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PubMed1978

[Biomechanical efficiency and biocompatibility of lubricating sprays PTFE or graphite (author's transl)].

The screws and plates used in operative treatment of fractures cause moments of friction between the bone screw head and the bone plate hole during the tightening of the screws. This results in hidden damage to the grinding metal surfaces, with the danger of erosion corrosion and in a reduction in the screw force. By covering the screw heads with the lubricating sprays PTFE or graphite friction was significantly reduced, the screw force increased by 40% and extensive damage to the surfaces avoided. Lubricating sprays or their extracts, in fetal calf serum or in dimethylsulfoxide, were added to fibroblast cultures. Toxicity was manifest as changes in the synthesis of DNA, as measured by autoradiography. Sprays or spray extracts in fetal calf serum did not inhibit cell proliferation. In vivo experiments in rats reflected the in vitro results, there being no evidence that toxic substances were released from the sprays by physiological solvents: There was a lack of histopathological changes in the inner organs and a local encapsulation of implants which was essentially like that in a teflon control group.

Aerosols↗

PubMed1996

Neurotoxin formation from pilot-scale incineration of synthetic ester turbine lubricants with a triaryl phosphate additive.

The high-temperature combustion of synthetic ester turbine engine lubricants has been performed by diluting the lubricant 5, 15, or 25% in diesel fuel and burning the mixture in a pilot-scale boiler facility. The effluent gas from this combustion system was carefully monitored for the formation of a potent neurotoxin, trimethylolpropane phosphate (TMPP). Although TMPP was not detected in the gaseous effluent, elevated levels of the neurotoxin were found in scrapings from the inside of the boiler system. Because of the extreme toxicity of this compound, significant dermal exposure could be a potential risk to incinerator operation and maintenance personnel.

Bridged Bicyclo Compounds, Heterocyclic↗

PubMed1999

Dermal exposure assessment of polycyclic aromatic hydrocarbons: in vitro percutaneous penetration from lubricating oil.

OBJECTIVES: Percutaneous penetration of polycyclic aromatic hydrocarbons (PAHs) is affected by various factors connected to exposure conditions. The nature of the matrix, such as that of oil, can strongly affect their percutaneous penetration. Risk assessment should consider these effects. We examined the effect of matrix on percutaneous penetration of PAHs, particularly that of lubricating oil. METHODS: The test apparatus consisted of an in vitro static diffusion cell system using full-thickness monkey (Cercopithecus aetiops) skin as the membrane and saline solution with gentamycin sulfate and 4% bovine serum albumin as receptor fluid. Chemical analysis of PAHs in the samples obtained from cells was carried out by inverse-phase HPCL, and the results were read by spectrofluorimetry. RESULTS: Comparing the penetration of 13 PAHs from a lubricating oil and from acetone solution with artificial sweat resulted in a significantly slower passage from the oil matrix for acenaphthene, anthracene, phenanthrene, fluoranthene, naphthalene, pyrene, fluorene (Mann-Whitney U test, P < 0.05). No significant differences in the passage were found for chrysene because, in the test with oil, its concentration was very often below the detection limit. For benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[a]pyrene it was possible to demonstrate a passage through the skin only when compounds were applied in acetone solution with artificial sweat. CONCLUSIONS: The results of the study suggest the necessity of dermal penetration data relevant for risk assessment, obtained under experimental conditions similar to the real exposure conditions.

Acetone↗

PubMed1983

Inhibition of motility of bovine, canine and equine spermatozoa by artificial vagina lubricants.

The effects of four vaginal lubricants on progressive spermatozoal motility were evaluated. Neat semen was exposed to 0, 5, or 10% (w/v) of H-R, sterile K-Y, nonsterile K-Y or Maxilube lubricating jellies for 10 min at 37 degrees C and then extended to 10x10(6) spermatozoa/ml. Spermatozoal motility was evaluated after 0, 1, 2, 4 and 6 or 8 h of incubation at 37 degrees C. For bovine spermatozoa, sterile K-Y jelly at 10% suppressed motility (P<0.05), but nonsterile K-Y, H-R and Maxilube jellies had no effect. Maxilube was toxic (P<0.01) to canine spermatozoa and is not recommended for use during collection or insemination of canine semen. Exposure of equine semen to 10% H-R jelly had no effect on spermatozoal motility, whereas 10% sterile K-Y, nonsterile K-Y or Maxilube jellies suppressed (P<0.05) motility. For all three species, the new, nonsterile K-Y jelly was no more deleterious to spermatozoal motility than the old, sterile K-Y jelly, and H-R jelly also was satisfactory. Fertility tests are required to determine the effect of these products on fertility.

Journal Article↗

PubMed1983

Genotoxicity studies with a blend of zinc dialkyldithiophosphate lubricant additives.

The mutagenic activity of a blend of primary zinc dialkyldithiophosphate lubricant additives suspended in process oils and a blend of the process oils alone was investigated in agar layer cultures of Salmonella typhimurium TA1535, TA1537, TA1538, TA98 and TA100, both with and without the incorporation of a rat liver microsomal activation system (S9). Zinc dimethyldithiocarbamate was tested as a structurally-related model bacterial mutagen, and, in additional control experiments, the mutagenic activity of zinc dimethyldithiocarbamate and benzo[a]pyrene was investigated in combination with the blend of process oils in selected bacterial tester strains. Transformation frequencies of BHK cells were determined by colony growth in soft agar culture following treatment with a blend of the zinc dialkyldithiophosphate lubricant additives suspended in process oils, a blend of the process oils, 7,12-dimethylbenzanthracene, both in the presence and in the absence of a blend of the process oils, or zinc dimethyldithiocarbamate. All experiments incorporated a rat liver microsomal activation system (S9). Application of a blend of the zinc dialkyldithiophosphate additives or a blend of the process oils used in their manufacture did not increase the reverse mutation frequencies of Salmonella typhimurium TA1535, TA1537, TA1538, TA98 or TA100, or significantly increase the transformation frequency of BHK cells under the experimental conditions described. Zinc dimethyldithiocarbamate increased the reverse mutation frequency in some bacterial tester strains, but did not significantly increase the transformation frequency of BHK cells under the described experimental conditions. The addition of the blend of the process oils in combination with the control materials, zinc dimethyldithiocarbamate or benzo[a]pyrene had an inhibitory effect on the mutagenic activity at high doses of each in the bacterial assays, and in the BHK assay the transforming ability of 7,12-dimethylbenzanthracene was suppressed in the presence of the blend of the process oils. Thus, the additive materials showed no evidence of genotoxic activity in the bacterial mutation assays, or in the BHK transformation assay under the experimental conditions described.

Animals↗

PubMed1995

Effects of spent lubricating oil on the growth of Capsicum annum L. and Lycopersicon esculentum Miller.

Susceptibility of the hot pepper (Capsicum annum L.) and the tomato (Lycopersicon esculentum Miller) to spent lubricating oil was investigated in soils supplemented with concentrations of oil ranging from 1-5% w/w. Treatment of soil with 4 and 5% spent oil consistently inhibited germination of both crops. Eighty-four days after sowing, the mean height and leaf area of C. annum in soil treated with 3% spent oil gave the lowest values. These were 3.14 +/- 0.6 cm and 0.24 +/- 0.01 cm(2) compared with respective values of 19.2 +/- 0.2 cm and 2.9 +/- 0.3 cm(2) for control plants. Premature death was observed in the case of L. esculentum plants treated with all tested strengths of spent lubricating oil.

Journal Article↗

PubMed2004

Steady flow and viscoelastic properties of lubricating grease containing various thickener concentrations.

The flow and viscoelastic properties of a lubricating grease formed from a thickener composed of lithium hydroxystearate and a high-boiling-point mineral oil were investigated as a function of thickener concentration. The flow properties of grease were measured using continuous shear rheometry, while the viscoelastic properties were measured using oscillatory shear measurements. The flow properties show that grease is a shear-thinning fluid with a yield stress that increases with thickener concentration. At concentrations of lithium hydroxystearate greater than 5% by volume, the storage modulus, G', was found to be greater than the loss modulus, G", with both moduli increasing with increasing thickener concentration, below this critical concentration G" was greater than G'. Slip at the wall of the measuring platens was a major problem encountered during the rheological measurement of grease, this is hardly surprising, and greases are designed to slip in their lubricating functions. Therefore the measuring platens were roughened by sandblasting and significantly higher yield values were recorded with the roughened geometries. Creep experiments were also performed. In the creep test, yield stresses of greases could be obtained. Zero shear viscosity was also calculated from the creep experiment and as a result viscosities over nine orders of magnitude were obtained. The power law index of the scaling law of the elastic modulus and yield stress with increasing volume fraction was found to be 4.7+/-0.2 suggesting that the flocculation of the particles that compose the grease is likely to be of the chemically limited aggregation variety.

Journal Article↗

PubMed1999

Multi-elemental analysis of jet engine lubricating oils and hydraulic fluids and their implication in aircraft air quality incidents.

The flight crews of aircraft often report symptoms including dizziness, nausea, disorientation, blurred vision and tingling in legs and arms. Many of these incidents have been traced to contamination of cabin air with lubricating oil, as well as hydraulic fluid, constituents. Considering that these air contaminants are often subjected to temperatures in excess of 500 degrees C, a large number of different exposures can be expected. Although the reported symptoms are most consistent with exposures to volatile organic compounds, carbon monoxide, and the organophosphate constituents in these oils and fluids, the involvement of these agents has not been clearly demonstrated. Possible exposure to toxic elements, such as lead, mercury, thallium and others, have not been ruled out. In order to assess the potential of exposure to toxic elements a multi-elemental analysis was done on two hydraulic fluids and three lubricating oils which have been implicated in a number of air quality incidents. A secondary objective was to establish if the multi-elemental concentrations of the fluids tested are different enough to allow such an analysis to be used as a possible method of identifying the source of exposure that might have been present during aircraft air quality incidents. No significant concentrations of toxic elements were identified in any of the oils or hydraulic fluids. The elemental compositions of the samples were different enough to be used for identification purposes and the measurement of only three elements was able to achieve this. Whether these findings have an application, in aircraft air quality incident investigations, needs to be established with further studies.

Aircraft↗

PubMedDate not supplied

Use of phase imaging in atomic force microscopy for measurement of viscoelastic contrast in polymer nanocomposites and molecularly thick lubricant films.

Phase contrast microscopy, using an atomic force microscope, is used to detect and quantify changes in composition across polymer nanocomposites and molecularly thick lubricated surfaces. The technique takes advantage of the contrast in viscoelastic (viscous energy dissipation) properties of the different materials across the surface. Some materials, especially polymers, are found to display viscoelastic behavior. For such materials, the strain response lags the stress by a phase angle that is characteristic of the material. In tapping (or intermittent contact) mode, phase angle contrast is found to be highly dependent on vibration amplitude and mean tip-to-sample distance (setpoint). Phase angle contrast seems to be a stronger function of viscoelastic properties at relatively high vibration amplitude and low mean tip-to-sample distance. In this regime the effects of sample deformation, and thus viscoelastic properties, are dominant. In these contrast images, low phase angle corresponds to materials with low viscoelastic properties. This technique was used to find fairly reproducible phase angle contrast for polyethylene terephthalate (PET) films with embedded ceramic particles, metal particle (MP) magnetic tape, and Si(100) with a nonuniform Z-15 lubricant film. Very little correlation is found between phase angle images and friction force images for PET films with embedded ceramic particles and MP tape; phase angle images give information that cannot be obtained from topography or friction images. A numerical vibration model verifies that viscoelastic properties are dominant for high vibration amplitude and low mean tip-to-sample distance. For these conditions, the model also verifies that low phase angle corresponds to low viscoelastic properties.

Journal Article↗

PubMedDate not supplied

Nanotribological characterization of molecularly thick lubricant films for applications to MEMS/NEMS by AFM.

Molecularly thick perfluoropolyether (PFPE) films are considered to be good protective films for micro/nanoelectromechanical systems (MEMS/NEMS) to reduce stiction, friction, and improve their durability. Understanding the nanotribological performance and mechanisms of these films are quite important for efficient lubrication for MEMS/NEMS devices. These devices are used in various operating environments and their effect on friction, adhesion and durability needs to be clarified. For this purpose, mobile and chemically bonded PFPE films were deposited by dip coating technique. The friction and adhesion properties of these films were characterized by atomic force microscopy (AFM). The effect of rest time, velocity, relative humidity, and temperature on nanotribological properties of these films was studied. Durability of these films was also measured by repeated cycling tests. The adhesion, friction mechanisms of PFPE at molecular scale, and the mechanisms of the effect of operating environment and durability are subject of this paper. This study found that adsorption of water, formation of meniscus and its change during sliding, viscosity, and surface chemistry properties play a big role on the friction, adhesion, and durability of the lubricant films.

Journal Article↗

PubMed2005

Silica surfaces lubrication by hydrated cations adsorption from electrolyte solutions.

Adsorption of hydrated cations on hydrophilic surfaces has been related to a variety of phenomena associated with the short-range interaction forces and mechanisms of the adhesive contact between the surfaces. Here we have investigated the effect of the adsorption of cations on the lateral interaction. Using lateral force microscopy (LFM), we have measured the friction force between a silica particle and silica wafer in pure water and in electrolyte solutions of LiCl, NaCl, and CsCl salts. A significant lubrication effect was demonstrated for solutions of high electrolyte concentrations. It was found that the adsorbed layers of smaller and more hydrated cations have a higher lubrication capacity than the layers of larger and less hydrated cations. Additionally, we have demonstrated a characteristic dependence of the friction force on the sliding velocity of surfaces. A mechanism for the observed phenomena based on the microstructures of the adsorbed layers is proposed.

Journal Article↗

PubMed2006

Quasi-equilibrium AFM measurement of disjoining pressure in lubricant nano-films I: Fomblin Z03 on silica.

We have identified conditions in which the atomic force microscope can be used to stretch a meniscus of a perfluoropolyether (PFPE) lubricant pinned between an AFM tip and a nanometer-thick PFPE film to obtain the disjoining pressure of the film. Under quasi-equilibrium conditions, the chemical potential of the film can be equated to that of the stretched meniscus. A theory is presented that provides a complete description of the capillary force of a stretched meniscus. Fits of the theory to quasi-equilibrium force-extension curves yield the effective meniscus curvature and, by extension, the disjoining pressure of the underlying film. AFM force curves collected at varying film thicknesses compare very well with predictions from Lifshitz theory of dispersive interactions in thin films, with no adjustable parameters. This complete description of meniscus deformation during atomic force microscopy force-extension experiments makes possible the measurement of unknown disjoining pressures as required for screening of lubricant-overcoat combinations required for next-generation data storage systems.

Journal Article↗

PubMed2001

Spectroscopic analysis of the tribological behavior of a model boundary layer lubricant.

Highly ordered alkanethiol self-assembled monolayers (SAMs) on gold substrates are suitable models of boundary layer lubricants and may be used in actual nanoscale device applications. Here, such monolayers were studied by spectroscopic methods as a function of tribological wear (rubbing) using a pin-on-disk microtribometer. The coefficient of friction (COF) (ratio of the frictional force to the load) was measured with the tribometer, and reflectance infrared spectra and X-ray photoelectron spectra were obtained as the monolayer film failed and the COF changed. The results show that it is possible to correlate disorder in the monolayer film with tribological failure of the film, and that continued rubbing produces a chemical change in the monolayer film. Disorder in the monolayer is distinct from the influence of wear in the underlying gold substrate. Aged SAMs, having sulfonate rather than thiol headgroups and initially less well ordered, behave differently to the well-ordered freshly prepared SAMs. Interestingly, they show a lower COF over many more cycles of exposure to the rubbing pin. The impact of the mechanism of film failure in boundary layer lubrication is discussed.

Journal Article↗

PubMed2004

Anatomical study of subcutaneous adipofascial tissue: a concept of the protective adipofascial system (PAFS) and lubricant adipofascial system (LAFS).

The subcutaneous adipofascial tissue over the entire body was radiographically and macroscopically investigated in 20 fresh and embalmed cadavers. The subcutaneous adipofascial tissue was made up of two adipofascial layers. Because the superficial layer forms a solid structure and is thought to protect against external forces, the adipofascial system formed by the solid structure was named the "protective adipofascial system (PAFS)". Because the deep layer forms a mobile layer and is thought to lubricate musculoskeletal movement, the adipofascial system formed by the mobile structure was named "lubricant adipofascial system (LAFS)". By classifying subcutaneous adipofascial tissue by its functional characteristics, we found we could understand the subcutaneous adipofascial structure over the entire body well.

Adipose Tissue↗

PubMed1999

Elastohydrodynamic Lubrication of Porous Substrates. Application to Synovial Joint Analysis.

This work presents computational results for an elastohydrodynamic model with a porous wall. The model - inspired by the cartilage exudation phenomenon arising in living joints - allows the lubricating fluid to be transferred from the porous walls to the flow channel and viceversa. The system is represented through a strongly coupled set of nonlinear equations which involves hydrodynamic lubrication, plane elasticity and continuity in porous media. The solution technique employed is based on the finite element method, Newton iteration and parametric continuation processes. The predictions obtained uncover mechanisms that might be responsible for the extremely low friction coefficients found in synovial joints.

Journal Article↗

PubMed1999

The Otto Aufranc Award. Wear and lubrication of metal-on-metal hip implants.

The implication of polyethylene wear particles as the dominant cause of periprosthetic osteolysis has created a resurgence of interest in metal-on-metal implants for total hip arthroplasty because of their potential for improved wear performance. Twenty-two cobalt chromium molybdenum metal-on-metal implants were custom-manufactured and tested in a hip simulator. Accelerated wear occurred within the first million cycles followed by a marked decrease in wear rate to low steady-state values. The volumetric wear at 3 million cycles was very small, ranging from 0.15 to 2.56 mm3 for all implants tested. Larger head-cup clearance and increased surface roughness were associated with increased wear. Independent effects on wear of material processing (wrought, cast) and carbon content were not identified. Implant wear decreased with increasing lambda ratio, a parameter used to relate lubricant film thickness to surface roughness, suggesting some degree of fluid film lubrication during testing. This study provided important insight into the design and engineering parameters that affect the wear behavior of metal-on-metal hip implants and indicated that high quality manufacturing can reproducibly lead to very low wear.

Analysis of Variance↗

PubMed2000

Microscopic and macroscopic effects of surface lubricant films in granular shear

Experiments were conducted to investigate the link between particle-particle interaction forces and the bulk properties of granular shear using an idealized system of near-spherical, monosized glass beads. The atomic force microscopy colloidal probe technique was employed to investigate the adhesion and friction between a single bead and a second glass surface, while the annular shear cell was used to measure the shear properties of the bulk granular material. A covalently bound monomolecular film of aliphatic chains was introduced to alter the tribological interactions between the particles. The atomic force microscope was used to measure the reduction in the particle-particle surface forces resulting from the addition of the boundary lubricant, while the shear cell showed that the effect of the lubricant film was to reduce the coefficient of internal friction and the dilation during shear. This is an experimental study to provide quantitative data linking particle-particle interaction forces and the shear properties of a granular body.

Journal Article↗

PubMed2001

Sliding lubricated anisotropic rough surfaces.

The object of this paper is to study the effects of lubricant film flow, pressurized and sheared between two parallel rough surfaces in sliding motion. The influence of microscopic surface roughness on lubricant film flow macroscopic behavior is described through five nondimensional parameters called flow factors. These macroscopic transport parameters are related to the local geometry of apertures and surfaces. Short- and long-range-correlated surface roughnesses display very different macroscopic behaviors when surfaces are close to contact. These behaviors are related to underlying surface roughness parameters such as the correlation length and the self-affine Hurst exponent. The problem is numerically studied, and results are compared to some analytical asymptotic results.

Journal Article↗