Transport Properties of Polystyrene Solutions Swollen with Carbon Dioxide
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Date
2005-01-16
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Abstract
The viscosity and diffusion coefficient of polystyrene (PS) in decahydronaphthalene (DHN) were measured in the presence of CO₂ to investigate the effect of CO₂ on the transport properties of polymers in solution. The viscosity of 1-15 wt% PS in DHN was measured, using a moving piston viscometer. The effects of CO₂ pressure (0 to 3000 psi), polymer concentration (1-15 wt%), temperature (33-150°C), and molecular weight (126 to 412 kDa) on viscosity were investigated. Viscosity measurements of PS in DHN showed the viscosity increase with increasing concentration was described by the Martin equation. Addition of 30-40 wt% CO₂ resulted in the maximum viscosity reduction for all temperatures, polymer concentrations, and molecular weights. Viscosity reduction was greatest for high molecular weight polymer, high polymer concentrations, and low temperatures. At the highest CO₂ pressures, the viscosity of all polymer solutions converged to approximately 1-3 cp. The viscosity of PS/DHN/SF₆ was also measured. The viscosity reduction with SF₆ was approximately the same as that with CO₂. In addition, the diffusion coefficient of 0.5- 1.25 wt% 412,000 M[subscript n] PS in DHN was measured from 25-150°C. The diffusion coefficient results were extrapolated to zero concentration to determine the infinite dilution diffusion coefficient, D₀. The hydrodynamic radius was calculated from D₀. The hydrodynamic radius increased with temperature, indicating an increase in solvent quality of DHN with increasing temperature. Upon addition of CO₂ to 0.75-1 wt% 412,000 M[subscript n] PS in DHN, the diffusion coefficient increased, approximately doubling in value. The decrease in viscosity and increase in diffusion coefficient with CO₂ show that CO₂ is effective as a facilitator of improved transport.
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Keywords
diffusion coefficient, viscosity, decahydronaphthalene
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Degree
MS
Discipline
Chemical Engineering
