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Graphite plays a crucial role in friction materials, since it has good thermal conductivity, lubricity and act as a friction modifier. The right type, amount, shape, and size of the particles control the performance of the brake-pads. The theme of the study was investigating the influence of size of graphite particles (having all other specifications identical) on performance properties of brake-pads containing graphite particles in the average size of 60 μm, 120 μm, 200 μm and 400 μm. Physical, mechanical and chemical characterization of the developed brake-pads was done. The tribological performance was studied using a full- scale inertia brake dynamometer following a Japanese automobile testing standard (JASO C406). Tribo-performance in terms of fade resistance, friction stability and wear resistance were observed best for smaller graphite particles. It was concluded that smaller size serves best for achieving best performance properties barring compressibility.

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.