respectively.The cross-linking assistants were prepared with the same mass fraction as UV-crosslinked polyethylene samples.The samples were tested in cross-linking characteristics,heat resistance,mechanical properties,direct current performance and the all-electron numerical orbitals.A principle method was used to calculate the electron energy density of the graft copolymerized polyethylene molecules,and the trap characteristics of the samples were tested by TSC experiments.The infrared spectroscopy experiments show that UV-crosslinked samples all have absorption peaks at the carbonyl C=O at 1735cm^-1,indicating that there are crosslinking auxiliaries in the prepared samples.The crosslinker is connected to the crosslinked polyethylene molecule.The UV-crosslinked samples all obtained a good degree of cross-linking,and the degree of cross-linking meet the requirements of the standard,indicating that the selected TMPTMA,TAIC,and PDM can be used as crosslinking assistants for the UV-crosslinking method.From the DSC experimental test results we can know,the degree of cross-linking of the three UV-crosslinked samples were similar.They are all lower than the LLDPE sample;XLPE-TMPTMA has the highest breaking stress and elongation at break in the stress-strain experiment.The DMA test results show that the UV-crosslinked sample difference between storage modulus and loss modulus is obvious at low temperature.UV-crosslinked polyethylene exhibits excellent ability to inhibit space charge injection.XLPE-TMPTMA has the best ability to suppress space charge injection.After 30minutes of short circuit,the peak space charge density at the cathode and anode is3.3C/m³ and 1.7C/m³.UV-crosslinked samples have lower electrical conductivity with a decrease of about two orders of magnitude.XLPE-TMPTMA exhibits the largest decrease in electrical conductivity at 90°C and a field strength of 5k V/mm,only for LLDPE 0.7%.The thermally stimulated current experiments show that the three cross-linking aids introduce deep traps of varying degrees in polyethylene.The XLPE-TMPTMA sample has a high current release peak at a peak position of 119°C and a peak value of about 110p A.The simulation software calculation results show that the crosslinking assistant grafted onto the polyethylene molecule produces different electron bound states in the energy band gap,and TMPTMA generates a trap energy level in the energy band gap of about 1.08e V Electron-bound state.The theoretical calculation results of the electronic energy density,further explain the reasons why the UV-crosslinked sample has excellent ability to suppress space charge injection and reduce electrical conductivity.