Abstract
This study investigates the preparation and properties of polymer composite bipolar plates (the thickness < 1.2 mm) for use in polymer electrolyte membrane fuel cells (PEMFCs). The composites contain vinyl ester resin, graphite powder, and multiwalled carbon nanotube (MWCNT). The polymer composite bipolar plates were fabricated by bulk molding compound (BMC) process. The MWCNTs studied include prinstine CNT, acid modified CNT, surfactant-modified MWCNT (CNT/POP400 and CNT/POP2000), and the functionalized MWCNT (CNT-mPOP400 and CNT-mPOP2000) prepared by free radical reaction with Poly(oxypropylene)-backboned diamine. The effect of the carbon nanotube content on the electrical, physical, mechanical, thermal properties and sigle cell test of the polymer composite bipolar plate were investigated. Both the flow field path and depth in composite bipolar plate were 0.8 mm and the flow field land was 0.8 mm. The thickness of the composite bipolar plate was 1.2 mm. The optimum composites bipolar plate was prepared with 2 phr CNT-mPOP2000. The porosity and the coefficient of thermal expansion (CTE) of the composite bipolar plate with 2 phr CNT-mPOP2000 was decreased from 0.270 % to 0.118 % and from 37.00 μm/moC to 16.62 μm/moC. The flexural strength, the electrical conductivity, and the corrosion current of the composite bipolar plate with 2 phr CNT-mPOP2000 were increased from 28.00 MPa to 48.33 MPa, and from 2.5×10-7 Acm-2 to 2.4×10-6 Acm-2 and from 155 S/cm to 1370 S/cm, respectively. The unnotched Izod impact strength of the composite bipolar plate with 1 phr CNT-mPOP2000 was increased from 53.56 J/m to 108.51 J/m. The gas permeability of composite bipolar plates in this study were no leak. All of the composite bipolar plates in this study met UL-94V0 and LOI>50. The maximum current density and the power density of single cell of the composite bipolar plate with 1 phr CNT-mPOP2000 were promoted from 1.03 A/cm2 to 1.32 A/cm2 and from 0.392 W/cm2 to 0.580 W/cm2.These data meet the DOE (Department of Energy U.S.A.)target. The overall performance confirms the bipolar plates prepared in this study are suitable for PEMFC.