Numerous studies have reported that good adhesion and fluorination of carbon materials in a fluoropolymer matrix enhance their electrical and mechanical properties. However, a composite reinforced with oxyfluorinated graphite has not been reported for improving mechanical properties. This paper discusses the fabrication of conductive fluorinated ethylene–propylene (FEP)/oxyfluorinated graphite (f-graphite) composite bipolar plates (BPs) via compression molding. To investigate the effects of fluorinating graphite, graphite with a large particle size of 500 μm was mixed with FEP powder with a small particle size of 8 μm through ball milling. The FEP/graphite composites exhibited high anisotropic electrical conductivity with the in-plane conductivity much higher than the through-plane conductivity because of the planar orientation of the graphite sheets. Therefore, the mechanical properties of the composites such as flexural strength tended to deteriorate with increasing graphite content. In particular, the FEP/f-graphite composites exhibited excellent flexural strength of 12 MPa, much higher than that of FEP/graphite composites at 9 MPa with a graphite content of 80 wt%. The interfacial interaction between FEP and f-graphite led to improved physical compatibilization, which contributed to enhance the mechanical properties of these composites. Our results are a step toward developing BPs for use in high-temperature fuel cells and heat-sink components.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Oxyfluorination of graphite surface
        2.3 Fabrication of FEPgraphite composites via compression molding
        2.4 Characterization
    3 Results and discussion
        3.1 Preparation of FEPgraphite and FEPf-graphite composites
        3.2 Effect of oxyfluorination on thermal stability and chemical bonding
        3.3 Electrical and mechanical properties of FEPgraphite and FEPf-graphite composites
        3.4 Surface morphology of FEPf-graphite composites
    4 Conclusions
    Acknowledgements 
    References

• Moon Hee Lee(Advanced Center of Engineering, Morgan Advanced Materials)
• Ho Young Kim(Department of Energy Science, Sungkyunkwan University)
• Jiwook Kim(Department of Chemical Engineering and Applied Chemistry, Chungnam National University)
• Joong Tark Han(Nano Hybrid Technology Research Center, Korea Electrotechnology Research Institute)
• Young‑Seak Lee(Department of Chemical Engineering and Applied Chemistry, Chungnam National University)
• Jong Seok Woo(Advanced Center of Engineering, Morgan Advanced Materials)