分子動力学シミュレーションによるポリカーボネートの体積クリープの静水圧依存性評価

抄録

Generally, polymeric materials show viscoelasticity because of their structures. It is difficult to measure the bulk creep compliance; however, it is becoming increasingly important to measure bulk properties because of increasing environments of high pressure, such as the inside of an injection molding apparatus. In this study, a molecular dynamics (MD) simulation was performed to understand the bulk creep mechanisms by investigating each potential energy during bulk creep analysis. An amorphous polycarbonate model was prepared and analyzed at three different temperatures under T_g. A hydrostatic pressure (7 conditions) was applied to the model for 10 ns to simulate the bulk creep test. The results indicate time, temperature, and pressure dependency; further, there is a high interrelationship between the hydrostatic pressure and creep speed. Master curves of the bulk creep compliance with hydrostatic pressure were obtained by shifting the bulk creep compliance curves, and the shift factors for hydrostatic pressure were also obtained. Furthermore, MD simulation could estimate the long-term bulk creep behavior for 100 s. From the viewpoint of energy change, the bulk creep behavior could be explained by the change in the dihedral angle potential energy.