Abstract:

Screw geometry has an important influence on the mixing characteristics of single screw extruder. Three kinds of six rhombic thread elements, four rhombic thread elements and tooth thread elements with special configuration were selected to design three new combined screws of single screw extruder for different processing requirements, and the flow and mixing characteristics of polylactic acid in the three combined screws were studied. The results show that there is a large pressure gradient at the pressure junction of the combined screw, the diamond thread element can provide high tensile action for the material, the residence time of the fluid in its channel is short, and the mixing performance is relatively poor; the toothed screw element can not only provide high shear effect but also high tensile effect for materials, with long residence time and good mixing effect.

Key words: Single screw extrude, Screw combination, Polyflow software, Numerical simulation

摘要：

螺杆的几何构型对单螺杆挤出机混合特性具有重要的影响。选取三种具有特殊构型的六菱形螺纹元件、四菱形螺纹元件和齿形螺纹元件，设计了三种针对不同加工工艺要求的新型单螺杆挤出机组合螺杆，研究了聚乳酸在三种组合螺杆中的流动和混合特性。结果表明，在组合螺杆压力交界处产生了较大的压力梯度；菱形螺纹元件可为物料提供高拉伸作用，流体在流道中停留时间较短，混合性能较差；齿形螺杆元件既可为物料提供高剪切作用，也可提供高拉伸作用，停留时间较长，混合效果较好。

关键词: 单螺杆挤出机, 螺杆组合, Polyflow软件, 数值模拟