Wu Wangqing, Duan Fengnan, Zhao Baishun, Qiang Yuanbao, Zhou Mingyong, Jiang Bingyan
State Key Laboratory of High Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
Polymers (Basel). 2022 Aug 8;14(15):3218. doi: 10.3390/polym14153218.
Wall slip directly affects the molding quality of plastic parts by influencing the stability of the filling flow field during micro injection molding. The accurate modeling of wall slip in nanochannels has been a great challenge for pseudoplastic polymer melts. Here, an effective modeling method for polymer melt flow in nanochannels based on united-atom molecular dynamics simulations is presented. The effects of driving forces and wall-fluid interactions on the behavior of polyethylene melt under Poiseuille flow conditions were investigated by characterizing the slip velocity, dynamics information of the flow process, and spatial configuration parameters of molecular chains. The results indicated that the united-atom molecular dynamics model could better describe the pseudoplastic behavior in nanochannels than the commonly used finitely extensible nonlinear elastic (FENE) model. It was found that the slip velocity could be increased with increasing driving force and show completely opposite variation trends under different orders of magnitude of the wall-fluid interactions. The influence mechanism was interpreted by the density distribution and molecular chain structure parameters, including disentanglement and orientation, which also coincides with the change in the radius of gyration.
壁面滑移通过影响微注塑成型过程中填充流场的稳定性，直接影响塑料部件的成型质量。对于假塑性聚合物熔体，纳米通道中壁面滑移的精确建模一直是一个巨大的挑战。在此，提出了一种基于联合原子分子动力学模拟的纳米通道中聚合物熔体流动的有效建模方法。通过表征滑移速度、流动过程的动力学信息和分子链的空间构型参数，研究了驱动力和壁-流体相互作用对泊肃叶流动条件下聚乙烯熔体行为的影响。结果表明，联合原子分子动力学模型比常用的有限可扩展非线性弹性（FENE）模型能更好地描述纳米通道中的假塑性行为。发现滑移速度会随着驱动力的增加而增大，并且在不同量级的壁-流体相互作用下呈现出完全相反的变化趋势。通过密度分布和分子链结构参数（包括解缠结和取向）解释了其影响机制，这也与回转半径的变化相一致。
