Film forming behaviour of oil soluble polyalkylene glycols

2015 ◽  
Vol 67 (2) ◽  
pp. 133-138 ◽  
Author(s):  
Martin Greaves ◽  
Ksenija Topolovec Miklozic
Keyword(s):  
Contact Pressure ◽  
Film Formation ◽  
Surface Film ◽  
Electrical Contact ◽  
Electrical Contact Resistance ◽  
Content Type ◽  
Film Forming ◽  
Specific Contact ◽  
Surface Active ◽  
Forming Behaviour

Purpose – The purpose of this paper was to examine the film-forming behaviour of simple compositions of polyalphaolefin (PAO) containing an oil-soluble polyalkylene glycol (OSP) alone, a zinc dialkyl dithiophosphate (ZDDP) alone and then combinations of an OSP and ZDDP. Design/methodology/approach – A Mini-Traction Machine with Spacer Layer Imaging technology was used to evaluate friction and film formation under a specific contact pressure, temperature and slide-to-roll ratio. Electrical contact resistance measurements were used to follow surface film formation. Findings – The inclusion of an OSP to a PAO showed evidence of friction-reducing behaviour with low friction values over the rubbing cycle but no significant tribo-film build up. When a ZDDP (1 per cent) is added to the PAO, a thick tribo-film forms of about 100 nm. Addition of an OSP (10 per cent) shows this film still forms despite the OSP being a polar and surface-active additive. Research limitations/implications – The study was conducted under a narrow range of test conditions (e.g. temperature and contact pressure), and future work will focus on friction and film formation across a broader set of conditions. Practical implications – Despite OSPs being polar and surface-active, they do not interfere with the ZDDP in forming an anti-wear film in a PAO and, therefore, their inherent properties of good deposit control could enhance the performance of modern lubricants. Originality/value – OSPs offer promising benefits as friction reducers in PAOs. The research also suggests that OSPs do not negate the formation of ZDDP anti-wear tribo-films when in combination in a PAO.

Stick-Slip\Smooth Slip as a Function of Ambient Gases and Pressures Disproving Previous Models of Adhesive Wear

1988 ◽  
Vol 140 ◽  
Author(s):  
Chao Gao ◽  
Doris Kuhlmann-Wilsdorf ◽  
David D. Makel
Keyword(s):  
Film Formation ◽  
Surface Film ◽  
Substrate Surface ◽  
Electrical Contact ◽  
Copper Substrate ◽  
Ambient Atmosphere ◽  
Surface Films ◽  
Electrical Contact Resistance ◽  
Stick Slip ◽  
Average Value

AbstractFive different slip modes have been identified for bundles of copper fiberssliding on a smooth copper substrate in atmospheric air, argon and nitrogenat pressures from atmospheric to 0.01 Torr. These are stick-slip, variable sliding, intermittent stick sliding and two kinds of smooth sliding, one apparently a basic property of clean surfaces and the other due to contaminants. These forms of sliding are rather persistent once established, and they follow some trends. Specifically, low-pressure smooth sliding is coordinated with a value of the coefficient of friction (μ) near 0.15 and is seen when the surface film is exceptionally thin, while intermittent stick sliding appears to be due to “pads” on the substrate surface,and variable sliding to small particles caught in between the fibers and the copper substrate. However, the five slip modes are erratic in that under the same conditions one or another or yet a third may be observed, even though the electrical contact resistance (R) depends rather reproducibly on time, load, velocity, ambient atmosphere and pressure. That dependence indicates an equilibrium between film destruction through sliding and film formation, overwhelmingly through the presence of oxygen. In the stick-slip mode the difference between pst tic and ųK itic appears to be roughly proportional to ų 0.15, i.e. tfiee xcess of e average value of the friction coefficient above 0.15, being about 20% for ų 0.3 andvanishing near ų =0.15. During slip episodes, R spikes roughly in proportion to their magnitude. Some tentative interpretations are offered, based on the concept that ų consists of three additive components, namely due to the bulk (ųBulk), due to debris (ųDebris), and dueto scoring of surface films (ųFilm).At any rate, the conclusion that the results contradict all previous models of “adhesive” wearis inescapable.

scholarly journals The Wear Process During the “Running-In” of Steel in Lubricated Sliding

1987 ◽  
Vol 109 (4) ◽  
pp. 587-591 ◽  
Author(s):  
M. Suzuki ◽  
K. C. Ludema
Keyword(s):  
Contact Resistance ◽  
Surface Film ◽  
Electrical Contact ◽  
Mineral Oil ◽  
Entrance Region ◽  
Engine Oil ◽  
Small Range ◽  
Electrical Contact Resistance ◽  
Metallic Contact ◽  
Wear Process

Steel cylinders were slid against flat steel disks, using a liquid lubricant, in order to study the progression of events associated with “running-in.” It was found that, when using mineral oil, the electrical contact resistance varied over a small range of high values indicating no metallic contact, whereas with engine oil a high resistance with an intermittent negligible contact resistance was found. A surface film forms from the additives in the engine oil which produces lower wear, slightly higher friction, a retarded running-in, and a rougher surface finish in the direction of sliding than does the mineral oil. A film which is composed only of Fe3O4 is formed when mineral oil is used. In addition, the mineral oil lubricated surfaces develop a conforming waviness across the sliding tracks. The oxide must have enhanced this surface conformity since it was not seen in the surfaces lubricated with engine oil. The role of the oxide may be further seen in experiments in which wear debris that accumulated in the entrance region of specimen contact was removed at frequent intervals. Little conforming waviness was seen in the latter case, suggesting that oxide which gathered in the entrance region abraded grooves in the steel surfaces. After the oxides were dislodged the friction increased and the contact resistance decreased for a time, indicating that the oxide acted like a solid lubricant.

Surfactant convertase action is not essential for surfactant film formation

1997 ◽  
Vol 273 (5) ◽  
pp. L907-L912 ◽  
Author(s):  
N. J. Gross ◽  
R. Veldhuizen ◽  
F. Possmayer ◽  
R. Dhand
Keyword(s):  
Surface Tension ◽  
Film Formation ◽  
Surface Film ◽  
Lower Surface ◽  
Diisopropyl Fluorophosphate ◽  
Surfactant Film ◽  
Surface Active ◽  
Lower Surface Tension ◽  
Surface Balance

A serine-active enzyme, “surfactant convertase,” is required for the conversion of surfactant from the tubular myelin (TM) form to the small vesicular (SV) form. This transformation involves at least two steps, the conversion of TM to a surface-active film at the air-fluid interface and the reorientation of the film into the surface-inactive SV form; we asked if convertase was required for the first of these steps. Rat and mouse TMs were pretreated with diisopropyl fluorophosphate (DFP) to inactivate endogenous convertase activity or with vehicle and then were analyzed for their ability to lower surface tension in vitro as an index of the conversion of TM to a surface film. DFP pretreatment did not alter the ability of TM preparations to lower surface tension, as assessed by pulsating bubble, and it did not affect the behavior of TM in a surface balance. In an experiment designed to test the ability of TM to feed a surface film to exhaustion, TMs that had been pretreated with DFP or vehicle performed similarly. These experiments show that convertase activity is not required for the conversion of TM to a monolayer and suggest, instead, that convertase acts at a post surface film stage.

The Degradation of Electrical Contact Resistance of Metal Films at Low Contact Force

2004 ◽  
Author(s):  
Daniel J. Dickrell ◽  
Michael T. Dugger
Keyword(s):  
Contact Resistance ◽  
Contact Force ◽  
Environmental Control ◽  
Surface Film ◽  
Electrical Contact ◽  
Electrical Contact Resistance ◽  
Small Surface ◽  
Underlying Mechanisms ◽  
Cyclic Degradation ◽  
Current Reduction

The quality of electrical contact resistance is important to the performance and reliability of metal-contact microelectromechanical system (MEMS) relays and switches. The cyclic degradation of contact resistance was examined for a metal multilayer sphere-on-flat contact at low contact force. The relationships between the degradation and underlying mechanisms, particularly surface contamination effects, were investigated through experimentation and analysis. Results indicated that the degradation severity could be significantly decreased with environmental control and contact current reduction. Micro-arcs at very small surface gaps, which can decompose adsorbed contaminants and leave an insulating surface film, were proposed as a cause of the resistance degradation.

scholarly journals Snowpack-stored atmospheric surface-active contaminants traced with snowmelt water surface film rheology

2020 ◽  
Author(s):  
Stanisław J. Pogorzelski ◽  
Paweł Rochowski ◽  
Maciej Grzegorczyk ◽  
Katarzyna Boniewicz-Szmyt
Keyword(s):  
Surface Pressure ◽  
Water Surface ◽  
Temporal Evolution ◽  
Surface Film ◽  
Virial Equation ◽  
Rheological Parameters ◽  
Film Material ◽  
Structure Characteristics ◽  
Film Forming ◽  
Surface Active

Abstract The aim of the study was to quantify the adsorptive and thermo-elastic properties of snowmelt water surface films and their spatial-temporal evolution with snowpack structure characteristics and the entrapped surface-active organic composition. Surface pressure–area (π-A)T isotherms, surface pressure-temperature (π-T)A isochors, and stress–relaxation (π-t) measurements were performed using a Langmuir trough system on snowmelt water samples collected in a large-scale field studies performed at several industrialized and rural Tricity (Gdansk, Poland) areas at various environmental conditions and subsequent stages of the snowpack melting progress. Since the snow-melted water composition and concentrations of surface active organic matter fractions therein are largely undetermined, the force-area isotherm scaling formalisms (2D virial equation and 2D film scaling theory of polymeric films) were adapted to the complex mixture of surfactants. The surface film parameters and their spatial and temporal evolution turned out to be unequivocally related to principal signatures of the film-forming materials: surfactant concentrations (π, Alim), surface activity (Eisoth, |E|), film material solubility (R), surface material miscibility and 2D architecture complexity (y, βs), molecular thermal mobility (πk), and a timescale of the relaxation processes within the film (τi, |E|). Moreover, the parameters appeared to be correlated with snowpack structure characteristics (snow density ρ, specific snow area SSA, snow cover thickness), sample age time, and anthropogenic atmospheric contamination pressure source locations. In particular, Eisoth was found to be related to ρ and SSA, while R correlated with the solubility of film-forming organics which turned out to be long-chain fatty acids; similarly, spatial profiles of Eisoth revealed the peak values next to the areas being under a severe anthropogenic air pollution pressure. Snowmelt water films stand for a structurally heterogeneous (y > 10) interfacial system where several transition processes of differentiated time-scales (relaxation times from 7 to 63 s) took place leading to the apparent surface viscoelasticity. To sum up, the established surface rheological parameters could serve as novel indicators, based solely on physical attributes, allowing to follow the snowpack evolution, and its melting polymorphism in order to test or improve the existing snow-entrapped organics release models based on chemical analyses. The cross-correlation functional dependences of practical value remain to be established on the larger data set.

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