Present knowledge and perspectives on the role of copper in brake materials and related environmental issues: A critical assessment

Potential health risk for residents around a typical e-waste recycling zone via inhalation of size-fractionated particle-bound heavy metals

“…The abundances of these elements in coarse and fine particles were approximately equal to each other with three peaks at 0.56-1.0, 1.0-1.8, or 3.2-5.6 m. It is interesting to note that Cu exhibited different size distribution patterns from other anthropogenic elements, which may be attributed to its specific emission sources. Cu is one of the most important elements in typical printed circuit boards and automobile brake lining, with approximately 16% and 1-14% of the contents [34,35]. Brake dynamometer testing [36] and measurements in an urban near-highway environment [37] demonstrated that airborne particle-bound Cu was concentrated in particles with diameters >1.0 m. It should be noted that the electrical low-pressure impactor used in these experiments was similar in size-segregated particles efficiency to the MOUDI sampler [36] used in the present study.…”

Pin-on-Disc Testing of Low-Metallic Friction Material Sliding Against HVOF Coated Cast Iron: Modelling of the Contact Temperature Evolution

“…The coatings were deposited to improve wear resistance of the discs, considering that they contribute by up to 50 wt% to the wear of a brake system. Incidentally, the reduction in the disc wear is functional to the reduction in the emissions of airborne wear particles from brake systems, an environmental issue that is becoming increasingly important [3,4,14,41]. The aim of the present study is twofold.…”

“…Dynamometer and road tests are mandatory to obtain design-oriented information and for product certification. However, plain PoD testing is very useful to obtain focused information on the wear mechanisms and on their role on the tribological behaviour of real systems [6,7,[11][12][13][14]. Moreover, considering the complexity of the formulation of friction materials for brake pads, it is paramount to have a reliable selection tool for the development of novel compositions [10,15].…”

Effect of nanoparticulate copper, zirconia and graphite: contribution to the friction coefficient and transfer layer formation in dry sliding tests with interfacial media addition.

“…In this sense, the suppression of copper alongside with the overall improvement of brake pads, considering environmental aspects, is a clear challenge within the green tribology field. Straffelini et al (2015) reported the existence of copper-free brake pad formulations [52][53][54] available in patents [55] . As copper suppression becomes a reality, the final answers to this challenge reveal, once more, the industrial secrecy aspect of brake materials development.…”

“…In that sense, Österle and Dmitriev (2016) stated [16] and showed by the use of computational models [27,59,60,70,[74][75][76] that soft metallic particles may adopt the function of solid lubricants like graphite or metal sulphides. More recently, Straffelini et al (2015) [55] reviewed the past efforts on unveiling how copper acts on the transfer layers. They showed copper was reported to promote the formation of compacted transfer layers in the pad's surface [13,71,76] .…”