Abstract: With the example of the amorphous polymethyl methacrylate (PMMA) polymer material, the molecular dynamics simulation experiments were performed to study the flowing morphology and mechanical behavior of the macromolecular during the injection molding produce. A cubic PMMA cell consisting of 10 molecular chains of 20 units was constructed. The energy initialization was performed using the energy minimization method followed by the Simulated Anneal method. By coupled with the periodic boundary conditions, COMPASS (condensed-phase optimized molecular potentials for atomistic simulation studies) force field and the Velocity-Verlet algorithm, the simulation was launched with isothermal conditions. The results indicate the deformation of the chains cell need first to overcome the “activation energy”, involving the internal energy, relation and unwrapping energy. There was a time and a stress threshold during the filling stage. The former presents the coordination course of the internal energy with a transitional loaded condition, and the later reveals the relaxation and disentanglement of the flexible chains with a higher shear stress loaded. The radius of gyration distributions of the C atom in main chains show the macromolecular gives an orientation direction with the flowing direction under the loaded conditions. The bigger of the shear stress, the more sensible of the orientation. While the excessive shear stress leads to the macromolecular break then elastic recovery. Furthermore, the mean square displacement (MSD) data indicate that the flowing essence of the molten polymer is the directional migration and orientation arrangement of the macromolecule chains. The results also confirm that the “activation energy” is the principal obstacle for chains motion. After overcoming this obstacle, the migration rate gives a nonlinear increase trend with the rise of the shear stress.
曹文华, 辛勇, 刘东雷. 注塑充模聚合物流动形态与力学行为分子机制研究*[J]. 《材料导报》期刊社, 2017, 31(2): 142-149.
CAO Wenhua, XIN Yong, LIU Donglei. Research on Flow Pattern and Molecular Mechanisms of Polymer Molten During Injection Filling Stage. Materials Reports, 2017, 31(2): 142-149.
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2017, Vol. 31 
