Particulate matter (PM) emissions from the brake friction material were investigated, focusing on the effect of space fillers on the concentration and size distribution of airborne particles. Brake emission tests were carried out using a 1/5 scale brake dynamometer enclosed in a chamber, and the particle concentration was measured using an electrical low-pressure impactor (HR-ELPI+). Results show that brake emission, disc wear, and pad surface characteristic were considerably affected by the choice of the filler among BaSO4, Ca(OH)2, and CaCO3. The brake emissions ranked in descending order were BaSO4, Ca(OH)2, and CaCO3. The friction material with CaCO3 showed thicker friction films on the steel fibers than Ca(OH)2, whereas bare steel fibers were found with BaSO4, indicating considerable effects by the filler-dependent coverup layers on the steel fibers, which was confirmed by microhardness tests. The filler effect on PM suggests that a proper selection of space fillers can reduce brake emissions from grey iron discs by preventing direct adhesion with steel fibers.

Korea University: Mr. Jongsung Park; Hyundai Motor Company: Dr. Yun Cheol Kim; Korea University: Mr. Hyungjo Seo, Prof. Ho Jang