Generation and Collection of Airborne Wear Particles from Commercial Brake Materials for Subsequent Chemical and Toxicological Studies

Two commercial brake pad materials, classified as low-metallic and non-asbestos organic, were tested against commercial grey cast iron brake discs in a pin-on-disc configuration using an RTEC MFT-5000 tribometer. Prior to testing, pin specimens were machined from the brake pads using a milling machine, while disc specimens were cut from the brake discs by water jetting. The friction materials were tested at a sliding velocity of 2 m/s and a contact pressure of 0.5 MPa, corresponding to the mild braking conditions of a passenger car operating in urban traffic.  The friction pair was mounted inside an isolated aerodynamic chamber to eliminate interference from external sources of airborne particle emissions. Filtered air was supplied to the chamber, and particles generated during friction were transported by the airflow to an ELPI+ cascade impactor, where particle concentration was measured and airborne particles were collected on ELPI+ substrates according to their aerodynamic diameter. The collected particles were subsequently used for analyses of their chemical composition and toxicological effects on A549 lung epithelial cells.