硅氧烷共聚物辐射交联中乙烯基的增强效应

THE EFFECT OF VINYL CONTENT ON THE ENHANCEMENT OF THE RADIATION INDUCED CROSSLINKING IN SILOXANE COPOLYMER

本文选取了几种不同乙烯基含量的硅氧烷共聚物,考察其在结晶态和非晶态时,乙烯基对辐射交联反应的影响。结果表明,分子中引入乙烯基,使凝胶化剂量降低而交联G值增加,结晶态下(-78℃)辐照,此种作用更为显著。核磁共振谱测定溶胶中乙烯基含量的结果表明,无论室温还是-78℃辐照后,溶胶中的乙烯基含量均无变化。用Charlesby-Pinner关系式处理实验结果,含有乙烯基的试样对S+S^(1/2)与1/r的线性关系均有所偏离,且乙烯基含量愈多,偏离愈大。

The radiation-induced crosslinking of siloxane copolymers with va-rious contents of vinyl group has been studied. It was found that the existance ofvinyl groups in the copolymer macromolecules could reduce the gelation dose and henceincreases the G value of crosslinking. The variation of the content of vinyl groups in sol fraction of irradiated sampleswith dose was followed by NMR. It has been shown that they remain unchangedwith radiation dose. Such a result indicates that the vinyl group is very sensitive toradiation-induced crosslinking. The effect of vinyl group on the enhancement of cro-sslinking could be well understood. When a semi-crystalline copolymer at -78℃ was irradiated such an effect wasmuch pronounced. It results from concentrating of vinyl group in the amorphous re-gion so that greater probabilitv exists in reaction with radical before they decay witha process without crosslinking formation. The vinyl group in siloxane copolymer could also influence the deviation fromthe linear relationship given by Charlesby and Pinner. The effect of vinyl content onthe relationship between crosslinking density and radiation dose is expected to be in asimilar situations.