Injection moldable conductive aromatic thermoplastic liquid crystalline polymeric compositions

Abstract

A method for making a shaped article or a shaped article having a volume resistivity of less than 10 2 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.

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-  to  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    25 , 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    27 , wherein the nickel-coating represents about 45 to about 60% of the total weight of e  the 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. 
     
     
       24. The process of  claim 1 , wherein the graphite fibers are metal- coated graphite fibers.   
     
     
       25. The process of  claim 24 , wherein the metal- coated graphite fibers are nickel - coated graphite fibers.   
     
     
       26. The shaped article of  claim 12 , wherein the graphite fibers are metal- coated graphite fibers.   
     
     
       27. The shaped article of  claim 26 , wherein the metal- coated graphite fibers are nickel - coated graphite fibers.