高压电缆绝缘用可交联聚乙烯结构、性能及交联过程的研究

【作者】 杨永柱；

【导师】 杨红梅；

【作者基本信息】 浙江大学 ， 高分子材料， 2010， 硕士

【摘要】 论文概述了电力电缆的种类及特点、交联聚乙烯绝缘电缆料的优势、国内外现状及发展趋势、聚乙烯的不同交联工艺、交联机理、交联配方及交联动力学的相关知识;系统分析了两种商业化绝缘电缆料的结构参数及完全交联后试样的热性能、拉伸性能、凝胶含量及交联密度;研究了聚乙烯交联过程的流变行为,考察交联温度及交联时间对交联结构的影响,以建立结构-性能关系。选择两种国产低密度聚乙烯(PE-1,PE-2)作为基础树脂,通过配方筛选和工艺优化制备可交联聚乙烯(XLPE);比较了不同基础树脂的结构参数,考察了交联剂(DCP)的含量对完全交联后试样的热性能、拉伸性能、凝胶含量及交联密度的影响;随着交联剂含量的增加,凝胶含量及交联密度增加,熔融温度、结晶温度及结晶度降低,拉伸强度增大,断裂伸长率减小。2份交联剂含量的试样的综合性能与两种商业化的电缆料的性能接近。采用稳态流变学方法研究不同加工温度下交联反应对不同配方试样流动性的影响;采用动态流变学方法研究试样在不同温度下交联过程的流变行为,考察不同配方试样化学交联过程中结构演化与线性粘弹行为的关系;根据橡胶弹性理论,尝试利用完全交联试样的频率扫描末端区的动态储能模量(G′)计算体系交联点之间的平均分子量(Mc),并与用常规的平衡溶胀法测得的Mc相比较;探索用流变学方法研究聚乙烯交联过程结构演化的新方法。采用动态流变学方法及DSC测试法研究不同配方试样的交联动力学特征,经计算,得到体系交联活化能在140 kJ/mol-170 kJ/mol之间,其反应趋于一级反应;同时考察了振荡剪切频率、预剪切对交联活化能的影响。根据交联不同时间下试样的红外谱图,分析不同牌号LDPE基础树脂中,不同种类双键的含量在交联过程中的变化,从而推断双键对聚乙烯交联的贡献,以指导基础树脂的结构设计,为交联聚乙烯电缆绝缘料的生产提供理论指导和实验基础。更多还原

【Abstract】 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 whereω→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.更多还原