Polyolefin Research Articles

Risk Assessment of Agricultural Plastic Films Based on Release Kinetics of Phthalate Acid Esters.

Plastic films have become an integral part of fruit and vegetable production systems, but their release of phthalate acid esters (PAEs) is a threat to human health. The release kinetics of PAEs and measures of risk are still not well understood. We investigated 50 agricultural films, with concentrations ranging from 2.59 to 282,000 mg kg-1. The seven commercially available film types included were polyvinylchloride (PVC), metallocene polyethylene (mPE), ethylene vinyl acetate (EVA), polyolefin (PO), and three mulch films. Bis(2-ethylhexyl) phthalate (DEHP) was detected in most of films, and its release fitted well into the first-order kinetic model. The release rate of DEHP was negatively related to the film thickness. The potential carcinogenic risks of DEHP in the air of six kinds of plastic greenhouses to human health were estimated. We found that the carcinogenic risks associated with PVC and mPE greenhouse films warrant greater attention. Though EVA, PO greenhouse, and mulch films were lower risk, we advise keeping plastic greenhouses well ventilated during the first month of use to reduce direct human exposure to volatile PAEs.

MIXED CONVECTION HEAT TRANSFER OF SIO2-WATER AND ALUMINA-PAO NANO-LUBRICANTS USED IN A MECHANICAL BALL BEARING

In this study, the mixed convection heat transfer in a mechanical ball bearing filled with nano-lubricants were investigated theoretically. In our case, the bearing including eight balls revolving in counter clockwise while the inner shaft rotates in clockwise direction and the inner and outer walls of bearing were kept at constant hot and cold temperatures, respectively. Two kinds of nano-lubricants SiO2-water and Alumina- Polyalphaolefin (PAO) with different shapes of nanoparticles were considered. The governing equations including velocity, pressure, and temperature formulation were solved based on the Galerkin finite element method. The governing parameters such as nanoparticle volume fraction, Reynolds and Rayleigh numbers, etc., were discussed. It turns out that the average Nusselt number increases by increasing the nanoparticle volume fraction (averagely 15% for each 0.02 increase) and the oil-based nano-lubricant has greater Nusselt number than the water based one. More importantly, the Nono-rod Alumina was found to show much greater heat transfer performance (averagely 5%) than the spherical alumina nanoparticles and nano-rod Alumina-PAO has the best performance and maximum Nusselt numbers for the heat transfer.

Aging Behavior of Flame-retardant Cross-linked Polyolefin under Thermal and Radiation Stresses

In this study, flame-retardant cross-linked polyolefin, which is an important polymeric insulation material for electric power cables, is aged under severe thermal and radiation stresses. After aging, the samples are analyzed mechanically, thermally, and electrically. The degradation of this polymer is found to become very severe when it is aged thermally than when aged by a combination of heat and gamma irradiation. The formation of densely cross-linked structures, induced by the gamma irradiation, appears to make the polymer harder and more resistant against oxidation and against its resultant scission of chemical bonds.

Friction reduction mechanism of glycerol monooleate-containing lubricants at elevated temperature - transition from physisorption to chemisorption.

The friction reduction mechanism of glycerol monooleate (GMO) was investigated under boundary lubrication with elevated temperature. Tribological performances were tested using reciprocating test rig by adding 5 wt.% GMO into Poly-alpha Olefin (PAO) base oil. Friction coefficient and wear were recorded during experiments. The used oil was evaluated by infrared detection after experiments. Results show that GMO could reduce friction coefficient at both low and high temperature. At elevated temperature, the friction coefficient of PAO-GMO blend climb up gradually, followed by a decrease tendency, and the wear increase gradually with temperature. The results of Quartz Crystal Microbalance show that the physical adsorption film plays the main role in friction reduction at low temperature. While at high temperature, the Infrared Spectrum and X-Ray Photoelectron Spectrum show that the GMO involves into the chemisorption with friction surface, producing Fe(OH)O and Fe3O4. The friction reduction mechanism of GMO transferred from physisorption to chemisorption, which reduced friction coefficient at both low and high temperature.

Tribological characterization of ZnO nanofluids as fastener lubricants

Thread galling is a common problem when tightening fasteners. In this research, zinc oxide (ZnO) nanofluids are studied as potential thread lubricants with the goal of eliminating or minimizing galling. The agglomeration of nanofluids results in severe wear, higher friction and other antagonistic behaviors. Therefore, it is important to find suitable surfactants to sufficiently disperse and stabilize the nanoparticles. In this study, various ratios of ZnO nanoparticles were mixed with oleic acid (OA) and polyisobutylene succinic anhydride (PIBSA) surfactants in a polyalphaolefin (PAO) base oil. Dynamic light scattering (DLS) was used to measure the size of ZnO nanoparticles mixed with OA/PIBSA before and after tribotests. PIBSA mixed with ZnO nanoparticles produced superior dispersion and stability than OA mixed with ZnO nanoparticles both before and after tests. A ball on disk rotational tribometer was employed to characterize the friction and wear performance of the prepared nanofluids. Generally, the base oil resulted in significant adhesive wear and microploughing. The addition of OA or PIBSA mitigated the adhesive wear and only mild microploughing was found, because of adsorbed monolayers. However, the addition of nanoparticles led to the recurrence of adhesive wear.

Superlow Wear Realizable Tribofilms from Lubricant Oil Containing Hydrothermally Synthesized Magnesium Silicate Hydroxide/Carbon Core-Shell Nanoplates.

This paper reports on the hydrothermal synthesis of a novel 2D material, magnesium silicate hydroxide/carbon (MSH/C) core-shell nanoplate, in a graphite-MgO-SiO2-NaOH system at 300 °C and 12 MPa for 48 h. Its significant potentials as an antiwear additive in lubricant oil were subsequently demonstrated. The 2D nanoplates consist of an MSH core and a 1-6 nm thick sp2-hybridized carbon shell with a layer spacing of 0.34 nm. In typical four-ball tests at a maximum Hertzian pressure of 3.4 GPa, the MSH/C core-shell nanoplates nearly eliminated wear, whether suspended in poly alpha-olefin oil or fully formulated lubricating oil, and the corresponding volume wear rates were reduced by 96.33% and 72%, respectively. The excellent antiwear performance was ascribed to the formation of a tribofilm consisting of diffusedly distributed Fe3O4 nanocrystals and carbon- and/or SiOx-containing amorphous structures.

Effect of magnetic field on the tribological behaviors of Fe3O4@MoS2 as polyalphaolefin additive in the steel/steel friction interface

To explore ways to improve wear of friction pairs and the efficiency of nano additives, a magnetic lubricating particle, Fe3O4@MoS2 core–shell nanocomposite, was developed as solid additive for polyalphaolefin (PAO) 6, and a magnetic field was applied to steel/steel friction interface for enhancing lubrication effect. The effect of magnetic field on the tribological properties of PAO 6 containing the nanocomposites was investigated using an adapted tribometer. The friction results indicate that although the prepared Fe3O4@MoS2 nanocomposites exhibits good lubrication performance in PAO 6, the friction reduction and anti-wear effect could be further enhanced after applying a magnetic field, and the effect of the magnetic field on tribological properties is closely related to the concentration of nanocomposites in PAO 6. The mechanism of magnetic field on lubrication effect of the magnetic nanocomposites in PAO 6 was analyzed by simulation software, coupling the technology of SEM and XPS.

Effect of long-term aging on waste tire rubber and amorphous poly alpha olefin compound modified asphalt binder and its mixtures

The aging resistance of asphalt mixture has an important impact on the long-term quality and service life of asphalt pavements. This research aims at studying the effects of long-term aging on waste tire rubber (WTR) and amorphous poly alpha olefin (APAO) modified asphalt binder and mixtures. The prepared compounds included, 12%WTR + 4%APAO and 15%WTR + 4%APAO modified asphalts, were used as experimental objects. Base asphalt binder (70 penetration grade), 15%WTR modified asphalt and styrene–butadiene-styrene (SBS) modified asphalt were the reference objects. First, pressure aging vessel (PAV) and long-term oven aging (LTOA) were used to simulate the long-term aging of asphalt binder and mixture, respectively. Secondly, the performance tests of asphalt binder and mixture were carried out, and the evaluation indexes of the effects of long-term aging on performance were proposed. For the asphalt binder, the results show that the incorporation of WTR and APAO significantly improves the post-aging conventional properties, rheological properties and fatigue properties. The Fourier transform infrared spectroscopy (FTIR) results were found to correlate to the physical tests results. In the asphalt mixture part, the results show that 15%WTR + 4%APAO modified mixture has better high temperature and fatigue performance after aging, among the rubber-based asphalt mixtures. The low-temperature performance of WTR/APAO asphalt mixture was not compromised after aging. Compared with the SBS modified asphalt mixture, the high and low-temperature performance of 15%WTR + 4%APAO asphalt mixture after aging are better. Overall, 15%WTR+4% APAO asphalt mixture has better advantages to counteract the influence of oxidative aging.

Modern trends in the processing of linear alpha olefins to technologically important products. Part 2

This review is a continuation of the first part, which considered modern trends in the processing of linear alpha olefins to (co)polymers of ethylene, anionic and non-ionic surfactants. Important directions in LAO processing are briefly described: alkylation leading to the formation of linear alkylbenzenes, oligomerization of alpha olefins to poly alpha olefins, sulfation yielding alpha olefin sulfonates, and other bulky processes.

Taguchi optimization of various parameters for tribological performance of polyalphaolefins based nanolubricants

This research paper addresses the optimization of various control parameters by using the Taguchi method to assess the tribological properties of PAOs based nanolubricants. The concentration of COOH-functionalized multiwalled carbon nanotubes (MWCNTs), applied load, sliding velocity and kinematic viscosity of polyalphaolefins (PAOs) were selected as process parameters or control factor. The MWCNTs at a varying concentration (0.025-0.15 wt.%) were blended separately in PAOs to formulate the nanolubricants. The tribological experimentations were performed by Taguchi’ L18 mixed orthogonal array using “ball on disc” type tribometer. The analysis of variance (ANOVA) was adopted to estimate the most prominent factors influencing the tribological performance of nanolubricants. The statistical results showed that the applied load, followed by a concentration of MWCNTs conferred the most significant impact on the frictional characteristic. In contrast, the kinematic viscosity of PAOs, followed by concentration of MWCNTs has been observed the most significant influencing factors on the antiwear properties of nanolubricants. The probabilistic rationale for the advancement in friction and wear properties were assessed through various analytical tools.

Effectiveness of glycerol-monooleate in high-performance polymer tribo-systems

High performance polymers possessing superior mechanical properties may replace metal components and improve machine efficiency. Successful replacement, however, relies on the compatibility of these polymers with current engineering systems, including lubricants and their additives. This study examines the compatibility of two high performance polymers, polyetheretherketone (PEEK) and polyamide-imide (PAI), with glycerol monooleate (GMO), an organic friction modifier (OFM) commonly used in steel-steel rubbing contacts. Friction tests were conducted with a ball-on-disc geometry in reciprocating motion at 100 °C in polyalphaolefin (PAO) base oil. GMO reduces friction in polymer-steel and polymer-polymer contacts. When steel is involved, the use of GMO and oleic acid (OA) give similar friction coefficients. Since OA is believed to be a hydrolyzed product of GMO in steel-steel contacts, our results show that the interaction of OA with steel controls friction in polymer-steel contacts when GMO is the additive. Results from FTIR and Raman spectroscopies show that steel surfaces contain little to no polymeric materials, nor iron oxides after rubbing against polymers in GMO- and OA-containing PAO. This supports OFM layers are formed on steel surfaces. These OFM layers prevent polymer transfer layer formation and possibly protect steel surfaces from oxidation. Our results show that using OFM that interacts strongly with steel can, contrary to dry friction, eliminate the need of polymeric transfer film on steel for achieving low friction in polymer-steel contacts.

Heat transfer measurements of Polyalpha-Olefin- boron nitride nanofluids for thermal management and lubrication applications

In this paper, the first study is reported combining Polyalpha-Olefin (PAO) oil with hexagonal Boron Nitride (hBN) to produce new class of nanofluids for heat transfer and lubrication applications. The heat transfer performance of the nanofluids is studied experimentally along with their viscosity, specific heat, thermal diffusivity and thermal conductivity. Thermophysical properties relations are derived as a function of temperature and nano particle concentration. Heat transfer experiments are conducted for both the PAO base fluid and nanofluid as a function of Reynolds number. It is found that PAO/hBN nanofluids exhibit Newtonian behavior as a function of temperature (from −20 to 70 °C) and volume concentration (0.25–1%). The viscosity decreases with temperature for both base fluid and PAO/hNB nanofluids and increases with concentration. The specific heat increases with temperature by 44% from 45 °C to 95 °C for pure PAO and by 48% for nanofluid with 1% concentration. The thermal conductivity of nanofluids is significantly higher than that of pure PAO and it increases by increasing hBN concentration. The thermal conductivity decreases with temperature for pure PAO and nanofluids unlike other nanofluids. The heat transfer enhancement in terms of Nussel Number showed average and maximum values of 10%–13%, 17%–20% and 26%–29% for hBN concentration of 0.25%, 0.6% and 1%, respectively. Two competing phenomena affect the heat transfer performance: the increase/decrease in resistance to thermal diffusion sublayer when thermal conductivity increases and viscosity decreases, respectively. For the PAO/hBN nanofluids, the increase in thermal conductivity caused the heat transfer enhancement.

Enhanced lubricating properties of oils containing graphene synthesized in atmospheric plasmas

The use of gas-phase-synthesized graphene (GSG) as a lubricant additive that is capable of significantly enhancing the tribological properties of widely used oils is reported herein. GSG is pure, highly ordered, and exhibits an inherently crumpled morphology that causes the nanomaterial to self-disperse and resist aggregation in base oils and fully formulated lubricants. Micro-tribometer tests revealed that the wear of sliding surfaces was significantly reduced by up to 53% when relatively minute amounts of GSG (≤ 0.1 wt%) was added to canola oil, polyalphaolefin (PAO), fully-formulated petroleum oil, and fully-formulated full synthetic oil. Additionally, the wear reduction of surfaces caused by GSG remained consistent as the concentration of the nanomaterial was reduced in PAO, which indicates that GSG concentrations below 0.025 wt% in base oil could achieve similar reductions in wear. A controllable GSG segregation phenomenon in PAO is reported, which has the potential to enable the controlled wear of sliding surfaces and the recycling of GSG additives. GSG is produced in a single step through an environmentally friendly atmospheric plasma process. Our results demonstrate that GSG holds promise as a sustainable and effective anti-wear additive for lubricants used in engines and other tribological applications.

Origin of the tribofilm from MoS2 nanoparticle oil additives: Dependence of oil film thickness on particle aggregation in rolling point contact

The lubrication effectiveness of MoS2 nanoparticles as an oil additive remains unclear, restricting its application in industry to reduce friction. The goal of this work was to explore the lubrication mechanism of MoS2 nanoparticles as an oil additive. In this study, the oil film thickness behaviors of MoS2 nanoparticles in poly-alpha olefin (PAO4) base oil, PAO4 with 3 wt% dispersant (polyisobutyleneamine succinimide, PIBS), and 0W20 engine oil were investigated using an elastohydrodynamic lubrication (EHL) testing machine. Following the EHL tests, the flow patterns around the contact area and the tribofilm covering rate on contact area were studied using optical microscopy to understand the lubrication mechanism. The results indicate that both the dispersant and nanoparticle aggregation significantly affected the oil film thickness. The expected oil film thickness increase in the case of 0.1 wt% MoS2 in PAO4 base oil was obtained, with an increase from 30 to 60 nm over 15 min at a velocity of 50 mm/s. Flow pattern analysis revealed the formation of particle aggregation on the rolling path when lubricated with 0.1 wt% MoS2, which is associated with a tribofilm coverage rate of 41.5% on the contact area. However, an oil film thickness increase and particle aggregation were not observed during the tests with 0.1 wt% MoS2 blended with 3 wt% PIBS as the dispersant in PAO4 base oil, and for 0.75 wt% MoS2 in 0W20 engine oil. The results suggest that nanoparticles responsible for tribofilm formation originated from aggregates, but not the well-dispersed nanoparticles in point contact. This understanding should aid the advancement of novel lubricant additive design.

Insights into the tribological behavior of IF-WS2 nanoparticle reinforced mild extreme pressure lubrication for coated chromium/bulk grey cast iron interface

This study reports a novel synergetic approach combining nano-lubrication and conventional extreme pressure additivation, to explore the tribological performance of piston ring/cylinder liner conformal contact. Three typical lubricating formulations, viz, (i) PAO (poly-alpha-olefin) base oil (ii) base oil with mild extreme pressure (MEP) additive, and (iii) base oil with composite blend of mild extreme pressure (MEP) additive and WS2 nano-particles, were investigated using an ASTM G-99 Standard customized universal tribometer for evaluating friction and wear behavior of coated chromium/bulk grey cast iron (CI) tribopair. The lubricant formulations were tested at engine working temperature of 200 °C, reciprocated under a normal load of 30 N, stroke length of 10 mm and a constant sliding velocity of 0.2 ms−1. Wear attributes were evaluated by employing non-contact based 3 D optical profilometry. For assessment of tribo-surface morphology and associated surface characterization, Elemental Dispersion Spectral (EDS) incorporated Scanning Electron Microscope (SEM) was utilised. Green Laser Raman spectroscopy investigated tribo-chemistry, synergetic interactions and tribo-film formations. A state approaching super-lubricity and ultralow friction was achieved by sliding grey CI (Plateau Honed) cylinder liner against electroplated chrome stainless steel top compression ring with PAO10 base oil ultrasonically dispersed with 1 vol% of Isopropyl phenyl Phosphate (IPP), a mild extreme pressure (MEP) triaryl phosphate additive & 1 wt.% of WS2. Results obtained therein demonstrated four dominating forms of wear on the cast iron surface, i.e. plowing wear, abrasive wear, adhesive wear and oxidative wear. Counterpart chromium surface exhibited plowing and abrasive wear only. This substantial friction and wear reduction are attributed to the coalesced intrinsic characteristics of MEP and IF-WS2 additives, thus improving the overall lubrication characteristics of base oil.

Acute and two-week inhalation toxicity studies in rats for Polyalphaolefin (PAO) fluid

ABSTRACT Formal occupational exposure limits (OELs) for polyalphaolefin (PAO) fluids have not been proposed. Specific PAO fluids are utilized as aircraft hydraulics or heat sink coolants for electronics and aircraft service air. Toxicity was compared for a PAO fluid in male and female Fischer 344 rats using acute inhalation (0, 100, 500, or 1000 mg/m3 aerosol for 6 hr) and two-week inhalation (0, 20, 100, or 300 mg/m3 aerosol for 6 hr/day, 5 days/week) studies. Neurobehavioral tests following acute exposure showed that both genders were less responsive after exposure to 1000 mg/m3 PAO, and to a lesser extent following 500 mg/m3 PAO. Body weight, food, and water consumption were also affected with recovery after 24 hr. Histopathology for the acute group demonstrated an exposure response increase in severity (minimal to mild) of lesions in the posterior nasal cavities and lungs. Severity of lesions was reduced in the recovery groups (normal to minimal). Acute effects were short-lived and recoverable. Following the two-week exposure, effects were limited to lesions only in the posterior nasal cavities and lungs of the high exposure group, with less severity than in the acute exposure high concentration group. Short-term repeated exposure did not result in any cumulative effects except for minimal respiratory tract changes in the 300 mg/m3 exposure group. Data-driven operational exposure limits (OpELs) were proposed based upon Acute Exposure Guideline Levels process resulting in values of 28, 28, 14, 3.5, and 1.7 mg/m3 for 10 and 30 min, 1, 4, and 8 hr, respectively.

Study of pressure dependence on sinterable zirconia nanoparticle tribofilm growth

Tribological sintering of antiwear films as a function of applied load has been investigated using a novel zirconia nanoparticle antiwear additive. Spherical five nanometer diameter zirconium oxide (ZrO2) nanoparticles are dispersed in polyalphaolefin (PAO) synthetic base oil and tested between AISI 52100 steel counterfaces in a ball-on-disk tribometer with a slide-to-roll ratio of 50%. The apparatus allows tribofilm thickness data to be tracked in-situ at set intervals, and tribofilms reaching a maximum thickness of 160 nm have been measured. A tribofilm formation dependence on load has been found, as higher loads assist initial growth and final thickness. Contrary to the chemical tribofilm formation processes of traditional antiwear additives such as zinc dialkyldithiophosphate (ZDDP), testing suggests the primary mechanism of tribofilm growth for zirconium oxide is nanoparticle adsorption followed by particle accumulation and sintering. A strong correlation between friction force, tribofilm width and Hertzian contact theory has been found. Initial tribofilm growth rate grew exponentially with applied load, whereas isolation of the linear growth phase yielded a linear relationship. Mechanical stylus, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) are employed to investigate the roughness, morphology and chemical nature of the sintered tribofilms, respectively.

The Tribological Mechanism of Cerium Oxide Nanoparticles as Lubricant Additive of Poly-Alpha Olefin

Oleylamine (hereinafter referred to as OM)-modified CeO2 nanoparticles were synthesized by a one-pot pyrolysis method. The tribological properties of the as-prepared CeO2 nanoparticles as the lubricant additive in poly-alpha olefin (PAO) were investigated with a four-ball machine, and their lubricating mechanism was discussed in relation to worn surface analyses by SEM, EDS, and XPS. Findings indicate that these nanoparticles exhibit good dispersibility as well as excellent anti-wear ability in PAO. This is because OM-modified CeO2 nanoparticles can catalyze the oxidation of metallic Fe to form ferrite oxide-containing tribo-film. Under the condition of ASTM D2266-2001, the same lowest WDS was obtained at the concentration of 0.2 wt% and 1.8 wt%. When the concentration of CeO2 is 0.2 wt%, a compact catalytic oxidation tribo-film is formed, which has more outstanding long-term anti-wear ability. When 1.8 wt% CeO2 is added, the tribo-film formed is the combination of catalytic oxidation film and ceria deposition film, which has more significant bearing capacity.

Excessive shaft wear due to radial shaft seals in lubricated environment. Part I: Analysis and mechanisms

Within the last years, the amount of fluorelastomer (FKM) seals are increasing dramatically in industrial applications such as gearboxes due to its outstanding characteristics and superior performance. In terms of thermal stability resistance and compatibility towards lubricants FKM has wider application ranges compared to other sealing elastomers. However combined with low-viscosity, synthetic lubricants i.e. polyalphaolefin (PAO) or polyalkylene glycols (PG) macroscopic wear grooves were reported on hardened shafts. This can, but does not necessarily lead to leakage and the breakdown of a sealing system, which may cause serious damage to the environment and the machine, where the functionality of the seal is often crucial for the whole system. So far a clear explanation does not exist, just a few theories or assumptions, for this behavior can be found in the literature.Driven by that fact this article presents a detailed wear analysis of a critical combination for shaft wear in a system of fluorelastomer seal, polyalphaolefin lubricant and case hardened and twist-free ground shafts of AISI 5115 (1.7131,16MnCr5). The wear behavior of state-of-the-art radial shaft seals out of fluorelastomer seals was investigated. This wear phenomenon was reproduced using endurance tests on a multi-shaft test rig. Typical characteristic parameters and values of the sealing system performance were analyzed and correlated to shaft wear. For further understanding of this system, selected samples were analyzed with different recent methods of surface and thin film analysis.The results indicate that there is a clear relation between seal and shaft wear. The occurrence of shaft wear is also caused and influenced by a complex combination of lubricant-elastomer interaction. Based on this findings, a wear hypothesis is derived.

Formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a diamond‐like carbon (DLC) coating

AbstractDiamond‐like carbon (DLC) coatings are nowadays successfully applied on industrial components like pistons, piston rings and bearings in lubricated tribological contacts due to friction and wear reducing effects. In contradiction thereto, todays lubricants and additives are designed for tribological steel/steel contacts, whereby the knowledge on tribochemical layer formation on steel surfaces is comprehensive in contrast to the physical‐chemical interactions between diamond‐like carbon coatings, lubricants and additives. Therefore the formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a zirconium modified diamond‐like carbon coating a‐C : H : Zr (ZrCg) in lubricated tribological contacts were analyzed by means of pin‐on‐disc (PoD) tribometer by varying the distances from s = 200 m–3,000 m under boundary and mixed friction conditions at T = 90 °C and a contact pressure p = 1,300 MPa regarding the application of diamond‐like carbon coatings on gears. The base lubricant poly‐alpha‐olefin (PAO) was formulated using the anti‐wear (AW) and extreme pressure (EP) additive zinc dialkyldithiophosphate (ZnDTP) and the friction modifier (FM) additive molybdenum dialkyldithiophosphate (MoDTP). The chemical composition of the tribochemical reaction layers by means of and Raman spectroscopy and x‐ray photoelectron spectroscopy (XPS) as well as for the thickness differ significantly by varying the additivation.