Emission and properties of airborne wear particles from train brake friction materials based on novolac phenolic resins and butadiene rubbers

The emission of airborne particulate matter from a train brake depends on the formulation of its friction material. This study investigates the emission and properties of wear particles from train brake friction materials based on straight or resorcinol-modified novolac phenolic resin and nitrile or styrene butadiene rubber used as binding ingredients. The wear particles are generated by a pin-on-disc tribomachine inside an aerodynamic chamber, counted and collected using aerosol measurement techniques, subjected to microscopic and elemental analysis. It has been found that the modification of novolac phenolic resin with resorcinol has no considerable effects on the emission of wear particles and their properties. By contrast, replacing styrene butadiene rubber with nitrile butadiene rubber leads to a significant decrease in the emission of 0.1–10 μm wear particles.