The Modified Sanchez−Lacombe Equation of State Applied to Polydisperse Polyethylene Solutions

Abstract

The modified Sanchez-Lacombe equation of state (MSL-EOS) is Neau's version of the Sanchez-Lacombe equation of state modified to include a Pe ´neloux-type volume translation. The purpose of this work is to report parameters for modeling the phase behavior of polyethylene solutions. The MSL equation is an empirical equation that contains four parameters to define each pure compound whether a solvent or a polydisperse polymer. The MSL equation uses conventional linear and quadratic mixing rules. A parametrization can be used to obtain the pure compound parameters from the molar mass, critical temperature, critical pressure, and acentric factor. These properties cannot be defined for polydisperse polymers, and parameters were determined from a combination of liquid density (PVT) data and polymer + solvent cloud point (xPT) data. Binary interaction parameters have been obtained for over 50 mixtures by correlating the fluid phase boundaries. Binary mixtures including ethylene, hexane, and/or cyclohexane are of particular interest to polyethylene production. A single binary interaction parameter is usually sufficient to represent vapor-liquid equilibrium, but temperature dependence is required to accurately represent liquid-liquid equilibrium. The MSL equation of state can be used to correlate the cloud points of polyethylene solutions at high pressures.

Maximal cell density predictions for compressible polymer foams

“…For quantitative pre dictions, this condition could be relaxed. These sort of quantitative predictions and possible relationships between a generalized SCFT derived SL EOS and different modifications of the SL EOS, such as those suggested in references [23] and [24], are beyond the scope of this work.…”

Combined EoS and elastic constraints models to predict thermodynamic properties for systems involving semi-crystalline polyolefins

“…SL EoS assumes the presence of empty sites (i.e., holes) in the lattice which differentiates it from Flory-Huggin's model and enables it to account for the compressibility and density changes with system temperature and pressure. Details on the SL EoS can be found elsewhere [30][31][32]. Generally, SL EoS can be written as…”

Measurement and Calculation of the Liquid–Liquid Phase Boundaries and Phase Equilibria for the Hexane+Polyethylene System at High Temperatures

“…(4) represents the binary interaction parameter. In the calculations for polymer solutions including polydisperse polymer, the polymer was often regarded as a mixture of monodisperse polymers with different molecular weights (Koak and Heidemann, 2001;Krenz and Heidemann, 2007;Krenz et al, 2009). In the present work, the polydispersity of PE was represented as a mixture of 16 types of monodisperse PE for the LL phase boundary calculations in the same manner as with the previous work (Haruki et al, 2011).…”