高分子链柔顺性及链活动能力对辐射交联反应的影响

THE EFFECT OF CHAIN FLEXIBILITY AND CHAIN MOBILITY ON RADIATION CROSSLINKING REACTIONS OF POLYMERS

高分子分子链的柔顺性是影响辐射交联的重要因素,分子链柔顺性好的高分子容易交联,凝胶化剂量低,反之分子链较僵硬的高分子辐射交联较困难,某些特别僵硬分子链的高分子,必须在高温下,分子链有一定的活动力后才能进行辐射交联反应。分子链的柔顺性还影响裂解度和辐照剂量的关系,在溶胶分数和辐射剂量的关系式中引入表征分子链柔顺性的β因子,从而修正了Charlesby-Pinner关系式[1],得到适用范围更广的新的溶胶分数和辐射剂量的关系式。分子链的柔顺性亦影响辐射交联反心机理,从多种高分子实例看出,柔顺性好的高分子Tg较低,分子内旋转位阻因子小,这类高分子辐射交联反应机理以H型为主;而僵硬链高分子Tg较高,分子内旋转位阻因子大,这类高分子辐射交联反应机理以T型(或称Y型)为主。

Flexibility of polymer chains is an important factor to effects of radiation crosslinking of the polymer. Polymers with flexible chains are easier to be crosslinked, with lower dose of gelation, than polymers with more rigid chains. And it is known that most polymers with abnormal rigidity can be radiation-crosslinked only at high temperatures when the molecular chains get enough mobility. The flexibility of polymer chains also influences the relationship between degree of degradation and radiation dose. A chain flexibility factor 0 has been introduced to modify the Charlesby-Pinner equation of sol-fraction and radiation dose. The new relationship equation applies to a wider range of polymers in radiation crosslinking. Studies also show that for flexible polymers with lower Tg and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in H type, whereas for rigid polymers with higher Tg and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in T type.