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Carbonyl peak index technique in the study of lubricant oxidation
Author(s) -
Maduako A. U. C.,
Ofunne G. C.,
Ojinnaka C. M.
Publication year - 1992
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.3010050105
Subject(s) - crankcase , base oil , lubricant , chemistry , hydrocarbon , base (topology) , metal , base metal , petroleum , induction period , petroleum product , organic chemistry , chemical engineering , composition (language) , catalysis , metallurgy , materials science , thermodynamics , composite material , scanning electron microscope , mathematical analysis , linguistics , physics , mathematics , philosophy , welding , engineering , internal combustion engine
A technique known as the Carbonyl Peak Index (CPI) is used to assess the relative oxidation stabilities of two competing grades of commercial automotive crankcase oils, their base oils, and the oxidation characteristics resulting from oil/metal interactions. The CPI provided empirical data from the infrared spectra which enabled a more lucid explanation of the oil soluble acidity and sludge deposition characteristics of the oils. A combination of these parameters has confirmed that the hydrocarbon type composition of the oils gave some stability to the fully formulated monograde oil. Consequently, the monograde base oil was found to possess a greater stability towards oxidation than the multigrade base oil under the conditions of test. However, the fully formulated oils were found to be more stable than the base oils, mainly due to the added antioxidants. Metals in the oils acted as antioxidants initially, but later turned to pro‐oxidants. The reversal of metal action from inhibition to autooxidative catalysis was also found to be base‐oil hydrocarbon‐type dependent and this has been related to the natural antioxidant capacity of the oils.