聚合物共挤成型界面位置的三维黏弹数值模拟

3D Viscoelastic Simulation of the Interface in Coextrusion Process of Polymers

采用 Giesekus 本构方程,建立了预测方形截面共挤口模中两种聚合物熔体层间界面形状和位置的三维黏弹数值模型,利用 polyflow 进行了数值求解,将计算结果同 Karagiannis 等的实验结果进行了比较,并分析了模拟误差产生的原因。结果表明:此数值模型能较为准确地预测共挤层间界面位置,数值模拟界面位置略高于实际界面位置,口模中央界面位置模拟误差较小,在壁面处略大。界面表面张力和壁面边界条件是影响共挤界面位置数值模拟准确度的主要因素。

The numerical model with Giesekus constitutive equation was established for the 3D isothermal coextrusion flow within a die with the square shaped cross section. The simulation of the moving interface between two polymer melts was performed using Polyflow. The numerical results were compared with the experimental data of Karagiannis, et al and the numerical error was discussed. The analysis shows that the interface position in coextrusion could be predicted at a relatively high order of accuracy for the numerical model with viscoelastic constitutive equation and slight-slip wall boundary condition. The interface obtained from simulation is a little higher than the real interface obtained from experiment. The simulation error at the center part of the die is less than that beside the wall. Surface tension on interface and wall boundary condition are the main factors which affect the accuracy of the simulation on moving interface in coextrusion process.