Combinatorial Effects of Clay-Type Silicate and MgO on Friction Braking Performance of Hybrid Phenolic Composites

Abstract

Halloysite (tubular), montmorillonite (platy), and wollastonite (acicular) type clay silicate morphologies-based magnesium oxide (MgO) filled compression-molded hybrid friction composites were fabricated followed by their mechanical (compressive), thermal (onset of degradation), thermo-mechanical (loss modulus), and tribological performance (CoF, fade, recovery, wear) evaluation. The friction-fade and friction-recovery due to braking-induced heating and cooling cycles vis-a-vis the instantaneous braking performances were evaluated following SAEJ661, on a chase-type friction tester. The combination of halloysite–MgO in the friction composite led to minimum fade (∼2.2%), whereas that of wollastonite–MgO showed a maximum friction coefficient (∼0.47) with enhanced rotor friendliness as indicated from optical surface profilometry. Montmorillonite–MgO-based composites showed a maximum wear resistance along with a greater extent of friction stabilization as supported by ID/IG data from Raman spectra. The performance attributes remained governed by the compressive stiffness of the friction composites, hardness, thermal stability, and morphological aspects of the clay-type silicates, and their induced contact dynamics as evident from scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDX) studies. The heat dissipation mechanism, the disc temperature rise, and friction coefficient under instantaneous braking condition were found to be controlled by MgO in the composites. The study demonstrates that clay-type silicate morphologies in combination with MgO as a mild abrasive may lead to synergistic fade–recovery performance without compromising the compressive stiffness response of the braking surface, enabling increased wear resistance.