Commercial vehicle brake pads play an important role in the environmental impact caused by road transport. Their complex raw material requirements and increasingly prevalent contribution to traffic pollution is forcing the industry to look for alternative solutions. Natural lignocellulosic fibers have already been investigated as sustainable brake pad ingredients, and while braking performance results appear promising, important characteristics such as wear resistance and particulate matter emission are either deteriorated or outright neglected. In this study, rice husk, a byproduct waste of the agricultural industry, is investigated as possible environmentally friendly natural ingredient in friction material composition. Additionally, rice husk ash, obtained through thermal treatment of rice husk, was also investigated as friction material ingredient. Friction material samples based on a commercial formulation were modified by adding different percentages of rice husk, rice husk ash, and a reference CaCO3-BaSO4 filler material. The samples were then tested with a pin-on-disc tribometer, which was modified to include some airborne particle collecting equipment essential to assess the environmental implications of using the alternative ingredients in friction materials. SEM analyses, including EDXS, were carried out on the collected emissions, on the external surface and on the cross-section of the contact surfaces. The results obtained from this investigation suggest that limited yet substantial amounts of widely available rice husk could successfully substitute conventional filler ingredients in brake pad formulations, as an effective approach in lowering their environmental impact.

Dr. Davide Carlevaris, PhD Student, University of Turin; Dr. Mara Leonardi, Testing application engineer R&D, Brembo S.p.A.; Prof. Giovanni Straffelini, Professor, Università degli studi di Trento; Prof. Stefano Gialanella, Professor, Università degli studi di Trento