The processing of functional films typically involves the transition from entangled polymer liquids (melts or solutions) to solid states. Therefore, the rheological behavior of entangled liquids forms the basis for understanding polymer processing behavior. In this context, the Engineering Laboratory has conducted the following three areas of research on the structural evolution and nonlinear rheological characteristics of polymer melts with different topological architectures, covering the transition from the nonlinear regime of startup shear to steady-state shear conditions:
(1) Under startup shear fields, the nonlinear rheological behavior and structural evolution of linear chains, comb-like chains, and ring polymers were investigated using non-equilibrium molecular dynamics (NEMD) simulations;
(2) Under steady-state shear flow, a comparative study was carried out on the molecular mechanisms of chain flipping in polymer melts and solutions;
(3) To address flow instabilities, the Engineering Laboratory developed a finite element method (FEM) to study the phenomenon of extensional resonance during film casting and its relationship with processing parameters and rheological properties.
