熔体层厚对聚合物共挤出胀大的影响

摘要

基于流变学理论和Phan-Thien-Tanne本构方程，建立了三维等温黏弹共挤成型流动过程的数值模型。运用有限元方法对数值模型进行了模拟计算，研究了熔体层厚对共挤成型的影响，分析了熔体层厚对挤出胀大率、偏转变形及界面形貌的影响。结果表明：熔体层厚对挤出胀大率和界面形貌的影响较大，随着熔体层厚的增加，挤出胀大率减小；随着共挤出熔体层厚差值的增大，界面形状趋于不稳定；熔体离开口模后产生低黏度熔体向高黏度熔体一侧偏转变形，但变形程度受熔体层厚的影响不大。%Based on the rheology theory and Phan-Thien-Tanne (PTT) constitutive equation, the three-dimensional model of isothermal viscoelastic modeling through co-extrusion channel is established for numerical simulation which is carried out by the finite element method. The effect of melt thickness on co-extrusion processes is studied as well as that on die swell, deformation and interface profile. The results show that the melt thickness exerts more impact on die swell and interface profile. The die swell rate decreases with the increasing of melt thickness and the interface profile tends to be instable with the difference of the co-extrusion melts thickness enhancing. The melt deformation happens from the lower viscosity melt to the higher viscosity part after leaving the die, but the melt thickness had little influence on deformation degree.