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Polytetrafluoroethylene (PTFE) has great potential for applications in water-lubricated bearings; however, in heavy load conditions at low speeds, PTFE suffers from severe friction and abrasion because of its poor wear resistance. In this study, silicon carbide (SiC) content and particle size are investigated in relation to PTFE water-lubricated composites' tribological properties. The results show that the wear resistance of PTFE composites can be significantly improved when the filling amount of SiC particles was between 3 and 5 wt.%, and the composites containing 5 wt.% SiC reduced wear loss by 99.44%. The composites' friction and wear properties decreased as SiC particle size increased, and wear mechanism for the composites shifted from adhesive to abrasive. Wear loss on PTFE composites filled with 40 nm SiC particles was reduced by 97.03%, showing the best wear resistance. This study provides an experimental basis for the development of high-performance PTFE water-lubricated bearings. [ABSTRACT FROM AUTHOR]

With the development of green tribology in the shipping industry, the application of water lubrication gradually replaces oil lubrication in stern bearings and thrust bearings. In terms of large-scale and high-speed ships, water-lubricated bearings with high performance are more strictly required. However, due to the lubricating medium, water-lubricated bearings have many problems such as friction, wear, vibration, noise, etc. This review focuses on the performance of marine water-lubricated bearings and their failure prevention mechanism. Furthermore, the research of marine water-lubricated bearings is reviewed by discussing its lubrication principle, test technology, friction and wear mechanism, and friction noise generation mechanism. The performance enhancement methods have been overviewed from structure optimization and material modification. Finally, the potential problems and the perspective of water-lubricated bearings are given in detail. [ABSTRACT FROM AUTHOR]

Lignum vitae, one of the earliest manufacturing materials used in water-lubricated bearings, is renowned for its exceptional tribological performance. The key factor behind this remarkable wear resistance lies in Lignum vitae's internal vessel structure. In this study, a lubrication model based on the natural hollow-tube vessel was conducted to simulate the hydrodynamic lubrication of Lignum vitae in actual working condition and a novel biomimetic composite was manufactured. The influence of the hollow-tube structure on tribological performance was investigated both theoretically and experimentally. Through an extensive series of simulations, wear tests, and characterization under water-lubricated conditions, the results demonstrated that the presence of the hollow-tube structure positively impacts tribological performance. Moreover, it is found that the size and density of these tubes are directly correlated with this improvement; specifically reducing the coefficient of friction by 47 percent and reducing the wear volume by 69 percent. By combining simulation and experimental data, our discussion reveals that the hollow-tube structure significantly enhances lubricant storage capacity and reduces abrasion at frictional interfaces. This comprehensive analysis sheds light on Lignum vitae's internal structural parameters while establishing clear correlations between these parameters and its tribological performance. [ABSTRACT FROM AUTHOR]

In order to investigate the friction and wear properties of polymer materials used for mechanical seals of ship stern shafts in actual working environments, five materials, namely, cast polyurethane elastomer (CPU), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), glass fiber modified polyhexamethylene butylamine (CF/PA46) composite, and glass fiber modified polytetrafluoroethylene (CF/PTFE) composite, were selected, and their friction and wear performance tests were conducted under the load of 0. 5 MPa and the linear velocity of 7 m/s. The results show that CPU, PET, PBT, CF/PA46 materials exhibit varying degrees of peeling and furrowing under high load and high rotational speed conditions, resulting in large friction coefficients and wear losses, while CF/PTFE composites only exhibit some relatively slight tears and wear marks, exhibiting optimal friction and wear performance. Compared to CPU, PET, PBT, and CF/PA46, the average friction coefficient of CF/PTFE is decreased by 66. 6%,80. 4%,86. 1%,and 87. 8%,respectively, and the wear amount per unit time is decreased by 91. 7%,92. 7%,88. 6%,and 97. 0%, respectively. The friction and wear performance is optimal. [ABSTRACT FROM AUTHOR]

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]

Aboard ship, the use of lubricating oil in mechanical equipment is sometimes difficult to achieve and applied oil can easily leak. The use of self‐lubricating materials can largely solve this problem. In this study, three kinds of solid lubricant‐enhanced 304 stainless steel‐backed ultrahigh molecular weight polyethylene (UHMWPE) fabric composites were fabricated with the addition of graphite, molybdenum (IV) disulfide, or polytetrafluoroethylene (PTFE). They were tested under various rotating speeds and compared with pure steel‐backed UHMWPE fabric composites. The tribological performance of these composites was evaluated by analysis of friction coefficient, wear rate, and worn face morphology. The results showed that PTFE‐enhanced composites exhibited the best friction reduction performance under all test conditions, better antiwear ability at rotating speeds under 200 rpm, and optimized wear surface morphology, thus indicating better synergy between PTFE and UHMWPE fabric. [ABSTRACT FROM AUTHOR]

Polyetheretherketone (PEEK) is a kind of polymer with excellent mechanical properties combined with good wear resistance and has been widely used in the engineering field. In order to explore the possibility for PEEK using as a water‐lubricated bearing material, an in‐depth study on the water lubrication performance of PEEK was conducted by using a series of experiments. The water lubrication performances combined with the lubricating mechanism were evaluated both by the friction coefficient and by the wear behavior of PEEK. The results indicated that PEEK was suitable for water‐lubricated bearing productions. The water film could form effectively between the friction pairs under high sliding velocity, while the transfer film could form under low sliding velocity. Both the water film and the transfer film could improve the water lubrication performance for the friction pairs. Moreover, sliding velocities and contact pressures highly influence the water lubrication performance of PEEK. The increase in contact pressure or the decrease in sliding velocity would exacerbate the wear of material. The stick–slip phenomena also occurred on the specimens under low sliding velocity. The main purpose of this study is to provide an experimental basis for PEEK using as a water‐lubricated bearing material. [ABSTRACT FROM AUTHOR]

Purpose Water-lubricated bearings can significantly reduce the pollution to environment because the traditional oil lubricant is replaced by water in the bearings. The ultrahigh molecular weight polyethylene (UHMWPE) has proven to be effective and reliable for the manufacturing of water-lubricated bearings. However, limited work has been done to address the improvement of the tribological performance of the UHMWPE-based water-lubricated bearings using surface texture processing. This paper aims to investigate the effects of bar-grooved surface on the tribological performance improvement of UHMWPE-based water-lubricated bearings.Design/methodology/approach For the first time, the bar grooves were processed on the surfaces of UHMWPE-based water-lubricated bearings. The CBZ-1 friction and wear tester have been used to test the wear and friction performance of the bearing samples. The LI laser interference surface contour graph and the digital microscope have been used to measure the surface morphology of the specimens. The tribological characteristics of the tested bearings were analyzed.Findings With bar grooves added on the surfaces of the specimens, the friction coefficient of the specimens were lower than that of the specimens without surface texture processing; the wear quantity of the two kinds of specimens were almost the same; by using the LI laser interference surface contour graph and the digital microscope to measure the surface morphology of the specimens, the furrows of the specimens with bar grooves were narrower and shallower than that of the specimens without bar grooves.Practical implications The paper implicates that the surface texture processing using bar grooves can reduce the friction coefficient and prolong the service life of the water-lubricated bearings in practical applications.Originality/value This paper fulfills an identified need to provide important theoretical and experimental support to the design of water-lubricated bearings in practical applications. [ABSTRACT FROM AUTHOR]

ABSTRACT: Polyurethane (PU) has been studied as alternative bearing material for marine water‐lubricated stern tube due to its excellent wear resistance, remarkable mechanical properties and so on. In this study, nine types of PU samples which are composed of different additives were prepared and tested in order to investigate their tribological properties under various working conditions. A pin‐on‐disc tribo‐tester was used to conduct tests. Then comparison analyses were conducted from three aspects, including the friction coefficient, wear mass loss, and the wear surface topography. The analysis results showed that: (1) the different additives as well as the mass fraction of these additives lead to significant difference in terms of tribological properties of PU; (2) the lubricating grease, as one of additives, improved the wear resistance and friction performance effectively; (3) modified PU is eligible to work as matrix because of satisfied mechanical properties and specific internal morphology. It is believed that understandings in this study are beneficial to the improvement of the tribological properties of PU and also provide the real practical basis for the studies of polymer materials which applied on water‐lubricated marine stern tube bearing. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46305. [ABSTRACT FROM AUTHOR]

Wood is a natural and clean material with lightweight and satisfactory mechanical properties and has been widely used at present. In order to better understand the relation between the anatomical properties and the tribological properties of wood, three representative kinds of wood have been used for experiments. The anatomical structure, extractives combined with the mechanical properties of the selected wood have been examined. A series of specially designed tribological experiments have also been carried out. The influence of the anatomical properties of wood on its tribological properties has been detailedly analyzed based on the experimental results. The results indicate that the tribological properties of wood were greatly influenced by its anatomical properties. Sufficient extractives can perfectly improve the tribological properties of wood by reducing the friction coefficient and enhancing the lubrication performance to improve the wear resistance. Besides, the anatomical structure also highly influenced the wear resistance of wood. Due to the thickest cell wall, the smallest diameter and the densest arrangement of the wood cells, additionally with the high content of resin and axunge, the Lignum vitae presented the best wear resistance. • The anatomical properties of wood highly influence its tribological properties. • Extracted resin and axunge can improve the tribological properties of wood. • High-density anatomical structure can improve the wear resistance of wood. [ABSTRACT FROM AUTHOR]

Polyurethane, as one versatile family of material, has been studied widely for water-lubricated bearings material. However, the connection between tribological performance and their internal material structure, in particular, crosslinks, remains elusive. Here, the effect of crosslink on the tribological performance of thermoplastic polyurethane (TPU) has been elucidated. TPUs with different crosslink degree were obtained by strengthening hydrogen bonded effect via Gamma-ray. The result shows that the friction coefficient increases with the increase of crosslink degree overall. It is because that enhanced crosslink means more molecular chains crosslink together by hydrogen bonds, resulting in more energy consumption during the friction process. In addition, incremental and larger particles produced during friction leads to third-body mechanism, acting on wear behavior of TPU. • Intermolecular hydrogen bonds forming in thermoplastic polyurethane reflects its crosslinking density. • Increased dose of Gamma-ray radiation causes enhanced crosslinking density, causing higher friction coefficient overall and different wear behaviors. • Higher crosslinking density means more molecular chains to move restrictively and it costs more energy during the friction process. • Many TPU particles produced during friction, which suggests a possible third-body mechanism. [ABSTRACT FROM AUTHOR]

As one of the most important supporting components, the lubricating performance of the water-lubricated bearing greatly affects the safe operation of the whole propulsion system. However, the lubricating performance of the water-lubricated bearing under low speed is difficult to be guaranteed due to the water film is difficult to form under such harsh conditions. Groove seem to be an effective means to improve lubricating performance and have been widely used. Unfortunately, the effect of the groove parameters on the lubricating performance of the water-lubricated groove bearing (WLGB) under low speed lacks of systematic reporting. Herein, a numerical model based on the average flow Reynolds equation was developed and verified. The effect of groove kinds (rectangular, triangle and cuneal), locations, sizes and amounts on the lubricating performance of WLGB under low speed was detailedly investigated. The results confirmed that the water-lubricated bearing without groove presented a poor lubricating performance under low speed. Additionally, the groove parameters highly influenced its role and the rectangular groove with suitable parameters could feasibly improve the lubricating performance of the WLGB. The load-carrying force of the rectangular groove bearing with suitable groove parameters was improved and the friction coefficient was decreased under simulated conditions. It is believed that this study will provide a theoretical basis for grooves selection of WLGB. • The effect of the groove parameters on the lubricating performance is simulated. • The influence of the groove parameters is investigated and detailedly analysed. • Grooves improve the lubrication performance by changing the pressure distribution. [ABSTRACT FROM AUTHOR]

The insufficient lubrication caused by the low viscosity of water has greatly limited the application of water-lubricated bearing, especially under the conditions of heavy load and low speed. In order to solve this problem, a composited strategy is proposed by using the hydration lubrication of polyacrylamide (PAAm) hydrogel to improve the tribological performances of UHMWPE. The PAAm hydrogel microspheres were synthesized by emulsion polymerization, and the PAAm hydrogel microsphere/UHMWPE composites were prepared by melt blending method. The effects of particle size, crosslinking density and filling content of PAAm microspheres on the tribological performances of the composites were tested and analyzed. The results show that the PAAm fragments can form a hydration lubrication layer and improve the tribological performances of the composite. The design of PAAm microsphere/UHMWPE composite provides a novel method to develop high-performance materials for water-lubricated stern tube bearing. • A new approach to use hydration lubrication in engineering applications is proposed. • The composite consisting of soft matter and engineering polymer is prepared. • PAAm hydrogel microspheres can provide hydration lubrication for the composite. [ABSTRACT FROM AUTHOR]

• Cellulose nanocrystal is added into polyalphaolefin base oil as lubricant additive. • CNC is modified by stearoyl chains to improve its compatibility with PAO oil. • The viscosity of hybrid oil is modified due to the chains entanglement. • The friction and wear of hybrid oil are reduced from CNC mending effect. With the increasing requirement of environmental protection, the development of lubricating materials with non-toxicity and good biodegradability becomes more and more significant. As the novel green nanomaterial derived from natural cellulose, cellulose nanocrystals (CNCs) in the present work were prepared from native cotton and added into polyalphaolefin (PAO) base oil as the lubricant additive. To improve the compatibility of CNCs with PAO, the surface of CNCs were grafted by stearoyl chains, which entangled with polyolefin chains and led to a good dispersibility and stability of the colloidal solution. This hybrid oil with the elevated viscosity improved the formation of lubricant film in the boundary lubrication regime. Combining with the mending effect of CNC particles on the surface roughness and scars, both the friction and the wear were dramatically reduced. Specifically, the introduction of 2 wt% modified nanocrystals (mCNC) in PAO base oil reduced the coefficient of friction (COF) by 30%. The results of this study suggest that cellulose nanocrystal is a promising ecofriendly and effective lubricant additive. [ABSTRACT FROM AUTHOR]

In order to apply the hydration lubrication of soft material in heavy load engineering fields, a series of polyacrylamide (PAAm) hydrogel particle/high-density polyethylene (HDPE) composites were prepared. Their mechanical property, soaking surface morphology, wettability, friction property and lubrication mechanism were experimentally obtained and analyzed. The results show that PAAm hydrogel particles played an important role in the lubrication and antifriction of composites, and the friction properties of 1 wt% PAAm hydrogel particle composite were superior to others of different concentrations. The present study suggests that the composite possesses both the high mechanical properties of HDPE and the excellent hydration lubrication of PAAm hydrogel particles. This finding will provide a novel approach for improving friction properties of water-lubricated materials and are conducive to practical application in engineering fields. Image 1 • A new approach to use soft matters in engineering applications is proposed. • The composite combined hydration lubrication and high strength is prepared. • PAAm hydrogel fragments can provide the good lubricating performances. [ABSTRACT FROM AUTHOR]