Transient behavior of entangled polymers at high shear rates
Transient behavior of entangled polymers at high shear rates
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高剪切速率下缠结聚合物的瞬态行为
DOI：
10.1002/polb.1991.090291304
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
G. Marrucci
中科院分区：
文献类型：
--
作者：
D. Pearson;E. Herbolzheimer;N. Grizzuti;G. Marrucci
提出了一种描述高剪切速率下纠缠聚合物液体随时间变化流动的新模型。将Doi和Edwards理论扩展到包括链拉伸的影响，得到了结果。当聚合物的剪切速率与纵向弛豫时间的乘积大于1时，就会出现这种非线性现象。如果在这些条件下开始恒定剪切速率流动，则表明剪切应力和法向应力明显大于原始重复模型所预测的应力。我们还发现，这两个应力在达到稳定状态之前都可以通过最大值，并且达到这些最大值所需的时间是与剪切速率无关的常数。一般来说，新模型需要耦合偏微分方程的数值解。然而，在最高剪切速率下，重复松弛不再重要，找到了应力的解析解。所得结果与实验数据吻合较好，是对最近提出的一个较简单模型的改进。
A new model is presented for describing the time‐dependent flow of entangled polymer liquids at high shear rates. The results were obtained by extending the Doi and Edwards theory to include the effect of chain stretching. This nonlinear phenomenon is predicted to occur when the product of the shear rate and longitudinal relaxation time of the polymer exceeds one. If a constant‐shear‐rate flow is started under these conditions, it is shown that the shear stress and the normal stress are considerably larger than that predicted by the original reptation model. We also find thatbothof these stresses can pass through maxima before reaching a steady state and that the times required to reach these maxima are constants independent of the shear rate. In general the new model requires the numerical solution of coupled partial differential equations. However, at the highest shear rates where reptative relaxation is no longer important, an analytical solution for the stresses is found. The results obtained here are shown to agree well with experimental data and to be an improvement over a simpler model recently proposed.