Sliding Behavior and Particle Emissions of Cu-Free Friction Materials with Different Contents of Phenolic Resin

The present work aims to investigate the sliding friction and wear behavior and related emissions of airborne particulate matter of Cu-free barite containing friction materials for vehicular brake pads. In particular, the effect of different concentrations of phenolic resin used as a binder has been considered. Tribological tests were conducted using a pin-on-disc laboratory tester. During running-in, the friction coefficient and the emission rate of airborne particles follow the same trend and both are influenced by the content of phenolic resin. The friction material with an intermediate content of phenolic resin, up to 6.5 wt%, showed the best behavior. This was explained considering that the phenolic resin increases the mechanical integrity of the composite friction materials but also increases its compliance, thus increasing the area of contact during sliding and the extension of the relevant secondary plateaus.