Effects of die configuration on the electrical conductivity of polypropylene reinforced milled carbon fibers: An application on a bipolar plate

Abstract

Die configurations, filler orientations, electrical conductivity, and mechanical properties of polypropylene reinforced milled carbon fibers were studied as functions of their manufacturing processes. Series of manufacturing processes often deteriorate the material properties, hence, finding a suitable process aid is key to improving the electrical and mechanical properties of composite materials. Compared with the conventional manufacturing process, extrusion is a key process in the production of a highly conductive composite. A twin-screw extruder was used at a temperature of 230 °C and a rotational speed of 50 rpm before the compression molding process was carried out at 200 °C and 13 kPa. This research examined different die configurations, namely rod and sheet dies. The results indicated that the rod dies showed better mechanical properties and electrical conductivity with 25 MPa and 5 S/cm compared to the sheet dies. Moreover, rod dies are able to orientate to 86° and obtain longest filler length with 55 μm compared to the sheet dies. The alteration of the filler orientation in the produced material at a high shear rate further enhanced the electrical conductivity of the material.