Antiwear Performances of Dicarboxylic Acids in Vegetable Oils

Abstract

This study deals with the evaluation of antiwear performance of the vegetable oils [soybean oil, corn oil, rapeseed oil, and sunflower oil] and their blends, containing varying amounts of acetone, and organic acids [oxalic acid, succinic acid, and adipic acid]. Four-ball tribometer was employed as the wear tester. Extensive optimization with respect to the test oil composition was performed in order to explore the conditions under which the test oil demonstrated superior antiwear performance. In all cases, the desired conditions were obtained under a narrow range of test oil composition. It was observed that under the constant applied load of 78 N, test duration of 1 h, and given oil viscosity, succinic acid was found to be the most effective antiwear additive, i.e., resulted in smaller wear scar diameter [WSD] among the employed acids in all the test oils. For example, at 0.02 wt % of the succinic acid loading, the relative wear [WSDacid-loaded oil / WSDacid-free oil] was found to be 0.53, 0.62, 0.65, and 0.67 for the soybean oil [vis., 35 cSt], corn oil [vis., 33 cSt], rapeseed oil [vis., 47 cSt], and sunflower oil [vis., 36 cSt], respectively. The values of of the relative wear obtained under similar conditions with the same oils in the presence of oxalic acid and adipic acid were on the higher side of those obtained with the succinic acid. Further work is in progress in order to formulate energy saving and high performance environmental friendly lubricants for a wide range of practical applications.