| Abstract
| - The surface tension of polymers in a supercritical fluid is one of the most important physicochemical parametersin many engineering processes, such as microcellular foaming where the surface tension between a polymermelt and a fluid is a principal factor in determining cell nucleation and growth. This paper presents experimentalresults of the surface tension of polystyrene in supercritical carbon dioxide, together with theoretical calculationsfor a corresponding system. The surface tension is determined by Axisymmetric Drop Shape Analysis-Profile(ADSA-P), where a high pressure and temperature cell is designed and constructed to facilitate the formationof a pendent drop of polystyrene melt. Self-consistent field theory (SCFT) calculations are applied to simulatethe surface tension of a corresponding system, and good qualitative agreement with experiment is obtained.The physical mechanisms for three main experimental trends are explained by using SCFT, and none of theexplanations quantitatively depend on the configurational entropy of the polymer constituents. These calculationstherefore rationalize the use of simple liquid models for the quantitative prediction of surface tensions ofpolymers. As pressure and temperature increase, the surface tension of polystyrene decreases. A linearrelationship is found between surface tension and temperature, and between surface tension and pressure; theslope of surface tension change with temperature is dependent on pressure.
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