Empirical Analysis of the Effect of Recycled Tyre Rubber Incorporation on the Mechanical and Tribological Properties of Brake Pad Composites

The growing volume of waste automotive tyres in Nigeria presents both an environmental management challenge and a potential feedstock for value-added engineering material applications, and the incorporation of devulcanised tyre rubber into brake pad composite formulations has been proposed as a route to reducing both waste disposal burden and friction material import dependency. This study empirically analyses the effects of incorporating recycled tyre rubber particles at weight fractions of 5, 10, 15, and 20 percent as a partial replacement for conventional organic fibres in asbestos-free brake pad composite formulations. The composite matrix comprised phenol-formaldehyde resin, cashew dust, barium sulphate, and graphite, with devulcanised tyre rubber crumb substituted for jute fibre at the specified fractions. Mechanical properties including hardness, compressive strength, and flexural modulus were measured following standard ASTM procedures. Tribological characterisation was conducted on a Chase-type friction material test machine at four temperature levels representing normal and severe braking conditions. Coefficient of friction stability, wear rate, and fade resistance were evaluated. Results showed that the 10 percent rubber content formulation achieved the best balance of properties, with a hot friction coefficient of 0.41, wear rate of 0.0021 cubic centimetres per Newton-metre, and acceptable fade recovery performance. Mechanical property analysis confirmed that compressive strength and hardness remained within the regulatory requirements for non-metallic brake pads. Scanning electron microscopy revealed uniform rubber particle distribution at low substitution levels, with particle agglomeration emerging at 20 percent. Keywords: recycled tyre rubber, brake pad composite, tribological properties, friction material, waste tyre.