THERMODYNAMICS OF POLY(TETRAFLUOROETHYLENE) SOLUBILITY

We have directly observed the dissolution behavior of poly(tetrafluoro ethylene) (PTFE) in sealed glass tubes placed in aluminum heating bloc ks. Both oligomers of PTFE and other perfluorocarbons were studied as solvents for specially prepared, well-characterized low moleuclar weig ht PTFEs. Solution melting points and recrystallization temperatures w ere determined as well as the temperature above the solution melting p oint where liquid-liquid phase separation occurs. We have also modeled the phase behavior of PTFE-fluorocarbon systems using the Flory, Orwo ll, Vrij theory and obtained qualitative agreement with the visual obs ervations. Saturated perfluorocarbons with aliphatic ring structures a nd high critical temperatures were found to be the preferred solvents for allowing solubility at the lowest temperatures and pressures.