Ashless Additives Research Articles

Effect of metallic lubricant additives on morphology, nanostructure, graphitization degree and oxidation reactivity of diesel particles

This paper investigates the impact of metallic lubricant additives on the morphology, nanostructure, graphitization degree, and oxidation reactivity of diesel exhaust particles. The experiments were conducted on a turbocharged heavy-duty diesel engine. Four typical lubricant oil additives, including Ca-based, Zn-based, Mo-based and ashless additives, were mixed into diesel at 0.5% and 1.0% by mass. Analytical characterization equipment used in this study includes a high resolution transmission electron microscopy (HRTEM), a Raman spectroscopy, and a Thermogravimetric analyzer (TGA). Results showed that the lubricant additives significantly changed the soot properties. Diesel fuels blended with ashless and Zn-based additives led to a more disordered nanostructure of diesel particles, thereby improving their oxidation reactivity. When Ca and Mo additives participated in combustion, the oxidation mass loss curve of soot particles shifted to a higher temperature range due to the combined effect of the physical and chemical characteristics of soot particles and the catalytic oxidation of metallic ash. Although Ca, Mo, and other metals in lubricant additives could promote the soot oxidation, the changes in the physicochemical properties of soot particles (including increased fringe length, reduced fringe tortuosity, and higher graphitization degree) rendered it more difficult to oxidize.

The Influence of Steel Composition on the Formation and Effectiveness of Anti-wear Films in Tribological Contacts

The effectiveness of antiwear additives in laboratory tests is commonly evaluated using specimens made of AISI 52100 through-hardened bearing steel. However, many lubricated machine components are made of steels with significantly different material compositions, which raises an important practical question of whether the performance of antiwear additives with these other steel types is different from that established with AISI 52100. To help answer this question, this paper investigates the influence of steel composition on the formation and effectiveness of antiwear films. Four steels that are commonly used in tribological applications, namely AISI 52100 through-hardened bearing steel, 16MnCr5 case-carburised gear steel, M2 high speed steel and 440C stainless steel are tested in rolling-sliding, ball-on-disc contacts lubricated with three custom-made oils, one containing ZDDP and two containing different types of ashless antiwear additives. The relative effectiveness of their boundary films was assessed by measuring their thickness and associated wear and friction over 12 h of rubbing at two specimen roughness levels. For ZDDP it was found that the formation of antiwear film was not significantly influenced by steel composition or specimen surface roughness. A similar tribofilm thickness, final tribofilm roughness and friction was observed with all four steels. No measurable wear was observed. By contrast, for the ashless antiwear additives the thickness and effectiveness of their tribofilms was strongly influenced by steel composition, particularly at higher roughness levels. The exact trends in film thickness vs steel relationship depended on the specific chemistry of the ashless additive (ester-based or acid-based) but in general, relative to AISI 52100 steel, M2 steel promoted ashless tribofilm formation whilst 440C retarded ashless tribofilm formation. This behaviour is attributed to the presence of different alloying elements and the ability of the additives to extract metal cations from the rubbing surfaces to support the growth of a tribofilm. In all cases ZDDP films were thicker and rougher, and produced higher friction than those formed by the ashless additives. However, unlike ZDDP, ashless blends generally produced significant wear, particularly with 16MnCr5 and M2 steels. The results indicate that to ensure reliable performance of a given machine component, the chemistry of an ashless antiwear additive should be matched with the types of steel present in the lubricated machine.

Chemical and physical properties of tribofilms formed by the interaction of ashless dithiophosphate anti‐wear additives

AbstractPhysiochemical properties of tribofilms generated from octadecylthioperoxydiphosphate (SSC18) and octadecylphosphorofluoridothioate (PFC18) were compared with zinc dialkyl dithiophosphates (ZDDP) in this study. PFC18 and SSC18 were chemically synthesised and mixed in mineral base oil to prepare test oil formulations. Additionally, PFC18 and SSC18 were mixed at different concentrations and evaluated for their compatibility and tribological performance using high frequency reciprocating rig (HFRR) tribometer. All lubricant formulations with ashless additives exhibited superior anti‐wear characteristics compared to ZDDP. Comprehensive surface analysis of tribofilms was conducted using scanning electron microscopy, nano‐indentation and X‐ray absorption near edge spectroscopy. Formulations containing only SSC18 and PFC18 exhibited a uniform and continuous tribofilm formation, while formulations with a combination of SSC18 and PFC18 had a stable pad‐like structure. X‐ray absorption near edge structure (XANES) results indicate ashless PFC18 and SSC18 by themselves and in combination form iron phosphate enriched tribofilms with a mixture of iron sulfides and/or sulfates.

A modified oil‐soluble polyether used as multifunctional ashless additives with enhanced lubricating and corrosion protection performance

AbstractA novel oil soluble polyether derivative (OSPSA) was synthesized by the mono‐esterification of oil soluble polyether (OSP) with succinic anhydride (SA). The product was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, thermogravimetry, and acid value. The friction test results indicate that OSPSA exhibited obvious improvement on the friction reduction (by 35.7%) and anti‐wear performance (by 50.3%) comparing with the base oil. Additionally, OSPSA was also found to display excellent anticorrosion properties. OSPSA can be used as multifunctional ashless additive to provide excellent lubricity and corrosion protection properties. It can be speculated from the electrochemical experiments that the corrosion inhibition performance of OSPSA is mainly controlled by anode and the corrosion inhibition efficiency can reach 82.9%.

Obtaining of Ashless Additives for Diesel Fuel Impoving the Lubricating, Anticorrosion and Protection Properties

The production of “ultra pure” diesel fuels is connected with the deterioration of their certain performance characteristics. The lubricating properties of ultra pure diesel fuels are poor; their relative stability worsens; they tend to be corrosion-aggressive toward metal surfaces; and their electrophysical properties sharply deteriorate to increase the possibilities for accumulation of static-electric charge by transportation and feeding into vehicles (Tasheva, Petkov, and Ivanov, 2003; 2004). These negative properties of the ultra pure diesel fuel are usually overcome by adding special substances to improve their lubricating properties, electric conductivity, and oxidation stability and to eliminate their corrosion aggressiveness.

Study of a novel anti‐wear additive used in ashless anti‐wear hydraulic fluid

PurposeThe purpose of this paper is to develop novel ashless additives and to meet the need for formulating ashless anti‐wear (AW) hydraulic fluid or other industrial lubricating oils. This paper also aims to investigate the tribological behaviours and mechanism of an acrylate of dialkyl dithiophosphoric acid (ADDP), as an additive in some group I/II base oils compared with some traditional s‐p containing AW additives.Design/methodology/approachADDP is synthesized in the laboratory. The chemical composition and structure of the lubricating additive are analyzed by means of infrared spectroscopy. Its extreme pressure (EP), AW and friction reduction properties as additive in base oils, compared with some traditional s‐p containing AW additives, are investigated using a four‐ball machine according to relative testing standards. The tribological mechanism is discussed according to the scanning electron microscope (SEM) analytical data.FindingsThe results indicate that the four‐ball PB value of the prepared ADDP in HVIWH650 is better than that of the IRGLUBE 353; the thermal stability of ADDP is equivalent to the zinc dialkyl dithiophosphate (ZDDP) and the SEM data show that the prepared ADDP additive could form a layer of uniform film on the worn surface serving as lubricant and protective film. This may be the chief reason why the prepared ADDP possesses better AW property than ZDDP.Research limitations/implicationsHowever, more experimental studies such as the synergic effect with other additives should be performed, from which it could be learned whether the novel AW additive would be applicable in industrial oils.Practical implicationsThe results may be useful for the researchers to formulate some ashless industrial oils.Originality/valueA novel additive was synthesized in the laboratory; it would find a promising industrial application as an ashless AW additive.

Reactions of zinc-free anti-wear additives in DLC/DLC and steel/steel contacts

In this work, the ability of ashless anti-wear additives to form protective tribofilms on diamond-like carbon (DLC) and steel surfaces was investigated and compared to the reactions of ZnDTP. Reciprocating sliding tests were performed under mild tribological conditions for steel/steel and DLC/DLC contacts to avoid wearing through the DLC coating. A comparison of the friction behavior of ZnDTP with two ashless additives, a butylated triphenyl phosphorothionate (b-TPPT) and an amine phosphate (AP), indicated that the latter additive behaved in a different manner to the first two. b-TPPT shows the lowest friction coefficient for DLC/DLC contacts whereas the AP give the lowest friction coefficient for steel sliding against steel. AFM and ESEM were performed to analyze the surfaces and showed the build up of tribofilms from ZnDTP and b-TPPT onto both the steel and DLC surfaces. No evidence of such a film formation on DLC was observed when the AP were used.

Study of Factors Influencing High-Temperature Detergency of Alkylated Phenyl Salicylates

Lubricants with longer drain interval should be easy to maintain, economical, and environment friendly. Compact and high-performance machines require high-performance lubricants. Under these circumstances, alternative ashless additives exhibiting sufficient high-temperature stability and antioxidancy have to be developed. We have found that the addition of alkylated phenyl salicylates to the lubricants leads to good high-temperature detergency. In this paper, we report the factors affecting the high-temperature detergency of the alkylated phenyl salicylates and their utility.

Combination of ashless antiwear additives with metallic detergents: interactions with neutral and overbased calcium sulfonates

The interactions of neutral and overbased calcium sulfonate detergents with ashless thiophosphate oil additives under boundary lubrication were studied. The ashless additives used were neutral and acidic dialkyldithiophosphate (DTPs) and neutral triaryl monothiophosphate (MTP). This study uses three surface analytical tools to provide elemental and chemical information at the surface and in the bulk of the derived tribochemical films. The elemental composition of the tribofilms was studied using X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDX) (combined with scanning electron microscopy (SEM)). Corresponding P and S X-ray absorption near edge structure (XANES) spectroscopy was also used to provide further insight into the chemical composition of the films. SEM images of the derived tribofilms revealed that each film had distinct topographical features associated with it. XPS and EDX revealed that when oil is blended with calcium sulfonate, considerable amount of calcium is incorporated into all the tribochemical films. The phosphorus content of the tribofilm was reduced substantially when the overbased detergent was combined with MTP additive. XANES spectroscopy of the P L-edge provided direct evidence for the formation of calcium phosphate in tribofilms from the ashless additives in combination with the detergent. S K-edge revealed that sulfate is the main sulfur species formed in the bulk for all three tribofilms in the presence of the neutral detergent while a mixture of sulfite and sulfide species are formed when the overbased was used. S L-edge XANES showed that calcium sulfonate has undergone some oxidation at the surface. A more antagonistic effect was observed for MTP, with the formation of a very thin phosphate film. Tribological performance was also evaluated. Surprisingly, combination of the neutral detergent with any of the AW additives did not result in any significant change in wear to the substrate. For MTP plus neutral detergent, the thinner phosphate film produced, combined with very little change in wear protection confirms that, not only is the tribochemistry dominated by calcium sulfonate, but also confirms the anti-scuffing and AW properties that are associated with it as well. Even more surprising, was the significant decrease in wear when the overbased detergent is used. This illustrates not only that the tribochemistry was dominated by the detergent, but also the exceptional AW properties of calcium carbonate.

The Correlation of Microchemical Properties to Antiwear (AW) Performance in Ashless Thiophosphate Oil Additives

X-ray absorption near-edge structure (XANES) spectroscopy at macro-scale (mm 2 ) and X-ray photoelectron emissions microscopy (X-PEEM) at micro-scale (lm 2 ) have been used to investigate the chemistry and spatial distributions of chemical species in tribochemical films generated from ashless thiophosphate oil additives on steel. Two different ashless thiophosphate additives were used: a triaryl monothiophosphate (MTP) and a dialkyldithiophosphate (DTP). Atomic force microscopy (AFM) and secondary electron microscopy (SEM) were also used to investigate the thickness and the topography of the tribofilms. Macro-scale XANES analysis showed that both ashless thiophosphates reacted with the steel surface to produce short to medium chain polyphosphates as the main constituent and sulfur species as minor component. From the PEEM experiment, it was found that the DTP tribofilm was microchemically heterogeneous, with areas of varying degrees of polyphosphate chain length. Conversely, MTP formed a tribofilm microchemically homogeneous, with areas comprised of only short chain polyphosphates. From, the different areas of polyphosphate chain length within the DTP tribofilm, colour-coded polyphosphate distribution map was generated. AFM, X-PEEM and SEM revealed that the DTP film was thicker and was composed of AW pads that were wider in area than MTP. This resulted in a smaller wear scar width (WSW) value for DTP. This is the first time that all these analytical techniques have been combined to better understand the nature of the tribofilms from ashless additives. We have concluded that an ideal AW film is comprised of a thick film with pad-like structures that are wider in area and microchemically heterogeneous, with areas of varying polyphosphate chain length.

Tribological performance and action mechanism of S-[2-(acetamido) thiazol-1-yl] dialkyl dithiocarbamate as additive in rapeseed oil

There has been a growing concern for the use of environmentally friendly lubricants because of the worldwide interest in environmental issues. This has promoted the development of new environmentally friendly lubricants and additives. In this paper, three potential ashless additives, S-[2-(acetamido) thiazol-1-yl] dialkyl dithiocarbamate, were prepared. The tribological behavior of the synthesized compounds as additives in rapeseed oil (RO) were evaluated with a four-ball wear tester. The elemental composition and chemical nature of the antiwear film generated on steel counterfaces were investigated with electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). It was found that the synthesized compounds as additives in rapeseed oil had shown improved extreme pressure and antiwear properties and friction-reducing behavior as compared with the rapeseed oil alone. The protective film containing a reaction layer and adsorption layer was found to be formed on the wear surface. The elemental sulfur contained in the dialkyl dithiocarbamate group and thiazole group may react with counterface metal, and result in the formation of reaction films containing sulfate, organosulfur compounds and FeS 2. The nitrogen element was merely adsorbed on the lubricating surface and did not react with the metal. In addition, the polymerized ester produced by rapeseed oil also played an important role in the adsorption film.

Synthesis of some additives from upgraded petroleum residues of lubricant oil refineries

Aromatic extract residues occur as by-products in petroleum refineries, through the process of refining lubricant oil. These residues are considered as having low economic value, and their disposal may even cause problems for the refineries. The present work looks at upgrading these residues by using them to synthesise different petroleum additives, e.g., antioxidants, ashless dispersants, pour-point depressants, and flow improvers for lubricating crankcase oils and for fuels. The antioxidants were synthesised by reacting mono-aromatics with phosphorus pentasulphide (P2S5) in the presence of zinc oxide (ZnO). Ashless dispersant additives were synthesised by reacting alkylated mono-aromatics (using chlorinated paraffin wax as an alkylating agent) with formaldehyde solution (37%) in the presence of polyisobutylene succinimide. Fuel pour-point depressants and flow improvers can be synthesised by acylating di-aromatics via a Friedel-Crafts reaction. Comparative evaluation of the synthesised products with commercial additives showed them to have good comparative performance properties.

Detergent-dispersant additives for motor oils. Alkylphenolates

Detergent-dispersant additives (DD additives) are widely used in modern motor oils. Detergents are ash additives and dispersants are ashless additives. Some of the most common metal-containing detergents used in the world are metal alkylphenolates, primarily calcium, barium, and magnesium alkylphenolates, which have a high degree of detergent properties. This is due to the broad spectrum of operating properties, relative availability of the initial stock, and simplicity of the manufacturning technology.

The friction and wear behaviors of S-[2- S-(2-hydroxylpropyl)benthiazole]dioctyldithiocarbamic acid ester as additive in liquid paraffin

There has been a growing concern for the use of mineral oils because of the worldwide interest in environmental issues. This has promoted the use of ashless additives as environmental friendly lubricants. A potential ashless additive, S-[2- S-(2-hydroxylpropyl)benthiazole]dioctyldithiocarbamic acid ester, was prepared in this work. The friction and wear behaviors of the synthesized compound as an additive in liquid paraffin were evaluated with a four-ball wear tester. The elemental composition and chemical nature of the antiwear films generated on steel counterface were investigated with electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). It was found that the synthesized additive had excellent antiwear performance. The additive reacted with counterface metal and generated a surface protective film consisting of FeS, organic sulfur compound, FeSO 4, and absorbed compound containing N.

Lubricating properties of ashless thiophosphates and dithiophosphates based on isononylphenol

Nitrogen-containing thiophosphates and dithiophosphates that are prepared from commercial isooctylphenol manifest antiwear properties in mineral oils. The structure of the hydrocarbon radical is a major factor in determining the effectiveness of these additives. Isooctylphenol that is obtained by alkylating phenol with polymer distillate in the presence of the cation exchange resin KU-2-8 as a catalyst is a wide fraction distilling at 100-180{degrees}C under a residual pressure of 667 Pa; dithiophosphate additives prepared from this material consist of mixed dithiophosphates with monosubstituted and partially substituted C{sub 4}-C{sub 16} alkylphenyl radicals. Because of the nonimiformity of structure of such additives, they are readily soluble and highly effective in naphthenic-aromatic base mineral oils. However, the presence of phenol and butylphenols in the alkylphenol has deleterious effects on the additive quality, including a reduction of its solubility in mineral oils. In order to expand the raw material base and improve the additive quality, we have synthesized and investigated certain ashless additives containing sulfur, phosphorus, and nitrogen, prepared with isononylphenol. This isononylphenol distills within the 120-130{degrees}C interval at 400 Pa; it consists of a mixture of p-isononylphenols in which the iso-C{sub 9} alkyl groups vary in structure. We have carried out a comparison of themore » functional properties of thiophosphate and dithiophosphate additives based on isooctylphenol and isononylphenol. As antiwear and antifriction additives for M-11 base oil, we investigated diethylenetriamine salts of dithiophosphoric acids based on isononylphenol (A) and isooctylphenol (A{prime}), and also amidothiophosphates based on isononylphenol (B, C) and isooctylphenol (ATF additive). The ability of these additives to reduce the wear of rubbing pairs was determined.« less

An investigation of the effectiveness of antifriction additives in motor oils by laboratory methods and engine tests

AbstractThe antifriction properties of motor oils with different additives (oil soluble metal‐containing compounds, molybdenum disulphide and graphite dispersions, and ashless additives) were investigated by means of laboratory methods. The influence of additive concentration on their effectiveness is evaluated. The effect of the action of antifriction additives (friction modifiers) depends on the base oil and motor oil additive packages. The results of experiments are analysed using Auger spectroscopy. A mechanism of action of different types of friction modifiers based on analysis of the experimental data is proposed. Diesel engine tests of motor oils with antifriction additives were used to show the influence of these additives on fuel consumption. The results of engine tests with oils with different additives, and tests conducted on laboratory friction‐machines, are compared. A description of the laboratory methods and engine test methods used, as well as recommendations for their practical use in evaluating antifriction properties of motor oil additives, is given.

Ashless dithiophosphate additives for lube oils

Ashless dithiophosphate additives for lube oils

Synthesis and Tribofragmentation of Monothio-Phosphates

Abstract Besides the well-known zinc dithiophosphates (ZDTP) phosphorus and sulfur containing ashless additives are used to improve the lubrication properties of modern engine and hydraulic oils. It is generally accepted that a wear reducing reaction layer is formed by additive tribofragmen-tation reactions in the friction zone of the metal surface. The composition of those reaction layers and the formation mechanism relative to the used additive is quite unknown. By systematic modification of monothiophosphates the influence of molecule parameters on the wear reducing properties were investigated (1).

Effect of ashless additives on antifriction and antiwear properties of mineral oil

The lubricating properties of oils containing amidothiophosphates, two non-Soviet ashless additives designated 1 and 2 for test purposes, and a molybdenum-containing dithiophosphate are evaluated. Additive 1 did not contain any heteroatoms; additive 2 contained 9.1% phosphorus. The additives were separately dissolved in M-11 lubricating base stock at a concentration of 2% by weight and the oils were tested for wear and friction reduction at 20-300 C and 2100 MPa. Dependence of lubricity on temperature and on the structures of the additives were determined. The amidothiophosphates were found to be equal to the molybdenum-containing additive for friction reduction. Additives 1 and 2 tested at much poorer friction reduction coefficients. Results are graphed and tabulated.

Effect of friction modifiers on antifriction properties of motor oil

A molybdenum-containing additive, AF-1, and two ashless additives, AF-2 and AF-3, were used as friction modifiers. The addition of the modifiers lowered the coefficient of friction. Test results on M-6z/10G/sub 1/ oil with various concentrations of the AF-1 additive are presented. The introduction of the modifier should reduce the mechanical losses and fuel consumption and increase the engine speed. The additives were examined for aftereffect; the AF-1 additive gave a prolonged aftereffect and had a high level of antifriction properties, depending on its concentration.