Phase Equilibria Calculations of Polyethylene Solutions from SAFT-Type Equations of State

Abstract

We present here phase equilibria calculations of polyethylene solutions in different solvents as obtained with two versions of the SAFT equation of state, soft-SAFT and PC-SAFT. The objective of this work is twofold: to check the accuracy of the soft-SAFT equation in providing reliable polymer solutions behavior and to propose a methodology from which systematic studies on polymer solutions can be made by the use of transferable molecular parameters. Some issues regarding the fitting of molecular parameters from polymer data as well as the numerical problems associated with polymer phase equilibria calculations are also mentioned. The methodology is applied to model the phase equilibria of polyethylene solutions with several solvents, differing in size and polarity, including n-pentane, n-hexane, butyl acetate, and pentanol, and results are compared to available experimental data. The phase behavior explored in this work is wide, from vapor-liquid equilibria to liquid-liquid equilibria, displaying upper critical solution temperatures and lower critical solution temperatures. We have also calculated the solubility of ethylene in polyethylene with the same models. Results obtained from the soft-SAFT equation are slightly more accurate in some of the cases than the PC-SAFT equation. Both equations, soft-SAFT and PC-SAFT, follow most of the experimental trends, providing accurate predictions from pure component parameters in some of the cases, while a binary interaction parameter was needed for the butyl acetate, 1-pentanol, and ethylene binary mixtures.

The Effect of Pure Component Characteristic Parameters on Sanchez–Lacombe Equation‐of‐State Predictive Capabilities

“…Different thermodynamics models have been developed and tested for the validation and prediction of monomer solubility in polymers. Activity coefficient models (ACM) and equations of state (EOS) models are well established classes of thermodynamic models that have been used extensively for the prediction of equilibrium monomer solubility in polymers 1–13. However, there is no universal thermodynamic model for the prediction of monomer(s) solubility in polymers at commonly implemented process conditions.…”

A Survey of Equations of State for Polymers

“…The soft-SAFT equation uses the spherical fluid of Lennard-Jones as a reference, including attractive and repulsive interactions, while the reference term in the PC-SAFT equation is the rigid sphere chain. The studies carried out by Pedrosa et al [153], which also dealt with vapor-liquid equilibrium, showed that results with soft-SAFT equation are slightly more accurate than those obtained with PC-SAFT in some cases.…”

“…Ethylene, ethane, propylene, propane, butane, 1-butene, hexane [73], [152], [153], [154], [155], [159], [161] Poly(ethylene)-co-olefine Ethylene, propylene, propane, 1-butene, 1-hexene, n-alkane (C6-C8) [144], [146], [163] Poly(vinyl-acetate) (PVA)…”

“…Pedrosa et al [153] presented phase equilibrium calculations for polyethylene solutions with varying solvents using two different versions of the SAFT equation: PC-SAFT and the soft-SAFT. The soft-SAFT equation uses the spherical fluid of Lennard-Jones as a reference, including attractive and repulsive interactions, while the reference term in the PC-SAFT equation is the rigid sphere chain.…”

Mass transport and high barrier properties of food packaging polymers

“…For details refer to Tihic et al (2008). Pedrosa et al (2006) compared the PC-SAFT model with the soft-SAFT model, in which the reference term involves spherical Lennard±Jones species. The chain feature was, however, included; a perturbation to the reference term (using Wertheim's theory) was applied, followed by the use of a radial 6.5 n-Pentane-polyethylene (l, left y-axis) and CO 2 -polyamide 11 (, right y-axis) experimental data and corresponding fits using the simplified SAFT model (lines).…”