Monitoring lubricant oil degradation using field-cycling NMR relaxometry

Abstract

Proton fast field-cycling nuclear magnetic resonance (1 HFFC-NMR) was used to study the effect of thermal stress in mineral base oil. The base oil underwent controlled thermal degradation and its relaxometric response was evaluated and interpreted in terms of self-diffusion and molecular rotations. Our results show slight changes in the relaxometric behaviour corresponding to samples exposed at typical engine working temperature (T = 90◦C),), whereas extreme heating treatment (T= 270◦C)) have produced degradation that is clearly evidenced in the profiles, particularly at low Larmor frequencies. Additionally, diffusion coefficients were calculated using a simplified method, showing the expected physical tendency with temperature and degradation level.