| 초록 |
The nonlinear viscoelasticity of the polymer melts has been intriguing topic over the years. One of the time-dependent measurements, stress relaxation is that the stresses relax monotonically to zero after the cessation of steady shear flow. However, molecular origin of time-dependent nonlinear response of the polymer melts is still unclear. In this work, we give a detailed molecular description of the stress relaxation via atomistic nonequilibrium molecular dynamics (NEMD) simulations of the linear polyethylene (PE) melts in a wide range of the Weissenberg numbers. We calculate not only the nonlinear properties of the stress relaxation including material functions, conformation or birefringence, also elucidate how different the molecular mechanism, compared with our previous studies regarding that of stress growth after onset of the steady shear flow. Also, we conduct entanglement analysis to show reconstruction process of the entanglement network via the well-known Z1-code. |
