Tribological and oxidation stability properties of saturated very-long-chain-fatty acids present in castor and jojoba oils have been investigated by the four ball tribosystem, pressure differential scanning calorimetry, optical micrographs and electron probe micro-analysis (EPMA). Test results of the oils additized with eicosanoic and octadecanoic acids in the oils were compared with those of zinc dialkyldithiophosphate (ZDTP). Results showed that eicosanoic and octadecanoic acids possessed better antiwear and lubricity properties compared to the popular ZDTP, though with reduced oxidation stability. EPMA and optical micrographs of worn surface morphology showed that lubricating films formed by these acids were metallic salts whose breakdown was not associated with tribochemical wear surface modification of the mating pairs.
In this study, locally available waste coconut (Cocos nucifera) shells (CSs) were investigated as possible replacement for asbestos-based brake pads. The CS-based brake pad was tested for its physicomechanical properties and compared with a commercial brake pad used as control sample. The results showed that (a) an improved interfacial bonding between the CS particles and the binder as the grain size decreases; (b) the 90 μm grain size sample had better physicomechanical properties than the control sample in all tests except the thermal conductivity and stability tests; and (c) the hardness, compressive strength, and density of the CS-based brake pad decreased with increasing grain size, whereas the absorption properties increased with increasing grain size. The study showed that further reduction of the grain size below 90 μm and matrix impregnation with metals of good thermal conductivity could provide significant improvements to properties of the CS-based brake pad.
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