Friction, Wear and the Role of Additives in Controlling Them

Bovington, C. H.

doi:10.1023/b105569_3

Cited by 16 publications

(18 citation statements)

References 39 publications

(43 reference statements)

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“…In the monolayer, the carboxyl groups are oriented towards the metal surface and the aliphatic tails to the concrete. The adsorption energy of this monolayer ranges from 10 to 30 kJ mol -1 [4] and corresponds to a hydrogen bond. The molecular chains of glycerol esters in the mono and multi layers are stabilized by van der Waals cohesion forces, which makes the film more resistant to stress in comparison with the film formed by mineral-based release agents [8].…”

Section: Discussionmentioning

confidence: 99%

“…The molecular chains of glycerol esters in the mono and multi layers are stabilized by van der Waals cohesion forces, which makes the film more resistant to stress in comparison with the film formed by mineral-based release agents [8]. Differing degrees of separation of the surfaces occur depending on the velocity of the concrete flow, the viscosity of the oil, the temperature and pressure (load) to which the film is subjected, and the surface structure of the materials in relative motion [4]. The minimum friction coefficient is observed in the elastohydrodynamic regime, where the thickness of the lubricating film is typically between 0.5 and 5 lm [23].…”

Section: Discussionmentioning

confidence: 99%

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Laboratory and field performance of biodegradable release agents for hydraulic concrete

et al. 2015

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Raw vegetable oils and their emulsions have been used as biodegradable release agents for concrete. However, there is no scientific explanation linking the chemical composition to their release performance. The present study was divided into two phases. In the first phase, different vegetable oils with varying degrees of refinement were chemically characterized by middle range Fourier transform infrared spectroscopy (Mid-FTIR), and their viscosities were measured. For comparison purposes, two commercial release agents based on mineral oil were used. In the second phase, emulsions containing bleached soybean oil, water and some emulsifiers were prepared. The performance of the oils and emulsions as demolding agents in steel/concrete interfaces was measured by visual rating, image analysis and bond strength. The results indicate that almost all of the vegetable oils showed better performance than that of the two mineral oil-based agents, which is explained by the higher affinity of glycerol esters for metal surfaces and higher intermolecular interactions. The Mid-FTIR espectrum analysis indicates that oils having larger absorption areas under the curve at the methylene group exhibit better performance as release agents. In addition, the Mid-FTIR analysis allowed identification of the main molecular groups and differentiation between oil samples. In the second phase, the water/oil emulsion stabilized with organophilic clay performed the best. In addition to the lubricating effect of the emulsion, the better performance was also due to the saponification reaction between the acylglycerides and the Ca(OH) 2 . The tangential adhesion was reduced to approximately 64 % compared to that of a mold without a release agent.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Laboratory and field performance of biodegradable release agents for hydraulic concrete

et al. 2015

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“…In general, the tribological characteristic of a certain lubricant is evaluated by the combination of its AW performance and friction-reducing performance [1].…”

Section: Friction-reducing Performancementioning

confidence: 99%

“…It is well known that lubricant additives are practically used to improve the tribological characteristic of the base stock, especially at some rigorous conditions [1,2]. But most traditional lubricant additives contain harmful components, such as Cl, P, and some heavy metals.…”

Section: Introductionmentioning

confidence: 99%

Tribological Behavior of Some Long-Chain Dimercaptothiadiazole Derivatives as Multifunctional Lubricant Additives in Vegetable Oil and Investigation of their Tribochemistry Using XANES

et al. 2012

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A series of novel long-chain dimercaptothiadiazole derivatives are prepared and used as antiwear (AW) and extreme pressure (EP) additives in vegetable oil, and their tribological performance is tested by using a four-ball tester. In order to understand the friction process further, X-ray absorption near edge structure spectroscopy is adopted to analyze the chemistry of tribofilms under AW/EP regime, and meanwhile thermal films are also considered for comparison. These derivatives are capable in improving the tribological characteristic of the base stock, and disubstituted derivatives are more effective than other derivatives. Though disubstituted derivatives and disubstituted polysulfur derivatives all fail in improving tribological performance at 0.1 wt%, they are still helpful at other additive concentrations. All these long-chain thiadiazole derivatives, in particular the disubstituted polysulfur ones, are good at improving the EP characteristic of the base colza oil. Thermal films generated from these derivatives are composed of ferrous sulfate and a small amount of adsorbed organic sulfide. During the heating process, these long-chain derivatives easily undergo thermal oxidation to generate high-valent sulfate on the metal surface. Ferrous sulfide is the main component of tribofilms generated by these derivatives, while ferrous sulfate in these films almost vanishes at 1.0 wt%. These long-chain derivatives tend to react with metal surface to generate low-valent sulfide under rubbing conditions. On the other hand, ferrous sulfide is also the main component of EP films generated by monosubstituted derivatives and disubstituted polysulfur derivatives at 1.0 wt%. But the EP films formed by disubstituted derivatives are composed of ferrous sulfide and ferrous sulfate.

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“…Lubricity additives are one of the most important classes of all additives in lubricant formulations used for improving tribological characteristics of the base stocks [1]. Traditional lubricity additives like zinc dialkyldithiophosphate (ZnDDP) contain S, P, Zn, etc.…”

Section: Introductionmentioning

confidence: 99%

An Investigation on the Lubricity Characteristics of Polyethylene Glycol Blends with Cellulose Palmitates

Singh

Kukrety

Singh

et al. 2015

Waste Biomass Valor

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Three cellulose palmitate samples, viz CellPlam-A, Cell-Palm-B and Cell-Palm-C, were synthesized by known esterification reaction between microcrystalline cellulose and varying molar ratios of palmitoyl chloride (CH 3 (CH 2 ) 14 COOCl). A combination of N,N-dimethylacetamide (DMAc) and lithium chloride (LiCl) is used as a solvent, while DMAP (4-dimethylaminopyridine) was used as catalyst. The three samples with different degree of substitution (DS) were then characterized using infrared, nuclear magnetic resonance spectroscopy, elemental analysis (CHN), thermogravimetry, scanning electron microscopy and X-ray diffraction to confirm the conversion of the cellulose into the cellulose fatty ester. Cell-Plam-A, Cell-Palm-B and Cell-Palm-C were found to have DS values 1.85, 2.37 and 2.63, respectively. The synthesized cellulose palmitate samples were then tested for lubricity properties in terms of wear scar diameter (WSD) and friction coefficient using a high-frequency reciprocating rig following modified ASTM D6079. It was found that the 3 % Cell-Plam-C in PEG-200 reduces the WSD from 560 to 503 lm, while the average friction coefficient decreases from 0.079 to 0.048.

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Friction, Wear and the Role of Additives in Controlling Them

Cited by 16 publications

References 39 publications

Laboratory and field performance of biodegradable release agents for hydraulic concrete

Laboratory and field performance of biodegradable release agents for hydraulic concrete

Tribological Behavior of Some Long-Chain Dimercaptothiadiazole Derivatives as Multifunctional Lubricant Additives in Vegetable Oil and Investigation of their Tribochemistry Using XANES

An Investigation on the Lubricity Characteristics of Polyethylene Glycol Blends with Cellulose Palmitates

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