The recently introduced environmental legislation in the federal states of California and Washington (US) has put into question the role of copper powder in organic-based, asbestos-free, brake pads for passenger cars. Copper guarantees a pretty much unique combination of friction properties such as efficient heat removal, stabilization of friction behaviour, noise reduction, and low wear of both pad and disc. With no other direct substitute available - with the exception of precious metals - an investigation on both new materials and formulations is necessary. This research presents a joint effort on the way to innovative copper-free formulation. Different combinations of metallic powders as copper replacements were used within a standard formulation to prepare experimental brake pads, which were subsequently characterised in their physical, thermal and mechanical properties. Friction behaviour was assessed using AK-Master test procedure, determining the influence of speed, pressure and temperature on the friction coefficient and fade resistance/recovery. Friction surfaces of pads and discs were investigated through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Focused Ion Beam (FIB) analysis and roughness profiles. The knowledge about materials behaviour and interactions was then implemented in the re-formulation of copper-based industrial mixes, substituting it without compromising braking performance.

Ane Maite Martínez, Jon Echeberria, Antonio Di Loreto, Matteo Zanon, Ilaria Rampin - CEIT, Gama, S.p.A, Pomerton Power S.p.A