The role of scorching treatment on the wear and emission behavior of friction materials with and without copper

The present work aims at investigating the correlations between friction, wear and particle matter emission in copper-containing and copper-free automotive friction materials with particular emphasis on the effect of the scorching treatment. The tribological tests have been conducted using pin-on-disc laboratory equipment, and the airborne particles were measured in terms of number and mass. The results indicate that the number concentration of the airborne particles correlates well with friction coefficient, whereas their mass correlates better with the system wear rate. In addition, the copper-free material displayed a lower friction and wear and lower emissions than the copper-full. For this material, scorching was also found to reduce the friction coefficient, wear rate and emissions with respect to the pristine un-scorched condition, whereas no similar effects were found for the copper-full material. The results are discussed considering the characteristics and relevant role of the friction layers forming onto the pin surface.