Chain conformation and dynamics in ultrahigh molecular weight polyethylene melts undergoing extensional–shear coupled flow: insight from dissipative particle dynamics simulation

Abstract

AbstractA first attempt is made to present a detailed mesoscopic‐level description of the conformation and equilibrium dynamic properties of macromolecular chains in ultrahigh molecular weight polyethylene/polypropylene blends driven by extension‐dominated coupled flow, in comparison with shear‐dominated coupled flow. Extension‐dominated coupled flow can be defined as = 0.005, ≥ 0.1 and shear‐dominated coupled flow as = 0.1, ≥ 1, as verified by the time‐dependent evolution tendency of cell parameters and velocity profiles along the x, y, z directions. In the case of extension‐dominated coupled flow, the chains are greatly elongated and prefer to align along the flow direction, where the polypropylene chains appear to form a somewhat uniform layer. By comparison, the macromolecular chains assume a highly collapsed conformation and have a greater preference to align themselves perpendicular to the flow direction under shear‐dominated coupled flow, which can be ascribed to the rapid diffusion of polymer chains and a minor role of the weak van de Waals interaction in structural transitions. Analyses of conformational behavior derived from dissipative particle dynamics trajectories can, in general, serve as a useful guideline for experimental investigations of ultrahigh molecular weight polyethylene based materials prepared by eccentric rotor extrusion. © 2020 Society of Chemical Industry