Oil-based Lubricants Research Articles

Tribological and Thermal Transport Performance of SiO2-Based Natural Lubricants

Fluids and lubricants are critical for the mechanical manufacturing processing of metals, due to a high amount of friction generated, also reflected as heat, could wear and damage tooling and machine components. The proper application of lubricants increases machinery lifetime, decreases long-term costs, and energy and time consumption due to the maintenance or components exchange/repairs. Besides being non-renewable, mineral oils bring consequences to the environment due to their low biodegradability and could affect the user with respiratory and skin diseases. Recently, due to an increase in environmental awareness, the search of biocompatible and efficient lubricants has become a technology goal. The vegetable oil-based lubricants are slowly emerging as ecofriendly and high-performance alternatives to petroleum-based lubricants. This study evaluates soybean, sunflower, corn and paraffinic oils reinforced with SiO2 nanoparticles. The thermal and tribological evaluations were performed varying the temperature and nanofiller concentrations. The thermal conductivity improvements were observed for all nanolubricants as the temperature and filler fraction increased. The highest thermal conductivities were observed at 323 K with 0.25 wt % SiO2. The soybean and corn oils unveiled a maximum enhancement of ~11%. The tribological evaluations showed that SiO2 addition, even in small concentration, resulted into a significant improvement on a load-carrying capacity. For instance, at 0.25 wt % enhancements of 45% and 60% were observed for soybean and sunflower oils, respectively. The coefficient of friction performance also showed enhancements between 10% and 26%.

Ultralow concentration of graphene oxide nanosheets as oil-based lubricant additives

The nano-lubricant can largely enhance the tribological property of base oil, while the higher addition will cause a serious aggregation of nanoparticles. In this paper, the hexadecane-based oil (16C) with ultralow concentration of graphene oxide (GO) nanosheets as lubricant additives were successfully prepared by phase transfer method. The tribological behavior of the hexadecane with different concentration of GO has been investigated by subjecting it to macroscopic ball-on-disc friction tests using SRV-4 tribometer. The steady-state coefficients of friction (COF) of 16C with 10 mg/L GO were ca. 0.146. Based on the tribological tests and analysis of the wear scar, a lubrication mechanism was proposed. It is believed that the adsorption of GO nanosheets on the lubricated surfaces of both the ball and disk is the key to reduce friction and wear. The proper addition of GO nanosheets can easily enter into the contact area and efficiently protect the surface of the sample from wear.

An Automated Method for Chemical Composition Analysis of Lubricant Base Oils by Using Atmospheric Pressure Chemical Ionization Mass Spectrometry.

Since its invention in the 1950s, field ionization mass spectrometry (FI MS) has been, and currently is, the go-to technique employed by the petrochemical industry for the identification of the different types of nonvolatile compounds in their products. Unfortunately, FI MS has several inherent drawbacks, such as poor reproducibility. The performance of positive-ion mode atmospheric pressure chemical ionization mass spectrometry (APCI MS) with O2 gas as the sheath/auxiliary gas and a saturated hydrocarbon solvent/reagent was recently compared with that of FI MS and found to show promise as an alternative, highly reproducible method for lubricant base oil analysis. We report here on the automation of the APCI/O2/saturated hydrocarbon MS method. Isooctane was chosen as the optimal APCI solvent/reagent for base oil ionization due to the low level of fragmentation it provided for model compound mixtures. Three minutes was determined to be the shortest possible cleaning time between samples, regardless of the base oil viscosity. The total analysis time for each sample was 5 min. The reproducibility of the method was assessed by determining within-day and between-day precisions and total precision for hydrocarbon class distributions measured for three different base oils. All total precision values were found to be better than 6.2%, suggesting that the automated (+)APCI/O2/isooctane method is reproducible and robust.

Molybdenum Oxide-Modified Iridium Catalysts for Selective Production of Renewable Oils for Jet and Diesel Fuels and Lubricants

Supported inverse metal–metal oxide catalysts have received significant research interest owing to their effective hydrodeoxygenation (HDO) activity toward biomass substrates, but the high cost of the reported catalysts poses a challenge for commercialization. We present the synthesis of a series of metal–metal oxide catalysts, Ir–MOx/SiO2 (M = Re, Mo, W, V, or Nb) and M′–MoOx/SiO2 (M = Rh, Ru, Pt, or Pd) and their HDO performance on multifuran (high carbon) substrates to produce renewable jet and diesel fuels and lubricant base oils. A MoOx-modified Ir/SiO2 catalyst with a Mo/Ir ratio of 0.13 (Ir–MoOx/SiO2) exhibits the highest product yield (78–96%) under mild reaction conditions. Controlled experiments using probe substrates reveal that furan ring hydrogenation and C–O hydrogenolysis of saturated and unsaturated furan rings occur in a sequential manner. The carbon atom adjacent to the furan or saturated furan ring of substrates or intermediate compounds undergoes slow C–C bond scission, resulting in a ...

Assessing the Performance of Nano Lubricant on Zinc Aluminium Alloy

In the field of tribology, Zinc Aluminium (ZA) alloys have been widely investigated for their superior wear characteristics. They were found to be suitable alternatives for bearing bronzes for the operating conditions of high mechanical load and moderate sliding speeds. Addition of nano-particles in the lubricating oil (base oil) to enhance the characteristics of the base oil is known as nano lubrication. In this study, sliding wear behaviour of ZA27 was investigated under dry, base oil and nano oil lubrication conditions, by varying load, sliding distance and sliding speed. With the base oil as SAE 40, nano graphite was added in two step method which was further used to identify the lubrication regime under different lubrication conditions. From the limited study of single melt samples, the results appear that the wear behaviour of ZA27 alloy improved under nano lubrication conditions with reduction in operating temperature. It could be observed from SEM images that the presence of nano-particles reduced scarring and wear, leading to enhancement in the tribological performance of ZA27 alloy.

Friction and Wear Properties of Si3N4/TiC Ceramic Composite under Nano Lubrication

The present research evaluated the tribological behavior of Silicon Nitride based composite reinforced with 1 wt. % of Titanium Carbide under dry and lubrication conditions. The lubricant base oil used in this study is 85W140; with nanoparticles additives poly tetra flouro ethylene and Copper (PTFE & Cu) Nanoparticles were added in the base oil to review the performance of the nanoparticles as additives. Ball-on-disc wear tests were conducted to explore the effects of Nano additive in lubricant for ceramic-ceramic tribo-pair. Results showed that friction and wear decreased using nanoparticle in the lubricant oil, as compared to, dry as well as base lubricant oil conditions. It was reported that 0.1 wt. % of PTFE Nano particles and 0.3 wt. % of Cu Nano particles shows minimum value for the coefficient of friction (COF). Rheological studies were also done on these lubricants samples. The findings from the present work encourage the modification of nanoparticle based lubricant to improve the friction and wear properties and to improve the life of the component.

Estimating Antiwear Properties of Ionic Liquids as Lubricant Additives Using a QSTR Model

The antiwear properties of ionic liquids (ILs) as lubricant additives were studied with polyethylene glycol (PEG) used as the lubricant base oil. The quantum parameters of the ILs were calculated using a Hartree–Fock ab initio method. Correlation between the scale of the wear scar diameter and quantum parameters of the ILs was studied by multiple linear regression (MLR) analysis. A quantitative structure tribo-ability relationship (QSTR) model was built with a good fitting effect and predictive ability. The results show that the entropy of the ILs is the main descriptor affecting the antiwear performance of the lubricant system. To improve the antiwear performance of the lubricants, the entropy of the system should be decreased, reducing the system randomness and increasing the system regularity. A major influencing factor on the entropy of a system is the intra- and intermolecular hydrogen bonds present. Therefore, enhanced antiwear properties of lubricants could be achieved with a three-dimensional netlike structure of lubricant formed by hydrogen bonding.

Tribological Conditions Using CO2 as Volatile Lubricant in Dry Metal Forming

Deep drawing is the most important manufacturing process in order to produce sheet metal parts in mass production. In this study, volatile carbon dioxide (CO2) is used as lubricant in order to replace mineral oil-based lubricants. CO2 is injected into the void between the forming tool and the metal part through laser drilled microholes in the forming tool and acts there as a highly efficient lubricant. In order to investigate the tribological conditions during the drawing process, a new test bench having optical access to the CO2 lubricant is designed, built and used in this study. Additionally, the CO2 flow through the microholes is modeled using CFD simulation. Both the experimental and the theoretical study reveal a critical influence of the geometry of the microholes on the phase of the CO2 in the forming tool and on the friction during the drawing process. Thereby, these investigations confirm that the CO2 is in solid and/or gaseous state dependent on the surface pressure and the geometry of the microholes. Consequently, these results support the concept of microstructure-designed forming tools allowing dry metal forming for locally adjusted and environmentally friendly friction conditions.

Evaluation of thermal and oxidative stability of three generations of phenolic based novel dendritic fuel and lubricant additives

Antioxidants, particularly those designed for use in hydrocarbon media, suffer from a variety of limitations including high volatility and poor solubility. Using 2,2-bis(hydroxymethyl)propionic acid as the branching unit, a series of novel dendrons featuring 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic ester chain ends have been synthesised to provide improved solubility of such hindered phenolic antioxidants. The thermal stability, assessed by thermogravimetric analysis, revealed that all the functionalised dendrons have enhanced thermal stability when compared to commercial antioxidants (BHT, Irganox L135 and Irganox L57). Antioxidant ability was evaluated using pressurised differential scanning calorimetry and when blended with a lubricant base oil, at 0.5% w/w, an increase in antioxidant performance was observed when compared to the commercial antioxidants.

Vegetable Oil-Based Lubrication in Machining: Issues and Challenges

The use of vegetable oil as a replacement for conventional mineral-based lubricant has gained many interests in recent years from the machining industries. This is due to the problematic issues with the use of conventional mineral-based lubricant that can cause negative effects on the manufacturing cost, operators’ health and the environmental. As vegetable oil is renewable, biodegradable, and non-toxic and has remarkable tribological characteristic from its triglycerides structure, it has been identified as the best replacement for mineral-based cutting lubricant. However, formulating vegetable oil into machining lubricant has its challenges where it must overcome its nature of poor low-temperature properties and low oxidative stability. Therefore, this paper will elaborate the present issues and challenges in formulating green machining lubricant using vegetable oil and its stand under sustainable machining. This includes the method and technique of formulating vegetable-based lubricant and the output performance obtained from vegetable-based lubricant under machining in comparison to the conventional mineral-based lubricant. The result shows that utilizing the vegetable-based lubricant at minimum quantity has comparable or better performance to conventional mineral-based lubricant in terms of surface finish. Therefore, the use of vegetable oil has its challenges and issues as machining lubricant, but it is one of the current best viable alternatives to the mineral-based lubricant in promoting sustainable machining.

Synthesis of oil-soluble WS2 nanosheets under mild condition and study of their effect on tribological properties of poly-alpha olefin under evaluated temperatures

Abstract A liquid phase method was adopted to encapsulate tungsten disulfide (WS2) nanosheets with oleylamine (OA) at a relatively lower temperature of 200 °C so as to acquire good solubility in organic lubricant base oil. The effect of OA-modified WS2 nanosheets on the tribological properties of poly-alpha olefin (PAO6) in a wide temperature range was examined with a four-ball machine and a UMT TriboLab test rig in a piston ring-cylinder liner contact mode. Results indicate that the OA-modified WS2 nanosheets added in PAO6 oil are able to improve the tribological properties of the lubricant base oil significantly at elevated temperatures; and they are advantageous over zinc dialkyldithiophosphates in improving the anti-wear ability of PAO6 from room temperature to 300 °C.

Morphology control synthesis of iron-rich Sinai clay by novel O, N, S-heterocyclic moieties: Magnetic organoclays for various strategic uses in lubricating oilfield industry

Herein, iron-rich Sinai clay (ATT) was chemically-modified by inventive azacoumarin (Az), spiropyrrolidine (Sp) and imidazothiadiazole (Im) compounds forming clay-containing hematite particles. Interplay between the chemistry of organo-compounds and the clay-sheet structure was interpreted by running DFT-calculations and physicochemical studies (XRD, FTIR, DLS, HR-TEM, N2-physisorption and magnetic analyses). The planar/nucleophilic Az-molecules preferentially occupied clay interlayer-spacings and weaken the combination between silicate-layers, forming large-sizes of completely intercalated clay layers of mesoporous structure with poor physicochemical properties. Besides, angstrom-size hematite particles (<20 Å) appeared in these spacings. The non-planar/electrophilic Sp-molecules promptly attack silicate-layers to form low-sized fully exfoliated clay particles with micro/meso- porous structure of developed magnetic and physicochemical properties. The planar Im-molecules of nucleophilic/electrophilic character enthused construction of intercalated/exfoliated clay system over which magnetic hematite-nanospheres (~10 nm) were splattered. A road ahead to setting-up these organoclays in lubricant-oil industry was planned. Magnetic Sp/ATT organoclay was promisingly behaving as base-oil lubricant additive of increased-efficiency (164%) to oil electrical property. Magnetic Im/ATT organoclay was candidate for being an easily-separable waste-oil regeneration agent, while Az/ATT was highlighted as efficient catalyst for acetic-acid production from waste-lubricant-oil (45% yield). Future studies to applicability of iron-rich organoclays in lubricant-oil industry are optimistic and withstand overwhelmingly positive thus far.

Insights into friction dependence of carbon nanoparticles as oil-based lubricant additive at amorphous carbon interface

Solid-liquid lubricating system, composed of amorphous carbon (a-C) and fluid lubricant, arouses enormous interest due to its excellent tribological performance. However, the friction response of a-C induced by carbon nanoparticles including graphene (G), fullerene (C60), and carbon nanotube (CNT) as oil-based additives and the underlying friction mechanism in synergism with base oil are unclear. Herein, using reactive molecular dynamics simulation, we comparatively investigated the friction dependence of G, C60, and CNT additives at the a-C interface. Compared with pure base oil, G results in the friction coefficient reduced by 90%, which exhibits the best anti-friction ability than C60 and CNT. The interfacial structure transformation, the interaction between the a-C, base oil, and additives, and the mobility of base oil indicate that being different with C60 or CNT which cross-links both the mating a-C surfaces, the G only anchors to one a-C surface to form a block physical protective film, which significantly smooths a-C surface, weakens the intermolecular interaction of a-C with base oil, and thus promotes the mobility of oil molecules, presenting a synergistic effect on the friction performance. These address the fundamental understanding on carbon additive-induced friction mechanism, and guide the design of a-C/lubricant composite system for tribological applications.

The selective determination of potentially carcinogenic polycyclic aromatic compounds in lubricant base oils by the DMSO extraction method IP346 and its correlation to mouse skin painting carcinogenicity assays

Mineral oils are produced by vacuum distillation of crude oil at temperatures from ∼300 °C to ∼600 °C. Subsequent refining processes to eliminate the carcinogenic potential of mineral oils (by extraction and/or hydrotreatment) are based on the principle of removing substances associated with carcinogenic activity; i.e. PAC (polycyclic aromatic compounds), which include PAH and N or S heterocycles. Traditionally, the carcinogenic potential of the refined product was tested in the mouse skin painting assay. This bioassay is considered the gold standard for petroleum derived products since it uses the most sensitive species and route of exposure, and because mice and humans develop the same type of skin tumors it is a relevant model to assess the carcinogenic potential of mineral oils.Mouse skin painting studies have also been important in distinguishing two types of aromatic compounds found in mineral oil. The first type includes the 3–7 ring PAC associated with potential carcinogenic effects found in the 340–535 °C boiling range, which are removed by refinement. The second type includes highly alkylated aromatic compounds (predominantly 1–2 rings) which are not bioactivated and non-carcinogenic, which are typical of a refined oil.Because mouse skin painting studies are time consuming, a DMSO based method was developed that is capable to distinguish these two types of aromatics. Although this industry method, known as the IP346, has been applied for more than 30 years, the background experimental data underlying its development has not yet been published.This paper presents and discusses the chemical and biological features of mineral oil PAC structures assessed by IP346, especially the crucial role of the DMSO extraction step which allows to discriminate between the two types of aromatics. The DMSO selectivity towards the toxicological relevant PAC is discussed by comparing the composition of the DMSO extract of a distillate aromatic extract and mineral oils of varying viscosities and refining conditions. PAC which have >3 rings (naked or partially alkylated) are preferentially encompassed by the DMSO extract, whereas those PAC which have relatively long alkyl side chains are not. Thus, according to the IP346, refined oils will have lower levels of DMSO extractable material compared to less refined oils.DMSO selectivity towards the potentially carcinogenic >3 ring PAC makes the IP346 method therefore highly correlated to the outcome of mouse skin painting studies, using a pass/fail dichotomy. The accuracy, including the false negative results of the IP346 in the prediction of mineral oil carcinogenicity is discussed.The DMSO based IP346 is thus a simple but clear reflection of refinement efficacy. It links manufacturing conditions to carcinogenic potential of an oil, supported by solid physical-chemical and toxicological associations. In Europe it is the only legally binding method to assess, classify and label lubricating base oils and inherently more reliable for hazard assessment than the determination of an arbitrary selection of PAH.

Effect of Carbon Diffusion on Friction and Wear Behaviors of Diamond-Like Carbon Coating Against Germanium in Boundary Base Oil Lubrication

Diamond-like carbon (DLC) coatings are designed to work under severe lubrication conditions. Depending on working environment, lubrication condition, and counterpart material, DLC coatings can exhibit crucial variations in their tribological behaviors. In the search of a counterpart material to improve tribological performances of DLC coatings in desired environment, we found out in previous work that carbon diffusion is an important parameter that influences the tribological behaviors of amorphous hydrogenated (a-C:H) coating in boundary lubrication. a-C:H coating exhibits high wear against steel counterpart material that has a high carbon affinity/solubility, while its exhibits lower wear against chromium counterpart material that has lower carbon affinity/solubility than steel. These recent findings imply that consideration of the carbon affinity/solubility when choosing a counterpart material for a-C:H coating in boundary lubrication might be of significant importance to improve tribological performances of a-C:H coating. This research investigates tribological behaviors of a-C:H coating against germanium counterpart material that has extremely low carbon affinity/solubility. Results show that there is no atomic interaction between a-C:H coating and germanium during friction and wear test, followed with a very low wear of a-C:H coating.

Highly Selective Synthesis of Polyalkylated Naphthalenes Catalyzed by Ionic Liquids and Their Tribological Properties as Lubricant Base Oil

AbstractNaphthalene, one of the most important components in coal tar, is now in serious surplus. The Ionic Liquids (ILs) of Et3NHCl‐AlCl3 were used as Lewis acidic catalysts for an alkylation reaction of naphthalene with medium‐chain alfa‐olefin (n‐hexene/n‐octene) to produce a lubricating base oil. Polyalkylated naphthalenes consisting of tri‐ and tetra‐alkylnaphthalenes can be obtained with a selectivity as high as 98% under mild conditions. We propose a plausible mechanism for the alkylation process catalyzed by Lewis acidic AlCl3 derived from the dissociation of [Al2Cl7]− anion in ILs. The physicochemical properties and tribological performances of synthesized polyalkylated naphthalenes, and especially poly‐octylnaphthalenes, are found to exhibit the properties of lubricating base oils, and are comparable to those of the conventional cycloalkyl base oil.

Biolubricant production from palm stearin through enzymatic transesterification method

The present study aims to develop environmentally benign lubricant from by-product of palm oil processing through enzymatic reaction. Candida antartica lipase was employed as catalyst to transesterified reaction between palm stearin and methanol in a solvent-free system. The reaction parameters were varied in terms of molar ratio of methanol-to-palm stearin (3:1 to 8:1), temperature (between 40 and 70 °C), time (2–12 h) and concentration of catalyst (from 2 to 10 wt.%). Enzymatic transesterification demonstrated around 95.26% maximum yield of palm stearin methyl ester under the following conditions: 4:1 methanol-to-PS molar ratio, reaction temperature of 60 °C, reaction time of 8 h and 6.0 wt. % of lipase concentration. The Structural modification of palm stearin resulted in improvement in both physicochemical and tribological properties. The produced biolubricant demonstrated superior viscosity index (>120) and friction properties over commercial mineral oil-based lubricant. This study showed that lubricant derived from palm stearin has a great potential to be used as a base stock in regard to favourable biodegradability and tribological performance.

Cholesteryl Liquid Crystals as Oil-Based Lubricant Additives: Effect of Mesogenic Phases and Structures on Tribological Characteristics.

Mechanical operation could be seriously affected by friction and controlling it by oil lubrication has been considered as an effective way. Good lubricant additives are very necessary to avoid the friction damages, and to find or design new additives is always a challenge. In this study, a systematic investigation of using cholesteryl liquid crystals (LCs) as lubricant additives to obtain exceptional tribological behaviors was performed. In total, four cholesteryl LC compounds were synthesized targetedly and their thermal and mesogenic properties were studied to see the inherent relationship between the mesogenic phases and antifriction and antiwear performance. Through a series of tribological and related tests, including the UMT TriboLab test, three-dimensional optical microscopy, oil film thickness and viscosity tests, etc., the effect of the mesogenic phases and structures of the synthesized cholesteryl LCs on their tribological properties as lubricant additives was investigated and a related mechanism was analyzed. The result showed that within and close to the mesogenic phase temperature ranges, which we called as effective temperature ranges of LC additives ( TEF), the LCs presented better tribological behaviors, meaning they could be used in special lubrication applications that need to be confined in certain temperature scopes; however, the ester groups with long alky tails could help dissolve in base oils and adsorb onto the friction pairs. Among the four LCs, LC-D with a long perfluoroalkyl tail brought widest mesogenic phase with considerably enhanced lubrication performance and increased oil film thickness, viscosity, and thermal stability, indicating that the perfluoroalkyl group could be well used in the structural modification of LC additives to give unexpected tribological performance. This study, in conjunction with our experimental data, suggested that the liquid crystals may be evaluated as potential friction modifiers for temperature-controllable lubrication and also shed a fresh light on the development of novel liquid crystal lubrication materials.

Green Refining of Waste Lubricating Oil: A China Perspective

Presently, many regeneration processes of waste lubricating oil, such as catalytic hydrogenation, are available. However, some of these processes are highly costly and not suitable for Chinese economic conditions, and some may produce contaminated impurities such as acid slag, which cannot meet environmental protection requirements. This study aims to develop a green process for the regeneration of waste lubricating oil into a base oil, which should meet the requirements of green chemistry, have the characteristics of simple operation, low cost, less pollution and high recovery rate, and turn wastes into renewable resources. The new process developed via this research has three stages. First, mechanical and large particle impurities in the waste lubricating oil were removed by pretreatment. Second, most of the colloid and asphaltene were removed by thermal extraction and sedimentation. Finally, the activated bleaching earth was used to further purify the waste lubricating oil. The performance evaluation of the finally obtained lubricating base oil conformed to the standard of the HVI-100 lubricating oil. The total recovery rate of the process was about 63.5%. Citation: Â Wu, J., Li, B., Wang, W., Yang, S., Liu, P., Yang, C., and Ding, Y. (2019). Green Refining of Waste Lubricating Oil: A China Perspective. Trends in Renewable Energy, 5, 165-180. DOI: 10.17737/tre.2019.5.2.0084

Effect of addition of copper nanoparticles on the tribological behavior of macadamia oil at different sliding speeds

ABSTRACTEnvironment degradation and non-biodegradability are the major problems associated with mineral oil-based lubricants. Non-edible vegetable oils are one of the suitable substitutes for the mineral oils. In this study, macadamia oil was used as lubricant to check its feasibility for the tribological behavior. Copper nanoparticles are added to the macadamia oil on weight-percentage basis. The variation of Cu nanoparticles concentration with macadamia oil was evaluated for coefficient of friction and wear analysis. Minimum coefficient of friction and wear was observed at 0.3% concentration which gets further increased at 0.4% concentration. Kinematic and dynamic viscosity reduces with temperature and minimum value was observed at bare macadamia oil. The smooth surface of the pin was observed at 0.3% Cu nanoparticles concentration with comparison to bare macadamia oil.