W. L. Gore & Associates, Inc.

Todd S Sayler

Lawrence A Ford

Gregory J Shafer

Michael E Kennedy

Shaofeng Ran

Yuri Ebata

A method of forming an unsintered biaxially expanded PTFE/thermoplastic polymer composite membrane is provided. The method includes blending fibrillatable polytetrafluoroethylene (PTFE) particles and thermoplastic polymer particles where the melting point of the thermoplastic polymer particles is less than the melting point of the fibrillatable PTFE particles. The method further includes forming the blend into a tape and expanding and heating the tape in a first direction at a first temperature. The expanded tape is then expanded, either concurrently or sequentially in a second direction to form an ePTFE composite membrane. The method does not include a sintering temperature. The ePTFE particles and thermoplastic polymer particles have an average particle size of less than 1 μm. In addition, the ePTFE composite membrane has a geometric mean matrix modulus to geometric mean matrix tensile strength ratio of at least about 6 and an absolute dimensional change percentage of less than about 1.5%.

Unsintered expanded polytetrafluoroethylene composite membranes having dimensional stability

A tetrafluoroethylene (TFE) copolymer film having a first endotherm between about 50&#xb0; C. and about 300&#xb0; C., a second endotherm between about 320&#xb0; C. and about 350&#xb0; C., and a third endotherm between about 350&#xb0; C. and about 400&#xb0; C. is provided. In exemplary embodiments, the third endotherm is approximately 380&#xb0; C. In some embodiments, the second endotherm is between about 320&#xb0; C. and about 330&#xb0; C. or between about 330&#xb0; C. and about 350&#xb0; C. TFE copolymer films have a methane permeability less than about 20 &#x3bc;g*micron/cm/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.

Dense articles formed tetrafluoroethylene core shell copolymers and methods of making the same

Dense articles formed from tetrafluoroethylene core shell copolymers and methods of making the same

A dense article that includes a dense TFE copolymer film is provided. The dense TFE copolymer film includes a first endotherm between about 50&#xb0; C. and about 300&#xb0; C., a second endotherm between about 320&#xb0; C. and about 350&#xb0; C., and a third endotherm between about 350&#xb0; C. and about 400&#xb0; 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&#xb0; 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 &#x3bc;g*micron/cm/min. The dense articles have a void volume less than about 20%.

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Bear, DE, United States of America

Todd S Sayler