The heat of fusion of copolymers of tetrafluoroethylene and hexafluoropropylene

The Clapeyron equation has been applied to determine the heat of fusion of two copolymers of tetrafluoroethylene and hexafluoropropylene. The values obtained are within experimental uncertainty of that for the homopolymer, PTFE. This study supports the conclusion of earlier workers that the CF 3 side groups are included in the crystal lattice. In both PTFE and polyethylene, C 1 side groups are included in the crystal but have little if any effect on its density. We believe that the same relationship between the crystallinity and the heat of fusion can be used for both PTFE and copolymers of TFE and HFP.