Adaptation of the Penn State Microoxidation Test for the Evaluation of Automotive Lubricants

Comparative Physicochemical Study of the Thermally and Thermo-oxidatively Decomposed Automotive Crankcase Oils

“…At 300 0 C the mixed stock gave a small absorption peak with increased intensity at 340 0 C. Above this temperature all the samples showed either diminished or broad peaks, indicating the involvement of carbonyls in high temperature processes such as polymerization and other complex reactions leading to the formation of high molecular weight products. This observation agrees with the reports by [15] that the main reactions at the later stage oil deterioration involve adol-type condensation resulting in the formation of high molecular weight resinous products. It must be noted however that the formation of various carbonyl compounds such as Ketones absorbing at 1750cm -1 , conjugated ketones (1675cm -1 ), aldehydes (1725cm -1 ), organic acids (1710cm -1 ), carboxylates (1610 -1550cm -1 ), esters (1745 -1725cm -1 ) are all influenced by temperature and chemical composition of the lubricants.…”

Assessment of Oxidation in Automotive Crankcase Lube Oil: Effects of Metal and Water Activity

“…The low levels of deposits found in all of the oils before the 20th hour is an indication that the formation of sludge in the oils is a secondary reaction in the process of oil degradation. Klaus et al had confirmed that the formation of high molecular weight insoluble sludge is the final stage of oil deterioration. He also proposed that sludge is a secondary polymerization product resulting from aldol-type condensation reactions of carbonyl compounds with mainly carboxylic acid functions.…”

“…The progressive increase in the intensity and broadness of both of the hydroxyl and carbonyl bands in all of the oils from the 10th hour to the 65th hour signified increased complexity of the oxidation products. Earlier reports 10,12 have shown that the main reaction at the later stages of oil aging involves aldol-type condensation leading to the formation of polymeric materials and intramolecular esterifications leading to the formation of lactones. The products of the reaction comprising both oil-soluble and -insoluble materials reduce the infrared transmittance, thereby causing the broadening of the spectral bands.…”

“…The latter, however, cannot be achieved without the understanding of the processes of sludge formation and the nature of the oxidized products . Although qualitative information is available, which reports the presence of acids, aldehydes, ketones, esters, and lactones in the oxidates of used crankcase lube oils, information on the extent of oxidation is scanty. − From the literature it appears that infrared analysis and gas chromatography are the main chemical tools applied to highlight the major oxidation products. Infrared, in particular, gives an indication of the changes in the hydrocarbon matrix of the oils at the molecular level.…”