Gilardi, R., Sarocchi, D., and Bounous, L., "Copper-Free NAO Brake Pad Formulation with Improved Electrostatic Paintability Based on Conductive Carbon Powders," SAE Technical Paper 2016-01-1916, 2016, doi:10.4271/2016-01-1916.
A wide range of different carbon powders is available and currently used in friction materials like coke, graphite and carbon black. The effect of the type of carbon on braking performance has been extensively investigated in the past and it has been demonstrated that graphite can play an important role in copper-free brake pads. However, there are no studies about the influence of carbon powders on the processability of brake pads. Brake pads need to be painted in order to avoid corrosion. Typically electrostatic painting is used on an industrial scale, which requires the brake pads to be conductive. NAO brake pads (and especially Cu-free NAO brake pads) are rather insulating, and therefore difficult to paint. In this presentation we’ll show how special carbon powders can increase the electrical conductivity and therefore allow easy painting of brake pads. Based on these investigations, a new copper-free NAO formulation has been developed. This new formulation shows good performance and can be produced without adapting the existing production equipment, and is therefore ready to be used for mass production. Overall, our results indicate that the type of carbon powder used in brake pads has strong influence not only on brake performance but also on the processability of brake pads. In particular, the use of special carbon powders allows easy painting of brake pads for high performing Cu-free NAO brake pad formulations.