黏弹性聚合物熔体多相成型界面不稳定的机理分析

Mechanism analysis of viscoelastic interfacial instability of polymer multiphase processing

基于动网格法和EVSS/SU等混合有限元技术,建立了黏弹性聚合物多相成型界面不稳定的数值模拟系统,模拟结果与Matsunaga的理论研究和Yamaguchi的实验研究结论相符合。通过研究流率、黏度和松弛时间(弹性)对界面不稳定的影响规律,发现在相应条件下流率、黏度和松弛时间都能使界面变得不稳定,而界面两侧第一法向应力差的阶跃是导致黏弹性界面不稳定的根本原因,进而揭示了黏弹性界面不稳定的机理,并对生产实践提出了若干指导原则。

Based on the moving mesh scheme and the mixed finite element methods of EVSS/SU （elasticviscous split stress/streamline upwind）, a numerical simulation system of viscoelastic interfacial instability of polymer multiphase processing was established. The results of simulation showed a good agreement with the experimental data and theoretical calculation reported in literature. By means of simulation, the effects of flow rate, viscosity and relaxation time of molten polymer on interfacial instability were investigated. It was found that the jumps in the first normal stress difference across the interface were the radical causes of interfacial instability. Then the mechanism of interfacial instability was revealed, and several useful guiding principles for engineering practice were proposed.