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以PP/RPP/PP三层共挤出板材为例,采用有限元方法对非牛顿流体在共挤出流道内的等温流动过程进行了三维数值模拟。重点分析了三层复合共挤出板材机头流道中每层物料黏度比和松弛时间比对出口界面位置偏移的影响。数值模拟分析结果表明:随着物料黏度比的增大,出口界面越来越稳定。熔体层间物料黏度差异越小,界面位置越接近理想界面。随着物料松弛时间比的增大,出口界面越来越稳定;熔体层间物料松弛时间差异越小,界面位置越接近理想界面位置。
Taking the PP / RPP / PP three-layer coextruded sheet as an example, the three-dimensional numerical simulation of isothermal flow of non-Newtonian fluid in the co-extrusion runner was carried out by finite element method. The influence of material viscosity ratio and relaxation time ratio of each layer on the position shift of exit interface of three-layer composite coextruded plate head was analyzed emphatically. Numerical simulation results show that as the viscosity ratio of materials increases, the exit interface becomes more and more stable. The smaller the viscosity difference between the melt layers, the closer the interface is to the ideal interface. With the increase of material relaxation time ratio, the exit interface becomes more and more stable. The smaller the difference of relaxation time between materials in the melt layer, the closer the interface position to the ideal interface position.