Brake wear particles account for a large part of non-exhaust particle emissions in urban areas. In present study, the influence of brake conditions on airborne wear particle emissions was investigated. Low metallic (LM), semi metallic (SM) and non-asbestos organic (NAO) brake pads sliding against an iron disc were tested using a pin-on-disc tribometer. Results show that friction coefficient and specific wear rate decrease with increasing contact pressure and sliding velocity. Particle number size distribution has a single peak around 100 nm for all brake pads. Total number concentration (TNC) and particle mass concentration (PMC) increase with increasing sliding velocity and contact pressure in most cases. Both sliding velocity and contact pressure can significantly affect the TNC and PMC results. These is no special trend for geometric mean diameter (GMD) with the variations of sliding velocity and contact pressure.

Long Wei, Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong; Yat Sze Choy,