Thermal Properties of Epoxy Based Expanded Graphite Composite for Bipolar Plate of Polymer Electrolyte Fuel Cells

The application of polymer electrolyte fuel cell (PEMFC) to the electrical vehicles is restricted by high material cost and complicated manufacturing process. The epoxy based graphite composite has been prepared with various additives. The possibility for bipolar plate material at PEMFC was investigated by electrical and thermal properties. Density of bipolar plate with graphite composite was decreased from 5.40 to 2.57 as 80 w/o of graphite content were changed to 50 w/o of graphite content and 30 w/o of expanded graphite. The percolation thresholds showed around 75 w/o of graphite content was varied by molding pressure. From the TGA analysis, the glass transition temperatures were shown around 250 degrees and less that 3% of weight loss was found at 150 degree. The surface conductivity of epoxy/graphite bipolar plate showed from 4.5 S/cm to 87 S/cm and the highest value of conductivity was obtained using expanded graphite powder only. The improvement of thermal stability and electrical properties was accomplished by addition of expanded graphite powder.