Development of Highly Filled Graphite Compounds as Bipolar Plate Materials for Low and High Temperature PEM Fuel Cells

This paper focuses on the interactions between carbon filling materials and polypropylene as binder in compound based low temperature bipolar plates. The influences of size and morphology of graphite on the compounding and moulding processes are disclosed here. Without losses in electrical conductivity the throughput for the compounding process has been improved by a factor of twelve, only depending on the morphology of graphite. Moreover, the way of bipolar plate production by compression- or injection moulding leads to significant differences in their electrical conductivity. The process of compression moulding enables a higher processable filling load but due to an obtained alignment of graphite flakes within an injection moulded plate, this material tends to offer an adequate conductivity with fewer quantities of carbon filling particles. Additional to this work first approaches in the development of plate materials suitable for high temperature PEM operation (up to 200 °C) are presented. First plates based on compression moulded compounds have been analysed and operated in a high temperature PEM stack recently. In this paper the latest results of ZBT's material development project regarding high temperature compound based bipolar plate technologies are presented.