The effect of mold pressing pressure and composition on properties of nanocomposite bipolar plate for proton exchange membrane fuel cell

This paper is an attempt to introduce a suitable composite to be used in the bipolar plate of proton exchange membrane fuel cell (PEMFC). At first the effect of the mold pressing pressure and graphite content on the through-plane and in-plane electrical conductivities, flexural strength, hardness, density, porosity and water absorption of phenolic resin/graphite composite was investigated. The two mold pressing pressures, 15 and 740 bar were applied in 20, 30, 40, 50, 60, 70 and 80 wt.% graphite contents. The characterization was also conducted by an optical microscope, a stereoscope and the scanning electron microscopy. The results showed that the pressure considerably affects all properties and can dramatically change the porosity percentage of the composite. To improve conductivity and strength, the composite composition was modified by the nanosheet expanded graphite and carbon fiber. In an optimum composition, the in-plane and through-plane electrical conductivity and flexural strength reached 1518, 76 S/cm and 84 MPa, respectively. In this study, the contact resistance between the bipolar plate and carbon paper (as a gas diffusion layer) was also determined by changing the clamping pressure. (C) 2011 Elsevier Ltd. All rights reserved.