STUDY OF THERMAL STRESS IN A LUBRICANT BASE OIL USING FIELD-CYCLING NMR RELAXOMETRY

FRAENZA, CARLA C.; ERRO, EUSTAQUIO M.; ANOARDO, ESTEBAN; GERBINO, LEANDRO J.

Buenos Aires

Taller; IV Taller de resonancia magnética nuclear; 2018

Lubricant oils are complex mixtures of hydrocarbons composed of a base oil and additives [1]. They are indispensable in most of the mechanical systems that involves mobile parts, and it is expected that their performance results progressively affected as a consequence of fulfilling its functions [2]. A variety of physical and chemical factors combination changes the lubricant at molecular level. Heating is present in all internal combustion engines, and has an active role in processes as, nitrogen, oxygen and sulfur incorporation, hydrocarbon chains ruptures and ramifications [3-7].In this work, proton fast field-cycling nuclear magnetic resonance (H1 FFC-NMR) is used to study the effect of thermal stress in a lubricant 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 relaxation profiles corresponding to samples exposed at regular engine normal functioning temperature (T=90°C), whereas extreme heating treatment (T=270°C) have produced degradation that is clearly evidenced in the profiles, especially at low relaxation fields.The physical model used for nuclear magnetic resonance dispersions (NMRD?s) modelling considers that spin-lattice relaxation is dominated by two relaxation mechanisms: translational diffusion and rotational motions [8].References[1] Meyers R. A., Handbook of petroleum refining processes (New York, NY: McGraw-Hill Professional, 2004).[2] Ballari M., Bonetto F., Anoardo E., J. Phys. D: Appl. Phys. 2005, 38, 3746-3750.[3] Al-Ghouti M. A., Al-Atoum L., J Environ Manage. 2009, 90, 187-95.[4] Wang S. S., Lee S. H., Smolenski D. J., Sensors Actuators B. 1994, 17, 179.[5] Igarashi J., Japan. J. Tribol. 1990, 35, 1095.[6] Fox M. F., Picken D. J., Symons M. C. R., Thomson A. L., Tribol. Int. 1997, 30, 417.[7] Mortier R. M., Orszulik S. T., Chemistry and Technology of Lubricants (Suffolk, UK: Edmundsbury, 1997) pp 98?144.[8] Ballari M., Bonetto F. and Anoardo E., J. Phys. D: Appl. Phys. 2005, 38, 3746-3750.