Conductive Materials for Proton Exchange Membrane Fuel Cell Bipolar Plates Made from PVDF, PETand Co-continuous PVDF/PET Filled with Carbon Additives L. Nguyen 1,2 , F. Mighri 1,2 *, Y. Deyrail 1,2 and S. Elkoun 1,3 1 CREPEC, Center for Applied Research on Polymers and Composites, QC, Canada H3T 1J4 2 Department of Chemical Engineering, Laval University, QC, Canada G1K 7P4 3 Department of Mechanical Engineering, Sherbrooke University, QC, Canada J1K 2R1 Received September 16, 2009; accepted June 12, 2010 1 Introduction Fuel cells, especially proton exchange membrane fuel cells (PEMFCs), hold great promise for use as an environmentally friendly power source for future transportation technology. Progress made up in PEMFC technology offers large perspec- tives of applications. However, one of the key requirements in making PEMFCs commercially viable as automotive power systems is their cost reduction. A PEMFC unit is composed of a membrane electrode assembly, MEA, sandwiched between two electronically conductive bipolar plates (BPPs), which are used to distribute uniformly the reactive gas on the elec- trodes. These BPPs must be electrically conductive to trans- – [ * ] Corresponding author, frej.mighri@gch.ulaval.ca Abstract The aim of this work was to develop and characterise electri- cally conductive materials for proton exchange membrane fuel cells and bipolar plates (BPPs). These BPPs were made from highly conductive blends of polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF), as matrix phase. The conductive materials were developed from carefully for- mulated blends composed of conductive carbon black (CB) powder and, in some cases, graphite synthetic flakes mixed with pure PET, PVDF or with PVDF/PET systems. They were first developed by twin-screw extrusion process then compression-molded to give BPP final shape. As the devel- oped blends have to meet properties suitable for BPP appli- cations, they were characterised for their rheological proper- ties, electrical through-plane resistivity (the inverse of conductivity), oxygen permeability, flexural and impact properties. Results showed that lower resistivity was obtained with PVDF/CB blends due to the higher interfacial energy between the PVDF matrix and CB and also the higher density and crystallinity of PVDF, compared to those of PET. It was also observed that the lowest resistivity values were obtained with mixing PVDF and PET at controlled compositions to ensure PVDF/PET co-continuous morphol- ogy. Also, slow cooling rates helped to attain the lowest values of through-plane resistivity for all studied blends. This behaviour was related to the higher crystallinity obtained with low cooling rates leading to smaller amor- phous regions in which carbon particles are much more con- centrated. Keywords: Bipolar Plates, Conductive Blends, Co-continu- ous Blends, PEMFC, Percolation 938 © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim FUEL CELLS 10, 2010, No. 6, 938–948 ORIGINAL RESEARCH PAPER DOI: 10.1002/fuce.200900171