Effects of Initiators on the Properties of Low-density Polyethylene in the Tubular Processes
Low-density polyethylene(LDPE)resin is widely used in electrical insulation materials due to its excellent dielectric properties.Current researches mainly focus on the dielectric properties,processing technologies,and environmental factors of LDPE,but there are less researches on how the initiator choice affects the structural properties of LDPE.The high-pressure tubular production processes using oxygen or a peroxide as the initiator were compared,then the molecular structures,mechanical properties,dielectric properties,and rheological characteristics of LDPE(22E and 2240H)produced under the two initiator conditions were analyzed.The results show that 22E has a larger number-average molecular weight and a higher polydispersity index,but its melt strength is lower than that of 2240H.The reason is that the high degree of branching of 2240H increases the entanglements between molecular chains,enhancing the melt elastic and viscoelastic behaviors.The melt strengths of 2240H at 170 and 190 ℃ are significantly higher than that of 22E,and the processing energy consumption of 2240H is lower.The gel content of 2240H is higher,indicating a higher crosslinking density of 2240H.In summary,LDPE(2240H)produced with the peroxide initiator has higher degree of branching and melt strength,while LDPE(22E)produced with the oxygen initiator exhibits superior dielectric properties and mechanical strength.This study provides theoretical supports for optimizing the high-pressure tubular process.
万方数据
维普
