Study And Improvement Of Thermal Oxidative Aging Properties Of Cross-Linked Polyethylene

Cross-linked polyethylene（XLPE）is widely used in HVDC cable insulation material,but the high temperature environment inside and outside the cable poses new challenges to XLPE’s resistance to thermal oxidative aging.Studies have shown that polymer nanocomposites have many excellent properties in thermal,electrical and mechanical aspects.In this paper,the effects of thermal oxidative aging were explored with XLPE.In addition,the preparation and thermal aging of Nano-SiO₂/XLPE composites were carried out,and the effect of Nano-SiO₂on the anti-thermal oxidative aging ability of XLPE was explored,which provided a basis for the subsequent study of the thermal aging performance improvement of XLPE.The main research contents of this paper are as follows:Firstly,the thermo-oxidative aging process of pure XLPE at the thermal aging temperature of 150℃,165℃and 180℃was investigated.The elongation at break,tensile strength,cross-linking degree,crystallinity and density during thermal aging were monitored,and the change trend of different properties during thermal aging and the thermal aging mechanism of XLPE were explored.The thermal-oxidative aging life at different temperatures is calculated,and the thermal-oxidative aging life at other temperatures is predicted.The performance indicators that can be used for life evaluation and calculation are also explored.Then a nanoparticle doping scheme was designed and the nanoparticle doping device was improved.Processes and devices that can be used for polymer nanoparticle doping are discussed,and the deficiencies of existing devices are discussed.Using the principle of corona charging and based on a twin-screw extruder,a device for doping nanoparticles was designed,which could enhance the dispersion of nanoparticles in the polymer matrix.Finally,Nano-SiO₂/XLPE composites with different nano-silica contents（1 wt%,3 wt%and 5 wt%）were prepared,their thermal-oxidative aging performance at 165℃was explored,and the performance of different nanocomposites was calculated.Thermal oxygen aging life.The properties of Nano-SiO₂/XLPE composites during thermal aging were monitored,and their changing trends and reaction mechanisms were analyzed,and compared with those of pure XLPE.By analyzing the change trend of OIT of pure XLPE and Nano-SiO₂/XLPE composites during thermal aging,the mechanism of action of nanoparticles was explored.The effect was compared with the mechanism of action of nanoparticles.