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本文利用凝胶渗透色谱和应力松弛方法研究了顺-1,4-聚异戊二烯的粘弹性能对分子量及分布的依赖性。实验结果表明,生胶的松弛模量和最长松弛时间与分子量和分子量分布都有依赖关系,主要是改变τ_m=KM_w~6关系中的K值,对β值的影响甚小。由于本体聚合物的链缠结而导致的非牛顿效应使生胶的τ_m与M_w的关系偏离3.4法则,这可用缠结网络密度来校正。探讨了生胶的应力松弛过程是橡胶分子链的滑移和解缠结兼有的两种运动。低分子量级份对链缠结网络有显著影响,起稀释剂作用,使网络的临界缠结分子量增高。
In this paper, the dependence of viscoelastic properties of cis-1,4-polyisoprene on molecular weight and distribution was investigated by gel permeation chromatography and stress relaxation method. The experimental results show that the relaxation modulus and the longest relaxation time depend on the molecular weight and the molecular weight distribution, mainly changing the K value in the relationship of τ_m = KM_w ~ 6, and have little effect on the β value. The non-Newtonian effect due to chain entanglement of bulk polymers deviates the relationship of τ_m and M_w of gum from 3.4, which can be corrected by the density of entangled networks. It is discussed that the stress relaxation process of raw rubber is a combination of two kinds of movement, which are the slip and disentanglement of rubber molecular chain. Low molecular weight fractions have a significant effect on the chain entanglement network, acting as a diluent, increasing the critical molecular entanglement of the network.