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Non-exhaust airborne particulate matter (PM) from automobiles might lead to potential adverse effects on the respiratory system. In this work, we evaluated the impact of surface properties of disc rotors on brake wear PM emission for passenger vehicles. Dynamometric measurements using the novel cycle were made for gray cast iron (GCI), nitrocarburized (NC), and superhard ceramic coated (SCC) disc rotors using non-steel (N/S) friction materials. The brake emission factors (BEF) for the GCI and NC disc rotors ranged from 1.76 to 1.74 mg/km/vehicle, whereas that of the SCC rotor exhibited a much-reduced value of 0.50 mg/km/vehicle. As the hardness of the SCC rotor increases (> 1150 HV), lower BEF was obtained, whereas the coefficient of friction (COF) of the SCC disc was more than 20 % higher than the NC rotor. Temperature-dependent data indicated that disc temperature (Tdisc) for the SCC disc (~115 °C) was lower than that for the GCI and NC (Tdisc >130 °C).

Copper has been regarded as one of the indispensable ingredients in the brake friction materials since it provides high thermal diffusivity at the sliding interface. However, the recent regulations against environmentally hazardous ingredients limit the use of copper in the commercial friction material and much effort has been made for the alternatives. In this work, the role of the cuprous ingredients such as copper fiber, copper powder, cupric oxide (CuO), and copper sulfide (CuS) are studied using the friction materials based on commercial formulations. The investigation was performed using a full inertial brake dynamometer and 1/5 scale dynamometer for brake performance and wear test. Results showed that the cuprous ingredients played a crucial role in maintaining the stable friction film at the friction interface, resulting in improved friction stability and reduced aggressiveness against counter disk.