Abstract
The emission of vehicle brakes has become an important topic in the last few years. Before there was no negative aspect since asbestos was forbidden in brake pads and there was no discussion concerning the impact of nanoparticles in general. The current discussion started with complaints about brake dust staining of the wheel. Since then, several attempts were made to understand the synthesis, composition and distribution of brake dust because of the growing awareness of environmental and health effects, for example with antimony and copper in the brake pads. Beside the combustion engine, the brake is the main emitter of nano-sized particles on a passenger car.[1-3] The environmental problem of brake dust was reviewed in previous scientific work, e.g. “Method for visualization and handling of brake dust emissions” by Audi AG and TU Ilmenau, chassis.tech 2010. There are a few materials in brake pads or their reaction products which led to discussions, e.g. the content of copper or antimony.
The published results for the number and size of brake wear particles vary widely. [4-8] This is mainly because of the complex and susceptible characteristics of a brake system and the limited resolution of many measurement systems. With every change in temperature, braking speed, braking pressure, pad formulation, brake type and history of the friction partner, differences in the properties of brake dust particles will be recognizable. For precise measurements there are several methods known from the combustion engine particle measurement. A HORIBA SPCS1 was used for particle size measurement. The material composition was analyzed by XRD2 and XPS3, which give additional information about the crystallographic structure and chemical composition unlike the EDX4 method. Tests on a brake dynamometer were successful as the results were repeatable and it was detectable, that brake emissions increase exponential with braking energy.
Keywords: brake dust, brake wear, particle measurement, material analysis