Fabrication of a flow channel for the production of polymer composite bipolar plates through hot compression molding

Abstract

Materials used to fabricate polymer electrolyte membrane fuel cell (PEMFC) bipolar plates need to be light, strong, cheap, easily fabricated, mechanically stable, and have low surface contact resistance. Additionally, the performance of PEMFCs is greatly influenced by the materials used, flow channel design and shape to be fabricated on the bipolar plate surface. In this study, the fabrication of a flow channel through the hot compression molding method was developed. All materials used were in powder form, with graphite (G), carbon black (CB) and ferum (Fe) as fillers, and polypropylene (PP) acting as binder. The ratio of fillers (G/CB/Fe) to binder (PP) was fixed at 80:20. The fillers ratio was fixed in the range of (25 to 65 wt%) G, (10 to 30 wt%) CB and (5 to 25 wt%) Fe, and all fillers were mixed using a ball mill machine. The second stage of the mixing process involves the mixing of fillers and a binder, which was mixed using a internal mixer machine. Subsequently, the compaction process through hot compression molding was carried out. During the hot compression molding process, the flow channel of serpentine type, and U or V shapes were pressed onto the surface of the sample. The in-plane electrical conductivity and mechanical properties such as flexure strength, bulk density and shore hardness were then measured. Thus, a flow channel was investigated for accuracy of surface condition of flow channel dimensions (using a coordinate measurement machine), and subsequently compared with the actual drawings and its process ability. Based on electrical conductivity, flexure strength, bulk density and shore hardness, the sample with 15 wt% Fe was shown to yield the best results of 137.39 S/cm3, 34.04 MPa, 1.582 g/cm3, and 53.14 respectively. Meanwhile, based on the analysis of flow channel dimensions, the V shape is shown to give a smooth surface, with a dimensions difference between samples and the drawing of about -0.118 to 0.27%. Meanwhile, for the process ability, the V shape is much easier to release from the mold. In summary, this study revealed that the flow channel with V shape can be fabricated through the hot compression molding method with high accuracy.

Keywords

• graphite
• bipolar plate
• electrical conductivity
• polymer electrolyte membrane fuel cell