Injection moldable conductive aromatic thermoplastic liquid crystalline polymeric compositions

• US 6,379,795 B1
• Filed: 01/07/2000
• Issued: 04/30/2002
• Est. Priority Date: 01/19/1999
• Status: Expired

• 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: Cai, Yuqi, Andrin, Peter, Bisaria, Mukesh K., Abdou, Mohamed
• Primary Examiner(s): Kelly, Cynthia H.
• Assistant Examiner(s): GRAY, JILL M
• Application Number:
  US09/479,712
• Time in Patent Office: 844 Days
• Field of Search: 428/357, 428/359, 428/361, 428/367, 428/375, 428/378, 428/379, 428/389, 428/381, 428/383, 264/257, 264/328.1, 264/328.17, 264/328.18, 429/34
• US Class Current: 428/378
• CPC Class Codes: B29C 45/0013 using fillers dispersed in the moulding material, e.g. metal particles
• CPC Class Codes: B29C 70/882 partly or totally electrically conductive, e.g. for EMI shielding conductive floors or floor coverings H05F3/025; EMI shielding in general H05K9/00
• CPC Class Codes: B29K 2105/0079 Liquid crystals
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 8/0206 Metals or alloys
• CPC Class Codes: H01M 8/0213 Gas-impermeable carbon-containing materials
• CPC Class Codes: H01M 8/0221 Organic resins; Organic polymers
• CPC Class Codes: H01M 8/0226 in the form of mixtures
• CPC Class Codes: H01M 8/0228 in the form of layered or coated products
• CPC Class Codes: H01M 8/0263 having meandering or serpentine paths
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/249938 Composite or conjugate fiber [e.g., fiber contains more than one chemically different material in monofilament or multifilament form, etc.]
• CPC Class Codes: Y10T 428/2904 Staple length fiber
• CPC Class Codes: Y10T 428/2918 including free carbon or carbide or therewith [not as steel]
• CPC Class Codes: Y10T 428/2933 Coated or with bond, impregnation or core
• CPC Class Codes: Y10T 428/2938 Coating on discrete and individual rods, strands or filaments
• CPC Class Codes: Y10T 428/294 including metal or compound thereof [excluding glass, ceramic and asbestos]
• CPC Class Codes: Y10T 428/2958 : Metal or metal compound in coating
• CPC Class Codes: Y10T 428/30 : Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

A method for making a shaped article or a shaped article having a volume resistivity of less than 10² ohm-cm with a desired combination of properties and processibility in an injection moldable composition. In particular the shaped articles formed include injection molded bipolar plates as current collectors in fuel cell applications.

Claims

1. A process for fabricating a shaped article having a volume resistivity of less than 10⁻

2 ohm-cm, the process comprising;

combining an injection moldable aromatic thermoplastic liquid crystalline polymer resin and a composition comprising nickel-coated graphite fibers impregnated with a non-liquid-crystalline thermoplastic binder resin, to form a mixture at a temperature below the melting point of the thermoplastic liquid crystalline polymer resin, the graphite fibers being of a length of less than 2 cm and comprising about 5 to about 50% by weight of the mixture, and the binder resin comprising about 0.1 to about 20% by weight of the graphite;

feeding the mixture to an injection molding machine wherein the thermoplastic liquid crystalline polymer resin is melted and fed in the molten state to a mold;

cooling the mold to a temperature at which the thermoplastic liquid crystalline polymer in the mixture no longer flows; and

,

removing the molded mixture from the mold.

2. The process of claim 1, wherein the nickel coated graphite fibers comprise about 10- about 40% by weight of the total composition.

3. The process of claim 1, wherein the nickel-coated graphite fibers are of a diameter in the range of about 5 to about 15 micrometers.

4. The process of claim 1, wherein the nickel-coated graphite fibers have a nickel-coating representing about 45% to about 60% of a total weight of the nickel-coated graphite fibers.

5. The process of claim 1, wherein the aromatic thermoplastic liquid crystalline polymer is a polyester or a poly(ester-amide).

6. The process of claim 5, wherein at least 50% of the bonds to ester or amide groups are to carbon atoms which are part of aromatic rings.

7. The process of claim 6, wherein at least 75% of the bonds to ester or amide groups are to carbon atoms which are part of aromatic rings.

8. The process of claim 1, wherein the binder resin comprises about 5% to about 15% by weight of the graphite.

9. A shaped article formed according to the process of claim 1.

10. The shaped article of claim 9 comprising a form of a bipolar plate.

11. The shaped article of claim 9 further comprising fluid distribution channels inscribed upon the surface thereof.

12. A shaped article having a volume resistivity of less than 10⁻

2 ohm-cm comprising about 50 to about 95% by weight of a thermoplastic aromatic liquid crystalline polymer and about 5% to about 50% by weight of nickel-coated graphite fibers of a length less than 2 cm, and a non-liquid-crystalline thermoplastic resin at a concentration of about 0.1% to about 20% by weight with respect to the weight of the graphite.

13. The shaped article of claim 12, wherein the shaped article comprises about 10% to about 40% by weight of the nickel-coated graphite fiber.

14. The shaped article of claim 12, wherein the nickel-coated graphite fiber is of a diameter in the range of about 5 to about 15 micrometers.

15. The shaped article of claim 12, wherein the nickel-coating represents about 45 to about 60% of the total weight of e nickel-coated graphite fiber.

16. The shaped article of claim 12, wherein the aromatic thermoplastic liquid crystalline polymer is a polyester or a poly(ester-amide).

17. The shaped article of claim 16, wherein at least 50% of the bonds to ester or amide groups are to carbon atoms that are part of aromatic rings.

18. The shaped article of claim 17 wherein at least 75% of the bonds to ester or amide groups are to carbon atoms that are part of aromatic rings.

19. The shaped article of claim 12, wherein the binder resin comprises about 5% to about 15% by weight of the graphite.

20. The shaped article of claim 12, comprising a form of a bipolar plate.

21. The shaped article of claim 20, wherein the bipolar plate has a thickness in the range of about 0.1 to about 10 mm.

22. The shaped article of claim 21, wherein the bipolar plate thickness is in the range of about 1 to about 3 mm.

23. The shaped article of claim 20, further comprising fluid distribution channels inscribed upon the surface thereof.