Flexible, joinable bipolar plates

IKV is carrying out research into a new approach for the production of graphite-filled polypropylene compounds. The aim is to improve the mechanical properties of the compound compared with commercially available materials while maintaining the same electrical conductivity.

Fuel cell stack with bipolar plates made of a plastic compound | photo: Eisenhuth/IKV

For this, a blend of polypropylene and elastomer was first produced in order to increase the elasticity of the matrix material. A mixture of selected, electrically conductive graphitic fillers was then incorporated. Efforts were made to keep the filler content as low as possible while still ensuring the necessary electrical conductivity for the particular application. The potential usability of the new materials is demonstrated by producing bipolar plates for fuel cells.

Together with various project partners, IKV is developing a process in which the conductive part of the bipolar plate is compression moulded from the highly filled compounds, then overmoulded by injection moulding, and finally joined to form a composite part. It is important here that the bipolar plates are welded to one other securely enough to ensure that they are gas-tight, and also that process reliability and high efficiency are ensured. The necessary joining technology is being systematically developed at IKV. The composite material is subsequently tested in the fuel cell under conditions likely to be encountered in practice.

The newly developed, highly filled thermoplastic compound has considerable advantages over the currently used materials because of its reduced brittleness. A higher service life in the fuel cell and lower reject rates can also be achieved.

This joint project is financed by the German Federal Ministry of Education and Research (BMBF) over a period of two years.

The other partners involved are Allod Werkstoff GmbH & Co. KG, Burgbernheim, Calorplast Wärmetechnik GmbH, Krefeld, Eisenhuth GmbH & Co. KG, Osterode am Harz, Kessen Maschinenbau GmbH, Essen bei Oldenburg, Leibniz Institute for Polymer Research Dresden e.V., Dresden, and Protech GmbH in Pfullingen.