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Abstract

A dense article that includes a dense TFE copolymer film is provided. The dense TFE copolymer film includes a first endotherm between about 50° C. and about 300° C., a second endotherm between about 320° C. and about 350° C., and a third endotherm between about 350° C. and about 400° C. To form the dense article, a core shell TFE copolymer is formed into a pellet, ram extruded into a tape, dried into a dried preform, and then stretched into a dense TFE copolymer film that exhibits improved physical and mechanical properties. The dense TFE copolymer film is produced directly from the dried preform at a deformation temperature less than about 335° C. and without increasing the porosity of the dried preform, as would conventionally be done in expansion processes. The dense TFE copolymer films have a methane permeability less than about 20 μg*micron/cm²/min. The dense articles have a void volume less than about 20%.

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First Claim