POLYMER SOLUTIONS AND SOLVENT-SUPERCRITICAL CARBON DIOXIDE STUDIES APPLIYING PC-SAFT

Open Access
Author:
Catano-Barrera, Alma Maria
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 09, 2011
Committee Members:
  • Coray M Colina, Thesis Advisor
  • James Patrick Runt, Thesis Advisor
Keywords:
  • phase equilibria
  • supercritical carbon dioxide
  • polymer solutions
  • pc-saft
Abstract:
ABSTRACT In this thesis is presented the phase equilibria predictions for several polymer solutions and polymer-solvent-solvent systems with the presence of supercritical carbon dioxide (scCO2) applying Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). Two main studies were presented to calculate vapor-liquid, liquid-liquid and supercritical fluid-phase equilibria. In the first study, the capabilities and usefulness of several cubic equations of state (PR, SRK, SOF-PR, SOF-RK) as well as a molecular-based equation of state, PC-SAFT were explored. Specifically, the two phase fluid-fluid regions (VLE, LLE) of several demanding binary mixtures of aromatics as well as dichlorobenzoates (alkyl and semi-fluorinated) with supercritical CO2 were evaluated. Group contribution approaches were used to estimate the pure fluid parameters for the alkyl and semi-fluorinated dichlorobenzoates needed for each equation of state. We showed that these models can capture many important features of the complex phase behavior of highly asymmetric systems composed of supercritical CO2 and alkyl (nonfluorinated or semi-fluorinated) 2, 5-dichlorobenzotes. In a second study, the anti-solvent effects of supercritical carbon dioxide in the polystyrene-cyclohexane-carbon dioxide ternary system were predicted with the PC-SAFT model. The results, using polymer parameters calculated with a recently proposed parametrization strategy, satisfactorily predict the phase equilibria behavior of the ternary system and achieve good agreement with experimental data available in literature. Additionally, the swelling behavior of the ternary system as a function of pressure was calculated and several other derivative properties such as the coefficient of isothermal compressibility (âT), the coefficient of isobaric thermal expansivity (áP) and the heat capacity, Cp, were evaluated. Conventional problems in many industrial applications and engineering research areas have been solved with cubic equations of state with reasonable results. However, a powerful advance for industrial applications of polymer solutions and solvent – solvent mixtures under the influence of scCO2 have been presented in this work. The results using PC-SAFT, a molecular-based equation of state, can also help in the development and study of new polymeric materials.