The Effect of the Abrasive Particle Size in the Friction Material on the Concentration and Size Distribution of Particulate Matter (PM)
The correlation between the aggressiveness of the brake friction material and brake emission was investigated by using the abrasives in different sizes. The friction materials with three different zircon (ZrSiO4) particles in 1�m, 50�m, 150 �m in average diameter were produced. The emission test was carried out following a WLTC test procedure using a 1/5 scale brake dynamometer designed for brake emission measurements. The concentration and size distribution of the airborne particles were analyzed using an electrical low-pressure impactor (ELPI+). Results showed that the friction material with larger abrasives increased the wear rate of the gray iron disc and led to the high iron content in PM. The high iron content also changed the size distribution of the PM due to the electrostatic attraction changed by iron particles during the agglomeration of nano-sized wear particles. On the other hand, the friction material using smaller abrasives produced relatively large contact plateaus, resulting in high coefficients of friction and less wear on the disc.