Nano- and micro-sized particles emitted by braking of automobiles

J. Kukutschova, V. Matejka, M. Vaculik, P. Peikertova, P. Filip
Technical University Ostrava, CZ

Keywords: nanoparticle release, EHS

Summary:

More than one billion registered vehicles worldwide significantly contribute to environmental pollution. While the exhaust emissions and tire wear were addressed extensively, the particles released by the braking of the automobiles were studied to a considerably lesser extent. Our previous work indicated that the released wear particles can have a negative impact on the environment. A characteristic automotive brake pad is a multicomponent composite typically formulated of more than 10 constituents. Brake pad manufacturers worldwide use several thousand different raw materials, e.g. various metals and their compounds, ceramics, polymers and carbon-based components. This contribution addresses the character of wear particles released from a model and commercially available friction materials, used in a typical brake in USA, Europe, and Asia. Brake materials were subjected to the standardized brake dynamometer test simulations and the collected wear particles were further studied using a combination of analytical techniques including elemental, phase and morphological analyses. Our experiments demonstrated that the size of the released airborne wear particles was between 10 nm and 20 µm (see the TEM image below). Numerous newly formed compounds which were not present in the original bulk brake material were released during friction and detected by elemental and phase analysis. Nano-sized Cu, Fe, and Sn oxides and carbon-based particles were confirmed in the released coarse, fine and ultrafine wear debris fractions. These findings demonstrated that the wear process related to braking of automobiles contributes to the nano-particulate air pollution which may potentially pose health risks in areas with heavy traffic.