The study of the magnetization of the system protons in some synthetic motor oil 5W-40 as oligomers, which is in viscous-flow state

Abstract

Viscosity and magnetic relaxation of a system of protons in four clean and operational engine oil of the same group of viscosity SAE 5W-40 Mobil Super 3000, Shell Helix Ultra, Castrol Edge and Toyota were studied in the test temperature range 40–100 ° C. The viscosity of oils is measured on a rotational rheometer "Physica MCR 501" Anton Paar production (Switzerland). In all experiments we used geometry cone–plate. The base oil is considered as an oligomer, which is in a viscous-fluid state. The viscosity of pure oil at 40 ° C is in the range 38–93 mPa•s. Provides an explanation for why the viscosity of the operating oil becomes more or less than the viscosity of a pure. The activation energy of viscous flow pure and operating oils in the average does not change in the test temperature range is 30±2 kJ/mol. For measuring the times of longitudinal and transverse relaxation of proton system  NMR Minispec mq relaxometer at a frequency of 10 MHz was used by biexponential approximation of relaxation envelopes. The influence of proton subsystem of additives on the magnetic relaxation was not taken into account. T1(1) T2(1) represent short, and T1(2) T2(2) – long times, reflecting the impact of large-scale and small-scale molecular relaxators respectively. The activation energy of the magnetic relaxation of a system of protons was defined. On average, they equal 17 and 12 kJ/mol for clean and maintenance of motor oils, respectively. Based on the fact that the ratio T1(1)/T2(1) T1(2)/T2(2) at the exploitation of the oil increases, the conclusion about the shift of the molecular weight distribution of molecules of oligomers in the direction of large values.