Preparation and properties of expanded graphite/phenolic resin-polyvinyl butyral composite bipolar plates

A new kind of bipolar plate for proton exchange membrane fuel cell was prepared by compression molding method, using polyvinyl butyral (PVB) modified phenolic resin (PF) as binder and expanded graphite as the first conductive filler. The effects of PVB to PF mass ratio, the modified resin content and addition of carbon black on the conductivity, flexural strength of the expanded graphite/PF-PVB composite bipolar plate were also investigated. The results show that, when the mass fraction of resin is fixed at 30wt%, the expanded graphite/PF-PVB composite bipolar plate posses the highest in-plane conductivity(192.3 S/cm) and flexural strength(47.25 MPa) with the PVB:PF=0.5, which is increased by 12.3% and 14.2% respectively compared to the expanded graphite/PF composite bipolar plate samples without PVB addition. When PVB:PF=0.5, with the mass fraction of resin increase from 25wt% to 45wt%, the conductivity of the expanded graphite/PF-PVB composite bipolar plate declines while flexural strength increases. Further add carbon black to improve the conductivity of the expanded graphite/PF-PVB composite bipolar plate, when resin mass fraction at 45 wt%, the sample with 4 wt% carbon black shows the best in-plane conductivity (137 S/cm) and best area specific resistance (14.4 mΩ·cm²).