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In order to improve the bearing capacity of water-lubricated bearings, the tribological properties of thermoplastic polyurethane (TPU) bearing materials were improved by the hydration of hydrogels under water lubrication conditions. Hydrogel particles were prepared by using polyvinyl alcohol, sodium alginate, chitosan and other materials, and hydro-gel/TPU composites were prepared by melt blending. The friction and wear properties of the composites were tested under loads of 0. 3 MPa and 0. 5 MPa. The wear surface morphology was observed by laser interference surface profiler and scanning electron microscope, and the wear mechanism was analyzed. The results show that the hydrogel particles can improve the lubrication condition of the friction pair through hydration lubrication, thereby reducing the friction coefficient and wear amount, and improving the friction performance of the composite. When the mass fraction of hydrogel is 4%,the composite has the best friction and wear properties, and compared with the TPU sample, the average friction coefficient reduction rate under the working conditions of 0. 3 MPa and 0. 5 MPa is 52. 31% and 43. 94%, respectively. This research provides a method for developing high performance materials for water lubricated bearings. [ABSTRACT FROM AUTHOR]

Polyurethane has been extensively studied as a multifunctional material for water‐lubricated bearing materials. As one of the polyurethane elastomeric synthetic material, the content of 4,4′‐methylene bis(2‐chloroaniline) (MOCA) directly affects the intermolecular structure and thus the properties of the material. Five samples with different MOCA contents were prepared by casting molding and tested. The results showed that the optimal comprehensive performance was obtained when the ratio of the amino group to the hydrocyanic acid group was 0.95, with tensile, compressive, and bending strengths of 50.1, 91.8, and 12.6 MPa, respectively. Compared with other samples, the surface of the sample was smooth, which was conducive to the formation of the water film. The bearing capacity and lubrication condition are improved, and the best tribological performance was shown. This research for the application of polyurethane elastomer on the water‐lubricated bearing provides a theoretical basis. [ABSTRACT FROM AUTHOR]

Polyurethane elastomers are widely used as functional alternative materials in water-lubricated bearing materials. In this study, three kinds of polyurethane elastomers with different soft chains were prepared to investigate the influence of soft chain materials on their tribological properties. The test results show that the specimen with soft chain polyols as propylene glycol has the best wear resistance, and the friction coefficient is only 0.09 at 0.7 MPa. Due to the excellent buried property, the wear debris can be discharged in time, so the surface of the test specimen is relatively flat, which is conducive to the formation of lubricating water film. This study provides the experimental basis for polyurethane as an alternative material for water-lubricated bearings. • Polyurethane elastomers with different soft chain were designed and prepared. • The samples of different soft chain materials were compared and analyzed. • The influence mechanism of soft chain on PU wear resistance was revealed. [ABSTRACT FROM AUTHOR]

The existence of micro‐structures endows the materials with some novel characteristics. In this study, the hot‐spot material thermoplastic polyurethane (TPU) is used as the experimental object, and the water‐lubricating composites are prepared by introducing well‐hydrophilic polyvinyl alcohol (PVA) fibers, which can spontaneously and continuously produce micro‐convex textures in water. By observing and analyzing the internal structures, physical and chemical properties, coefficient of friction, wear surface, wear loss, etc. of the materials, the relationship between the micro‐convex structures on the material surface and its tribological properties is studied. The experimental results show that the existence of micro‐convex structures can make the material show better wear resistance during the friction process, and they will not disappear completely with the process. The most obvious effect is the sample containing 15% PVA fibers and with soaking and polishing treatments, its coefficient of friction is 0.11, which is 74.42% lower than that of the pure sample without any treatments, the main reason is due to the hydrodynamic lubrication effect and cavitation effect of the micro‐convex structures. For the wear mechanism, pure samples are adhesive wear, and modified samples are mainly abrasive wear. This work will provide new design ideas for tribology in the micro‐nano field. [ABSTRACT FROM AUTHOR]

Thermoplastic polyurethane (TPU) is one of the most popular marine bearing materials because of its excellent characteristics. However, severe wear often occurs under some extreme conditions. In order to improve the service life of bearing material, this work introduced the polyacrylonitrile (PAN) fiber as a reinforcement material to further enhance TPU tribological properties. Considering that the bearing material does not process self‐lubricating or cannot form a stable water film under some working conditions, the PAN fiber was hydrophilically modified to alleviate this problem. The effects of fiber addition, operation speed, and applied load on the tribological properties of the composites were examined by using a tribo‐tester. The friction coefficient of the samples, the surface morphology after rubbing, and the wear loss, and so on, were also comprehensively analyzed. It was found that the friction coefficient of 30% modified PAN fiber at 500 r/min and 0.8 MPa load was 0.08, and its friction coefficient was 81.8% lower than the pure sample under the same working condition, this is mainly due to the high hydrophilicity of the modified PAN fiber, which makes it easier to form a water film between the composite material and the copper disc. Furthermore, adhesive wear occurred in unmodified samples, while modified samples contained abrasive wear. This new material modification method and design idea can be used for improving the performance of water‐lubricated bearing materials. [ABSTRACT FROM AUTHOR]

Abstract In this reported study, 12 types of spherical convex surface textured thermoplastic polyurethanes (TPU) samples were produced using 3D printing technology to determine if these surfaces could improve the performance and service life of water-lubricated bearings. The wear process of the TPU/QSn7-0.2 friction pairs was analyzed using a specially designed testing apparatus under water-lubricated conditions. As part of the analysis, the friction coefficient, surface topographies, grinding marks and the wear mass from the worn specimens were examined. The analysis results showed that the spherical convex texture effectively improved the tribological properties of the TPU material. The friction coefficients between the friction pair were directly related to the test rotation speed and applied loads. Abrasive wear and adhesive wear were found to be the major wear mechanisms of the non-texture specimen, while the spherical-convex textures appeared to facilitate the removal of friction pair debris from the surfaces, reduced the adhesion between the friction pairs and strengthened the wedge effect and cavitation effects of the water flow. Compared to the non-texture samples, the 1/3 spherical texture samples with an S = 38% exhibited improved tribological properties, and the friction coefficient of these samples was decreased by 64.47% at 0.7 MPa and 250 rpm. These results provide an experimental foundation for the textured design and optimization of the water-lubricated TPU bearing surface. Highlights • The spherical convex texture effectively improved the tribological performance of TPU water-lubricated bearing material. • A wedge gap formed between the spherical convex texture and a QSn7-0.2 disc was helpful in forming a local high-pressure water-film. • Cavitation effects produced between adjacent convex bodies during the wear process improved the lubrication performance. [ABSTRACT FROM AUTHOR]

The water-lubricated bearing is one of the most important components in machine systems, and significantly affects safe operation. Poor lubrication makes it very difficult to ensure good wear resistance in water-lubricated bearings, especially at low speed or in complex load conditions. However, polyethylene wax (PEW) offers good self-lubricating performance, which may provide lubrication and the required wear resistance in water-lubricated bearing materials. In this reported study, a new water-lubricated bearing composite material comprised of polyurethane (PU) and a small amount of PEW were fabricated to improve the wear resistance of the PU-based water-lubricated bearings. The wear behavior of the PU-PEW composite material and the PU material was investigated at low speed and at different load conditions at room temperature using the CBZ-1 friction and wear tester. The wear resistance of these materials was evaluated based on the experimental results of the friction coefficient and wear morphologies. The experimental results indicated that the PEW additive was heated by the developed friction and was deposited on the surface of the composite material to form a lubricant film with good lubricity. As a result, the load bearing capacity of the lubricant film was improved, which effectively improved the lubrication conditions of the composite material, thereby improving the wear resistance and decreasing the effect of the load. These results suggest that this study may provide a novel approach for improving the wear resistance and lubrication condition of PU-based water-lubricated bearings. • The influence of polyethylene pax (PEW) used as the additive on wear resistance of polyurethane (PU) was studied. • The main wear form of PU basic was fatigue wear and abrasive wear under test conditions. The wear of the PU-PEW composite material mainly occurred in running-in stage. • The PU-based composite material with 6.8 wt% PEW presented the best wear resistance. [ABSTRACT FROM AUTHOR]

Polymer materials have poor thermal conductivity and prone to aging at high temperatures. Severe wear occurs at material friction interfaces at high or locally high temperatures. In this study, gradient structural design for polyurethane was realized by adding high thermal-conductivity wire into water-lubricated bearing material. Tribological performance was evaluated by analysis of friction coefficients, wear microscopy, and average temperature during steady-state thermal simulation analysis. The results showed that metal wire effectively transferred heat and reduced sample temperature and the formed surface film effectively reduced the friction coefficient. These findings provided a new method for improving the thermal conductivity and wear resistance of water-lubricated bearing materials. The poor thermal conductivity of polymer bushing and the tribological performance of bearing is improved. • Gradient-structured water-lubricated bearing materials were designed. • The new heat conduction pathways of friction pair were formed through the designed structure. • The reduction of the friction coefficient by metal wire addition was up to 40%. [ABSTRACT FROM AUTHOR]

Water-lubricated bearings are essential parts of marine propulsion systems. However, severe friction and wear of water-lubricated bearings usually occur under marine running conditions. Surface texture technology has been verified as an effective method for improving material tribological properties and been successfully applied in many fields. Here, the effects of surface spherical-platform texture parameters on the tribological performance of water-lubricated bearings were investigated using 9 types of spherical-platform textured high density polyethylene (HDPE) specimens, manufactured using 3D printer technology. Two groups of tests with different applied loads and rotational speeds were performed to simulate low-speed and heavy-load conditions of water-lubricated bearings. By analyzing the friction coefficient, wear mass loss, and surface topography, spherical-platform textures were concluded to have had a positive effect on the tribological performance of water-lubricated bearings. Specimens with 1/2 spherical-platform texture showed the best ability to promote the wedge-shaped effect and cavitation effect of lubrication, which improved the bearing tribological performance. This study provided an experimental foundation for optimizing the surface texture of water-lubricated bearings. • A new spherical-platform texture with 9 kinds of parameter for water-lubricated bearings was manufactured and studied. • The wedge effect and the cavitation effect were promoted by the spherical-platform texture to improve the tribological performance. • The specimen with 1/2 spherical-platform texture and 1 mm upper surface diameter presented the best tribological properties. [ABSTRACT FROM AUTHOR]

Frictional pairs tend to suffer severe friction and abrasion under low velocity and heavy load conditions even in aqueous environment. Polyester fibers (PETF) with different orientations were used to reinforce ultrahigh molecular weight polyethylene (UHMWPE) to prepare novel composites with multi-layer directional structure. The obtained composites were subjected to mechanical and tribological tests. The results revealed that adding PETF can improve the ultimate flexural strength and reduce friction coefficient of the composites. Moreover, the performance of the composites with fibers oriented along the axial direction was better than that of the randomly-oriented fiber composite (ROFC) in all cases. The oriented fibers could further enhance the composites and solve the high wear volume problem after the addition of PETF. • Novel oriented-fiber-reinforced-composites (OFRCs) have been prepared. • OFRCs with six different patterns have been systematically compared. • The OFRC with axial fiber orientation presented the lowest friction. [ABSTRACT FROM AUTHOR]

The lubricant temperature has a negative impact on the wear resistance of water-lubricated bearings. In this study, three different additive mass fractions polyurethane-polyethylene wax (PU-PEW) composite material were manufactured and tested under the high-temperature conditions compared with pure PU and THORDON. The tribological performance of different materials was then evaluated by the analysis of friction coefficient, wear mass loss and wear micrographs. The results show the PEW could perfectly improve the tribological performance of PU. The changes in average friction coefficient of PU-PEW1 (10 g PEW) is 0.015 lower than that of THORDON at condition of different lubrication temperature. The wear mass loss of PU-PEW1 was 6.33 mg lower and the worn surface has a higher flatness than that of THORDON. This reported study provided an experimental basis for water-lubricated bearing material selection under high-temperature and high-load conditions. • The novel polyurethane-polyethylene wax (PU-PEW) composite materials for water-lubricated bearing was designed. • The tribological properties of PU, THORDON and PU-PEW were investigated under the high-temperature and high-load conditions. • The PEW has positive effect on the tribological properties and PU-PEW's tribological properties is more stable than THORDON. [ABSTRACT FROM AUTHOR]

Water-lubricated bearings usually suffer severe abrasion under low-speed working conditions. Use of microencapsulated lubricants to modify the materials seems to be useful for reducing friction and wear in a bearing. In this reported study, palmityl palmitate microcapsules coated with a shell of urea-formaldehyde resin were prepared by in-situ polymerization and were then added to ultra-high molecular weight polyethylene (UHMWPE). Friction tests were performed using the microcapsule/UHMWPE composites by abrading them against tin-bronze discs under normal or heavy loads at low speeds. The experimental results showed that the addition of the microcapsules to the UHMWPE decreased its friction coefficient, reduced wear loss and optimized the wear surface morphology of the composites, consequently improving their tribological properties. • The palmityl palmitate microcapsules were synthesized by in-situ polymerization. • Composites with different concentrations of microcapsules were designed. • Series of tests were carried out to study the tribological properties of the composites. • The composite containing 15% microcapsules showed superior tribological performance. [ABSTRACT FROM AUTHOR]

Glass fiber (GF) is becoming one of the most popular reinforcement materials used in many fields. However, it still has some disadvantages such as brittleness and poor wear resistance. In order to improve its tribological property, the GF was modified and use high-density polyethylene (HDPE) as the matrix material to verify it. In this work, friction tests of HDPE samples with seven different compositions of modified GF were carried out. Different working conditions were applied to determine the tribological properties and service life as used in water-lubricated bearings. Their friction coefficient, surface morphology, wear scar, wear quality and wear mechanism were investigated. The results showed that the modified GF could significantly improve the HDPE tribological properties. Moreover, the wear mechanism of pure HDPE was mainly adhesive wear and slight fatigue wear, and the composite material was mainly abrasive wear. The 30% GF composite material had the best wear resistance, its friction coefficient was reduced by 51.56% under 0.4 MPa and 500 r/min. The findings from this experiment will provide a new method for reducing friction and wear of water-lubricated bearings. • The reinforced modification of GF was carried out by chemical method. • Composite materials with seven different concentrations of modified GF were designed. • Series of tests were carried out to study their tribological performance. • The model of modified GF in the friction process was established. • The HDPE containing 30% modified GF showed superior performance. [ABSTRACT FROM AUTHOR]

Abstract Ultra-high molecular weight polyethylene (UHMWPE) is commonly used to make water-lubricated bearing in industrial application. The Water-lubricated bearing components often experience boundary and mixed lubrication during operation, which induces the aging of UHMWPE material, affecting the mechanical and tribological properties of UHMWPE. This investigation aims to study how the wear resistance of UHMWPE is affected by aging. A CBZ-1 tribo-tester was used to conduct the sliding wear tests between UHMWPE pins and ZCuSn 10 Zn 2 discs rubbing pair under water lubrication. The comparison analyses of the shore hardness, friction coefficients, wear mass loss and worn surface morphologies were elevated. Also, the Raman spectrum, Infrared spectrum and the change of elements of aged UHMWPE samples were examined. The results showed that the accelerated aging had a significant effect on the mechanical and tribological properties of UHMWPE. Especially, compared with the original sample the average friction coefficient increases by 65.96% under 720 h, 80 °C aging condition. Moreover, accelerated aging also resulted in a fracture of molecular chains and chemical oxidation reaction of UHMWPE, the concentration of O element increased to 12.803% when the aging condition was 720 h, 80 °C, which was closely correlated with the deterioration of its wear resistance. The main wear mechanisms were fatigue wear and abrasive when the aged temperature was 40 °C, 60 °C and the aged time was 120 h, 240 h and 360 h. At the 80 °C, 480 h and 720 h aged conditions, the main wear mechanisms between rubbing pair were adhesin wear and fatigue wear. The knowledge gained herein will be useful for optimizing and designing water-lubricated material in extreme conditions to prolong the service life of water-lubricated bearings. Highlights • The accelerated aging condition had an obvious effect on the mechanical and tribological properties of UHMWPE samples. The average friction coefficient increases by 65.96% when aging time was 720 h and aging temperature was 80 ℃. • It was observed that the mechanical and tribological degradation correlated with molecular structure change of UHMWPE. Aging resulted in a fracture of molecular chains and chemical reaction of UHMWPE, which significantly damaged the properties of UHMWPE material. • With aging time and temperature increased, the wear mechanisms between rubbing pair were fatigue wear and abrasive wear, and then turned into adhesion wear and fatigue wear. [ABSTRACT FROM AUTHOR]

Water-lubricated bearings are subject to abrasive wear, leading to performance degradation. Herein, the use of PTFE and UHMWPE fibers was investigated to improve surface tensile strength and explore wear mechanisms. Through finite element analysis and friction and wear experiments, it is hereby demonstrated that fiber reinforcement significantly improves surface tensile strength and reduces surface wear compared to non-reinforced materials, and the wear of the bronze plates is reduced as well. Meanwhile, fiber-reinforced composite materials suppress the development of wear in a certain amount of time and exhibit outstanding frictional performance. • Fabric effectively improves the surface tensile strength of the material. • Fabric acts as shock absorbers, reducing friction fluctuation and enhancing stability. • The incorporation of fabric mitigates abrasions and minimizes material removal. • Fabric altered the wear mechanism, effectively preventing the development of wear. [ABSTRACT FROM AUTHOR]