Submitted to: Society of Tribologists and Lubrication Engineers
Publication Type: Abstract Only
Publication Acceptance Date: 5/11/2000
Publication Date: N/A
Technical Abstract: Thermo-oxidation is the primary cause resulting in increase of viscosity, acidity, corrosion, and sludge formation etc. of lubricant base oils in use. This phenomena results in frequent oil change and system failure. Base oils being the main component in finished lubricants, a complete understanding of the molecular composition is required for optimal lube formulation. Of late, due to stringent environmental regulations, the worldwide trend for predominantly saturate rich base oils (Group II and III) has been significant. NMR spectroscopy, of late, has been extensively used for total molecular level characterization and understanding the mechanism of oxidative degradation of base oils. The overall oxidative stability of these oils is fairly high, yet they degrade during extended high temperature applications. Oxidation mechanism of these oils with very low aromatic content depends entirely upon various isomeric saturates in base oil matrix. In the present study, quantitative carbon type distribution in base oils obtained by conventional and GASPE spectral editing NMR techniques are used to explain the oxidative degradation. Pressurized differential scanning calorimetry is used for monitoring the oxidative stability by estimating various thermodynamic and kinetic parameters of base oils. Variations in these parameters are explained in terms of the structural data obtained using NMR spectroscopy.