不同工艺参数时快速降压口模的数值模拟

在微孔塑料连续挤出成型中，运用Ployflow软件对快速降压口模内熔体流动进行模拟分析，研究了不同CO2浓度、不同熔体体积流量对口模内熔体压力、速度分布及挤出胀大影响。结果表明，口模内熔体压力降在一定的范围内随着熔体体积流量的增大而增大，随着CO2浓度的升高而降低；一定范围内，CO2浓度对口模出口处熔体平均速度的影响不明显，而熔体体积流量对口模出口处熔体平均速度的影响很明显；对于挤出胀大的影响，CO2浓度不宜过高或者过低，2 %（质量分数，下同）时表现最佳；在一定熔体体积流量的范围内，熔体体积流量越高，挤出胀大表现得越不明显。

Numerical Simulation of Melt Flow in Pressure Drop Die Under Different Process Parameters

During the extrusion of microcellular plastics, the melt flow in the pressure drop die was simulated using Ployflow software, and then the distribution of pressure and velocity and extrusion swell in the pressure drop die was studied under different CO2 concentration and melt volume flow. It was found that the melt pressure in the die increased with increasing melt volume flow, and decreased with increasing CO2 concentration. The melt average velocity at the exit was sensitive to the change of melt volume flow, but not to the change of CO2 concentration. The optimal CO2 concentration was found to be 2 wt%. The higher the melt volume flow, the less the extrusion swell.