OIT Measurement of Standard Motor Oils by Pressure DSC

摘要

Oxidation induction time (OIT) is a fast standardized method to characterize the stabilityrnof organic materials like polymers and oils against oxygen attack. Pressure DSC is required tornincrease oxygen concentration for faster reactions at lower temperatures and for the suppressionrnof evaporation of low volatile components. OIT measurements will be compared to standard longrntime tests.rnOther comparison is made using the Oxygen Onset Temperature (OOT) method to investigaternthe influence of oxygen concentration on the start of oxidation during heating of samplesrnof a mineral and a synthetic lubrication oil. The increase of O_2 pressure reduces the onset temperature.rnThe synthetic oil is affected by 36 K, the mineral oil by 33 K about in a similar amount,rnas the figure below demonstrates. But it is obvious, that the synthetic oils is much more temperaturernresistant than the mineral oil. This has an impact on the life time of the oils and also isrnreflected in the selling price of the oils.rnThe measurement parameters must be adapted if small differences between oils have tornbe analyzed. In such cases, isothermal methods are preferred with a careful selection the temperature.