FACTORS AFFECTING OXIDATION PROPERTIES IN DIFFERENTIAL SCANNING CALORIMETRIC STUDIES

Fundamental knowledge of the oxidative properties of commercial oils is necessary to predict the stability of these fluids. There is an industry-wide need for a hydrocarbon reference fluid that can be used to establish oxidation properties of motor oils, greases, diesel oils, transmission fluids and vegetable oils. A primary tool to determine the oxidation of oils is differential scanning calorimetry (DSC) or pressure DSC. A diluted passenger-car motor oil was used to establish an experimentally designed relationship between the variables and the oxidation induction time (OIT) by DSC or PDSC. The variables used for developing this protocol were temperature, pressure, heating rate, sample mass, gas flow rate, and gas type, air or oxygen. The DSC pan metallurgy played a significant role in the measured OIT. Statistical quality control charting of the oxidation properties focused on a special cause, out-of-control problem that was related to the impurities in the aluminum pans. Iron impurities caused a decrease in OIT of the reference oil. Increasing concentrations of chromium, probably as chromium oxide, stabilized the oxidation process.