【作者】 孙士强；

【导师】 冯连勋； 罗兵；

【作者基本信息】 北京化工大学 ， 机械设计及理论， 2006， 硕士

【摘要】 纳米(塑料)复合材料是目前新型材料的研究热点之一，而同向双螺杆挤出机是具有高分散混合能力的连续加工设备，因此纳米粉体与聚合物在同向双螺杆挤出机中熔融混合过程的研究对于纳米复合材料的生产具有理论指导意义和实际应用价值。 本文首先对粉体团块的内部结构及其在聚合物熔体流场中的破碎机理进行了分析，并引入团块尺寸在流场作用下随时间变化的微分方程。为了对不同混合元件的分散混合能力进行比较，本文对常规螺纹元件、窄捏合块元件、宽捏合块元件以及新型混合元件VCR元件流道的三维等温流场进行了模拟与分析。通过对流场流动状态模拟计算，得到了与分散混合及输送能力相关的剪切速率场和压力场；通过粒子示踪法对流场的动态模拟计算及其统计学后处理，得到了停留时间分布、最大剪切速率分布、固定百分比质点经受的剪切速分布随时间的变化、粉体团块尺寸分布随时间的变化等与混合元件分散混合能力有关的统计学结果。 数值模拟分析结果表明：在本文讨论的啮合同向双螺杆混合元件中，宽捏合块元件分散混合能力最强，VCR元件次之，常规螺纹元件最弱；而VCR元件分布混合能力最强，宽捏合块元件次之，常规螺纹元件最弱。 实验研究表明，实验所得混合元件的分散混合能力对比关系与模更多还原

【Abstract】 Nano composites(plastic) is one of the focus in present day, and co-rotating twin screw extruder has better dispersive mixing performance than other mixing device. As said before the study on melt mixing of nano powder and polymer in co-rotating twin screw extruder will achieve both theoretical and practical values.This article analyses the internal structure and dispersive mechanism of agglomerates in melt polymer flow field, and differential equation is introduced to calculate the evolution of agglomerates’ size. To compare the dispersive mixing ability of different mixing elements, 3D isothermal flow field of normal screw element, narrow kneading disc element, wide kneading disc, and VCR element which is one of the new mixing elements are simulated. Based on the numerical simulation of instantaneous static flow fields, the shear rate field and pressure field are analyzed. With the numerical simulation of dynamic flow fields by particle tracking analyze method and statistical analyses, residence time distribution, max shear rate distribution, shear rate distribution of certain percent particles vs. time and the size distribution vs. time of agglomerates are analyzed.更多还原