基于拉伸破碎原理的单螺杆拉伸混炼元件的研究

摘要

The deformation of polymers in processing contained shear and extensional components. It was identified that the dispersive mixing was strongly depended on shear stress or extensional stress and distributive mixing was mainly depended on the number of interfaces. Multiple-phase polymers could achieve a better mixing through extensional stress based on extensional disagglomeration. In this paper, a new mixing element prototype for single-screw extruder was developed and its dispersive and distributive mixing capacities and probability functions for stress and deformation rate in single-screw processing was analyzed by Polyflow. The flowing trajectories obtained suggested that more and more particles were subjected to greater shear and extensional rates with increasing of time. Meanwhile, a long resistance time, no vortex flow and no stagnalion of material in the processing showed a good shear and extensional mixing capacities of the new mixing element. Moreover, it was clear that the extensional mixing property was superior to that of shear mixing at low deformation rates from probability functions.%根据聚合物混炼过程中的分布混合主要取决于分流次数的多少，而分散混合则很大程度上依赖于剪切应力或拉伸应力的强度的原理，并基于拉伸形变的破碎效应，设计了一种新型单螺杆拉伸混炼元件。通过有限元软件Polyflow分析了该新型混炼元件的分散混合及分布混合性能，计算了混合过程中的压力、应力应变速率的概率函数。根据粒子轨迹研究发现，随着时间的延长，承受较大剪切速率或拉伸速率的粒子数逐渐增多，且流动过程中粒子具有较长的停留时间，无明显的回流与滞料现象，说明该新型拉伸混炼元件同时表现出良好的剪切与拉伸混合特征，但存低应变速率下拉伸混合性能要更加优越。