Development of preform moulding technique using expanded graphite for proton exchange membrane fuel cell bipolar plates

A preform moulding technique using expanded graphite is developed to manufacture composite bipolar plates for proton exchange membrane fuel cells (PEMFCs). The preform is composed of expanded graphite, graphite flake and phenol resin. Preforms utilizing the tangled structure of expanded graphite are easily fabricated at a low pressure of 0.07–0.28 MPa. A pre-curing temperature (100 °C) slightly above the melting point of phenol powders (90 °C) induces moderate curing, but also prevents excessive curing. After the preform is placed in a steel mould, compression moulding is carried out at high pressure (10 MPa) and temperature (150 °C). The fabrication conditions are optimized by checking the electrical conductivity, flexural strength and microstructure of the composite. The optimized electrical conductivity and flexural strength, 250 S cm⁻¹ and 50 MPa, respectively, met the requirements for PEMFC bipolar plates.