A tetrafluoroethylene (TFE) copolymer film having 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. 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/cm2/min. In addition, the dense articles have a void volume of less than about 20%. Methods for dense articles from core shell tetrafluoroethylene copolymers are also provided. The dense articles exhibit improved physical and mechanical properties such as adhesion and barrier properties.