Fernandes Célio, Fakhari Ahmad, Tukovic Željko
Institute for Polymers and Composites (IPC), Department of Polymer Engineering, Engineering School of the University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal.
Transport Phenomena Research Center (CEFT), Mechanical Engineering Department, Faculty of Engineering of the University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal.
Polymers (Basel). 2021 Dec 19;13(24):4454. doi: 10.3390/polym13244454.
Polymer extrudate swelling is a rheological phenomenon that occurs after polymer melt flow emerges at the die exit of extrusion equipment due to molecular stress relaxations and flow redistributions. Specifically, with the growing demand for large scale and high productivity, polymer pipes have recently been produced by extrusion. This study reports the development of a new incompressible non-isothermal finite volume method, based on the Arbitrary Lagrangian-Eulerian (ALE) formulation, to compute the viscous flow of polymer melts obeying the Herschel-Bulkley constitutive equation. The Papanastasiou-regularized version of the constitutive equation is employed. The influence of the temperature on the rheological behavior of the material is controlled by the Williams-Landel-Ferry (WLF) function. The new method is validated by comparing the extrudate swell ratio obtained for Bingham and Herschel-Bulkley flows (shear-thinning and shear-thickening) with reference data found in the scientific literature. Additionally, the essential flow characteristics including yield-stress, inertia and non-isothermal effects were investigated.
聚合物挤出胀大是一种流变现象，它发生在聚合物熔体流从挤出设备的模头出口流出后，这是由于分子应力松弛和流动重新分布所致。具体而言，随着对大规模和高生产率需求的不断增长，聚合物管材最近已通过挤出法生产。本研究报告了一种基于任意拉格朗日-欧拉（ALE）公式的新的不可压缩非等温有限体积法的开发，用于计算服从赫谢尔-布尔克利本构方程的聚合物熔体的粘性流动。采用了本构方程的帕帕纳斯塔西乌正则化版本。材料流变行为的温度影响由威廉姆斯-兰德尔-费里（WLF）函数控制。通过将宾汉和赫谢尔-布尔克利流动（剪切变稀和剪切增稠）获得的挤出胀大比与科学文献中的参考数据进行比较，验证了该新方法。此外，还研究了包括屈服应力、惯性和非等温效应在内的基本流动特性。
