A combinatorial approach for automotive friction materials: Effects of ingredients on friction performance

Abstract Raw materials used in automotive friction formulations were classified using a combinatorial approach into two groups in accordance with their ability to improve the wear properties of the mixture by two-phase friction composites. Components of group one, which improved the wear resistance, include softer additives (graphite, MoS 2 , and Twaron), harder additives (Al 2 O 3 and steel wool), and organic binder (benzoxazine). Softer additives have low friction coefficient ( μ ), low wear, and easily transferred debris to the surface of disc. Harder additives have intermediate wear, intermediate μ , and formed iron-containing surface layer transferred from cast iron disc to friction material pad. Benzoxazine has high wear and high μ and there is no transferred layer formed either on disc or pad in the case of benzoxazine used as pad. The wear of two-phase friction materials can be improved by adding Al 2 O 3 , graphite, MoS 2 , steel wool, and Twaron to benzoxazine and four wear improvement mechanisms were proposed: (1) lubrication mechanism (graphite and MoS 2 ); (2) abrasive mechanism (Al 2 O 3 ); (3) friction layer mechanism (steel wool); (4) reinforced mechanism (Twaron). Components of group two, which produced poor wear resistance, include BaSO 4 , BN, B 2 O 3 , brass chips, CaCO 3 , Ca(OH) 2 , cashew, copper chips, CuS, Cu 2 S, H 3 BO 3 , iron powder, MgO, oxidized PAN fiber, PMF (SiO 2  + CaO), Sb 2 S 3 , Ultrafibe (CaSiO 3 ), and ZrSiO 4 .