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Our previous study (Polymer Composites 2023, 44: 1252-1263) revealed the positive role of rubber in modifying the tribological properties of polymer composites. This concept was applied here by incorporating synthetic Eucommia rubber (TPI) to 3D printed polyether ether ketone (PEEK) skeletons with different infill densities. The formation of TPI/PEEK composite improved the friction and wear of PEEK matrix with some reduction in mechanical performance. The composite with 70% infill density is recommended in terms of its overall performance. Based on the morphological and chemical analysis, the composite's wear mechanism was discussed. The findings of this present study could pave a new route to modify friction-reduction and anti-wear performance of PEEK. Highlights * Novel composites were successfully prepared from thermodynamically incompatible synthetic Eucommia rubber (TPI) and polyether ether ketone (PEEK). * The tribological properties of TPI/PEEK composites were studied in association with the infill density of PEEK. * The TPI rubber helped improve the friction and wear properties of PEEK thanks to its role in enhancing the formation of transfer films on the counter steel surface. KEYWORDS friction and wear, polyetheretherketone (PEEK), synthetic Eucommia rubber (TPI), wear mechanism, 1 | INTRODUCTION Polymer-based self-lubricating composites are widely used in aerospace, automotive and medical applications due to their friction-reduction and anti-wear properties. (1) However, it has been the goal of [...]

Highlights A novel organic coating was created by dispersing solvent‐free covalent graphene oxide nanofluids (GO NFs) into a polyimide (PI) matrix. The tribological properties of GO NFs/PI composite coatings was tested against ball‐on‐disk tribometer. Even a low loading of GO NFs significantly improve the tribological properties of PI. MD simulation and nanoindentation tests reveal that GO NFs adsorbs the PI molecular chains, enhancing the composites' mechanical properties. Moreover, a stable tribofilm develops on the steel ball surface lubricated with the GO NFs/PI composite coating, with analyses indicating that the GO NFs promote its growth. The enhancement of mechanical properties and the formation of this tribofilm are essential for the improved tribological performance of the composite. This research aims to contribute to the development of novel PI composite coatings with superior anti‐friction and wear‐resistant properties. The GO NFs exhibited excellent dispersion stability and tribological properties. Novel GO NFs/PI composite coating with significantly enhanced tribological properties. A carbon‐based tribofilm forms on the steel ball. The strengthening mechanisms of composites were revealed by MD simulation. [ABSTRACT FROM AUTHOR]

Copper‐based metal–organic frameworks is anticipated to find applications in the field of friction materials owing to its plentiful surface‐active groups and distinctive framework structure. In this study, copper‐based metal–organic frameworks was synthesized through ultrasound‐assisted method and incorporated alone into carbon fiber reinforced epoxy composites or together with SiO2 nanoparticles towards the goal of improving the composites' friction and wear properties. It is revealed that copper‐based metal–organic frameworks alone cannot improve the friction and wear of carbon fiber reinforced epoxy composites simultaneously. The combination of copper‐based metal–organic frameworks and SiO2 nanoparticles was more effective in enhancing both the mechanical and tribological properties of studied composites. The composite material exhibits a friction coefficient of 0.104 under the specified test conditions of 10 MPa and 3.75 m/s. Additionally, the specific wear rate is impressively low, measuring only 5.64 × 10−7 mm3 N/m. Through morphological and chemical analysis on the worn surfaces and transfer films, the functioning mechanism of copper‐based metal–organic frameworks in modifying the mechanical and tribological properties was discussed. It was discovered that a tribological synergy exists between short carbon fibers, copper‐based metal–organic frameworks, and SiO2 fillers, leading to a shift in the wear mechanism of the composite materials from abrasive wear to adhesive wear. Concurrently, a shear‐prone transfer film forms on the surface of the counter steel surfaces. Findings of the present study pave a new route of designing high performance epoxy based tribo‐composites by using metal–organic frameworks. Highlights: Cu‐BDC nanosheets were synthesized using ultrasound‐assisted techniques and incorporated as tribological fillers in EP composites.The combined use of Cu‐BDC, SiO2, and SCF fillers synergistically enhances the mechanical and tribological properties of EP composites.The composite material exhibits a friction coefficient of 0.104 under the specified test conditions of 10 MPa and 3.75 m/s, the specific wear rate is impressively low, measuring only 5.64 × 10−7 mm3N/m.During the sliding friction process of the composite materials, Cu‐BDC and SiO2 play a crucial role in reducing SCF pull‐out wear through their anchoring effect.The dynamic coordination bond structure of Cu‐BDC contributes to the formation of uniform and continuous transfer films on counter metal surfaces. [ABSTRACT FROM AUTHOR]

Addressing the demand for integrating strength and durability reinforcement in shape memory polyurethane (SMPU) for diverse applications remains a significant challenge. Here a series of SMPUs with ultra‐high strength, self‐healing and recyclability, and excellent shape memory properties through introducing dynamic boron–urethane bonds are synthesized. The introducing of boric acid (BA) to polyurethane leading to the formation of dynamic covalent bonds (DCB) boron–urethane, that confer a robust cross‐linking structure on the SMPUs led to the formation of ordered stable hydrogen‐bonding network within the SMPUs. The flexible crosslinking with DCB represents a novel strategy for balancing the trade‐off between strength and durability, with their strengths reaching up to 82.2 MPa while also addressing the issue of durability in prolonged usage through the provision of self‐healing and recyclability. The self‐healing and recyclability of SMPU are demonstrated through rapid dynamic exchange reaction of boron–urethane bonds, systematically investigated by dynamic mechanical analysis (DMA). This study sheds light on the essential role of such PU with self‐healing and recyclability, contributing to the extension of the PU's service life. The findings of this work provide a general strategy for overcoming traditional trade‐offs in preparing SMPUs with both high strength and good durability. [ABSTRACT FROM AUTHOR]

Material extrusion additive manufacturing provides an effective solution for fabrication of highly customized polyether ether ketone (PEEK) composite parts with any complex shape. Nevertheless, compared with conventional methods, the mechanical strength of 3D printed carbon fiber reinforced PEEK (CF/PEEK) composites is unsatisfactory due to the weak interface bonding strength and high voids content induced by the temperature difference. To overcome this challenge, a temperature‐control 3D printer was used to investigate the effects of ambient temperature and annealing temperature on the microstructure, crystallization behavior and mechanical properties of 3D printed parts. Moreover, the tribological properties of parts printed at different ambient temperature were also studied under various contact pressure. Experimental results showed that the ambient temperature and annealing treatment directly affected the interfacial bonding (fiber/matrix, filament/filament, layer/layer), crystallinity of printed samples, thus affecting their mechanical and tribological properties. The CF/PEEK parts printed at high ambient temperature of 200°C exhibited outstanding mechanical and tribological properties. This study has positive significance for promoting the application of 3D printed PEEK composites in the field of structural load‐bearing and friction materials. Highlights: Structure–property relationships for 3D printed CF/PEEK composites.The ambient temperature strongly affects the thermal and microstructural propertiesInteraction between crystallization and molecular interface diffusion.Interfacial bonding and crystallinity determine the mechanical properties.Tribological properties are highly dependent on applied pressures. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polyether ether ketone (CF/PEEK) composites are widely used as tribo‐materials in the aerospace and automotive industry. To amplify the industrial utilization of extrusion‐based additive manufacturing fused deposition modeling in fabricating CF/PEEK tribo‐composites, the composites' microstructure–property relationship was studied with respect to carbon fiber content varying between 5 wt% and 30 wt%. This revealed that the incorporation of carbon fibers helped enhance the mechanical strength of PEEK greatly with an optimal content of 5 wt%, at which the composite material exhibited the highest crystallinity as well as the best mechanical performance. Tribological tests indicated that CF/PEEK composites were more suitable for high speed and heavy load conditions especially for 20 wt% CF/PEEK, which was associated with the establishment of high quality transfer films covered on counter steel surfaces. The present work provides a simple and low cost way of fabricating high performance PEEK composites used as tribo‐materials. © 2024 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The orientation of fibers in polymer matrix plays a crucial role in governing the performance of composites including friction and wear. In the present work, the effect of fiber orientation on tribological behavior of 3D printed short carbon fiber reinforced PEEK composites (CF/PEEK) was studied by two series of tribo‐tests, namely macro‐scale continuous sliding and micro‐scale multiple scratching. Fiber orientations studied included parallel, tilted and anti‐parallel relative to the sliding direction in both macro sliding and micro scratching. It was revealed that the effect of fiber orientation showed strong dependence on applied loads. In most cases, lower wear were obtained when the fiber orientation was tilted rather than parallel or anti‐parallel in macro continuous sliding. With tilted orientation, the composite also exhibited the best scratching behavior except for that at the lowest normal load. To reveal the mechanisms behind this orientation effects, the composite's worn surface, as well as those of the counter rings, were characterized. Findings of the present work indicates that scratching tests can help understand the macro sliding mechanisms and appropriate fiber orientation is beneficial in improving the tribological properties of polymer composites, which can be realized through 3D printing. Highlights: PEEK composites filled with highly oriented carbon fibers were manufactured by fused deposition modeling (FDM).Tribological anisotropy was studied through macro sliding and micro scratching measurements with respect to carbon fiber orientation.The coupling mechanism of load and fiber orientation was discussed in influencing the composites' friction and wear properties. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) materials with high strength, toughness, anti‐wear properties, and high heat resistance are in high demand for dynamic sealing applications. In this study, a series of high‐performance crosslinking polyurethanes (CPUs) were prepared by pre‐polymerization of polycarbonate diol (PCDL) with toluene‐2,4‐diisocyanate (TDI), followed by crosslinking with trimethylolpropane (TMP). The molar ratio (R) of PCDL/ TDI and the degree of cross‐linking were found to significantly affect the microphase separation. The results indicate that as the R‐value increases, the transition temperature of CPUs increases from 6.0°C to 82.4°C, and the tensile strength increases from 21.1 ± 2.5 MPa to 46.0 ± 3.6 MPa. Moreover, the CPUs exhibit excellent heat resistance (with a heat resistance index of ~150°C) and hydrolysis resistance, attributed to the high crystallinity of PCDL and the synergistic effect of chemical crosslinking. Additionally, the CPUs demonstrate low friction coefficient (COF = 0.01–0.062), exceptional anti‐wear properties (Akron wear, 0.11–0.07 cm3/1.61 km), and outstanding fatigue resistance. These desirable characteristics make CPUs suitable for use as dynamic sealing or lubricating materials in harsh conditions, thereby extending the service life of seals and preventing leakage and other related issues. [ABSTRACT FROM AUTHOR]

To make full use of the renewability of polylactide (PLA) and natural Eucommia ulmoides gum (EUG), novel fully sustainable thermal plastic vulcanizates (TPVs) with high toughness were developed via dynamic vulcanization technique based on modified EUG (referred to as EUG‐GMA). The latter greatly improved the toughness of PLA and the mechanism was discussed with respect to micro structure analysis. Aiming at providing theoretical guidance for PLA/EUG‐GMA TPVs in scratch related applications, the scratch behavior of TPVs with different EUG‐GMA content was studied in single‐pass and multiple‐pass scratching mode, after which the tribological mechanisms were discussed based on worn surface morphology and contact area analysis. It is revealed that the promoted interfacial adhesion due to in‐situ compatibilization and the co‐continuous phase structure of PLA/EUG‐GMA TPVs played crucial roles in enhancing the TPVs' toughness. In addition to tribo‐conditions, the above mentioned interfacial performance was also responsible for the variation of scratch behavior of different TPVs. It is expected that the present study would open up a new route of manufacturing sustainable composites combined with scratch resistance and toughness. [ABSTRACT FROM AUTHOR]

Towards the goal of improving the tribological properties of epoxy‐based composites, epoxy resin was firstly modified with carboxyl terminated butadiene acrylonitrile (CTBN), and then further modified by core–shell structured of SiO2@MoS2 fillers. The friction and wear properties of studied composites were tested on a Plate‐on‐Ring configuration under different loads and speeds. To reveal the tribological contribution of MoS2 and SiO2 in the hybrid fillers, tribo‐tests were also done on composites filled with single CTBN, MoS2 and SiO2. It is revealed that the transfer of both the EP/CTBN matrix and SiO2@MoS2 CSs fillers play an important role in governing the tribo‐properties of rubber toughened EP composites. Depending on contacting conditions, the SiO2@MoS2 CSs fillers might be released into the sliding interface and tribo‐chemical reactions might take place, both of which helped improve the tribo‐properties of studied composites. [ABSTRACT FROM AUTHOR]