Thermoplastic bipolar plate
A method of manufacturing a fuel cell bipolar plate comprising first and second thermoformed plates. The thermoformed plates comprise at least one thermoplastic polymer. The method includes providing film cast resin mixture and forming it into a substantially flat sheet having first and second opposing major surfaces. The sheet may be preheated to a predetermined temperature and thermoformed thereby creating separator plates of a desired size and shape. First and second plates are joined to form an integral bipolar plate.
1. A method of manufacturing a thermoplastic bipolar plate for a proton exchange membrane fuel cell, the method comprising:
forming a resin mixture comprising a thermoplastic polymer, an electrically conductive filler material, and a solvent;
rod coating the resin mixture onto a substrate to form a substantially flat film sheet having a first major surface and a second major surface opposite the first major surface;
abrading a portion of at least one of the first major surface and the second major surface;
after abrading, thermoforming the substantially flat film sheet with heat to form a thermoformed sheet;
cutting the thermoformed sheet to form a first separator plate having a first size and a first shape and a second separator plate having a second size and a second shape; and
joining the first separator plate and the second separator plate to thereby manufacture the thermoplastic bipolar plate so that the thermoplastic bipolar plate has an integral body.
2. The method according to claim 1 , wherein the electrically conductive filler material comprises at least one of expanded graphite, gold, platinum, nickel, palladium, rhodium, niobium, titanium, chromium, rare earth metals, graphite, carbon, and compounds, alloys, and mixtures thereof.
3. The method according the claim 1 , wherein the thermoplastic polymer comprises at least one of polycarbonate, polyphenylene oxide, polystyrene, polyvinyl styrene, polyvinylidene chloride, acrylonitrile butadiene styrene, polymethyl methacrylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate phthalate, polyamide-imide, polyamide, polyethylene terephthalate, polyetherimide, polybutene, polypropylene, polyphenylene sulfide, polybutylene terephthalate, and mixtures thereof.
4. The method according to claim 1 , wherein the solvent comprises at least one of methylene chloride, toluene, tetrachloroethane, dichloroethane, tetrahydrofuran, glyme, diglyme, and mixtures thereof.
5. The method according to claim 1 , wherein joining the first separator plate and the second separator plate comprises at least one of ultrasonic welding, solvent joining, thermal staking, laser welding, and combinations thereof.
6. The method according to claim 1 , further comprising preheating the resin mixture to a temperature of from about 100° C. to about 130° C. for from about 1 hour to about 3 hours to remove any moisture and/or dissolved water prior to thermoforming.
7. The method according to claim 1 , wherein thermoforming the substantially flat film sheet comprises at least one of concurrently heating and vacuum molding the substantially flat film sheet; concurrently heating and pressure molding the substantially flat film sheet; concurrently heating the substantially flat film sheet and applying direct mechanical force to the substantially flat film sheet; and combinations thereof.
8. The method according to claim 1 , wherein forming the resin mixture comprises ball milling the resin mixture for between about 1 hour to about 4 hours.
9. The method according to claim 1 , wherein abrading comprises scuffing at least one of the first major surface and the second major surface with an abrasive scrubbing pad.
10. The method according to claim 1 , wherein forming the resin mixture comprises mechanically stirring the resin mixture such that the resin mixture has a viscosity of between about 100 centipoise and about 1,000 centipoise.
11. The method according to claim 1 , wherein forming comprises dissolving the resin into the solvent at a ratio of about 1 part by weight resin to 13 parts by weight solvent.
12. The method according to claim 1 , further including, prior to rod coating, adding expanded graphite powder to the resin mixture.