Highly filled polymer composites with carbon-based nanofillers (e.g. graphite, carbon black, carbon nanotubes) are considered as very suitable thermal and electrical conductive materials. Therefore they find applications in energy industry as bipolar plates in fuel cells or heat exchanger’s housings. In both cases it is their task to carry away the heat and in case of fuel cells they need to conduct electrical current, providing efficient operation conditions in the cells. In this work, expanded graphite and polypropylene was melt mixed in a lab scale co-rotating twin-screw extruder and then compression molded to plates. The aim of the investigation was to study the influence of the filler content on thermal and electrical conductivity of the composites. For polypropylene (PP) based composites containing up to 86 wt.-% of different kinds of graphite values of thermal conductivity (laser flash analysis) up to 22.2±0.5 W/(m·K) and electrical volume resistivity as low as 0.17±0.02 Ohm·cm were obtained. Regarding the construction of a demonstrator from several parts, an assembly and sealing method of PP/graphite composite plates was investigated. Adhesive joints seem to be more efficient, easier and faster to apply than traditionally sealing used in those applications, e.g. pressed gaskets. An optimal adhesive system should exhibit good thermal stability (up to 80 °C), good water and chemical resistance, sufficient mechanical properties and good adhesion to PP/graphite. Epoxy, polyurethane and acrylate adhesives were put into consideration and examined to join such highly filled polymer materials. Keywords: Electrical conductivity, thermal conductivity, polymer composites, adhesive joint, fuel cells