THERMODYNAMICS OF POLY(TETRAFLUOROETHYLENE) SOLUBILITY

We have directly observed the dissolution behavior of poly(tetrafluoroethylene) (PTFE) in sealed glass tubes placed in aluminum heating blocks. Both oligomers of PTFE and other perfluorocarbons were studied as solvents for specially prepared, well-characterized low moleuclar weight PTFEs. Solution melting points and recrystallization temperatures were determined as well as the temperature above the solution melting point where liquid-liquid phase separation occurs. We have also modeled the phase behavior of PTFE-fluorocarbon systems using the Flory, Orwoll, Vrij theory and obtained qualitative agreement with the visual observations. Saturated perfluorocarbons with aliphatic ring structures and high critical temperatures were found to be the preferred solvents for allowing solubility at the lowest temperatures and pressures.