Oxidation Chemistry of a Pentaerythritol Tetraester Oil

Synthetic oils have come into widespread use due to their inherent stability, consistent physical properties, and reproducible composition. As ever increasing demands are being placed on oil performance in magnetic recording disk drives by increasing rotation rates up to 10,000 rpm, it is important to know the ultimate limitations of these functional fluids due to oxidation; In this study, the authors focus on a pentaerythritol ester oil. Accelerated aging tests were carried out on the oil at elevated temperature. Tests were also done with 50 ppm of dissolved iron in the oil. The progress of oxidation was followed by analytical techniques including UV/visible, infrared, and proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography, thin layer chromatography, viscometry, and differential scanning calorimetry. A new technique of laser desorption mass spectrometry with jet cooling, which provides the parent ion mass spectrum, provided the mass distribution of intermediate oxidation pr...