基于收敛—发散流动的CaCO_3/HDPE复合材料混合性能

Mixing Properties of CaCO_3/HDPE Composite based on Convergence-Divergence Flow

设计可产生周期性收敛—发散流动的模头,使流动过程中物料受到周期性的压缩与膨胀作用,物料受到拉伸应力与剪切应力的复合应力作用,从而有利于提高混合效果;通过改变物料流经收敛板的次数可调整物料受到压缩与膨胀作用的停留时间。利用该模头在单螺杆挤出机上进行了CaCO3填充高密度聚乙烯(HDPE)熔融共混实验,并对复合材料进行宏观力学性能测试与微观结构表征,测试结果表明:收敛—发散流动能提高复合材料的力学性能,物料受到反复压缩与膨胀作用的停留时间对复合材料性能的提高有重要影响,当CaCO3含量高时需要较长时间的压缩与膨胀作用才能达到提高复合材料性能的目的;从复合材料断面的扫描电镜照片可以看出经收敛—发散流动作用后复合材料中CaCO3粒径更细,粒径分布更均匀。

The materials suffer periodically changed compression and extensional stress during the process in a self-made die, which could generate convergence-divergence flow. The mixing effect could be improved with the interaction of extensional and shear stresses. The residence time of the materials in the complicated flow field could be adjusted by changing the number of convergence plates. The melt blending experiments of high density polyethylene （HDPE） filled with CaCO3 were conducted with single screw extruder and self-made die. Mechanical testing and microstructure characterization of the composite was carried out. The experimental results showed that convergence-divergence flow could improve the mechanical properties of the composite. The residence time of the materials in the compression and expansion field was very important to improve the composite＇ performance. It took long compression and expansion time to improve the performance of the composite when the CaCO3 content was high. As shown in the SEM photographs, the particle sizes of CaCO3 in the composite prepared by convergence-divergence flow was much smaller and the particle size distribution was more uniform.