Lubricating oil degradation analysis due to temperature through Raman spectroscopy

Abstract

Lubricating oils are essential in vehicles motors, and there are currently three variations in oil types: mineral, semisynthetic and synthetic. This work aimed to evaluate the degradation of these three types, by heating them in the laboratory between 120 to 150 oC for 48h, and subsequently evaluating their change in the composition through Raman spectroscopy. It was possible to observe compounds in common between the mineral and semi-synthetic oils in the peaks at 1002, 1380 and 1621 cm-1, and between the semi-synthetic and synthetic in the peak at 892 cm-1. In the evaluation of samples after heating, trough principal component analysis (PCA) technique, it was observed a decrease in the intensity of some peaks, suggesting molecular breakdown, as well as an increase in the intensity of other peaks suggesting formation of amorphous carbon. It was found a high correlation through heating time and peak intensity, by adjusting 2nd order polynomial curves, R² ranging from 0.96 to 0.99.