以聚碳酸酯(PC)为研究材料,基于分子动力学方法,对三维周期性边界条件下PC流动取向过程中分子链团迁移性能和形态演化进行了研究,与实验结果对比得到充模流动阶段聚合物分子链团的流动取向机制.分子链团均方位移表明流动取向过程实质上是分子链团的空间构象协调变形的结果,虽然随着剪切速率的增大,分子链团均方位移迅速增大、非键合能急剧减小,但分子链基本分子结构却仍然保持不变.同时,在取向过程中无规缠绕的分子链团一方面由于剪切拉伸作用沿流动方向排布,另一方面分子链团之间因发生解缠结而趋于相互分散.注塑实验结果表明,制品双折射率随注射速率的增加而增大,并沿流动方向递减,且取向方向上的拉伸性能随取向度的增加也有所提高,这与模拟结果中聚合物分子链取向机理一致.%Taking the polycarbonate (PC) as research objective,the migration properties and morphological evolution of polymer chains under three dimensional periodic boundary condition were studied based on molecular dynamics (MD) simulation.And the flow induced orientation mechanism of polymer was revealed by comparing simulated and experimental results.The mean square displacement indicated that the orientation process was actually an coordinated conformation of polymer conglomeration,although the mean square displacement increased largely and the non-bond energy decreased rapidly while the shear rate increasing,the structure of polymer chains did not changed at all.At the same time,the randomly entangled polymer chains not only arranged along flow direction,but also separated from each other and tended to be dispersive distribution.The experimental results showed that birefringence increased with the increase of the injection rate and decreased along the flow direction,while the tensile properties in the orientation direction also increased with the increase of the degree of orientation,which is well consistent with the migration behavior and morphology evolution rules indicated by the simulation results.
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