Identification of organic compounds released from low-metallic automotive model brake pad and its non-airborne wear particles

Abstract

The brake wear contribution to the environmental pollution has been extensively discussed, with major focus on asbestos and heavy metals released to the environment. Only limited attention was paid to released organic compounds generated during friction processes, although the organic and carbonaceous components are not the minor part in brake lining formulations.

Friction processes in brakes are associated with relatively high temperatures and high pressures on the friction surfaces which relates to the thermal decomposition of the organic components in friction materials and to brake lining thermal fade. Thus, this study focuses on the identification of organic compounds released from a model low metallic brake material. Several methods were used for the analysis: GC/MS screening of brake pad samples, brake wear debris and carbonaceous raw materials used in formulations of model pads; GC/MS screening of brake pad samples pyrolyzed at 300, 750, and 1000 degrees C, respectively, and FTIR analysis of brake pads and their wear debris.

Higher quantity of organic compounds was identified in extract of the milled brake pad composite compared to the wear debris. More than 80 organic compounds were identified to be potentially released during braking. The major constituents were phenols, aliphatic and aromatic hydrocarbons, and their derivatives. Some of the identified compounds are known to have adverse effects even with mutagenic and carcinogenic potency to humans.