Thermal characterization of tetrafluoroethylene‐perfluoroalkylvinylether copolymers: Melting behavior and low‐temperature transitions

Abstract

Differential scanning calorimetry has been used to study the melting and the low‐temperature transitions of tetrafluoroethylene‐perfluoroalkylvinylether copolymers (PFA). Melting is similar to that of PTFE in that it is subject to superheating, moreover the melt‐crystallized samples show temperatures and heats of fusion lower than the native ones. At temperatures lower than room temperature, crystal‐crystal transitions are observed for copolymers containing 2 mol % of perfluoromethyl‐, perfluoroethyl‐, and perfluoro‐n‐propylvinylether. In the case of perfluoromethylvinylether as a comonomer, low‐temperature transitions are present only up to a content of 4 mol %. The effect on melting and low‐temperature transitions of both the comonomer content and of the type of side groups has been investigated. The temperatures and heats of transitions show the expected dependence as a function of the comonomer concentration and have been found to be independent on the chemical nature of the side group. © 1994 John Wiley & Sons, Inc.