The hierarchical multi‐mode molecular stress function (HMMSF) model developed by Narimissa and Wagner [Rheol. Acta 54, 779–791 (2015), and J. Rheol. 60, 625–636 (2016)] for linear and long‐chain branched (LCB) polymer melts were used to analyze the set of transient elongational and shear viscosity data of two LCB low‐density polyethylenes (1840H and 2426 k), and a linear poly‐(ethylene‐co‐α‐butene), PEB A‐780090 as reported by [Li et al. J. Rheol. 64, 177 (2020)], who had developed a new horizontal extensional rheometer to extend the lower limits of elongational viscosity measurements of polymer melts. Comparison between model predictions and elongational stress growth data reveals excellent agreement within the experimental window, and good consistency with shear stress growth data, based exclusively on the linear‐viscoelastic relaxation spectrum and only two nonlinear model parameters, the dilution modulus G_D for extensional flows, and in addition a constraint release parameter for shear flow.

中文翻译：

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低粘度聚合物熔体的非线性拉伸和剪切流变学建模

Narimissa和Wagner [Rheol。《 Acta 54，779–791（2015）》和J. Rheol。60，625–636（2016）]使用线性和长支链（LCB）聚合物熔体分析了两种LCB低密度聚乙烯（1840H和2426 k）的瞬态伸长率和剪切粘度数据集，线性聚（乙烯-共-α-丁烯），PEB A-780090，[Li et al。J.Rheol。64，177（2020）]，他开发了一种新的水平延伸流变仪，以扩展聚合物熔体的延伸粘度测量的下限。模型预测结果与伸长应力增长数据之间的比较表明，实验窗口内的一致性极佳，并且与剪切应力增长数据具有良好的一致性，G _D用于拉伸流，另外还包括用于剪切流的约束释放参数。