Lithium Grease Research Articles

Eco-Friendly Multipurpose Lubricating Greases from Vegetable Residual Oils

Environmentally friendly multipurpose grease formulation has been synthesized by using Jatropha vegetable residual oil with lithium soap and multifunctional additive. The thus obtained formulation was evaluated for its tribological performance on a four-ball tribo-tester. The anti-friction and anti-wear performance characteristics were evaluated using standard test methods. The biodegradability and toxicity of the base oil was assessed. The results indicate that the synthesized residual oil grease formulation shows superior tribological performance when compared to the commercial grease. On the basis of physico-chemical characterization and tribological performance the vegetable residual oil was found to have good potential for use as biodegradable multipurpose lubricating grease. In addition, the base oils are biodegradable and non toxic.

A study on tribological behaviours of ZDDP in polymer thickened lubricating greases

Zinc Dialkyl Dithiophosphate (ZDDP) is a well-known multifunctional additive for soap based lubricating greases. Polymers are being studied for their performance as lubricating grease thickeners and rheology modifiers. In this work the tribological study of ZDDP was carried out in polypropylene (PP), maleated polypropylene (mPP) and linear low density polyethylene (PE) thickened lubricating greases. Performance of lithium grease was taken as a reference. The tribological properties were evaluated using a four ball tester for EP properties and Optimol SRV-III machine for coefficient of friction. The mechanism of action of ZDDP in polymer greases was established through analysis of the worn surface of steel balls with scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDAX). The results show that the performance of ZDDP depends on the thickener system. The antiwear and EP property exhibited by ZDDP varies from polymer to polymer. Poor performance was observed with PP type thickener whereas performance in PE and lithium grease was comparable. Copyright © 2015 John Wiley & Sons, Ltd.

Lubrication properties of modified lard and rapeseed oil greases with sodium and lithium thickeners

Purpose – The purpose of this paper is to conduct research on the possibility of improving the tribological and utilization properties of lard and rapeseed oil bio-based greases by mixing it with ethanol and selection of thickener and modification with special biological additives. Design/methodology/approach – Rapeseed oil- and lard-based greases with sodium and lithium soap thickeners were mixed with either water or ethanol and modified with a special biological anti-wear additive. Tribological properties of modified lubricants evaluated on a four-ball machine. Findings – Rapeseed oil- and lard-based greases suspended in ethanol and modified with bio-additive have the same wear resistance as the industrial non-biological lubrication grease and much higher wear resistance as bio-based reference grease. The tribological efficiency of the additives is higher in greases of rapeseed oil and less efficient in lard-based greases. Oxidation and wear tests show that investigated bio-based greases have comparatively stable tribological properties also after their aging. Modified greases have sufficient consistence according penetration measurements and high thermal resistance according drop-point temperature measurements. All produced experimental greases pass within the category of the easily degradable materials. Originality/value – The greases mixed with the ethanol make possible to form more homogeneous and stable grease mixture. Modified bio-based greases have significantly higher wear resistance as bio-based reference grease, their lubrication properties are stable also after the aging and are categorized as easily degradable materials.

Production of biodiesel with lithium glyceroxide

Alkoxide/hydroxide catalysts were synthesized by heating aqueous solutions of lithium hydroxide with glycerol under vacuum. The dehydration rates for different mole ratios of lithium hydroxide to glycerol were 3:1<2:1<1:1. Temperature showed a clear effect on dehydration rate while the effect of vacuum was less important. The resulting base catalysts were characterized by X-ray powder diffraction (XRD), Nuclear Magnetic Resonance (NMR), and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). Catalysts prepared with 2:1 and 3:1 mole ratios comprised mono and a novel di-lithium substituted glyceroxide, as well as lithium hydroxide. Transesterification reactions of canola oil with methanol were conducted using equivalent mole amounts of sodium methoxide (0.0104mol, 0.5wt.%) and glycerol lithium base catalysts (0.0104mol, 0.2wt.%). The lithium glyceroxide/hydroxide catalyzed rapid transesterification though the reaction was slower than observed for sodium methoxide. All catalysts resulted in a high methyl ester yield (>99wt.%). The catalytic activity was 1:1<2:1<3:1 (lithium hydroxide:glycerol), and was not significantly influenced by conditions used in preparing the catalyst. The crude glycerol remaining after the lithium glyceroxide catalyzed reaction was reacted with free fatty acid to prepare glycerol insoluble lithium soap. A recovery of most of the lithium (85%) as a lithium soap was possible by filtration of the glycerol fraction producing a substantially ion free glycerol solution. This novel reaction afforded glycerol that was substantially free of catalyst and a value added lithium soap suited for use as commercial grease.

Study of Conductive and Friction Properties of Grease Containing Carbon Black Additive

The conductive and fiction properties of overbased calcium sulfonate complex grease and lithium grease containing carbon black (CB) additive were investigated in detail. The results indicate that CB can dramatically improve the conductivities of the greases. Also the tribol-test results indicate that the CB can dramatically improve the tribological properties of the greases. The lithium greases containing CB, have better tribological properties than overbased calcium sulfonate complex greases. Among the lithium greases, 5% CB contained grease performs the best friction reduction properties, and among the overbased calcium sulfonate complex greases, 6% CB contained grease performs the best friction reduction properties.

Synthesis and effect of nanogrease on tribological properties

This study aims to improve the lubrication performance of grease by letting Tin (Sn) nanoparticles dispersed in lithium grease, and tests the tribological properties of nanogrease. We use the chemical reduction method to prepare Sn nanoparticles of different particle sizes. After applying Sn nanogrease on the self-made pin-on-disk tribology tester that meets ASTM G99 standards, this study explores the properties of wear resistance and friction decreases of nanogrease with nanparticles of different particle sizes, concentrations and loads. Experimental results show that adding Sn nanoparticles to lithium grease can enhance wear resistance and reduce the coefficient of friction. Under the condition that Sn nanoparticles are in smaller particle size and at a concentration of 1.0 wt.%, friction and wear can both be reduced significantly. Compared to pure lithium base grease, when the grease has loads of 39.2 N and 49 N respectively, the friction coefficients reduce from 0.05434 to 0.01985 and from 0.05635 to 0.02155, with reduction rates at around 63.5% and 61.8%, respectively. Moreover, wear scar diameters decrease from 0.7651 mm to 0.3145 mm and from 0.8263 mm to 0.3658 mm, with reduction rates at around 58.9% and 55.7%, respectively. Additionally, through SEM photographs, this study proves that Sn nanoparticles produce filling and sedimentary effects on wear surfaces.

Tribological Properties of Layered a-Zirconium Phosphate as Lithium Grease Additive

Tribological Properties of Layered a-Zirconium Phosphate as Lithium Grease Additive

Effect of heat treatment on the lubricating properties of lithium lubricating grease

The lubricating properties of lithium grease are improved by fibrous entangled variations rather than chemical structural variations after being heated.

Lubrication Life and Deterioration Process of Lithium Soap Greases for Ball Bearings

Lubrication Life and Deterioration Process of Lithium Soap Greases for Ball Bearings

Evaluation of Calixarenes as Antioxidants in Complex Lithium Grease

Abstract The thermal stability and antioxidant performance of 4-tert-butylcalix[4]arene (B4) and 4-tert-butylcalix[8]arene (B8) were investigated and compared with those of 3,5-di-tert-butyl-4-hydroxytoluene (BHT). Both B4 and B8 were superior to BHT in thermal stability. In addition, B4 and B8 also showed obvious antioxidant capacity in complex lithium grease (LG). Hence, calixarenes are promising antioxidants with good thermal stability and antioxidation performance.

Anti-wear and friction properties of nanoparticles as additives in the lithium grease

TiO2/CuO nano-particles were dispersed into lithium grease to improve the lubricating properties of the greases. Then, the process of sliding friction was tested. The friction force of the contact interface between a ball and a flat surface with TiO2/CuO nano-grease was measured for a ball on a flat sliding wear tester. The worn surface was examined by a surface roughness tester and scanning electron microscopy (SEM). The tested lithium grease was synthesized with 0.5wt.%, 1.0wt.%, 1.5wt.% and 2.0wt.% TiO2/CuO nano-particles. Results indicate that the TiO2/CuO nano-particle additives can improve the wear resistance of lithium grease and decrease the friction coefficient. In addition, the results show that a 1.0 wt% content of TiO2 nano-particles is the most efficient in reducing friction and wear, and can significantly reduce the friction coefficient of the rubbing interface by about 40%, according to the friction tests. The wear of the lithium grease with a 2.0wt.% content of CuO nano-particles added can reduce wear about by 60% in comparison with lithium grease. Furthermore, the SEM analysis results demonstrate that the addition of tribo-film forms and TiO2/CuO nano-particles on the worn surface is responsible for the decrease in friction and wear.

Tribological Behavior of Carbon Nanotubes as an Additive on Lithium Grease

Carbon nanotubes (CNTs) with 10 nm average diameter and 5 μm in length were synthesized by electric arc discharge. The morphology and structure of CNTs were characterized by high resolution transmission electron microscopy (HRTEM) and X-ray powder diffraction. The tribological properties of CNTs as an additive on lithium grease were evaluated with a four ball tester. The results show that the grease with CNTs exhibit good performance in antiwear (AW) and decrease the wear scare diameter (WSD) about 63%, decrease friction reduction about 81.5%, and increase the extreme pressure (EP) properties and load carrying capacity about 52% with only 1% wt. of CNTs added to lithium grease. The action mechanism was estimated through analysis of the worn surface with a scanning electron microscope (SEM) and energy dispersive X-ray (EDX). The results indicate that a boundary film mainly composed of CNTs, Cr, iron oxide, and other organic compounds was formed on the worn surface during the friction process.

Studies of the Kinetics of Lithium Grease Microstructure Regeneration by Means of Dynamic Oscillatory Rheological Tests and FTIR–ATR Spectroscopy

As part of this research, the kinetics of soap grease thickener microstructure regeneration during 24-h relaxation after 1-h shearing were studied. A lubricating grease, based on mineral oil ORLEN OIL SN-400, containing associated molecules of lithium 12-hydroxystearate was subjected to analysis. Rheological dynamic oscillatory and FTIR–ATR (Fourier Transform Infrared Attenuated Total Reflectance) spectroscopy were used to study the kinetics of thickener microstructure regeneration. Changes in the values of storage modulus G′ and loss modulus G″ of the investigated grease during its relaxation in the linear viscoelastic range were examined. In addition, the mechanical stability of the thickener microstructure at a variable oscillation frequency was tested, and changes in the cohesive energy of the grease versus the latter’s relaxation time were assessed. FTIR–ATR spectroscopy was used to study the physicochemical interactions between the associated molecules of lithium 12-hydroxystearate. Infrared bands were assigned to the vibrations of the particular functional groups of the grease components, and the spectral parameters in the absorption spectra in the range of 700–3,700 cm−1 were examined. The studies carried out using the two investigative methods have revealed that the intensity of thickener microstructure regeneration was the highest in the first hour of grease relaxation after shearing. In this time interval, the largest changes in the vibrations of the main functional groups of the grease components were observed. In the next hours, the kinetics of thickener microstructure regeneration were substantially lower.

Comparison of Several Common Types of Grease Performance Based AR 2000ex Remoter

Different substrates grease composition due to differences in their varying degrees of change in viscosity after shearing studied the rheological properties of three different substrates grease. Used AR2000ex rheometer, investigated the effects of different sessions on the rheological properties of the grease. It was found that the stability of lithium grease from the grease either stops working, or their work situation by cutting lubrication properties, are superior to calcium-based grease and urea-based grease. Urea-based grease on the shear sensitivity is smaller relatively than lithium and the recovery of viscosity after being subjected to continuous shear weak, easily lost during use based the grease flow curves with Herschel-Bulkley model, and the impact performance of the grease thixotropic grease is yield stress.

Research on Micro-Pool Drill and its Drag Reduction Effect

To the problem that drills are easy to break off during working, apply micro-pool lubrication technology in the field of drill cutting. Drill a micro hole with a diameter of 70μm, a depth of 30μm and a space of 100μm on the oblique plane of the front-end blade of a common drill with HDM-50 semiconductor side pump YAG laser to form a micro-pool drill which constitutes a contrast group with a common drill. Lubricate both of the two kinds of drills with 2# micro high pressure lithium grease and use them to drill holes on a 25mm A3 plate. The experiment indicates that: when the depth of the processed holes are 5mm, the average powers of the micro-pool drill at the speeds of 600R/min, 850R/min and 1100R/min are 3.243% higher than those of the common drill; and the average power of the micro-pool drill is 4.547% lower than that of the common drill when the depth is 12mm; and the average power of the micro-pool drill is 4.09% lower than that of the common drill when the depth is 22mm.

Rheological and Tribological Characterization of a New Acylated Chitosan–Based Biodegradable Lubricating Grease: A Comparative Study with Traditional Lithium and Calcium Greases

This work compares the thermal, rheological, and tribological properties of a new gel-like biodegradable formulation, prepared using an acylated chitosan thickener and castor oil, with properties exhibited by two conventional greases thickened with lithium and calcium soaps, respectively, taken as benchmarks. Thermogravimetric (TGA), rheological (small-amplitude oscillatory shear [SAOS], rheodestruction, and viscous flow) and tribological (friction and wear analysis) tests, as well as roll-stability measurements were carried out to characterize the three grease samples. In addition, infrared spectroscopy and differential scanning calorimetry (DSC) were used to chemically characterize the acylated chitosan thickener agent. From a thermogravimetric point of view, the new formulation displayed better thermal resistance than the calcium and lithium lubricating greases. The evolution of the linear viscoelasticity functions with frequency and viscosity values in the shear rate and temperature ranges studied were similar to those obtained with the commercial lubricating greases. However, the linear viscoelasticity functions of the biodegradable formulation were slightly more affected by temperature. The mechanical stability behavior and recovery of the rheological functions found in the biodegradable formulation were also better than that exhibited by the calcium-based grease. However, the friction coefficient measured at low rotational speed is slightly higher than that obtained with the benchmarks, with similar or lower values obtained at a high rotational speed. Resulting wear marks obtained after the frictional tests using the acylated chitosan–based grease were larger than those obtained with the commercial greases.

Tribological behaviours of ultrafine Sn/heat treated serpentine powder in grease

In order to improve the tribological performance of traditionally based lithium grease, ultrafine serpentine powder of 0·33 μm and Sn powder of 120 nm were prepared by ball mill and direct current arc plasma evaporation respectively. The milled serpentine powder was heat treated at 200, 500, 600 and 800°C in a muffle furnace separately with a four-ball wear test. Then, the tribological behaviours of lithium grease modified with complex powder with different ratios of ultrafine Sn/heat treated serpentine were investigated, and the effects of total concentration and load were discussed too. The optimal performance was achieved by the compound grease with 1 wt-% complex powder and 1∶1 Sn/serpentine powder (heated at 200°C). The friction coefficient and wear scar diameter decreased 25·5 and 42·5% respectively under 392 N compared with pure grease. The compound grease is much more suitable under high load rather than low load.

Grease thixotropy: evaluation of grease microstructure change due to shear and relaxation

Purpose – The thixotropy of lubricating grease thickened with lithium 12-hydroxystearate with mineral base oil was investigated. The thixotropy has a significant influence on the flow resistance and pressure drop in the structural components of lubrication systems, which is of major importance as today the latter are being centralized and automated. The paper aims to discuss these issues. Design/methodology/approach – Rheometer studies on thixotropy were carried out and the grease microstructure was visualized using atomic force microscopy (AFM). Total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to study the physicochemical interactions which indicate the disintegration and recovery of the grease microstructure. Findings – A qualitative assessment of the physicochemical interactions between lithium soap floccules was made and a theory of the self-ordering effect of lithium 12-hydroxystearate associated molecules during shearing and their aggregation and flocculation during relaxation has been proposed. Originality/value – Because of the complexity of the disintegration and recovery of the lubricating grease thickener microstructure, there is still limited physical understanding of the mechanism of this process. Therefore, the present research was undertaken to identify the phenomena involved.

Tribological behaviors of some novel dimercaptothiadiazole derivatives containing hydroxyl as multifunctional lubricant additives in biodegradable lithium grease

Purpose – In order to meet the requests of exploring environmental-friendly and multifunctional lubricant additives, some novel dimercaptothiadiazole derivatives containing hydroxyl are prepared and used as antiwear (AW) and extreme-pressure (EP) additives in biodegradable lithium grease. The paper aims to discuss these issues. Design/methodology/approach – The tribological performances of the grease samples containing these derivatives are evaluated by using a four-ball tester. X-ray absorption near edge structure (XANES) spectroscopy is used to analyze the chemistry of tribofilms under AW/EP regime, and thermal films are also considered for comparison. Findings – The tribological tests show that these derivatives are all effective in reducing wear, especially at lower additive concentrations, but they are basically failed in reducing friction. They are also helpful in improving the EP characteristic of the base grease. The thermal films generated by these derivatives are composed of adsorbed organic sulfide and ferrous sulfate, though for short-chain derivatives, organic sulfide is the only component at 5.0 wt.%. Ferrous sulfide is the main component of the tribofilms formed by these derivatives at various additive concentrations. But for short-chain derivatives, these tribofilms consist of ferrous sulfide and ferrous disulfide at 5.0 wt.%, and the appearance of disulfide suggests that the interfacial temperature between the upper ball and three lower balls under these conditions is considerably low. The EP films generated by short-chain derivatives are all composed of organic sulfide and ferrous sulfide, while for long-chain derivatives, ferrous sulfide is the main component. Originality/value – These low-toxic and oil-soluble dimercaptothiadiazole derivatives are effective in improving the tribological characteristic of the biodegradable lithium grease, and these heterocyclic derivatives may be good substitutes for some harmful traditional additives.

Analysis of Rheological Properties of MR Fluid Based on Variation in Concentration of Iron Particles

The main aim of this study is to synthesize magneto-rheological fluid in laboratory using silicon oil as carrier oil and it is mixed with variation in concentration of iron particles of size around 4-9 µm, fine lithium grease is used as surfactant. Prepared MR fluid is tested under plate and cone type rheometer for finding is rheological properties like shear stress, shear rate, shear viscosity, storage modulus and loss modulus.