氢氧化铝含量对硅橡胶结构及憎水恢复性的影响

Study on the Microstructure and Hydrophobicity Recovery of Silicon Rubber with Different Content of ATH

氢氧化铝(ATH)作为阻燃剂是复合绝缘子硅橡胶的基本原料。为研究ATH含量对硅橡胶结构和憎水恢复性的影响,炼制ATH质量分数分别为40%、45%、50%和55%的硅橡胶试样,对试样进行正电子寿命谱、邵氏硬度测试,及5 min Ar等离子体老化实验。结果表明:ATH质量分数从40%增加到55%时,次长寿命强度I3从7.8%下降到6.1%,而最长寿命强度I4从24.8%锐减至18.6%。随ATH质量分数增加,硅橡胶中2种自由体积的尺寸基本不变;但ATH颗粒容易发生团聚,这些颗粒占据了分子链运动空间,限制了大分子链的运动,使得大尺寸自由体积数量减少,特别是使大尺寸孔洞的数量锐减。邵氏硬度随ATH质量分数增大而变大,说明样品由弹性体朝无机体转变。经相同等离子体处理时间后,硅橡胶憎水恢复速度随ATH质量分数增加而减慢,结合正电子湮没寿命结果可知,ATH的加入限制了体系内硅橡胶分子链的运动,自由体积数量减少,使得小分子输送通道变少。

Aluminum hydroxide（ATH） as fire retardant is one of the basic ingredients of silicon rubber composite insulators. In order to study how the ATH content influences the microstructure and hydrophobicity recovery of silicon rubber, we made silicon rubber samples with ATH quality contents of 40%, 45%, 50% and 55%, and conducted testes of positron lifetime spectra, shore hardness, and Ar plasma treatment of five minutes with the samples. The results showed that when the mass ratio of ATH increased from 40% to 55%, I3 decreased from 7.8% to 6.1% and I4 decreased sharply from 24.8% to 18.6%. Increasing content of ATH has no effect on the sizes of the two types of free volume holes. ATH particles are easy to form agglomerations, which will obviously restrict the movement of macromolecules chains, resulting decrease of the numbers of big free volume holes. The shore hardness of the samples increases with the mass ratio of ATH. This indicates that the samples changed from elastomer to inorganic. After the 5-min Ar plasma treatment, the samples＇ hydrophobicity recovery speed decreases with increasing mass ratio of ATH. Combining the results with the obtained positron lifetime spectra, it is concluded that the addition of ATH in silicone rubber limits the movement of macromolecule chains, and hence reduces the number of free volumes as well as small molecular channels.