Study On Aging Characteristics Of Linear Low Density Polyethylene And Its Ultraviolet Irradiation Crosslinking Material

Because of the good electrical and mechanical properties,Polyethylene is widely applied in the field of cable insulation.However,in actual operation,cable insulation are susceptible to the heat,electricity,water and mechanical stress and then aging occurring,due to it,insulation performance declining,and resulting in the insulation deterioration,eventually the insulation will lost.Therefore,the study on aging factor of cable insulation materials under the action of the changing of gas properties has important meaning to judge insulation aging state by detecting and assessing cable running state and establish an reasonable and effective method.In this dissertation,linear low density polyethylene(LLDPE)and the ultraviolet light crosslinking polyethylene(UV-Light XLPE)these two kinds of cable insulation materials were used as the research objects,and used the heat and electricity as the single factor aging stress,researching the change of breakdown voltage,conductivity,dielectric constant,dissipation factor,the elongation at break,tensile strength and other properties,and then establishing reasonable thermal and electrical aging model respectively according to the experimental results.The experimental results show that,at the beginning of the thermal aging experiments,breakdown voltage,the conductivity and mechanical properties of this two kinds of insulating material appeared a smaller degree of reduced,and a tiny increasing occurred in dielectric constant and dissipation factor.With the increasing of aging time,stable molecular bond ruptured,producing more small molecular groups and oxidation products,causing the significant declining of disruption field strength and mechanical properties.At the same time,a significant increasing occurred in conductivity,dielectric constant and dissipation factor,and electrical performance and mechanical properties are subject to serious damage,and the higher the temperature,the more serious the damage of longer aging time performance.In addition to the subtle differences,it has the same change rule in performance parameter of two kinds of experimental material.Building the two kinds of material thermal aging model respectively,through the checking,it was found that the heat aging properties of UV-Light XLPE was better.The results of the electrical aging experiment showed that under the effect of electrical aging which was setting in this dissertation,their breakdown voltage of the experimental materials was lower,the electrical conductivity and dielectric loss were increased,the elongation at break and tensile strength had little change,the of mechanics properties is smaller when the electrical aging time is short.Conductivity,the results show that the UV-Light XLPE has good resistance to electrical aging,which can be verified from the established mathematical models of electrical aging test.