Dielectric Properties Of New Ultraviolet Crosslinked Polyethylene And LDPE/LLDPE Composite

Initiator and crosslinked agent of traditional UV-crosslinked polyethyleneare small molecular structure, which have obvious heat transference. In theprocess of long irradiation crosslinked they are volatilized and attached to theUV-light source what makes efficiency reduce. All of these can influence on thereliability of the cable insulation materials. As a kind of thermosetting material,crosslinked polyethylene can′t be recycled and doesn′t conform to industrialdevelopment theme of energy conservation and environmental protectionnowadays. So the development of new type of cable insulation materials isattracting more and more attention. This paper researches the dielectric propertiesof new UV-crosslinked polyethylene triggered by macromolecule photoinitiatorsystem and LDPE/LLDPE composite respectively. Their breakdown fieldstrength and dielectric spectrum are tested, and analyze the influencing factors ofdielectric properties through crystallization behavior. It is designed to provideexperimental basis for further development of good dielectric properties of thecable insulation materials.Firstly, the composition of macromolecule photoinitiator system isresearched theoretically, and the crosslinked principle of macromoleculephotoinitiator system is expounded. Secondly, the breakdown field strength ofnew UV-crosslinked polyethylene and LDPE/LLDPE composite in hightemperature are researched respectively. Dielectric permittivity, dielectric lossand crystallinity of new UV-crosslinked polyethylene and LDPE/LLDPEcomposite are tested through dielectric spectrum, DSC and XRD.It finds that the efficiency of macromolecule photoinitiator system increasedby5%compared with traditional photoinitiator system, and new type photoinitiator system has less volatile in high temperature. There is a relationshipbetween crystallinity and breakdown field strength, the greater the degree ofcrystallinity, the greater breakdown field strength by experiments. XLPE(3910AA) and LDPE/LLDPE composite have good electric strength in hightemperature. LDPE/LLDPE composite provides the reference for thedevelopment of non-crosslinked cable insulation material of high voltage level.