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The rheology of a conventional lithium-12 hydroxystearate bearing grease changes significantly when it is subjected to mechanical shear. Often this shear energy–along with the consequent entropy–is measured and used in engineering and thermodynamic models, leading to grease life models for predicting bearing seizure due to insufficiently thick film or loss of lubricity of the base oil/grease. In this degradation process, the bonds between the individual molecules, consisting mainly of the fairly weak van der Waals bonds and/or hydrogen bonds, are broken during this shearing process. In this article, we show that only a very small portion of the shear energy is needed to break these bonds and that the vast majority is dissipated as heat due to the lubricant viscosity, also known as viscous dissipation. We model the thickener as rod-shaped fibers, wherein the grease viscosity is reduced by a factor of 5 when the length of a fiber is reduced by a factor of 2.5. The energy needed to break the bonds between the molecules to shorten these fibers is 6 to 7 orders of magnitude smaller than the energy applied by shear. Hence, it is very difficult to measure this fiber structure breakage energy from grease shear aging experiments directly. [ABSTRACT FROM AUTHOR]

This article studies the tribological behavior of the lubricant film when the Q1-224 hydrostatic turntable is operated at constant cutting speed. First, the rotational speed equation of the worktable under the constraint of constant cutting speed is derived. Based on the lubrication mechanism of hydrostatic turntables, the flow-rate equation of the oil film, the temperature-rise equation of the oil film, and the bearing-capacity equation of the double rectangular cavity are deduced. Furthermore, the prediction model of the lubrication performance of hydrostatic turntable operating at constant cutting speed is established. Meanwhile the quasi-steady-state analysis is carried out by numerical simulation to obtain the change law for the lubricating oil film temperature, pressure, and other performance indicators with time under the different loads. Finally, these laws are verified by designed experiments. It is found that the load has a large effect on the change of oil film performance; it affects the temperature rise of the oil film by influencing the dissipation capacity, and there is a nonlinear relationship between the increase of the load and the average temperature rise of the oil film. [ABSTRACT FROM AUTHOR]

For this article, oleic acid surface-modified zeolitic imidazolate framework-8/graphene oxide (OA-ZIF-8/GO) nanocomposites were prepared by a facile in situ synthetic method. The as-prepared composite samples were analyzed and characterized by means of transmission electron microscope (TEM), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TG). The tribological behaviors of the OA-ZIF-8/GO with different GO contents as the lubricating oil additives were investigated comparatively using a four-ball tribological machine. The results showed that compared with the base oil, the OA-ZIF-8/GO with different GO contents when added to the base oil can all reduce friction and wear. The oil sample with 1.0 wt% of OA-ZIF-8/GO (53%) nanocomposite had the lowest friction coefficient and wear scar diameter. The reduction of friction coefficient and wear scar diameter is attributed to a stable protective film formed on the worn surface via physical deposition and a complicated tribochemical reaction. The study provides a strategy for fabricating graphene-based nanocomposites that were used for lubricating oil additives. [ABSTRACT FROM AUTHOR]

In this paper, through the continuous analysis of the engine oil of a 2600HP tugboat in 4 years, the detection data of spectrum, viscosity, moisture, degree of vulcanisation, pH, fuel dilution, flash point, and oxidation degree are obtained. The variable of these parameters over time is discussed. Nothing abnormal wear is found in the main friction parts of the engine. Lubricating oil is seriously vulcanised and acidification, which affects the oxidation degree. The performance of oxidation, sulphisation, PH, and fuel dilution is seriously degraded. The coupling effects of water content, acid value, alkali value, vulcanisation degree, and mechanical impurity should be considered in determining the oxidation and ageing of lubricating oil. It should be noted that excessive loss of alkaline additives in tugboat operation. The results provide an effective reference basis and experience guidance for better judging the wear state of the friction pair and condition-based maintenance based on lubricating oil. [ABSTRACT FROM AUTHOR]

This paper discusses the potential of using palm-castor oil blends as lubricating oil in industrial applications. Laboratory experiments to measure kinematic viscosity, flash point, copper corrosion, demulsibility, pour point and total acid number were conducted and compared with commercial lubricating oils. Change in kinematic viscosity with temperature of different palm-castor blends were best fitted to the Arrhenius model with R2 value higher than 0.95 and AARD% is less than 1.5%. Addition of 40 and 50% of castor oil to 60 and 40% of palm oil resulted solutions with similar properties of Hydraulic68 and SAE30, respectively. [ABSTRACT FROM AUTHOR]

Oils and grease have beneficial effects on moving parts such as connecting rod, gears, shafts, and engine to reduce wear and friction. The properties of lubricants such as tribological and rheological properties are an important role in oils and grease characterization. Nano additives on lubricant oils play an important role in anti-wear; reduce the coefficient of friction and enhance the rheological properties. The Tribological and rheological behavior of base oil 15W50 which have different concentrations of multi-wall Carbon Nanotubes (MWCNTs) (0.5, 1, 1.5, and 2 wt%), and constant amount of graphene nanosheets (GNSs) (0.5 wt%) were investigated. This research is the first one in studying the effect of hybrid nano additives of (MWCNTs) and (GNs) on the tribological and rheological properties of lubricant oils. Tribological characterization was carried out on four ball testing model under different loads (200, 400, 600, and 800 N). The kinematic viscosity, flash point, pour point, and thermal conductivity of nanofluid added 15W50 lubricant are estimated and compared with base oil. The results showed that nano additives improve the wear scar and coefficient of friction by 78% and 48%, respectively. The flash point, thermal conductivity, kinematic viscosity, and pour point, were improved by 15%, 77%, 76.8%, and 20%, respectively compared with the base oil. The hybrid addition of CNTs/GNs nanoparticles enhanced the properties of 15W50 engine oil. [ABSTRACT FROM AUTHOR]

The application of vegetable oil based additive for lubricating oil has attracted considerable interest due to their biocompatibility and multifunctional performances compared to conventional additives. In the present work, we have synthesized homopolymer of castor oil and copolymer of castor oil with styrene by thermal method without any solvent at different percentage composition by using BZP (benzoyl peroxide) as initiator. Characterization of the additives was completed by spectral technique (FT-IR and NMR spectroscopy). The molecular weight of the prepared additives was determined by gel permeation chromatography method (GPC method). Thermo gravimetric analysis (TGA) method was used to study the thermal stability of the prepared polymers. Standard ASTM methods were used to investigate the performance of all the prepared polymers in SN150 mineral oil as viscosity index improver (VII), pour point depressant (PPD) and antiwear. Biodegradability of all the polymers was determined disk diffusion method. From the experimental results, it was found that copolymers are more effective as VII, PPD and antiwear than homopolymer. Moreover, average molecular weight, thermal stability and performances as VII and antiwear increase with increasing the percentage of styrene in copolymers. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to evaluate carbon spheres as a green lubricant additive in 5W30 engine oil to reduce friction and wear. Carbon spheres with a diameter of ∼400 nm are synthesized from glucose by using a hydrothermal process. Lubrication is studied using a ball-on-disk tribometer by measuring the friction coefficient and wear in the boundary lubrication regimes. The worn surfaces were analyzed by Raman spectroscopy. Carbon spheres are found to be stably dispersed at 0.5 wt% concentration in base oil. The experiments revealed that carbon spheres are effective in reducing both friction and wear when lubricating by using base oil. Raman results show that the enhanced tribological performance is owing to a carbon-rich boundary film, the formation of which is attributed to the deposit of carbon particles during the sliding process. [ABSTRACT FROM AUTHOR]

Homopolymer of rice bran oil and its copolymer with dodecyl acrylate and styrene were synthesized and characterized by spectral (NMR, IR), thermogravimetric analysis and gel permeation chromatographic methods. Performance of these polymers was evaluated by standard ASTM methods in base oil and showed very effective as pour point depressants and viscosity modifiers. Biodegradability of all these polymers was tested which showed excellent results. A comparison of their performances has also been evaluated and reported. The copolymers showed biodegradability in addition to the multifunctional additive performance (PPD and VM), and so are considered as being more useful in field applications compared to the existing conventional additives. [ABSTRACT FROM AUTHOR]

Carbonium ion can be generated easier when low-carbon alcohols are added to hydrocracking tail oil, which initiate the cracking reaction of macromolecular n-paraffin. So the yield of lube oil base oil increases, while that of paraffin decreases, but the total yield of the two products increases. When the low-carbon alcohol is added to the raw oil for non-hydrodewaxing reaction of hydrocracking tail oil, the pour point of lubricating oil base oil declines, the flash point and the viscosity increases slightly, and the distillation range of paraffin declines slightly, but the properties of products changes little, so they can meet the actual production requirements of the factory. By examining the influence of low-carbon alcohol on the yield and properties of lubricating oil base oil and paraffin, tert-butyl alcohol is an ideal chain initiator, and the most suitable addition is 1.0 w%. [ABSTRACT FROM AUTHOR]

Re-refining of used lubricating oil has appeared as a valuable technique to re-refining of used engine and industrial oils. This paper focused on the vacuum distillation thin wiped film evaporation technique of used lubricating oil recycling. The whole process consists of dehydration, gas oil evaporation, thin wiped film evaporation and clay treatment. The produced base oils are in group I through determination of sulfur contents, percentage of saturate compounds and viscosity indexes. The obtained results are practicable with most of the American Society for Testing and Materials (ASTM) properties and reduced most of worn metals in the refined base oils. [ABSTRACT FROM AUTHOR]

Dispersant viscosity index improvers were synthesized by free radical copolymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA), dodecyl methacrylate, octadecyl methacrylate, and styrene in solution of mineral base oil. Studies included the dependence of the pour point and low-temperature crystallization behavior (characteristic temperatures and enthalpies) of the solutions of these polymer viscosity modifiers (VMs) on the amount of dispersant comonomer, DMAEMA, in the copolymer, weight average molecular weight of the copolymer, and concentration of the polymer in oil. Incorporation of dispersant comonomer in poly(styrene-alkyl methacrylate) structure additionally decreases the pour point of its solutions even for a very small concentration: the pour point of the base oil reduces from −9 to −25°C and −33°C for the 0.1 and 0.5 wt% concentrations of polymer, respectively. For concentrated 50 wt% solutions the enthalpy of crystallization decreases linearly with a decrease in the long-chain alkyl methacrylate share in copolymer. There is no unambiguous correlation between the pour point and crystallization parameters of semidiluted and diluted polymer solutions obtained by differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

Homopolymer of acrylate of a mixture of myristyl (C14), dodecyl (C12), and decyl (C10) alcohols in 2:1:1 molar ratio was synthesized by two different ways, microwave-assisted method and thermal method using benzoyl peroxide as initiator. The polymers were characterized by spectroscopic (NMR, IR) and viscometric analysis. Performances of each of them as a pour point depressant and viscosity modifier for lubricating oil (lube oil) were also evaluated by standard ASTM methods. Oil thickening property of the polymers has also been investigated and reported here. Thermal stability of the polymers was determined by thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Most modern engine oils contain a friction modifier additive to reduce boundary friction and thus contribute to improved fuel economy. Considerable research work has been carried out to measure the effectiveness of friction modifiers, both in base oil and in fully formulated engine oils. Most of this work has studied the behavior of friction modifiers on rubbing ferrous surfaces. However, engine oils generally also contain the antiwear additive zinc dialkyldithiophosphate (ZDDP) and it is well known that this additive reacts rapidly with rubbed ferrous surfaces to form a thick iron and zinc phosphate-based coating. Thus, to be effective, a friction modifier additive has to form a friction-reducing film not on a ferrous surface but on a zinc phosphate one. In the current study, the friction-reducing properties of friction modifiers on steel surfaces have been compared with their performance on surfaces having a ZDDP reaction film coating. It has been found that additives that are effective in reducing friction on steel surfaces are not necessarily effective in reducing friction on a phosphate coating and vice versa. The reasons for these observed differences are discussed. [ABSTRACT FROM AUTHOR]