Abstract
Abrasives, such as oxides of alumina (Al), silica (Si), zirconia (Zr), chromium (Cr) etc., are added to raise the friction level and also to remove the glaze on the disc so that surface will be rejuvenated continuously during braking and will contribute to maintain the desired friction level. However, these inorganic particles have less adhesion with the resin/binder and hence are easily dug out during wearing process contributing to higher wear. If efforts are made to enhance the filler-matrix adhesion, not only the wear of friction material (FM) should reduce, the particles may stay for a longer time on the tribo-surface of the pads to contribute fully towards controlling the coefficient of friction (μ). In the present study, alumina particles were selected for siloxane treatment to improve the filler-matrix adhesion. Two types of eco-friendly (free from asbestos and Cu) brake-pads were developed using alumina as a theme ingredient (treated and untreated) keeping all the parent formulation identical. An additional type of brake-pads without alumina particles was also developed to observe the effect of abrasive particles on the tribo-performance. The performance properties (physical, mechanical, and tribological) of brake-pads were compared when evaluated in identical conditions. The tribo-testing was done on full-scale brake inertia dynamometer following the procedure in Japanese automobile standard (JASO C 406). It was observed that siloxane treatment affected both friction and wear of brake-pads in a beneficial way. Wear resistance got increased 35% for siloxane treated pads. Worn surfaces were analysed using scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX) technique.
Highlights
Brake friction materials (FMs) should be designed to achieve a stable friction in desired range (coefficient of friction (μ): ~0.30 to 0.45) depending on the type of vehicle apart from several diverse demanding performance properties and formulation of friction materials (FMs) is one of the most challenging tasks
Stretching vibration of Si−O− bond was confirmed by the broad band observed at 1,060 cm−1 whereas out-of-plane Si−O− stretching for the siloxane group attached to alumina particles was observed for 1,150 cm−1 [17]
Before tribological evaluation on full-scale brake inertia dynamometer, brake-pads were characterized for physical, mechanical and chemical properties as per standard procedure as reported elsewhere [18, 19]
Summary
Brake friction materials (FMs) should be designed to achieve a stable friction in desired range (coefficient of friction (μ): ~0.30 to 0.45) depending on the type of vehicle apart from several diverse demanding performance properties and formulation of friction materials (FMs) is one of the most challenging tasks. Commercial brake-pads contain approximately 1−8 vol% of abrasive particles, such as zirconia, alumina, silica quartz, Zr-silicate etc., and the type, hardness, shape, size and amount of control the final performance apart from their compatibility with resin. These particles are believed to influence noise and vibration (NV) performance since they directly abrade the disc surface and play a key role in the film formation that. Chemical modification/siloxane treatment to Prosopis juliflora fibers (PJFs) and scallop shell and periwinkle shell powder improved the thermal stability, shear strength, hardness and adhesion with the matrix and reduced the wear of composites [12−13]. One more type of brake-pads was developed without inclusion of alumina to understand the consequences on the performance properties and results are presented in the subsequent sections
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