Fuel cell gas diffusion layer coating process and treated article

Abstract

A method is provided for making a hydrophobic carbon fiber construction, such as a fuel cell gas diffusion layer, by electrophoretic deposition of a highly fluorinated polymer, which may be followed by sintering of the fluoropolymer. A hydrophobic carbon fiber construction is provided, such as a fuel cell gas diffusion layer, which is coated with a monolayer of particles of a highly fluorinated polymer, which may be sintered.

We claim:  
     
         1 . A method of making a hydrophobic carbon fiber construction comprising the steps of: 
 a) immersing a carbon fiber construction in an aqueous dispersion of a highly fluorinated polymer;    b) contacting said dispersion with a counterelectrode; and    c) electrophoretically depositing said highly fluorinated polymer on said carbon fiber construction by applying electric current between said carbon fiber construction and said counterelectrode.    
     
     
         2 . The method according to  claim 1  wherein said highly fluorinated polymer is selected from the group consisting of polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkyl acrylates, hexafluoropropylene copolymers, and tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymers.  
     
     
         3 . The method according to  claim 1  wherein said highly fluorinated polymer is polytetrafluoroethylene (PTFE).  
     
     
         4 . The method according to  claim 1  wherein said carbon fiber construction is a woven carbon fiber construction.  
     
     
         5 . The method according to  claim 1  wherein said carbon fiber construction is a non-woven carbon fiber construction.  
     
     
         6 . The method according to  claim 1  wherein said step of electrophoretically depositing said highly fluorinated polymer has a duration of not more than 30 minutes.  
     
     
         7 . The method according to  claim 1  wherein said step of electrophoretically depositing said highly fluorinated polymer has a duration of not more than 15 minutes.  
     
     
         8 . The method according to  claim 1  wherein said electric current is applied at a voltage of between 6 and 100 volts.  
     
     
         9 . The method according to  claim 1  additionally comprising the step of: d) sintering said highly fluorinated polymer by heating said carbon fiber construction.  
     
     
         10 . The hydrophobic carbon fiber construction made according to the method of  claim 1 .  
     
     
         11 . The hydrophobic carbon fiber construction made according to the method of  claim 9 .  
     
     
         12 . The hydrophobic carbon fiber construction according to  claim 10  which is coated with a monolayer of particles of a highly fluorinated polymer.  
     
     
         13 . The hydrophobic carbon fiber construction according to  claim 11  which is coated with a monolayer of particles of a highly fluorinated polymer.  
     
     
         14 . A hydrophobic carbon fiber construction coated with a monolayer of particles of a highly fluorinated polymer.  
     
     
         15 . The hydrophobic carbon fiber construction according to  claim 14  wherein said highly fluorinated polymer is selected from the group consisting of polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkyl acrylates, hexafluoropropylene copolymers, and tetrafluoroethylene/hexafluoropropylene/vinylidene fluoride terpolymers.  
     
     
         16 . The hydrophobic carbon fiber construction according to  claim 14  wherein said highly fluorinated polymer is polytetrafluoroethylene (PTFE).  
     
     
         17 . The hydrophobic carbon fiber construction according to  claim 14  wherein said carbon fiber construction is a woven carbon fiber construction.  
     
     
         18 . The hydrophobic carbon fiber construction according to  claim 14  wherein said carbon fiber construction is a non-woven carbon fiber construction.  
     
     
         19 . The hydrophobic carbon fiber construction according to  claim 14  wherein said particles of a highly fluorinated polymer are sintered.