Uniform graphite plate
A substrate useful for the formation of, inter alia, a flow field plate for a proton exchange membrane fuel cell, the substrate formed of at least one resin-impregnated sheet of compressed particles of exfoliated graphite comprising two major surfaces, the substrate having an active area with flow field channels thereon, the sheet of compressed particles of exfoliated graphite having a local web thickness in at least about 50% of its active area that is no more than about 55% greater than the minimum web thickness of the active area of the substrate.
1. A substrate for the formation of a flow field plate for a proton exchange membrane fuel cell, the substrate comprising at least one resin-impregnated sheet of compressed particles of exfoliated graphite comprising two major surfaces, wherein the substrate is assembled in the proton exchange membrane fuel cell, the substrate having an active area with flow field channels thereon, wherein the flow field channels have a depth of from about 0.2 mm to about 2.0 mm, wherein the active area is provided with mirror image corrugations on each of the major surfaces, which form ridges and furrows, the sheet of compressed particles of exfoliated graphite having a local web thickness in the active area which is no more than about 40% greater than the minimum web thickness of the active area, wherein the at least one resin-impregnated sheet of compressed particles of exfoliated graphite has a density of at least about 1.5 g/cc.
2. The substrate of claim 1 , wherein the furrows on one of the major surfaces of the substrate comprise flow field channels.
3. The substrate of claim 2 , wherein the ridge to ridge distance of the corrugations measured from the center of one ridge to the center of an adjoining ridge is from about 0.75 mm to about 4.0 mm.
4. The substrate of claim 3 , wherein the ridge to ridge distance is from about 0.8 mm to about 2.8 mm.
5. The substrate of claim 2 , wherein the flow field channels have a depth of from about 0.1 mm to about 4.0 mm.
6. A substrate for the formation of a flow field plate for a proton exchange membrane fuel cell, the substrate comprising at least one resin-impregnated sheet of compressed particles of exfoliated graphite comprising two major surfaces, the substrate having a mirror image corrugated cross-sectional configuration on each of the major surfaces, wherein the substrate is assembled in the proton exchange membrane fuel cell, the corrugated cross-section comprising alternating ridges and grooves, wherein the substrate has an active area where the grooves comprise flow field channels, wherein the flow field channels have a depth of from about 0.2 mm to about 2.0 mm, wherein at least 50% of the graphite sheet within the active area, based on surface area, has a local web thickness which is no more than about 40% greater than the minimum web thickness of the active area, wherein the at least one resin-impregnated sheet of compressed particles of exfoliated graphite has a density of at least about 1.5 g/cc.
7. The substrate of claim 6 , wherein the ridge to ridge distance of the corrugations measured from the center of one ridge to the center of an adjoining ridge is from about 0.75 mm to about 4.0 mm.
8. The substrate of claim 7 , wherein the ridge to ridge distance is from about 0.8 mm to about 2.8 mm.
9. The substrate of claim 6 , wherein the flow field channels have a depth of from about 0.1 mm to about 4.0 mm.
10. The substrate of claim 6 , wherein the thickness of the entire active area is no greater than about 40% greater than the minimum web thickness of the active area.