交联聚乙烯交联度对材料击穿强度的影响

为了研究XLPE材料交联度对其电气性能的影响,制备不同交联度的XLPE样本并对其进行电气击穿实验,分析在不同的交联度区间范围内样本击穿场强变化。利用温度-时间控制法制备六组不同交联度的XLPE样本;利用差式扫描量热仪测量得到样本结晶度;利用交流变压器测量得到样本的击穿强度。实验结果表明,随着交联度上升,样本击穿场强呈先上升后下降趋势。在交联度为0%～75%区间范围内,样本击穿场强增加2%。在交联度为75%～88%范围内,样本击穿场强增加21.2%。而在交联度为88%～92%范围内,样本击穿场强下降5.3%。分析认为,样本的击穿强度与样本交联度和材料均匀程度有关。当交联度较低时,样本的击穿强度主要由样本交联度决定,随着交联度上升,样本击穿强度增加。但由于此时局部材料结构较为不均匀,因此击穿强度增加幅度不大。而当交联度上升至75%时,材料形成较为密集、均匀的三维网状结构,导致样本击穿场强大幅上升。而当交联度继续增加时,此时样本结晶度下降幅度较大,局部材料结构变得不均匀,导致样本击穿强度下降。

Influence of Degree of Crosslinking of XLPE Material on Its Breakdown Strength

To investigate the influence of the degree of crosslinking of XLPE material on its electrical properties, XLPE samples with different degrees of crosslinking are produced and breakdown experiment are applied on the samples, and the changes of the breakdown strength of the samples in different regions of degrees of crosslinking are analyzed. First six groups of XLPE samples with different degree of crosslinking were produced by T-t (temperature-time) controlling method, and the crystallinity of the samples are measured by the Differential Scanning Calorimetry (DSC) instrument. The breakdown strength of the samples were measured by an alternating current transformer. The experimental results show that with the increase in the degree of crosslinking of the samples, the breakdown strength of the samples first increase and then decrease. When the degree of crosslinking of the samples were 0%-75%, the breakdown strength of the samples increase by 2%. When the degree of crosslinking of the samples were 75%-88%, the breakdown strength of the samples increase by 21.2%. When the degree of crosslinking of the samples were 88%-92%, the breakdown strength of the samples decreases by 5.3%. It is believed that the breakdown strength of the XLPE material is related with the degree of crosslinking and the uniformity of the material. When the degree of crosslinking of the samples is low, the breakdown strength of the samples is mainly determined by the degree of crosslinking. With the increase in the degree of crosslinking, the breakdown strength of the samples can be promoted. However, since the partial parts of the material can be nonuniform, the increment of the breakdown strength of the samples increase little. When the degree of crosslinking increases to 75%, dense, uniform three-dimensional network structure can form in the material, which leads to the significant increase of the breakdown strength. When the degree of crosslinking further increases, the decrease amplitude of the crystallinity can be large, and the structure of the partial material become nonuniform, which result in the decrease of the breakdown strength.