High Voltage Cable Insulation Can Be Cross-linked Polyethylene Structure, Performance And Cross-linking Process,

Characteristics of different kinds of power cable insulation,advantages,current conditions and developments of crosslinkable polyethylene(XLPE) insulation granules,the crosslinking techniques and mechanism of polyethylene,the main component of insulation granules and the studies of cure kinetics were summarized. Two kinds of commercial cable insulation granule were chosen as samples to study. The structure parameters of LDPE resin,the thermal properties,mechanical properties, gel content and crosslinking density of totally crosslinked samples were analyzed systematically.The rheological behavior during crosslinking process was measured, and the effects of crosslinking temperature and time on network structure were investigated.The relationship between structure and property was discussed.Two kinds of low density polyethylene(LDPE) resins(labeled as PE-1,PE-2, respectively) were bought in the domestic market,and LDPE cable insulation granules with different amounts of DCP were prepared through optimization of process.Some structure parameters such as molecular weight,molecular weight distribution,melting point,crystallization temperature and crystallinity degree were measured.The effects of DCP content on thermal properties,mechanical properties,gel content and crosslinking density for totally crosslinked samples were investigated.The gel content and crosslinking density increased and the melting point,crystallization temperature and crystallinity degree of totally crosslinked samples decreased with the increase of DCP content.Also the tensile strength increased but elongation at break decreased with the increase of DCP content(less than 2 phr).Sample that contains 2 phr amount of DCP had similar performances with the two kinds of commercial cable insulation granules.The influence of crosslinking reaction on the viscosity of different samples at different temperatures was investigated by steady rheology test.The rheological behaviors of different samples at different temperatures were measured through dynamic time sweep,and the relationship between structural evolution and linear viscoelastic response during crosslinking process was investigated.As a characterization of crosslinking density,number-average molecular weight between the junctions of the network for crosslinked samples,Mc,was calculated on the theoretical basis for the rubber elasticity,using the data of dynamic modulus G′getting from the curve of G′vs.frequencyωat terminal zone whereωâ†'0.The values of Mc of totally crosslinked insulation cable getting from rheological method and conventional equilibrium swelling method were compared and it was found that rheological measurement can be a feasible method to calculate Mc.The kinetic parameters of the crosslinking reaction for different samples were measured through rheological test and DSC measurement.The activation energy of the crosslinking reaction for samples with different DCP contents ranged from 140 kJ/mol to 170 kJ/mol and the order of the reaction approach 1.The effects of measurement frequency and preshear on activation energy were also investigated.Content changes for different kinds of double bond in the LDPE resin during crosslinking process were investigated through the IR measurement data for samples which have been crosslinked for different times.The contribution of different kinds of double bond to crosslinking reaction was learnt,and it supplied usefull information to the structure design of LDPE molecular chain.The structure parameters of LDPE resin and kinetic parameters of the crosslinking reaction were of great importance from the economic point of view,since they provided experimental foundation and theoretical basis for the production of cable insulation and insulation granules.