Articles including expanded polytetrafluoroethylene membranes with serpentine fibrils

• US 20130183515A1
• Filed: 01/16/2012
• Published: 07/18/2013
• Est. Priority Date: 01/16/2012
• Status: Abandoned Application

• Current Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Original Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Inventors: White, Charles F.
• Application Number:
  US13/351,052
• Publication Number:
  US 20130183515A1
• Time in Patent Office: Days
• US Class Current: 428/297.4
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29K 2105/04 cellular or porous
• CPC Class Codes: Y10T 428/24994 Fiber embedded in or on the surface of a polymeric matrix

Abstract

Articles including expanded fluoropolymer membranes having serpentine fibrils are provided. The fluoropolymer membranes exhibit high elongation while substantially retaining the strength properties of the fluoropolymer membrane. The membrane may include a fluoropolymer and/or elastomer. Additionally, the article has an elongation in at least one direction of at least about 100% and a matrix tensile strength of at least about 50 MPa. The article may be formed by (1) expanding a dried, extruded fluoropolymer tape in at least one direction to produce an expanded fluoropolymer membrane and (2) retracting the expanded fluoropolymer membrane in at least one direction of expansion by applying heat or by adding a solvent. The application of a tensile force at least partially straightens the serpentine fibrils, thereby elongating the article. The expanded fluoropolymer membrane may include a microstructure of substantially only fibrils. The membranes may be imbibed with an elastomeric material to form a composite.

Claims

1. An article comprising an expanded fluoropolymer membrane including serpentine fibrils.

2. The article of claim 1, wherein said article has an elongation in at least one direction of at least about 50% and a matrix tensile strength of at least about 50 MPa

3. The article of claim 1, wherein said article has an elongation in at least one direction of at least about 100% and a matrix tensile strength of at least about 50 MPa.

4. The article of claim 1, wherein said article has an elongation in at least one direction of at least about 200% and a matrix tensile strength of at least about 50 MPa.

5. The article of claim 1, wherein said article has an elongation in at least one direction of at least about 600% and a matrix tensile strength of least about 50 MPa.

6. The article of claim 1, wherein said article has an elongation in at least one direction of at least about 100% and a matrix tensile strength of at least about 100 MPa.

7. The article of claim 1, wherein said article has an elongation in at least one direction of at least about 200% and a matrix tensile strength of at least about 100 MPa.

8. The article of claim 1, wherein the fluoropolymer comprises polytetrafluoroethylene.

9. The article of claim 1, wherein the expanded fluoropolymer membrane comprises a microstructure of substantially only fibrils.

10. The article of claim 1, wherein said fluoropolymer membrane exhibits an increase in modulus when elongated to at least about 80%.

11. An article comprising an expanded fluoropolymer membrane having a microstructure including serpentine fibrils produced by the process comprising:

a. expanding a dried, extruded fluoropolymer tape in at least one direction to produce an initial expanded fluoropolymer membrane; and

b. heating the initial expanded fluoropolymer membrane to thermally retract the expanded fluoropolymer membrane in at least one direction of expansion.

12. The article of claim 11, wherein the initial expanded fluoropolymer membrane has a microstructure of substantially only fibrils.

13. The article of claim 11, wherein the expanded fluoropolymer membrane is thermally retracted in at least one direction to less than about 90% of the initial, expanded fluoropolymer membrane length.

14. The article of claim 11, wherein the expanded fluoropolymer membrane is thermally retracted in at least one direction to less than about 75% of the initial, expanded fluoropolymer membrane length.

15. The article of claim 11, wherein the expanded fluoropolymer membrane is thermally retracted in at least one direction to less than about 50% of the initial, expanded fluoropolymer membrane length.

16. The article of claim 11, wherein the expanded fluoropolymer membrane is thermally retracted in at least one direction to less Than about 25% of the initial, expanded fluoropolymer membrane length.

17. The article of claim 11, wherein the expanded fluoropolymer membrane is restrained in at least one direction during said thermal retraction.

18. The article of claim 11, further comprising imbibing at least one material into said fluoropolymer membrane prior to retracting said fluoropolymer membrane.

19. The, article of claim 18, wherein said at least one material is selected from the group consisting of a fluoropolymer, an elastomer and combinations thereof.

38. The article of claim 18, wherein at least one material is imbibed into said expanded fluoropolymer membrane prior to retracting said expanded fluoropolymer membrane.

39. The article of claim 18, wherein at least one material is imbibed into said expanded fluoropolymer membrane as said expanded fluoropolymer membrane is retracted.

40. The article of claim 18, wherein at least one material is imbibed into said expanded fluoropolymer membrane subsequent to retracting said expanded fluoropolymer membrane.

20. An article comprising an expanded fluoropolymer membrane having serpentine fibrils and at least one additional material.

21. The article of claim 20, wherein the additional material is selected from the group consisting of a fluoropolymer, an elastomer and combinations thereof.

22. The article of claim 21, wherein the fluoropolymer is fluorinated ethylene propylene.

23. An article comprising an expanded fluoropolymer membrane including serpentine fibrils'"'"'and at least one additional material incorporated at least partially into the expanded fluoropolymer membrane.

24. The article of claim 23, wherein the at least one additional material comprises a fluoropolymer.

25. The article of claim 23, wherein the at least one additional material comprises an elastomer.

26. The article of claim 23, wherein the expanded fluoropolymer membrane has a microstructure of substantially only fibrils.

27. The article of claim 23, wherein the expanded fluoropolymer membrane,is thermally retracted in at least one direction.

28. The article of claim 27, wherein the expanded fluoropolymer membrane is restrained in at least one direction during said thermal retraction.

29. The article of claim 23, wherein said fluoropolymer membrane exhibits an increase in modulus when elongated to at least about 80%.

30. An article comprising an expanded fluoropolymer membrane and an elastomer, said membrane having serpentine fibrils and, a percent unrecoverable strain energy density of less than about 85%.

31. The article of claim 30, wherein the expanded fluoropolymer membrane has a percent unrecoverable strain energy density of less than about 70%.

32. The article of claim 30, wherein the expanded fluoropolymer membrane has a percent unrecoverable strain energy density of less than about 60%.

33. An article comprising an expanded fluoropolymer membrane having a microstructure including serpentine fibrils produced by the process comprising:

a. expanding a dried, extruded fluoropolymer tape in at least one direction to produce an initial expanded fluoropolymer membrane; and

b. adding a solvent to the initial expanded fluoropolymer membrane to retract the expanded fluoropolymer membrane in at least one direction of expansion.

34. The article of claim 33, wherein at least one material is imbibed into said expanded fluoropolymer membrane prior to retracting said expanded fluoropolymer membrane.

35. The article of claim 34, wherein said at least one material is selected from the group consisting of a fluoropolymer, an elastomer and combinations thereof.

36. The article of claim 33, wherein at least one material is imbibed into said expanded fluoropolymer membrane as said expanded fluoropolymer membrane is retracted.

37. The article of claim 33, wherein at least one material is imbibed into said expanded fluoropolymer membrane subsequent to retracting said expanded fluoropolymer membrane.