Accurate viscosity predictions of linear polymers from n-alkanes data

The design of processes involving heavy alkanes and polymers relies on the accurate knowledge of their viscosity, as it strongly affects the flowing behavior, and hence, the final performance. Most classical viscosity modeling methods are unable to predict the behavior at high-pressure, high-temperature conditions, neither to capture the change in the slope of the zero-shear viscosity with the molecular weight. We present here results of coupling two molecular theories, the soft-SAFT Equation of State and the Free-Volume Theory (FVT), for viscosity calculations of n-alkanes and linear polyethylene up to 32,100 g/mol, in a transferable manner. A new procedure, named Spider-Web, is implemented to obtain reliable parameters for the FVT. The procedure provides accurate predictions for the viscosity of n-alkane mixtures in agreement with experimental data, including high pressure and high temperature conditions. The molecular model is also able to predict the dependency of the entanglement molecular weight with temperature and pressure.