Membranes of fluorinated ionomer blended with nonionomeric fluoropolymers for electrochemical cells

• US 7,557,164 B2
• Filed: 08/18/2004
• Issued: 07/07/2009
• Est. Priority Date: 08/19/2003
• Status: Expired due to Fees

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Escobedo, Gonzalo, Khanna, Ram-Tirth, Felix, Vinci Martinez
• Primary Examiner(s): Smith; Duane
• Assistant Examiner(s): WU, IVES J
• Application Number:
  US10/920,486
• Publication Number:
  US 20050043487A1
• Time in Patent Office: 1,784 Days
• Field of Search: 525/199, 525/200, 210/490, 210/640, 210/650, 204/252, 204/296
• US Class Current: 525/199
• CPC Class Codes: C08J 2327/18 Homopolymers or copolymers of tetrafluoroethylene
• CPC Class Codes: C08J 5/2237 containing fluorine
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 2205/03 containing three or more polymers in a blend
• CPC Class Codes: C08L 2205/035 containing four or more polymers in a blend
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C08L 27/18 Homopolymers or copolymers or tetrafluoroethene
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 2300/0091 in the form of mixtures
• CPC Class Codes: H01M 8/1023 having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
• CPC Class Codes: H01M 8/1039 halogenated, e.g. sulfonated polyvinylidene fluorides
• CPC Class Codes: H01M 8/1048 Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
• CPC Class Codes: H01M 8/1067 characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

Blends of fluorinated ionomer with at least two nonionomeric fluoropolymers provide fuel cell membranes whose tensile strength and conductivity are superior to blends using a single fluoropolymer.

Claims

1. A melt extruded membrane consisting essentially of a melt blended mixture of (a) about 70 to about 95 wt % fluorinated ionomer in acid or salt form or precursor thereof and (b) about 30 to about 5 wt % of two melt-processible crystalline fluoropolymers that are substantially free of ion-exchange groups, and that differ from each other in melting point by at least about 5°

C., wherein the first of said two other fluoropolymers that are substantially free of ion-exchange groups has a melting point within about 10°

C. of the melting point of the fluorinated ionomer, and the second of said two other fluoropolymers that are substantially free of ion-exchange groups has a melting point at least about 15°

C. higher than the melting point of the fluorinated ionomer.

2. The membrane of claim 1 wherein the fluorinated ionomer comprises about 80-90 weight % of the total composition.

3. The membrane of claim 1 wherein the fluorinated ionomer comprises two fluorinated ionomers of different equivalent weights.

4. The membrane of claim 1 wherein the fluorinated ionomer is perfluorinated ionomer.

5. The membrane of claim 1 wherein at least one of said two fluoropolymers that are substantially free of ion-exchange groups is a perfluoropolymer.

6. The membrane of claim 1 wherein said first fluoropolymer is present in amount equal to or greater than said second fluoropolymer.

7. The membrane of claim 1 having a thickness of about 0.2 to about 200 micrometers.

8. The membrane of claim 1 wherein said ionomer has sulfonic acid groups.

9. An electrochemical cell comprising the membrane of claim 1.

10. The electrochemical cell of claim 9 wherein said electrochemical cell is a fuel cell.

11. The membrane of claim 1 wherein at least one of said two fluoropolymers that are substantially free of ion-exchange groups is a copolymer selected from the group consisting TFE/HFP, TFE/PAVE, and TFE/HFP/PAVE.

12. The membrane of claim 1 wherein the second of said two other fluoropolymers that are substantially free of ion-exchange groups has a melting point at least about 3000 higher than the melting point of the fluorinated ionomer.