2018 Volume 63 Issue 5 Pages 324-331
Two types of oil-soluble polymer as new tribomaterials are introduced based on recent research by the authors. One is polymethylmethacrylate (PMMA) including high concentration methyl group. Film forming properties of polyalkylmethacrylates determined with an optical EHL tester significantly depended upon alkyl group, functional group and molecular weight. Among them, PMMA with high molecular weight showed the greatest oil film thickness under the low rolling conditions due to strong adsorption of the polymer onto the metal surface. As a practical performance of additive, the effect of polymer on the rolling fatigue life of bearings was evaluated with a thrust bearing tester. As a result, the oil with PMMA showed much longer life than the oil without PMMA. Another novel polymer was polylaurylacrylate with hydroxyethyl group (PLA/HEA) recently developed. When the boundary friction-speed behavior was examined, the coefficients of friction for most oils increased with decreasing sliding speed, meanwhile that for PLA/HEA kept low level. It was inferred from the surface analysis that excellent tribological performances of PLA/HEA were brought about by a tribofilm formed based on reaction of hydroxyethyl group with the sliding surface. Then, PLA/HEA was applied to the drawing process of stainless steel AISI304 sheets, in which continuous possible working time was evaluated as the drawability. As a result, PLA/HEA was superior to the other commercially available lubricants except for chlorine-based oil.
