| The cable production technology of UV-irradiation crosslinked polyethylene（UV-XLPE）is a new type cable manufacturing technology which has been applied on a large scale in China in recent years.Its outstanding advantages are fast production speed and long continuous production time.Since the UV-crosslinked technology is a non-thermal crosslinked technology,it will not produce the scorched materials due to the long processing time,and its potential advantage is the production of cable insulation layer less defects.Therefore,UV-irradiation crosslinked is expected to realize the industrial production of high-voltage class and large-length XLPE insulated cables.At present,UV-irradiation crosslinked cable technology can only be used in the production of low voltage cables.There are still two problems in this technology for the XLPE cables production of high voltage grade（≥10k V）.One is that the shielding layer material（arbon black）of semi-conductive shielding layer structure for cables have a strong absorption effect on ultraviolet,so ultraviolet cannot penetrate the outer semi-conductive shielding layer for irradiation crosslinking.Second,the insulation layer thickness of cables is larger,so it is necessary to extend the stay time of UV-XLPE cable material in the equipment to achieve the purpose of full crosslinked in the actual crosslinking process.In addition,the small molecule photoinitiator and the auxiliary crosslinker used in the ultraviolet irradiation materials are easy to be volatilized by heat.Once the volatile substance is attached to the lamp shade of the ultraviolet light source,it not only reduces the transmission efficiency of ultraviolet light,but also reduces the crosslinked efficiency of the photoinitiator system.At present,relevant research work has been done to solve the problems in the manufacturing technology of high voltage UV-irradiation crosslinked cables.Therefore,this paper mainly solves the problems in the production of high voltage grade UV-XLPE insulation materials,such as the light-induced system volatile and poor electrical properties.Macromolecular photoinitiators 4-hydroxy diphenyl ketone lauric acid ester（BPL）and crosslinking agents diamine propylene diamine-2,2?,4,4?-four allyl cyanuric acid ester（DTAC）were prepared by introducing long carbon chains into the molecular structures of photoinitiators and auxiliary crosslinking agents.Its structure and properties were experimentally studied by means of nuclear magnetic resonance hydrogen spectrum（1H NMR）,thermogravimetric analysis（TGA）,solvent extraction and fourier infrared spectroscopy（FTIR）.The results showed that the thermal stability of BPL and DTAC was improved,and they could be used as photoinitiating systems for high voltage grade UV-irradiation crosslinked polyethylene insulation materials.And the BPL participates in cross-linking reaction and forms cross-linking by-products through ketone carbonyl in molecular structure,while DTAC participates in cross-linking reaction and forms interpolymer crosslinking points through allyl double bonds in molecular structure.The differential scanning calorimetry（DSC）and the other analysis methods are used to study the crosslinking behavior of large molecule photoinduced systems.The first principle method is used to calculate and study the excitation state of the photoinitiator,free radical formation and crosslinking,as well as the the energy characteristics of the crosslinking by-product（PBBL）.The crosslinking reaction mechanism of macromolecule photoinitiator system is clarified,and the breakdown experiment proves that PBBL has the effect of voltage stabilizer.The radial crosslinked degree model of UV-XLPE cable products was established and studied theoretically.It can provides technical guidance for the manufacture of UV-XLPE insulated cable.High voltage grade UV-XLPE insulation material is prepared by macromolecular photoinitiation system.The advantages and disadvantages of macromolecule modified photocrosslinked polyethylene as insulation material for high voltage grade cables are systematically analyzed.The results show that the electrical properties of the macromolecular photomodified photocrosslinked polyethylene insulation materials are slightly inferior to those of the peroxides crosslinked polyethylene insulation materials,and the short-time AC/DC electrical resistance and the inhibition ability of polar space charge need to be further improved,especially the electrical performance at high temperature.In order to solve the problem of low breakdown field strength and poor space charge characteristics of UV-XLPE induced by large molecule photoinitiator system,an auxiliary crosslinking agent functional nano-silica（Si O2）hybrid material（TAIC-s-Si O2）are designed and synthesized.And nano-Si O2 is introduced into the crosslinked structure of auxiliary crosslinked modified nanocomposite by using BPL induced photo-crosslinking reaction.The results of FTIR et al showed that the crosslinking agent is successfully bonded to the surface of Si O2 and could be used as an auxiliary crosslinking agent to participate in the photocrosslinking reaction of polyethylene.The study of electrical properties shows that the auxiliary crosslinked modified nanocomposites with the 1.0wt%addition of TAIC-s-Si O2 has the best improvement effect on the breakdown field strength and better space charge inhibition effect.In addition,the photoinitiator 4-acryloxy diphenyl ketone（ABP）with unsaturated double bond was designed and synthesized.The grafted modified nanocomposites were prepared by cross-linking reaction of DTAC and Si O2 particles with surface-modified sulfhydryl groups.And the slow crosslinking reaction rate of the auxiliary crosslinking modified nanocomposite was effectively solved.The problem of the slow reaction rate of the auxiliary crosslinked modified UV-XLPE nanocomposites was effectively solved and the uniform dispersion of nanoparticles was improved.The study of electrical properties shows that the AC/DC breakdown field strength of grafted crosslinked modified nanocomposites is significantly improved,and the space charge accumulation is significantly inhibited.Especially under the high temperature environment of 60～80℃,it still shows excellent space charge inhibition effect. |
