Rheological Characterization of Long Chain Branching in a Melt of Evolving Molecular Architecture
Rheological Characterization of Long Chain Branching in a Melt of Evolving Molecular Architecture
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DOI：
10.1021/ma010370n
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发表时间：
2001-06
期刊：
影响因子：
5.5
通讯作者：
C. Tsenoglou;A. Gotsis
中科院分区：
文献类型：
--
作者：
C. Tsenoglou;A. Gotsis
提出了一种简单的流变学方法，用于估计长链支化度，x（分支链的分数，或等价地，每条链的平均分支数），聚合物熔体经历的早期阶段的交联诱导反应性改性。该模型进行了测试的一系列的聚丙烯的增加x，所有生产的相同的线性前体中存在的不同的过氧化物浓度。从分析样品的零剪切粘度预测的支化指数是在良好的协议与尺寸排阻色谱结合特性粘度测量的评价。改变聚合物的分子结构是定制聚合物加工特性和最终产品性能的最有效方法之一。长期以来，有用的经验知识是，例如，虽然线性聚合物由于其低“熔体强度”而通常不适合于拉伸流动加工，但在甚至有限的聚合物存在下，情况显著改善。
A simple rheological method is presented for estimating the degree of long chain branching, x (fraction of branched chains or, equivalently, the average number of branches per chain), of a polymer melt undergoing the early stages of a cross-link inducing reactive modification. The model is tested on a series of polypropylenes of increasing x, all produced from the same linear precursor in the presence of varied peroxide concentrations. The branching indices predicted from analyzing the zero shear viscosity of the samples are in good agreement with those evaluated by size exclusion chromatography combined with intrinsic viscosity measurements. Varying the molecular architecture is one of the most effective methods of tailoring processing characteristics and end-product properties of polymers. It has long been a useful empirical knowledge, for example, that while linear polymers are often unsuitable for extensional flow processing due to their low “melt strength”, the situation improves significantly in the presence of even limited