Monitoring of lubricating oil degradation via fast field cycling NMR relaxometry

ERRO, E.M.; ANOARDO, E.

The Environment in a Magnet: Applications of NMR Techniques to Environmental Problems

Royal society of chemistry

Lugar: Palermo; Año: 2024; p. 205 - 221

Motor oils are composed of a hydrocarbon mineral or synthetic blend (base oil), conveniently additivated with specific chemicals aimed to prevent degradation and increase its functionality and lifespan. Oxidation, nitration, sulphating and contamination are the most common factors to consider, while thermal stress is one of the most aggressive chemical degrading mechanisms. The Fast Field-Cycling NMR relaxometry technique has been successfully used to characterize chemical degradation in oil bases and lubricants. Our studies suggest that the spin-lattice relaxation rate R1 measured at low field (Larmor frequencies lower than 2MHz) and preferably at room temperature (or lower), meets optimal analytical conditions that are vastly superior to spin-spin relaxation R2 analytics at low temperatures (-10ºC to 10ºC) in the MHz frequency range. The proposed theoretical relaxation model showed a good consistency with pulsed field-gradient measurements of diffusion, and other relaxation experiments performed at fixed field instruments. Among other, applications in a short time includes detection of adulteration and other forensic needs related to oils, fingerprint fast testing, efficiency and durability of additives and quality determinations of mineral or synthetic bases.