Physical characteristics of XLPE heat shrinkable tubes

As we all know, PE has excellent electrical characteristics, and XLPE maintains this electrical performance, while in several other aspects of performance is higher than PE, such as heat shrink tube, its volume resistivity above  10¹⁵Ωcm, than PVC and oil paper insulation resistance is much higher, the media loss angle is cut to 10^-4 and below, And does not change (or slightly increase) with temperature at normal temperatures. According to the data, PE and XLPE breakdown intensity with the trend of temperature changes, in about 105 ℃ PE has been extrude no electrical strength, and the breakdown strength of XLPE also appeared here a mutation, which can be explained as XLPE material in this temperature range began to appear obvious molecular loosening, structural closeness changes.

In addition, XLPE and PE and other organic synthetic insulation materials are larger coefficient of thermal expansion, PE and XL PE are in the 1.3*10^-5℃~-20*10^-5℃ range, so under heavy load operation, due to the temperature rise, so that the XLPE itself has a large thermal expansion, but the expansion coefficient of the insulated metal object is small (0.7*10^-5℃), Thus, the insulation expansion produces uneven, the insulation table and serious distortion, this change changes the uniformity of the original power field of the cable, and then makes the cable life change accordingly.

Secondly, according to the data report, the electric field strength of polymer materials and the elastic modulus of materials correspond to the temperature, that is, the rapid decline of the elastic modulus so that the electrical strength of the XLPE material also decreases accordingly, and the higher the temperature, the more obvious this change.

XLPE绝缘材料物理特性

XLPE电气与物理特性关系

众所周知，PE具有优良的电气特性，而XLPE保持了这一电气性能，同时在其他几个方面性能更高于PE，例如热缩管，它的体积电阻率在10¹⁵Ωcm以上，比PVC和油纸绝缘电阻高得多，介质损耗角正切为 10^-4 及以下，且在正常温度下不随温度变化(或略有升高)。据资料介绍，PE和XLPE击穿强度随温度变化的趋势发展，在105℃左右PE己经基木没有耐电强度，而XLPE的击穿强度也在此出现一个突变，这可解释为XLPE材料在此温度范围开始出现明显的分子松动，结构紧密程度发生改变。

另外，XLPE和PE等有机合成绝缘材料的热膨胀系数均较大，PE和XL PE均在

1.3*10^-5℃~-20*10^-5℃ 范围，因此在大负荷运行下，由于温度上升，使XLPE本身发生很大热膨胀，但绝缘外的金属物的膨胀系数却较小((0.7×10的-5次方℃一)，从而使绝缘膨胀产生不均匀，绝缘表而严重畸变，这种变化改变了电缆原电场的均匀性，进而使电缆寿命发生相应变化。

其次，根据资料报导，高分子材料的耐电场强度与材料弹性模量随温度有对应的规律，即弹性模量的迅速下降使XLPE材料耐电强度也相应下降，且温度越高，这种变化越明显。