Friction of Poly(n-Alkyl Methacrylates)

The friction coefficient of solid poly(n-alkyl methacrylates) decreases progressively with increasing length of the alkyl group. This behavior parallels the behavior of adsorbed films of these polymers from solution on solid surfaces. Durability of thin films of these polymers (approximately 3,500 Å thick) increases with increasing length of alkyl group. For example, when the alkyl is C₂₂ the durability is four times greater than when the alkyl is C₁₂ (polymer film on a 1020 steel substrate). The film durability is strongly substrate dependent, e.g., durability of poly(n-dodecyl methacrylale) is three times greater on glass than on 1020 steel when rubbed with a 440 C rider. The friction and durability are attributed to side chain crystallinity of the polymer. Side chain crystallinity has been observed by others using x-ray and other techniques when the alkyl group is at least 10 or 12 carbons long. Friction measurements may be a more sensitive way of detecting side chain crystallinity. The friction behavior of adsorbed films from solution of the poly(n-alkyl methacrylates) suggests that side chain crystallinity also pertains to suck adsorbed films.     

Biodegradable Lubricants: What Does ‘Biodegradable’ Really Mean?

A minimum level of biodegradability for either the base fluid(s) or the formulated product is stipulated in all the major schemes for defining an environmentally acceptable lubricant (EAL). Unfortunately, there are many standard tests for assessing biodegradability, while differences in the test conditions and how biodegradation is measured (e.g., carbon dioxide evolution, oxygen consumption, loss of parent material) affect the level of biodegradation measured. This means that the stated biodegradability of the base fluid (or any other component) of an EAL will be dependent on both its molecular properties and the test method used. This paper describes suitable test methods for assessing the biodegradability of EALs and gives examples of the confusion that can arise with the different test methods. It is recommended that ‘biodegradable’ for an EAL is defined as achieving at least 60% ThCO₂ (net CO₂ production as percentage of theoretical maximum) after 28 days, when tested according to OECD Test Guideline 301 B (CO₂ evolution test).     

New citric esters with aromatic content and a complex structure considered for use as tribological fluids

This paper presents the results of research carried out to produce synthetic ester oils with a mixed structure, based on citric acid, with beneficial tribological properties and potential biodegradability. Two series of unsymmetrical triesters have been synthesised by varying the molar relationship between aliphatic alcohols from C₁, to C₁₃ along with an alcohol of a complex alkyl‐aryl structure, namely 2‐[(p‐nonyl)phenoxy]ethanol. The variation of the principal properties as a function of the length of the aliphatic chain introduced by the aliphatic alcohol and the aromatic content introduced by the alkyl‐aryl alcohol has been assessed. The wide range of viscosities of these triesters demonstrates their versatility, and the natural citric acid origin holds potential for their having good ecological characteristics.     

毛细管气相色谱法测定塑料包装及其内食品中酞酸酯

建立了用毛细管气相色谱-氢火焰离子化检测器测定塑料食品袋及袋内包装食品中5种酞酸酯（邻苯二甲酸二甲酯（DMP）、邻苯二甲酸二乙酯（DEP）、邻苯二甲酸二丁酯（DBP）、邻苯二甲酸二正辛酯（DOP）和邻苯二甲酸二（2-乙基己基）酯（DEHP））的方法。样品用无水乙醇超声提取，经干燥脱水过0．45μm滤膜过滤，直接注入气相色谱仪进行分析。用保留时间定性，外标法定量。5种酞酸酯的回收率为71．5％～125．5％；精密度（RSD）为1．6％～3．2％；DMP、DEP、DBP、DOP和DEHP的检测限分别为0．18ng、0．13ng，0．13 ng、0．15ng和0．14 ng。该方法准确度和灵敏度高，样品用量少，前处理简单，可同时测定塑料食品袋及包装内食品中5种酞酸酯。     

Thickness and scratch resistance of adsorbed film formed by triblock symmetrical copolymer solutions

The thickness and scratch resistance of adsorbed films formed on mild steel samples (MS1020), which have been immersed in water copolymer solutions, are reported. The effects of bulk temperature and the copolymer structures, normal, poly(ethylene oxide)_m‐poly(propylene oxide)_n‐poly(ethylene oxide)_m, and reverse, poly(propylene oxide)_n‐poly(ethylene oxide)_m‐poly(propylene oxide)_n, are elucidated. The films' thicknesses are independent of structure but not of temperature. The adsorbed films of above cloud point solutions are thicker than below cloud point. However, nanoscratch experiments carried out to measure the scratch resistance of the films reveal that despite of thicker film formed by above cloud point solutions, it is relatively more prone to being detached than the thinner films of below cloud point solutions. The effect of extreme pressure additive, alkyl phosphate ester (APE), is also investigated suggesting the normal copolymer has comparable scratch resistance with APE when used at below the cloud point. Copyright © 2016 John Wiley & Sons, Ltd.     

Potential genomic biomarkers of obesity and its comorbidities for phthalates and bisphenol A mixture: <i>In silico</i> toxicogenomic approach

This in silico toxicogenomic study aims to explore the relationship between phthalates and bisphenol A (BPA) co-exposure and obesity, as well as its comorbid conditions, in order to construct a possible set of genomic biomarkers. The Comparative Toxicogenomics Database (CTD; http://ctd.mdibl.org) was used as the main data mining tool, along with GeneMania (https://genemania.org), ToppGene Suite (https://toppgene.cchmc.org) and DisGeNET (http://www.disgenet.org). Among the phthalates, bis(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) were chosen as the most frequently curated phthalates in CTD, which also share similar mechanisms of toxicity. DEHP, DBP and BPA interacted with 84, 90 and 194 obesity-related genes/proteins, involved in 67, 65 and 116 pathways, respectively. Among these, 53 genes/proteins and 42 pathways were common to all three substances. 31 genes/proteins had matching interactions for all three investigated substances, while more than half of these genes/proteins (56.49%) were in co-expression. 7 of the common genes/proteins (6 relevant to humans: CCL2, IL6, LPL, PPARG, SERPINE1, and TNF) were identified in all the investigated obesity comorbidities, while PPARG and LPL were most closely linked to obesity. These genes/proteins could serve as a target for further in vitro and in vivo studies of molecular mechanisms of DEHP, DBP and BPA mixture obesogenic properties. Analysis reported here should be applicable to any mixture of environmental chemicals and any disease present in CTD.     

Detailed characterisation of sulphur and nitrogen components in a multifunctional,ashless lubricant additive by spectroscopic and chromatographic techniques

The work reported here used infrared (IR), multinuclear nuclear magnetic resonance (NMR), and chromatographic techniques to identify and characterise a commercial sulphur‐ and nitrogen‐containing ashless multifunctional additive. The proper assignment of signals in the ¹H/¹³C NMR and IR spectra of the sample has facilitated the identification of different types of sulphur‐ and nitrogen‐containing components. The methodology involves investigation by NMR and IR spectroscopies, thin‐layer chromatography (TLC) and high‐performance liquid chromatogaphy (HPLC) techniques to elucidate the types of components present. This requires the generation of NMR and IR spectral data for standard compounds of alkyl sulphides with different sulphur content and alkyl chain, and nitrogen and sulphur components such as thiadiazole, imidazoline, triazole, etc., and spectral comparison with the spectra of the unknown sample. Further, these components have been separated by silica/alumina column chromatographic and preparative TLC techniques and subsequently analysed for their exact chemical structure by spectroscopic techniques. The combined spectroscopic and chromatographic analyses have yielded the presence of four types of components: di‐t‐octyl polysulphide, di‐t‐octyl thiadiazole, a component containing amine ether functionality, and alkyl amine salts of mono/dialkyl phosphoric acid.     

Structural analysis and intergranular corrosion tests of AISI 316L steel

Pure AISI 316L steel is investigated after solution heat treatment (1050 °C/H₂O) and structural sensitization (650 °C). Two quite different intergranular corrosion tests are used to determine the degree of structural sensitization due to the precipitation of secondary phases along the grain boundaries (mainly the M₂₃C₆ and σ‐phase): the oxalic acid etch test and the electrochemical potentio‐kinetic reactivation test. Generally, the dissolution of chromium‐rich carbides (M₂₃C₆) is provoked by oxalic acid etch tests, whereas the chromium‐depleted zones, in the vicinity of chromium‐rich carbides (M₂₃C₆), are attacked by electrochemical potentio‐kinetic reactivation tests. Both intergranular corrosion tests are used to determine the maximum degree of structural sensitization. Thus structural analysis by carbon replicas reveals the Laves phase, and both the M₂₃C₆ and (Cr,Mo)_x(Fe,Ni)_y phases. The results of intergranular corrosion tests are related to the findings of the structural analysis.     

Liquid-liquid direct contact heat exchanger for solar application

In most direct contact liquid-liquid heat exchangers, oil or hydrocarbon with a density less than water is normally used as dispersed working fluid. The main difficulty that arises with this arrangement lies in the control of the interface at the top of the column. When it is closely connected with a solar collector which uses water as its working fluid, the main difficulties arise from the fact that the water can be frozen during winter time. In order to solve these problems and to demonstrate the technical feasibility of a direct contact liquid-liquid heat exchanger, liquids heavier than water with low freezing temperature has been utilized as dispersed phase liquids in a small laboratory scale model made out of pyrex glass. In the present investigation, dimethyl phthalate (C₆H₄(COOCH₃)₂) and diethyl phthalate (C₆H₄(CO₂C₂H₅)₂) are utilized as heavy dispersed phase working fluids. The results of the present investigation support the technical feasibility in the utilization of heavier dispersed working liquid in the spray column liquid-liquid heat exchanger for a solar system. The overall average temperature difference along the column is found to be almost half of the intial temperature difference between the dispersed and the continuous phase. Despite the fact that the two phthalates tested in the experiment differ significantly in some of their physical properties, the volumetric heat transfer coefficients in terms of dispersed fluid superficial velocities were found to be similar for both phthalates tests.     

Temperature‐dependent effects in base oils: Carbon‐13 NMR spin‐lattice relaxation time and viscometry studies

Carbon‐13 NMR spin‐lattice relaxation time (T₁) data have been used to study the molecular dynamic aspects of base oils with different physical properties. Relaxation time measurements have been carried out on a few model compounds and a number of mineral base oils at various temperatures (273–373 K). Effective correlation time (°_C) and rotational mobility data obtained for the model compounds and base oils have provided evidence of relationships between molecular flexibility and the temperature dependence of viscosity. It is possible to determine the average carbon alkyl chain lengths and the molecular weights of the base oils from the ratio of the T₁ values of C_β and C_int carbons and the optimised value of the microviscosity factor (f_r), respectively. A qualitative correlation between Arrhenius energies (E_a) for microscopic motion and macroscopic bulk properties such as viscosity and viscosity‐temperature characteristics has been observed. Base fluids having better viscosity‐temperature characteristics were also associated with lower values of E_a for micro‐ as well as macroscopic processes.     

Studies of inherent lubricity coatings for low surface roughness galvanised steel for automotive applications

Surface lubricity on TiO₂‐coated galvanised steels can be controlled by solution depositing perfluorooctanoic ( C8 ), lauric ( C12 ) or stearic ( C18 ) acids to avoid lubricating oils/emulsions or substrate pre‐etching to remove surface oxide that add cost and waste. Water contact angles reveal increased surface hydrophobicity on coated samples that correlate with linear friction testing, suggesting water contact angle can be used to screen lubricity compounds. Linear friction testing shows that C12 and C18 lower the coefficient of friction (μ ) by 50–60% compared with uncoated substrates whilst C8 drops μ from 0.31 to 0.22. Surfaces have been characterised by X‐ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy, whilst infrared confirms that as‐deposited coatings contain physisorbed and deprotonated acids chemisorbed through esters and thermal gravimetric analysis confirms increasing loadings from C8 to C12 to C18 . Surface washing removes physisorbed material and lowers μ by increasing surface organisation and alkyl chain packing that enhances frictional energy dissipation through steric quenching. Copyright © 2017 John Wiley & Sons, Ltd.     

Experience with evaluating biodegradability of lubricating base oils

Biodegradability analysis of lubricants by standardised tests provides valuable information for both legislation purposes and assessment of how chemical structure influences biodegradability. The choice of an appropriate test for evaluating the ultimate biodegradability of oils raises serious problems as the majority of lubricating base oils display a poor water solubility. The paper summarises the experience gained and the results achieved from the evaluation of primary and ultimate biodegradability of lubricating base oils differing in chemical structure, such as rapeseed oil, synthetic polyolester oils, poly(α-olefin) oils (PAO 4 and PAO 6) and the conventional mineral oil. Primary biodegradability was evaluated using the CEC L-33-A-93 test. To evaluate the ultimate biodegradability of oils in an aerobic aquatic environment, use was made of the testing methods OECD 301 B and OECD 310 for ready biodegradability. Oils that fail to fulfil the “ready biodegradability” criterion, e.g. pentaerythrite tetra(sec-capronate) oil (polyolester with steric hindrance around the ester bonds), PAO 4, PAO 6, and mineral oil, were evaluated for inherent biodegradability using the OECD 302 D (draft) test and the OECD 302 B method where the test vessels were prepared via a modified procedure. The oils belonging to this group differred in inherent biodegradability. Thus, PE tetra(sec-capronate) oil reached an extent of biodegradation amounting to 65%, that of PAO 4 and mineral oil being equal to 48% and 38%, respectively. Experiments have shown that ISO 14593 offers a convenient method for evaluating the ready biodegradability of base oils according to OECD 310 and makes it possible to evaluate (with the same apparatus and reagents) the inherent biodegradability of oils when the conditions and criteria recommended by the OECD 302D (draft) CONCAWE test are satisfied.     

Tribological properties of alkyl and hydroxyl groups on the imidazolium tetrafluoroborate ionic liquids

We present an investigation of effect of alkyl chain length and hydroxyl group functionalisation on the tribological properties of imidazolium tetrafluoroborate ionic liquids. Four kinds of hydroxyl‐functionalised ionic liquids with the alkyl chain of C₁–C₁₀ were synthesised, and the relationships between their structure and physicochemical properties such as viscosity, thermal stability and corrosion, before and after incorporation of a hydroxyl group, were measured. In particular, the studies on their lubrication properties as ionic liquid (IL) lubricants for steel–steel contacts, including the friction coefficient, the wear volume and so on, were particularly emphasised. Moreover, an in‐depth exploration about the function mechanism and failure mode of the ILs during the friction process were studied using the scanning electron microscope and X‐ray photoelectron spectroscope technologies, and a proposed interaction model between ILs and steel substrate was presented. Copyright © 2012 John Wiley & Sons, Ltd.     

The surface chemistry of alkyl and arylphosphate vapor phase lubricants on Fe foil

The surface chemistry of tributylphosphate (TBP) and tricresylphosphate (TCP) on a polycrystalline Fe surface was studied using temperature programmed reaction spectroscopy and Auger electron spectroscopy to illustrate some of the initial steps in the reaction mechanisms of alkyl and arylphosphate vapor phase lubricants. During heating, TBP [(C₄H₉O)₃P=O] adsorbed on the Fe surface decomposes via C–O bond scission to give butyl surface intermediates [C₄H₉–] that react via β-hydride elimination to desorb as 1-butene [CH₃CH₂CH=CH₂] and H₂ without appreciable carbon deposition onto the surface. The thermal decomposition of 1-iodobutane [I-C₄H₉] on Fe was observed to proceed via the same β-hydride elimination mechanism. In contrast to tributylphosphate, meta-tricresylphosphate (m-TCP) [(CH₃–C₆H₄O)₃P=O] decomposes on Fe via P–O bond scission to produce methylphenoxy intermediates [CH₃–C₆H₄O–]. During heating to 800 K, methylphenoxy intermediates either desorb as m-cresol [CH₃–C₆H₄–OH] via hydrogenation or decompose further to generate tolyl intermediates [CH₃–C₆H₄–]. Some of the tolyl intermediates desorb as toluene [CH₃–C₆H₅] via hydrogenation but the majority decompose resulting in H₂ and CO desorption and carbon deposition onto the Fe surface. The P–O bond scission mechanism of m-TCP was verified by showing that the temperature programmed reaction spectra of m-cresol yield products that are almost identical to those of m-TCP. These results provide insight into the origin of the differences in the performance of alkyl and arylphosphates as vapor phase lubricants. The alkylphosphates decompose via alkyl intermediates that readily undergo β-hydride elimination and desorb into the gas phase as olefins, thus removing carbon from the surface. In contrast, the arylphosphates generate aryloxy intermediates by P–O bond scission and aryl intermediates by further C–O bond scission. Neither of these intermediates can undergo β-hydride elimination and thus they decompose to deposit carbon onto the Fe surface. The higher efficiency for carbon deposition may be the primary reason for the superior performance of the arylphosphates over alkylphosphates as vapor phase lubricants.     

Ionic Liquids as Lubricants of Titanium–Steel Contact. Part 3. Ti6Al4V Lubricated with Imidazolium Ionic Liquids with Different Alkyl Chain Lengths

The tribological behaviour and surface interactions of Ti6Al4V sliding against AISI 52100 steel have been studied in the presence of three commercial methylimidazolium (mim) room-temperature ionic liquids (ILs) containing the same anion, bis(trifluoromethylsulfonyl)amide, [(CF₃SO₂)₂N] (Tf₂N), and cations with increasing alkyl chain length, 1-ethyl-3-methylimidazolium [C₂mim], 1-butyl-3-methylimidazolium [C₄mim] and 1-octyl-3-methylimidazolium [C₈mim]. Increasing alkyl chain length increases viscosity whilst reducing the onset temperature for thermal degradation in air, the surface tension and the molecular polarity of the ILs. At room temperature, the tribological performance of the three ILs has been compared with that of a mineral oil (MO). The results show the reduction of the running-in period for the ILs with respect to the MO. In contrast with previously described results for IL lubrication, wear rates for Ti6Al4V at room temperature increase as the alkyl chain length of the ILs increases. The maximum wear reduction, of a 39%, with respect to MO is obtained for the [C₂mim] cation, with only two carbon atoms on the lateral chain. This was the IL selected for the tests at 100 °C. At this temperature, the reduction of the mean friction coefficient with respect to the MO is higher than 50%, whilst the wear rate of Ti6Al4V is reduced by 78%. The friction-sliding distance records for the IL at 100 °C show sharp transitions, related to formation of wear debris and surface interactions between the Tf₂N anion and the aluminium present in the Ti6Al4V alloy. Surface tribolayers and wear debris have been studied by SEM–EDX observations and XPS analysis.     

High‐contrast optical microscopy of graphene sheets

In the way of making graphene an industry‐friendly material, it must be mass‐produced with high‐quality and reduced cost over large areas. Assisted by machine‐learning techniques, rapid, nondestructive and accurate determination of large graphene sheets on SiO₂/Si substrates has been made possible in recent years by the optical microscopy method. Optimization of the substrate to achieve the maximum contrast can further extend the application of the optical microscopy method for quality control of the mass‐produced graphene. Graphene/n₂/n₃three‐layer structures, where n₂ and n₃ are refractive indices, are routinely used for identifying the number of graphene layers by optical reflection microscopy. In this paper, two analytical equations are derived that can be easily used for high‐contrast optical imaging of graphene sheets without any need to resort to the cumbersome numerical methods. One of the equations is derived for choosing the best material with refractive index n₂ that when coated on a substrate with refractive index n₃, maximizes the optical contrast. The other equation is derived for finding the best thickness of the SiO₂ layer in graphene/SiO₂/Si structures, which are in common use for fabrication of graphene‐based devices. The results are implemented in a MATLAB GUI, see Supporting Information, to assist the users in using the equations.     

Detailed characterisation of heavy alkylated benzene fluids by multipulse one‐ and two‐dimensional NMR spectroscopy

In this paper, the results of a characterisation of heavy alkylated benzenes (HAB) using multipulse NMR spectroscopy are presented. Four commercial samples of heavy alkylated benzene have been characterised in detail in terms of various structural parameters, such as percentage aromatic carbon (Ca), degree of aromatic substitution, average alkyl chain length, type of alkyl chain and their proportions. Three of the HAB samples were very similar in structure, whereas, in the fourth, the structures present were entirely different. The latter had an abundance of 2‐phenyl alkane‐type structures, and did not contain methyl substituted tetralin or naphthalene type molecules. The influence of the structures on lubricating oil properties, including viscosity index, pour point, and viscosity, as well as Freon^TM floc point, are also discussed.     

Effect of two medium chain triglycerides‐supplemented diets on synaptic morphology in the cerebellar cortex of late‐adult rats

Ketogenic diets (KDs) have shown beneficial effects in experimental models of neurodegeneration, designating aged individuals as possible recipients. However, few studies have investigated their consequences on aging brain. Here, late‐adult rats (19 months of age) were fed for 8 weeks with two medium chain triglycerides‐supplemented diets (MCT‐SDs) and the average area (S), numeric density (Nv_s), and surface density (S_v) of synapses, as well as the average volume (V), numeric density (Nv_m), and volume density (V_v) of synaptic mitochondria were evaluated in granule cell layer of the cerebellar cortex (GCL‐CCx) by computer‐assisted morphometric methods. MCT content was 10 or 20%. About 10%MCT‐SD induced the early appearance of senescent patterns (decreased Nv_s and Nv_m; increased V), whereas 20%MCT‐SD caused no changes. Recently, we have shown that both MCT‐SDs accelerate aging in the stratum moleculare of CA1 (SM CA1), but are “antiaging” in the outer molecular layer of dentate gyrus (OML DG). Since GCL‐CCx is more vulnerable to age than OML DG but less than SM CA1, present and previous results suggest that the effects of MCT‐SDs in the aging brain critically depend on neuronal vulnerability to age, besides MCT percentage. Microsc. Res. Tech. 2009. © 2009 Wiley‐Liss, Inc.     

Inverse Gas Chromatographic Study of the Factors Affecting Surface Diffusivity of Gases over Heterogeneous Solids

Abstract

In the present work, the various parameters affecting the variation of the surface diffusion coefficients, determined by the novel methodology of reversed‐flow gas chromatography (RF‐GC), for CO adsorption on a well‐studied Pt/SiO₂ catalyst, are under investigation. These are the adsorption energy, ?, the lateral interaction energy, β, the surface coverage, θ and the surface concentration of the adsorbate, c _s *. The magnitude of surface diffusion coefficient values, determined by RF‐GC, is comparable to those obtained by other experimental techniques, ascertaining the potential of the method. Physicochemical parameters giving information for the surface mobility, such as adsorption energies, local isotherms, local surface concentration of the adsorbate, and energy distribution functions can be determined in a single kinetic run.     

The Effect of Concentration on Lubricating Properties of Aqueous Solutions of Sodium Lauryl Sulfate and Ethoxylated Sodium Lauryl Sulfate

The objective of this study was to formulate new ecological lubricating substances, primarily water-based, and to verify their tribological and physicochemical properties. Initially, simple binary solutions were investigated. Then, various additives were added depending on application targets. Two alkyl sulfates were selected as additives modifying lubricating properties of water: sodium lauryl sulfate (SLS) and ethoxylated sodium lauryl sulfate (ESLS). They have an identical hydrophobic part in the form of an alkyl chain consisting of 12 carbon atoms. The SO₄ ²⁻ anion forms the hydrophilic part in SLS molecules, whereas an ESLS molecule also contains two mers of ethylene oxide which cause an increase in its hydrophilicity relative to SLS. Both SLS and ESLS exhibit high surface activity measured by their surface tension. Micelles form in aqueous solutions of alkyl sulfates at low concentrations of the order of 1%, whereas the presence of liquid crystalline phases can be found at the concentrations of 40 and 70%. High surface activity and formation of structures in the solutions (micelles, mesophases) formed the basis for application of the compounds as additives modifying lubricating properties. Tribological properties of aqueous solutions of alkyl sulfates were verified with a four-ball machine (T02 tester) at a constant load of 2 kN. The values of friction coefficient (μ) were a measure of motion resistance, while the wear scar diameter (d) was a measure of wear. Alkyl sulfates significantly improve tribological properties of water. The coefficient of friction decreased sixfold and the wear scar diameter decreased by as much as twofold relative to the base. Non-monotonic changes in the tribological properties measured were observed as a function of concentration of additives. An attempt was made to relate those atypical changes with the presence of micelles and mesophases in both the surface phase and the bulk phase. In the model proposed the whole concentration range was divided into four areas in which tribological properties correspond well with physicochemical properties, particularly with the structures formed in solutions and at the interface.