Innovative Approach to Fuel Cell Bipolar Plate Using Conductive Polymer Blend Composites: Selective Localization of Carbon Fiber at the Interface of Polymer Blends

Carbon fiber-polymer blend composite bipolar plate is developed using epoxy resin and polypropylene as the polymer blend (PB) and short carbon fiber (CF) as conductive reinforcements by melt mixing and compression molding technique. A PB results in a lower percolation threshold, known as the double percolation threshold, compared to a single polymer which requires a high filler concentration. Via thermodynamic and kinetic factors, the selective localization of CF at the interface in the PB was predicted and later confirmed through SEM analysis. The electrical conductivity, flexural properties, tensile properties, impact strength, and water absorption are the characteristics used to evaluate the developed bipolar plates. The electrical conductivities of the prepared composites increased with the addition of CF and reached 16.7 S/cm for the 70 wt% CF reinforcement, as expected. The results showed that the flexural and tensile strength were decreasing with the rising additive ratio of CF. At 30 wt% of CF, PP/Epoxy/CF recorded the highest tensile strength (30 MPa) and flexural strength (72.7 MPa). On the other hand, the impact strength increased as the CF concentration increased from 30 to 60 wt%, reaching the highest value of 7.49 kJ/m2 at 60 wt%. However, at 70 wt%, the impact strength significantly decreased. The water absorption of the composites increased slightly as the CF content increased from 30 to 60 wt%, but significantly increased at 70 wt%. The developed composites met the DOE targets for mechanical properties and water absorption. However, the electrical conductivity of the composites still falls below the targets.