Electrically Conductive Polymer Composites for Injection-Molded Bipolar Plates

Abstract

This presentation reports the development of electrically conductive polymer composites as an alternative to the traditional metal alloys commonly used for fuel cell bipolar plates. Polymer composites can reduce both the cost and weight of the bipolar plate, while still providing sufficient electrical properties. Several factors impact the ability of a polymer composite to conduct electricity. The geometry, filler weight percent, and the physical properties of the fillers are crucial to forming an electrical pathway through the composite. In this study, carbon black and carbon fiber were added to nylon 6,6 at various weight percentages, ranging from 0 to 50%, in order to determine the optimal filler-to-polymer ratio. Samples were injection-molded and then compared by measuring the electrical conductivity using a four-point probe method. Conductive filler was added to the polymer with and without a compounding process prior to injection molding. Results show that compounding the additives via a twin-screw extruder helps to disperse the filler within the polymer but decreases conductivity due to shearing of the conductive carbon fibers. When the compounding process was removed, the conductive pathways from intact fiber bundles were maintained. Conductivities greater than 40 S/cm were achieved, nearing the United States Department of Energy technical target of 100 S/cm for bipolar plate electrical conductivity.