DISSOLVING PERFLUOROPOLYMERS IN SUPERCRITICAL CARBON-DIOXIDE

A copolymer of TFE (tetrafluoroethylene) and HFP (hexafluoropropylene) was dissolved in supercritical (SC) CO2 at about 200 degrees C and 100 MPa. The copolymer contained 19.3 mol % HFP and had an ultimate melting point of 200 degrees C. Theoretical predictions for phase diagrams of CO2 with TFE homo- and copolymers indicate solubility at greater than or equal to 100 MPa for all systems. The temperature requirements for solubility are about 300 degrees C and greater for PTFE [poly(tetrafluoroethylene)], with lower temperatures required for the copolymers. The experimental results for the low-melting HFP copolymers are reasonably consistent with these phase diagrams, leading us to believe that PTFE should be soluble near the predicted conditions.