Sanchez – Lacombe Research Articles

Measurements and modeling of cloud point behavior for polypropylene/ n-pentane and polypropylene/ n-pentane/carbon dioxide mixtures at high pressure

The phase behavior of polypropylene (PP) in n-pentane and n-pentane/carbon dioxide solvent mixtures has been studied using a high-pressure variable volume view cell. Cloud point pressures for polypropylene ( M w=50,400) in near-critical n-pentane were studied at temperatures ranging from 432 to 470 K for polymer concentrations of 1 to 15 mass%. Furthermore, cloud point pressures for polypropylene ( M w=95,400) in near-critical n-pentane were studied at temperatures ranging from 450 to 465 K for polymer concentrations of 1 to 8 mass%. Cloud point pressures were also measured for PP ( M w=200,000, 3 mass%) in n-pentane at temperatures ranging from 450 K to 465 K. The cloud point pressures for PP ( M w=50,400) in n-pentane/CO 2 mixtures were determined for PP concentrations of 3.0 mass% and 9.7 mass% with CO 2 solvent concentrations ranging from 12.6 mass% to 42.0 mass% at temperatures ranging from 405 K to 450 K. All of the experimental cloud point isopleths were relatively linear with approximately the same positive slope indicating LCST behavior. The experimental cloud point pressures were relatively insensitive to the concentration and molecular weight of polypropylene. At a given temperature, the cloud point pressure of the PP/ n-pentane/carbon dioxide system increased almost linearly with increasing carbon dioxide solvent concentration (for carbon dioxide concentrations less than 30 mass%). The Sanchez–Lacombe (SL) equation of state was used to model the experimental data.

Phase-separation behavior of the system pes/phenoxy: An application of the sanchez-lacombe lattice fluid theory

Cloud-point curves reported for the system polyethersulfone (PES)/phenoxy were calculated by means of the Sanchez-Lacombe (SL) lattice fluid theory. The one adjustable parameter ε12*/k (quantifying the interaction energy between mers of the different components) can be evaluated by comparison of the theoretical and experimental phase diagrams. The Flory-Huggins (FH) interaction parameters are computed based on the evaluated ε12*/k and are approximately a linear function of volume fraction and of inverse temperature. The calculated enthalpies of mixing of PES/phenoxy blends for different compositions are consistent with the experimental values obtained previously by Singh and Walsh [1].

A comparison of lattice-fluid models for the calculation of the liquid-liquid equilibria of polymer solutions

The group contribution lattice-fluid equation of state (GCLF) has been compared to the Sanchez-Lacombe (S-L) equation of state and experimental data for liquid-liquid equilibrium in polymer-solvent systems. Both equations of state are shown to be capable of predicting upper critical solution temperatures, lower critical solution temperatures, simultaneous upper and lower critical temperatures and “hour glass” behavior in which there is no upper or lower critical temperature. The predictions of the GCLF model and S-L model are compared to systems which show a LCST and both a LCST and UCST. The specific systems studied include: acetic acid dodecane , polyisobutylene n-pentane , polyethylene n-hexane , polystyrene n-hexane , polyisobutylene n-pentane , and polystyrene acetone . The GCLF showed good agreement with the experimental data for systems with a LCST. In all cases the GCLF model performed better than the S-L model. The GCLF showed good sensitivity to the molecular weight of the polymer, but failed to show the needed sensitivity to pressure. The enhanced performance of the GCLF model was attributed to using saturated vapor and liquid properties simultaneously to regress the group parameters for the model.

P‐V‐T properties of alternating poly(ethylene‐propylene) liquids

AbstractThe pressure‐volume‐temperature (P‐V‐T) properties of monodisperse alternating poly(ethylene‐propylene) (hydrogenated polyisoprene) melts of varying molecular weights are measured at 0.1 MPa < P < 200.1 MPa, and 290 K < T < 510 K in a dilatometer‐type apparatus. The Flory‐Orwoll‐Vrij (FOV), Modified Cell Model (MCM), Sanchez‐Lacombe (SL), and the Statistical Associating Fluid Theory (SAFT) equations of state are found to correlate the experimental data with excellent accuracy, except either at low pressures and high temperatures, or at high pressures and low temperatures. On average, MCM and SAFT fit the data slightly better than FOV and SL. The equation‐of‐state parameters are found to be independent of molecular weight, especially for SAFT, as required by the theory. © 1994 John Wiley & Sons, Inc.

Saturated phase equilibria and parameter estimation of pure fluids with two lattice-gas models

Accurate and reliable prediction of saturated pure fluid properties is essential for subsequent extension to multicomponent mixtures. The conventional cubic equations of state are accurate in correlation of non-polar fluid properties but often give poor results when applied to fluids with permanent dipole or quadupole noments. A simple alternative to the cubic equations are the lattice-gas equations of state, pioneered by Guggenheim, Simha, Sanchez and Lacombe, and Kleintjens and Koningsveld. We compare the performance here of the Sanchez-Lacombe (SL), Kleintjens-Koningsveld (KK), and Peng-Robinson (PR) equations of state in correlating the properties of pure non-polar and polar fluids. We also correlate the characteristic parameters in the two lattice-gas equations with critical and molecular properties. The KK model with four parameters, one of which is temperature-dependent, correlates the saturated fluid properties of polar fluids better than the SL model with three parameters. Both equations of state give better results for polar fluids than the conventional cubic equations, particularly in the prediction of saturated liquid densities.