Role of Attapulgite on Altering the Performance Properties of Cu-Free Brake-Pads 2020-01-1601
Attapulgite, a unique clay mineral is a crystalloid hydrous magnesium-aluminium silicate, composed of silicon oxide, aluminium oxide, magnesium oxide, iron oxide etc. having formula Mg5Si8O20(HO)2(OH2)4•4H2O. Its structure is somewhat between laminated and chain structure having very high surface area and porosity. Its magnesium silicate structure resembles a brick wall with every second brick missing. This leaves elongated porous channels that are highly absorbent. Its fibers were proven to be excellent substitute for asbestos in brake-pads. Hardly anything in details is reported on its exact role in controlling tribo-properties of friction materials (FMs) especially Cu-free FMs.
Hence, in this work a series of brake-pads with 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 10 % Cu and 10 wt. % attapulgite. The pads were characterised for physical, chemical and mechanical properties along with thermal conductivity measurements. The tribological characteristics were evaluated using full-scale inertia dynamometer as per JASO-C-406 standards under dry condition. The noise and vibration tests were conducted on Tribo Test Rig as per SAE J2521 standards. The results revealed that the attapulgite exhibited slightly lubricating properties by reducing average µ with increasing amount. However, it helped to increase wear resistance and NV properties. Failure mechanism was studied with SEM and EDAX techniques.
Keywords: Attapulgite, Cu-free NAO brake-pads, Dry sliding tribology, SEM-EDAX
Bhaskar Bhatt, Navnath Kalel, May Abdel-Latif, Jayashree Bijwe
Indian Institute of Technology, Nile University