Size effect of tire rubber particles on tribological properties of brake friction materials

Size effect of rubber particles on the friction and wear of brake friction materials was investigated since their morphology is often connected to friction instability. Friction materials were fabricated with recycled rubber particles of two different sizes, approximately 75 and 450 µm, and their frictional performance was examined with a reduced-scale brake dynamometer. The results showed that the specimen with small rubber particles showed higher contact stiffness than that with large rubber particles. However, the small rubber particles in the friction materials increased the friction level and friction instability, accompanied by a higher wear rate, which were attributed to the larger high-pressure contact plateaus produced at the sliding interface. This study indicated that the frictional instability of brake friction materials is strongly affected by the contact plateaus and suggested that friction instability can be reduced by regulating the recycled rubber particle size.