Synergy Effects of Conductive Fillers on Elastomer Graphite Composite Material for PEM Fuel Cell Bipolar Plates

Bipolar plates are necessary components in the current design of polymer electrolyte membrane (PEM) fuel cell stacks. The aim of this study is to investigate the elastomeric material with the addition of different types of graphite conductive fillers for the potential use as a bipolar plate in a PEM fuel cell stack. The conductive fillers investigated here include Cytec thermal graphite fibers, Asbury Carbons PAN AGM 99 fiber, synthetic graphite (4012), natural flake (3763), and different grades of graphite powder (TC 305). Some of these conductive fillers are implemented in a two component silicone slurry matrix (RTV 627 by Momentive Performance Materials) to make a composite material. The synergy effects between different fillers in a composite are studied through the percolation theory and scanning electron microscopy images. It has been found that binary blends of fillers resulted in lower resistivity values than individual components over wide composition ratios. A bulk electrical resistivity of 0.0310 Omega cm is achieved for the composite containing 28% by volume DKD fiber and 7% synthetic graphite flake (Asbury 4012) mixed in the elastomeric matrix.