Performance of naphthenic oils: thermal stability and lubricity

Abstract

Mineral oils are composed of organic molecules that show a complex thermooxidative degradation process. The objective of this work was to evaluate the thermal degradation kinetics of the naphthenic oils NH10, NH20 and NH140, using thermogravimetry, and to analyze the lubricity of NH20 and NH140 oils, by means of a mechanical system with gears (test bench). Activation energy and thermal resistance parameters were determined using the methodologies described in ASTM E1641-16 and ASTM E1877-17. The results indicate the highest-thermal stability for NH10, which can be confirmed by this oil thermal resistance (220.93° C) and activation energy (92.974 kJ mol-1), whose values are higher than those for NH20 (187.06° C, 42.856 kJ mol-1) and NH140 (133.53°C, 45.282 kJ mol-1). In the lubricity tests for NH20 (base for lubricants) and NH140 (base for grease), the parameters RMS, crest factor, and K factor were analyzed. The results for factor K, show that the value obtained from the nonlubricated gear system (187.75) was higher than that for the system lubricated with NH20 (185.16) and NH140 (28.88), and these values are consistent with the lubricant performance tests.