一种新型具有均匀流动分布的多流道片材机头的几何设计

Geometry Design of a Novel Multi-flow Channel Sheet Die with Uniform Flow Rate Across the Die Width

提出了一种新型的全部流道由平直板条组成的片材机头结构。全部流道中在熔体特征黏度相等的假定条件下 ,给出了确定构成流道的栅条尺寸的算法及相关计算公式。在幅宽为 0 .87m、口模间隙为 1mm的实验机头上进行了PP片材的挤出实验以证实机头结构的可行性和设计方法的正确性。结果表明 ,用这种形式的机头可以获得厚度均匀的挤出片材 (沿幅宽最小厚度与最大厚度的比值为 0 .97)。熔体沿幅宽的平均停留时间分布分析结果表明 ,平均停留时间分布在幅宽上是不均匀的 ,但其不均匀性远低于T形机头。

A die for sheet extrusion was designed,in which all the flow channels were formed with plates and straight strips.Based on the assumption that characteristic viscosity of the melt in all flow channels was equal,the algorithm to determine the size of strips forming the flow channels and relative expression were given.Lab scale PP sheet extrusion experiments were carried out using the designed die with a width of 0.87 m and a slit gap of 1 mm,and uniform PP sheet was successfully obtained.The ratio of the minimum and maximum sheet thickness along the width was only 0.97.The profile of residence time distribtuion (RTD) of polymer melt across the die width was analyzed.The result showed that the RTD was better than that of T type dies.