FACTORS AFFECTING OXIDATION PROPERTIES IN DIFFERENTIAL SCANNING CALORIMETRIC STUDIES

Fundamental knowledge of the oxidative properties of commercial oils i s necessary to predict the stability of these fluids. There is an indu stry-wide need for a hydrocarbon reference fluid that can be used to e stablish oxidation properties of motor oils, greases, diesel oils, tra nsmission fluids and vegetable oils. A primary tool to determine the o xidation of oils is differential scanning calorimetry (DSC) or pressur e DSC. A diluted passenger-car motor oil was used to establish an expe rimentally designed relationship between the variables and the oxidati on induction time (OIT) by DSC or PDSC. The variables used for develop ing this protocol were temperature, pressure, heating rate, sample mas s, gas flow rate, and gas type, air or oxygen. The DSC pan metallurgy played a significant role in the measured OIT. Statistical quality con trol charting of the oxidation properties focused on a special cause, out-of-control problem that was related to the impurities in the alumi num pans. Iron impurities caused a decrease in OIT of the reference oi l. Increasing concentrations of chromium, probably as chromium oxide, stabilized the oxidation process.