| abstract |
A dense article comprising a core/shell tetrafluoroethylene (TFE) copolymer film having a first endotherm between 50°C and 300°C, a second endotherm between 320°C and 350°C, and a third endotherm between 350"C and 400°C is provided. In exemplary embodiments, the third endotherm is approximately 380°C. In some embodiments, the second endotherm is between about 320°C and about 330°C or between about 330°C and about 350°C. TFE copolymer films have a methane permeability less than about 20 µg*micron/cm |