Molecular configuration evolution model and simulation for polymer melts using a non-equilibrium irreversible thermodynamics method

摘要

Almost all flows of polymers are accompanied by evolution of the molecular configuration, which has a great influence on material properties. However, the existing molecular configuration evolution models are mainly limited to the configuration evolution of a single molecular chain in a dilute solution ignoring intermolecular forces; it is impossible to predict the evolution of the molecular configuration of polymer melt with a complex entanglement network. Thus, we propose a non-isothermal compressible viscoelastic molecular configuration evolution model for polymer melt using non-equilibrium irreversible ther-modynamic methods. The proposed model can more accurately describe the Theological properties of polymer melts compared with the commonly used XPP model, especially at high shear rates. The predicted molecular configuration in rotary Couette flow agrees well with the measured dielectric anisotropy results. Finally, the present model and a simulation method are successfully applied to predict the evolution of polymer molecular configuration and birefringence in three-dimensional injection compression molding, and the predicted birefringence is consistent with the measured results. A typical skin-core structure, resulting from the competition of the flow field and the molecular Brownian thermal motion in the injection molding, is investigated.