COMPARISON OF SANCHEZ-LACOMBE AND SAFT MODEL IN PREDICTING SOLUBILITY OF POLYETHYLENE IN HIGH-PRESSURE FLUIDS

Sanchez-Lacombe and SAFT (statistical associating fluid theory) models are used to describe phase behavior of polyethylene solutions (M(w) = 2,150, 16,400, 108,000, and 420,000, and M(w)/M(n) = 1.14, 1.16, 1.32, and 2.66, respectively) in n-pentane and in n-butane at high pressures. In order to test the predictive capability of the two models, all the predictions were conducted without any adjustment of the binary interaction parameter. Even though both models correctly predict the general trends of the phase envelopes and the LCST (lower critical solution temperature) nature of the systems. SAFT gives predictions that are much closer to the experimental data than the Sanchez-Lacombe model. (C) 1995 John Wiley and Sons, Inc.