Change of concentration of additives under EHL conditions: observation by micro-FTIR

摘要

An analysis of the dynamic structure of lubricant films was performed by observations of the dynamic state of EHL oil films on a ball-on-disk-type lubrication tester by using the micro-FT-IR technique. A change of the concentration of additives in the EHL contact region was determined by performing lubrication tests that used different combinations of base oils, poly alpha-olefin, polybutene, and mineral oil with four additives: carboxylic acid, ester, succinimide and polymethacrylate. Obtained results showed that in the contact zone the concentration of additives was reduced. Test oils with added carboxylic acid showed a reduction of the concentration of carboxylic acid by one half in the contact zone. Test oils containing polybutene groups and test oils with added polymethacrylate showed an insignificant reduction of the concentration, which was explained by the promotion of the solidification or an increase in the viscosity of test oils by the additives. Also, it was found that the concentration-reducing behavior depended on the combination of a base oil and an additive, and for test oils prepared by adding ester to mineral oil, the additive concentration in the central part of the contact reduced from 10 wt% to 1 wt%.