Influence of Increasing Amount of Attapulgite on the Performance Properties of Cu-Free Brake-Pads (SAE Paper 2020-01-1601)
Copper is almost inevitable functional filler in the brake-material and efforts to replace it are continuing since it is now known as a hazard to the aquatic life. It is always desirable to search for ingredients for Cu-free brake-pads, which will be beneficial for friction-related properties and especially fade resistance. Attapulgite, is a mineral which was proven to be an excellent substitute for asbestos in brake-pads long back. However, hardly anything in details is reported on its exact role in controlling tribo-properties of friction materials (FMs). It was of interest, if it can be helpful in enhancing the performance of Cu-free FMs.Hence, in this work a series of brake-pads (five types) was formulated and developed with increasing amount of attapulgite (0, 5, 10 and 15 wt. %) by compensating with inert barite particles in Cu-free FMs. The parent composition was fixed and instead of Cu powder, 10 wt.% stainless steel powder was used. One more type of pads was also developed containing Cu and attapulgite (10 wt. % each) just to compare its performance with that containing 10 % stainless steel powder and attapulgite, (10 wt. % each) keeping every other ingredients in parent composition as constant. The pads were characterised for physical, chemical and mechanical properties. The tribological characteristics were evaluated using full-scale inertia dynamometer as per JASO-C-406 standards under dry condition. The results revealed that the attapulgite exhibited slightly lubricating properties by reducing average � with increasing amount. However, it helped to increase the wear resistance to small extent, but at the cost of deterioration in some beneficial properties such as fade resistance, fluctuations in �. Overall, its inclusion in Cu-free brake-pads did not prove beneficial as expected.