The Impact of Composition in Non-steel and Low-Steel Type Friction Materials on Airborne Brake Wear Particulate Emission
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ORIGINAL PAPER
The Impact of Composition in Non‑steel and Low‑Steel Type Friction Materials on Airborne Brake Wear Particulate Emission Sung‑Hun Kim1,2 · Wooyoung Shim2 · Sung‑Uk Kwon3 · Jung‑Ju Lee3 · Min‑Woo Seo4 · Je‑Kyun Kim4 · Jae‑Hwan Pee1 · Jong‑Young Kim1 Received: 10 August 2020 / Accepted: 18 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this work, airborne brake wear particulate matter (PM) emissions from a brake system were investigated by time-resolved and temperature-dependent measurement using a dynamometer. The measurement was performed for representative friction materials, 3 low-steel (LS) and 4 non-steel (NS), which are currently in worldwide use. The PM emission factor was found to be varied as large as by one order of magnitude depending on the composition of friction materials(pads). The airborne particle mass emissions from the LS materials ranged from 1.88 to 3.14 mg/km/vehicle, while the emissions from the NS ranged from 0.3 to 2.34 mg/km/vehicle, which is, in general, smaller than the LS. The time-resolved data imply that particle emissions in the extra-high-speed region of the WLTC cycle, where friction occurs at high temperature (Tdisk > 150 °C), is much higher than in the low-speed region, and determines the total PM mass emission factor. It was found that the friction materials containing metals such as Cu and Sn (LS-2/-3 and NS-4/-5) exhibited a lower PM emission factor. This result suggests that copper and tin, which forms an effective lubricating tribolayer in the interface between the pad and disk at high temperature, remarkably reduces PM emissions. It has been also found that the surface roughness of worn brake pads is positively proportional to PM emissions according to surface topography analysis, which is consistent with composition effect. These findings suggest that tribological engineering to provide sliding frictional behavior at elevated temperature is crucial to reducing PM emissions. Keywords Particulate emission · Brake wear · Dynamometer · Friction materials Abbreviations LS Low steel NS Non-steel XRF X-ray fluorescence spectrometer Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11249-020-01361-2) contains supplementary material, which is available to authorized users. * Jong‑Young Kim [email protected] 1
Icheon Branch, Korea Institute of Ceramic Engineering and Technology, 3321, Gyeongchung Rd., Sindun‑Myeon, Icheon‑si, Kyeonggi‑do 467‑843, Republic of Korea
Multi‑scale Materials Laboratory, Department of Materials Sciences & Engineering, Yonsei University, 50, Yonsei‑ro, Seodaemun‑gu, Seoul, Republic of Korea
2
3
Research Institute, Sangsin Brake Co. Ltd., Daegu, Republic of Korea
4
Central R&D Center, Mando Corporation, Pyeongtaek‑si, Gyeonggi‑do, Republic of Korea
CoF Coefficient of friction WLTC Worldwide harmonized Light duty driving Test Cycle LACT Los Angeles City Traffic EF Emission factor PN Particle number XRD X-ray diffraction
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