Phase equilibria of supercritical fluid-polymer systems

Sorption and swelling of silicone rubber (SR), polyisobutylene (PIB), polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), and polyethylene terephthalate (PET) in the presence of sub- and supercritical carbon dioxide have been measured at pressures up to 30 MPa at 308.2 and 323.2 K. Rubbery polymers (SR and PIE) and PMMA showed a sigmoidal increase in sorption with pressure, while other glassy polymers such as PS and PC and a crystalline polymer, PET, showed the monotonic increase/level-off sorption behavior. The well-known dual-mode sorption mechanism was found to be inadequate to describe the sorption behavior of glassy polymers at high pressures. The amount of sorption was successfully calculated from the experimental swelling data for SR. Density representation of sorption was much better than the pressure representation. Other sorption and swelling behaviors have also been analyzed and discussed. (C) 1998 Elsevier Science B.V.