Oil-based Lubricants Research Articles

Influence of green synthesized aluminum oxide nanoparticle concentration on wear and coefficient of friction of vegetable oil-based lubricants

Influence of green synthesized aluminum oxide nanoparticle concentration on wear and coefficient of friction of vegetable oil-based lubricants

Susceptibility of Poly–Alpha Olefin and Diisooctyl Sebacate Base Oils With Different Polarities to Oleic Acid Surface–Capped Ultra‐Small Cerium Oxide Nanoparticle

ABSTRACTA key issue for nano‐additive to effectively exert tribological function is to ensure its entrance to and adhesion on the frictional contact surfaces. But the adhesion of nano‐additive on the rubbed surfaces under oil lubrication faces the challenge of the competitive adsorption of lubricant base oil thereon. In this study, oleic acid–modified ultra‐small cerium oxide (OA‐CeO2) nanoparticle was synthesised by one‐pot liquid‐phase surface‐modification method in the presence of OA as the surface modifier. The susceptibility of non‐polar poly–alpha olefin 6 (PAO6) and polar diisooctyl sebacate (DIOS) base oils to the as‐prepared OA‐CeO2 nano‐additive was investigated, and the effect of the OA‐CeO2 nano‐additive on the friction‐reducing and anti‐wear abilities of the two kinds of base oils towards a steel–steel sliding contact was investigated with four‐ball friction and wear tester. Furthermore, the tribological mechanism of the adsorption and deposition of the OA‐CeO2 nano‐additive on the surface of friction steel and the competitive adsorption of base oil were discussed. Characterisations by scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy demonstrate that the as‐prepared OA‐CeO2 nanoparticle is of a spherical shape and has an ultra‐small average size of 1.2 nm. As the lubricant additive in PAO6 and DIOS base oils, the OA‐CeO2 nano‐additive exhibits different tribological properties, which is attributed to the difference in the base oils' polarity. Namely, the CeO2 nanoparticle in the non‐polar PAO6 base oil is more easily adsorbed on the rubbed surface of the steel–steel sliding contact, thereby forming the CeO2 deposition film to improve the tribological properties of the base oil. However, the CeO2 nanoparticle added in polar DIOS base oil is difficult to form the CeO2 deposition film, because of the competitive and preferential adsorption of the polar base oil on the rubbed steel surface. Therefore, it is imperative to select the base oils with proper polarity to better exert the friction‐reducing and anti‐wear functions of the OA‐CeO2 nano‐additive.

Friction Reduction Achieved by Ultraviolet Illumination on TiO2 Surface.

Controlling friction by light field is a low-cost, low-energy, non-polluting method. By applying ultraviolet light on the surface of photosensitive materials, the properties of the friction pairs or lubricant can be influenced, thus achieving the purpose of reducing friction. In this study, TiO2, an inorganic photosensitive material, was selected to investigate the modulating effect of light fields on friction lubrication when using polyalphaolefin (PAO) base oil as a lubricant, and the modulation law of light fields on the friction lubrication behavior was investigated under different loads (1-8 N), different speeds (20-380 mm/s), and different viscosities (10.1-108.6 mPa·s) of PAO base oil. The experimental results showed that light treatment could reduce the friction coefficient of PAO4 base oil lubrication from 0.034 to 0.016, with a reduction of 52.9% under conditions of 3 N-load and 56.5 mm/s-speed, and the best regulation effect could be achieved under the mixed lubrication condition. After TiO2 was treated with ultraviolet light, due to its photocatalytic property, PAO molecules were oxidized and adsorbed on the TiO2 surface to form an adsorption layer, which avoided the direct contact of rough peaks and thus reduced the friction coefficient. This study combines photosensitivity, photocatalysis, and friction, presenting a method to reduce the friction coefficient by applying a light field without changing the friction pairs or lubricants, which provides a new direction for friction modulation and gives new ideas for practical applications.

Insight into the catalytic behavior of ionic liquids and deactivation suppression technique in naphthalene alkylation

Lewis acidic ionic liquids as catalysts for alkylation reactions exhibited the potential for industrial application. Herein, the catalytic behavior of AlCl3-based ionic liquids with four organic ammonium salts was studied in the alkylation of naphthalene with n-octene for production of lubricating base oil, with special focus on the deactivation and recovery of ionic liquid. The Et3NHCl-AlCl3 ionic liquid exhibited better catalytic performance than others due to its stronger interaction with naphthalene, as evidenced by the adsorption test of naphthalene over ionic liquids. To understand the deactivation mechanism, the deactivated catalysts were extensively characterized by FT-IR and UV–vis. The protonation effect of ionic liquids on polyalkylation products in the presence of HCl was found to aggravate the deactivation of ionic liquid. The negative effect is easily reversed by the decompression treatment on the reaction system before catalyst recovery, this method markedly enhanced the cycling durability of ionic liquids for industrial application.

Sliding tribological properties of nano-sized ceramic particles as oil-based lubricant additives

The present research investigated the lubricating performance of ZnO, SiO2, and WS2 nanoparticles as oil additives applied on steel frictional pairs. The study consisted of two stages. In first stage, the lubricating properties of nanofluids were examined using the various nanoparticle concentrations. It was obtained that the 3wt% ZnO, 5wt% SiO2, and 3wt% WS2 nanofluids showed the best performance. In second stage, an orthogonal test matrix was designed to understand the influences of load, sliding frequency and surface roughness on the lubricating behavior of the nanofluids. It was found that the frequency and load had the most significant effects on the friction reduction and anti-wear properties of ZnO, SiO2, and WS2 nanofluids. By using scanning electron microscopy and energy dispersive X-ray spectroscopy for potential mechanisms. It was found that the nanoparticles could be physically embedded, and adhered to the worn areas to form tribo-films resulting in improved tribological performance.

Mechanochemical Synthesis of Thiadiazole Functionalized COF as Oil-Based Lubricant Additive for Reducing Friction and Wear.

In this work, the functionalized covalent organic framework (COF) was prepared via a convenient ball milling process. The aldehyde group terminated COF-F reacted with amino thiadiazole in the ball milling jar under mechanical forces; hence, the thiadiazole functionalized COF-F was obtained and denoted as Thdz@COF-F. The as-prepared Thdz@COF-F serves as an oil-based lubricant additive and exhibits remarkable tribological properties, which can reduce the average friction coefficient of base oil from 0.169 to 0.102 and decrease the wear volume by 87.0%. The antifriction and antiwear performances are mainly due to the repairing effect of Thdz@COF-F nanoparticles and the protective tribo-film that averts the direct contact of friction pairs. In addition, through the ball milling method, triazole and thiazole functionalized COF-F were also prepared and represented good lubrication performance, demonstrating the feasibility of this mechanochemical synthesis method for functionalized COFs.

Fabrication of 3D porous graphene materials for oil-based lubrication: Tribological and wear performance

Micro- and nano-scale carbon materials have been extensively investigated as additives in lubricants owing to their remarkable capability for friction reduction and enhancement of thermal conductivity within lubrication systems. Nevertheless, it is still highly desirable for oil-based lubricants to involve well-dispersed ultrafine carbonaceous particles without complicated chemical modification. Herein, we present a strategy to achieve 3D graphene additive in lubricants based on rapid laser irradiation. Notably, PAO4 containing 3D laser-induced graphene (LIG) additive exhibits excellent tribological properties in comparison with many other unmodified carbonaceous materials, including graphene, graphene oxide, single-wall nanotubes, and carbon black. In addition, the lubrication properties of PAO4 can be significantly improved by manipulating the concentration of the 3D LIG additive. With the addition of only 0.1 wt% 3D LIG-10, PAO4 lubricant system shows a reduction of 22% in coefficient of friction (COF) and a reduction of 95% in terms of wear coefficient compared to the base oil. In this work we provided a new strategy to produce 3D graphene oil additives for excellent tribological and wear performance.

Multifunctional Aluminum Pre-treatments from End-Functionalized Phosphonic Acid Self-Assembled Monolayers.

Aluminum alloys are used in advanced engineering applications as they possess a combination of favorable properties, including high strength, lightweightness, good corrosion resistance, machineability, and recyclability. Such applications often require forming the sheets into the final components, which is typically aided by an oil-based lubricant, followed by joining them using adhesives, which is hampered by residual lubricant. In this work, aluminum surfaces were modified with different self-assembled monolayers (SAMs), with the goal of significantly reducing the amount of lubricant while simultaneously improving friction properties, forming, and bonding performance. Our results show that SAMs terminated with hydrophilic and nucleophilic end groups give rise to high-energy surfaces with wetting properties that are stable over time. These surfaces showed significantly improved surface wetting by the lubricant, which in turn resulted in an improved forming performance at reduced lubricant coat weights. Moreover, the nucleophilic SAM termination provided outstanding performance in adhesive bonding tests under corrosive conditions.

Comparison between methacrylate copolymers and their magnetite nanocomposite as pour point depressant for lubricating base oil

A novel pour point depressant was synthesized by developing a polymeric nanocomposite using polymethacrylate and magnetite nanoparticles. The primary objective was to assess and compare the efficacy of PMA and PMA/Fe3O4 nanocomposite in reducing the gelation point, yield stress, apparent viscosity, and pour point of waxy crude oil. Extensive assessments were conducted to evaluate the performance of these additives. Rheometry tests were employed to measure the pour point of the lubricating oil pour point following the addition of PMA and PMA/Fe3O4 nanocomposite. The findings demonstrated a significant reduction in pour point, reaching values of − 18 °C, − 27 °C, − 24 °C, and − 36 °C for CP1, CP2, NP1, and NP2, respectively, at an optimal concentration of 10,000 ppm. Various characterization techniques such as Fourier Transform Infrared Spectrometer, Proton Nuclear Magnetic Resonance, X-ray Diffraction, Scanning Electron Microscope, Differential Scanning Calorimetry, Dynamic Light Scattering, Polarized Optical Microscope, and Gel Permeation Chromatography were utilized to analyze the polymers. Furthermore, the effectiveness of each polymer as a viscosity index improver (VII) and pour point depressant for mineral-based oil was evaluated. The mechanism of action of the polymers as pour point depressants was investigated through photomicrographic analysis. Additionally, the rheological properties of the formulated lubricant were assessed and reported. Thermogravimetric analysis was used to determine the thermal stability of the polymers, revealing that the copolymer nanocomposites exhibited higher thermal stability, viscosity index (VI), and molecular weights compared to the copolymers alone. These enhancements in thermal stability and molecular properties contributed to the improved pour point depressant (PPD) properties. Overall, the study successfully synthesized a novel pour point depressant and evaluated its performance using various tests and characterization techniques. The results demonstrated the effectiveness of the additives in reducing the pour point and improving the thermal stability of the lubricating oil.

Spiral-wound organic solvent membrane modules for dewaxing solvent recovery

The petrochemical industry is typically energy-intensive, involving frequent and intricate separation processes. SINOPEC is a globally recognized lubricant manufacturer and distributor, with a substantial production capacity exceeding 1.7 million tonnes in 2022. The dewaxing solvent recovery process in lubricant production necessitates a multi-stage flash and distillation treatment, resulting in substantial energy consumption and high costs. Utilizing organic solvent nanofiltration (OSN) membranes offers a feasible alternative approach to address this issue. A series of thin film composite OSN membranes with varying molecule weight cut-offs were prepared through precise adjustment of the chemical composition and proportion of the organic co-monomers. The application potential of the optimized membranes in the lubricant dewaxing solvent recovery was evaluated using lubricant base oil derived from the actual production line, specifically light deasphalted oil and vacuum cut2. The membrane exhibited a rejection of 99.3 % for light deasphalted oil and 95.6 % for vacuum cut2, with corresponding fluxes of 16.8 and 13.4 LMH under 2 MPa, respectively. Based on this, spiral-wound membrane modules (1.8″ × 12″) were fabricated and their suitability for dewaxing solvent recovery was further validated. The fabrication of spiral-wound membrane modules (8″ × 40″) is in progress, with intentions to conduct a pilot plant trial on the lubricant oil manufacturing line.

Preparation, Characterization, and Lubrication Performances of Water-Based Nanolubricant for Micro Rolling Strips.

Water-based nanolubricants are widely used in rolling processes due to their unique characteristics. As a common additive, nanoparticles could significantly improve the tribological properties of the lubricant. However, the effect of the physical properties of the particles on the anti-friction behavior is unclear. In this study, the effect of Fe3O4 nanoparticles as an additive for the prepared lubricant is studied. The tribological properties of Fe3O4 water-based nanolubricant are examined using a tribometer and a scratch meter. The absorption energy is calculated using the molecular dynamic simulation method, and the best parameters for the preparation of the nanolubricant are obtained. The developed nanolubricant is used in the rolling process. The results show that the processing quality of samples is promoted and the tribological properties of water-based lubricant can be significantly promoted by an Fe3O4 nanoparticle additive. An economical and environmentally friendly method is presented through which the water-based Fe3O4 nanolubricant can be prepared for the replacement of oil-based lubricant in cold rolling strips.

Investigative Analysis of Automatic Mode Detection for a Lubricant Base Oil Production Plant Using PCA and Machine-Learning Models.

Lubricants are important fluids and are commonly used to suppress friction between two metallic surfaces and as a medium for heat transportation. In an industrial plant considered in this study, the base oil mode changes can only be detected based on the kinematic viscosity values obtained using lab analysis. Since the lab analysis data are only available every 8 h, detecting the change in the production modes for 4, 6, and 10 cSt and the transitions among them are significantly delayed, causing unnecessary off-spec products that have to be directed to the slopping tank. In this paper, the innovativeness of the work comes from the idea of trying to unravel the underlying pattern of the plant data that correlate to the changes in the base oil modes and using that to classify hourly the kinematic viscosity values. Hence, a novel industrial application is presented to predict the class of base oil mode change on an hourly basis that can significantly reduce the losses in terms of off spec products and sloping tank wastes. The modes are segregated into three classes based on the values of kinematic viscosity. The classes are C-1 (4 cSt), C-2 (6 cSt), and C-3 (10 cSt). Anything in between the stipulated thresholds is called transition [T-12 (C-1 to C-2), T-21(C-2 to C-1), T-23 (C-2 to C-3), T-31 (C-3 to C-1), and T-32 (C-3 to C-2)]. To unravel the pattern, principal component analysis (PCA) is utilized on 42,000 operating plant data. After a thorough analysis, the third principal component provides the highest correlation to the eight classes of the base oil mode changes [C-1 (4 cSt), C-2 (6 cSt), and C-3 (10 cSt) and the transitions T-12 (C-1 to C-2), T-21(C-2 to C-1), T-23 (C-2 to C-3), T-31 (C-3 to C-1), and T-32 (C-3 to C-2)]. This third principal component is then utilized together with plant process variable values as inputs to four machine learning models, namely, XGBOOST, Random Forest, and CatBoost algorithms to predict the mode of the base oil hourly. The overall comparison analysis shows that utilizing the XGBoost algorithm for the prediction of the eight classes of the base oil modes at a faster hourly rate results in the most consistent classification accuracy of 92.96% for the test set and 89.22% in the deployment set. This capability to predict the mode change in the hourly basis can significantly reduce the losses in terms of off spec products in the production line.

Laser manufactured-liquid metal nanodroplets intercalated Mxene as oil-based lubricant additives for reducing friction and wear

Two-dimensional (2D) material MXene is a research hotspot in lubricating materials because of its unique layered structure, which provides weak interlayer interaction and easy shear ability. Herein, the liquid metal nanodroplets intercalated MXene were successfully prepared via pulsed laser treatment and self-assembly method. First, zero-dimensional (0D) nano gallium-based liquid metal (GLM) was synthesized by pulsed laser irradiation of bulk Ga80In20 in acetone. Then, the GLM nanodroplets were loaded onto 2D MXene nanosheets via the effect of electrostatic adsorption to prepare MXene@GLM composite material. The as-obtained GLM not only widens the interlayer distance between MXene nanosheets, making it more susceptible to interlayer shear, but also enhances its lipophilicity. The friction test results showed that the MXene@GLM has the best lubrication performance with 1.0 wt% additive. The coefficient of friction (COF) of base oil PAO-6 can decrease from 0.79 to 0.097, the wear volume is reduced by 90.3 %, and the maximum load sustained reaches 950 N. The good tribological properties are mainly owing to the synergistic lubrication of GLM and MXene, which can form a continuous and firm tribofilm on the friction contact surface and avoid the direct contact of the friction pair.

Rheological effects of montmorillonite and ethyl cellulose for Xanthoceras sorbifolium Bunge oil-based lubricants

Xanthoceras sorbifolium Bunge oil exhibits favorable characteristics such as excellent low temperature fluidity, high flash point, and degradability. However, it also suffers from drawbacks including low kinematic viscosity at low temperatures and significant loss of kinematic viscosity at high temperatures. In view of these characteristics of X. sorbifolium oil, it was modified in this work with a combination of ethyl cellulose (EC), montmorillonite (MMT), and cetyltrimethylammonium chloride (CTAB). The effects of temperature, time, and additive content on the rheological properties of lubricating oil were studied. The kinematic viscosity of the prepared lubricating oil reached up to 433 mm2/s at 40 °C and 51.1 mm2/s at 100 °C. The coagulation point could be reduced to -25 °C, the friction coefficient was 0.026, and the average wear spot diameter was 0.81 mm, The anti-friction performance was enhanced, and the anti-wear performance decreased somewhat. The prepared lubricating oil had the characteristics of high kinematic viscosity at high temperature and excellent rheological properties at low temperature. It also met the energy and environmental application requirements of a green, environmentally friendly, and biodegradable sustainable development strategy. This study greatly broadens the application range of lubricating oil.

Eksperimentalna procena biomaziva sa dodatkom nanočestica kalcijum karbonata (CaCO₃) iz otpada ljuske kapice kao tečnosti za sečenje korišćenjem minimalne količine podmazivanja (MKL) u CNC procesu glodanja

Nano-cutting fluid sprayed using the minimum quantity lubricant (MQL) method is one example of a green manufacturing process. Meanwhile, vegetable oil is an appropriate lubricating base oil as it offers very high lubricating performance and environmental friendliness. Further, CaCO₃ nanoparticles are popular for their capacity to improve lubrication properties and performance. However, the optimum impact of utilizing different types of vegetable oil remains inadequately investigated. Therefore, this study aims to analyze the effect of CaCO₃ nanoparticles on the performance of cutting fluid, specifically on the thermophysical, rheological, and tribological properties in the CNC milling process of AISI 1045 Steel material. The nano-cutting fluid was prepared using different vegetable oils (canola, corn, soybean) added with CaCO₃ nanoparticles with a mass concentration of 0.15%. The results showed that the thermophysical properties, including density and viscosity, were highest when using canola oil, and the addition of CaCO₃ to all samples did not significantly affect thermal conductivity. Meanwhile, for the rheological properties, we observed Newtonian for all cutting fluid samples. For tribological properties, canola, and corn oil were better for obtaining a minimum Ra value, while soyabean oil was more effective in reducing cutting temperature. Based on the results of tool wear calculations, each oil presents the best performance in reducing wear, especially with the addition of CaCO₃. For chip formation, on average, the samples produce irregular tooth morphology with C-type, comma, and elongation shapes. Meanwhile, the resulting chip color was dark purple, which changed to dark brown and light brown, then turned silvery white due to wear and tear on the different sides of the chisel.

Versatile Pickering emulsion gel lubricants stabilized by cooperative interfacial graphene oxide-polymer assemblies.

Although a large number of water- and oil-based gel lubricants have found extensive potential applications in industrial and biomedical fields, developing new-type emulsion-based gel lubricants that may effectively integrate their characteristics and preponderances remains a significant challenge. Here a water-in-oil Pickering emulsion gel lubricant that is able to combine the high colloidal stability of traditional Pickering emulsions, the good swelling and corrosion resistance of oil-based gel lubricants, and the high cooling capacity of water-based gel lubricants prepared from a binary mixture of aqueous graphene oxide (GO) dispersion and diamino-functionalized polydimethylsiloxane oil solution in a broad concentration, pH, and water volume fraction range is reported. It can provide favourable lubrication for the Si3N4/steel and Si3N4/silicone tribopairs either in air or under water owing to the formation of a sturdy adsorbed oil film and ball-bearing actions of the GO particles. It can also be printed into various colourful 2D and 3D geometries upon direct extrusion into water, thanks to its water-in-oil nature and inherent shear-thinning and thixotropic properties, which further shows good prospects in underwater operations and artificial biomimetic organs. Our study may provide new insights into the design and preparation of novel semi-solid materials for diverse industrial, engineering, and biomedical applications.

Catalytic synthesis of renewable lubricant base oils with methyl oleate and aromatics

Aromatic-ester and cyclo-branched alkane renewable lubricant base oils were produced from methyl oleate and biomass-derived aromatics by alkylation and alkylation followed by hydrodeoxygenation (HDO).

Impact of various parameters on the tribological performance of nano lubricants considering oxide nanoparticles in conventional, semi-synthetic, and fully synthetic lube oils

In the realm of lubrication, nanoparticles exert a notably positive influence on enhancing tribological performance, particularly certain oxide nanoparticles exhibit exceptional capabilities as friction and wear mitigators. However, a substantial research gap exists concerning the efficacy of oxide nanoparticles across various lubricant categories. Therefore, this study meticulously elucidates the effective integration of oxide nanoparticles in diverse lubricant categories. Using HRTEM, XRD, and FTIR, we characterize shape, size, and crystallinity. A Taguchi L18 orthogonal array is used for experimental planning, with performance characteristics of nano lubricants measured using four-ball testers. The experimental findings reveal a hierarchy of parameters governing the minimization of the coefficient of friction (COF), which are as follows: nanoparticle type, nanoparticle composition, load, speed, and lubricant, in that order. Similarly, the parameters controlling the reduction of wear scar diameter (WSD) are ranked as follows: load, nanoparticle composition, nanoparticle type, speed, and lubricant (base oil). Furthermore, an analysis of variance (ANOVA) is conducted to assess the contributions of these factors to COF and WSD. Regarding COF, 43.37% of the variance is attributed to nanoparticle type, 26.78% to nanoparticle composition, 14.49% to load, 11.8% to speed, and 2.36% to lubricant (base oil). In the case of WSD, the factor contributions are 47.67% for load, 22.4% for nanoparticle composition, 14.03% for nanoparticle type, 7.26% for lubricant (base oil), and 7.01% for speed.

Grafting–inspired bionic hierarchical structure for efficiently enhancing cemented carbide tool performance in green turning

Constructing bionic hierarchical structure on tool surface is an effective method for enhancing tool performance in vegetable oil-based minimum quantity lubrication (VMQL) assisted turning. Taking the features of VMQL assisted turning into account, the bionic hierarchical structure is expected to possess high durability and superoleophobicity. In this way, the structure function can be efficiently maintained and the vegetable oil droplets can be fully utilized. This work explored a novel grafting–inspired bionic hierarchical structure (GBHS) on cemented carbide tool surface. The agriculture technique named grafting provided inspiration for fusing the bionic structures obtained by examining dung beetle and lotus leaf. Two kinds of GBHS, namely VDGS and VAGS, were acquired due to the changes of the diameter Dc of the bionic circular recessed microstructure and the laser processing angle Al. Morphology, wetting behavior, durable superoleophobicity, mechanism and green turning performance were analyzed for GBHS. It was verified that GBHS integrated the advantages of the bionic structures of different scales and weakened the shortcomings of them. VDGS and VAGS separately exhibited highly durable low-adhesive superoleophobicity and highly durable high-adhesive superoleophobicity when they were subjected to mechanical load and high temperature. The use of VAGS prepared at the laser angle Al of 60° caused the best machining results in short-time turning. VDGS with a diameter Dc of 360 µm can be employed to acquire the optimum machining results in long-time turning. The construction strategy of GBHS can be extended to other tool materials and green machining conditions for obtaining enhanced tool performance.

Synthesis of polyelectrolyte-decorated polydopamine nanoparticles via surface reconstruction for enhancing oil-based lubrication

Polydopamine nanoparticles (PDA NPs) show bright prospects in the field of lubricant additives due to their high interface adhesion and reaction properties. However, the synthesis of PDA NPs with excellent dispersibility and lubricity in lubricating oils remains a great challenge. In this work, a class of polyelectrolyte-decorated PDA NPs (PPDA NPs) were synthesized by surface reconstruction of PDA NPs. The lipophilic PPDA NPs can be stabilized in PEG200 base oil without any sediments over 6 months. Compared with PEG200 base oil, the PPDA NPs (1.0 wt%)/PEG200 dispersion not only reduced the friction coefficient (COF) by 37.3 % and wear volume by 51.6 % but also performed well under heavy loads, high speeds, and long duration. Wear surface analyses confirmed that the structural evolution from PPDA NPs to nanosheets induced the formation and deposition of hybrid tribofilm with robust tribological behaviors, enabling desirable oil lubrication. Overall, the synergistic effects between PDA cores and PPDA shells contributed to the superior lubricity of PPDA NPs. This study provides a promising protocol for designing and synthesizing oil-dispersible PPDA NPs, brightening the application prospect of organic polymer NPs in tribology.