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C 1s XPS spectra measured on the heated polyimide surfaces covered without (upper) and with (bottom) PAO4 oil. Insets respectively showing the related optical images of heated polyimide samples
Source publication
Wear of polyimide composite cage due to lubrication failure has a significant impact on the lifetime of bearing, but the related mechanisms are still far from understanding due to the complex movements of bearing parts, such as rolling, sliding et al. in the real operations. Here, the tribological behaviors of polyimide composite against steel ball...
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Citations
... Based on the analyses of the stability, skidding degree, ball-cage collision, wear distribution, and wear rate during the running, Gao et al. [20] indicated that the blackening phenomenon is due to the frequent impulse collisions and wear between the ball and the PPI cage pocket. Jiang et al. [21] studied the tribological behaviors of PPI against a steel ball under a motion compounded with rolling and sliding and found that the rolling-sliding motion facilitated the wear of PPI and the formation of black products. Although the blackening phenomenon has been attracted considerable attentions, its underlying mechanism is far from fully understanding, suppressing the further improvement of tribological performance especially for long-time running of PPI cage. ...
... Previous study [21] has demonstrated that the PPI is vulnerable to be worn and occur blackening failure under heating condition, so the thermal decomposition of PPI material was proposed as one of the reason for the generation of black products. In this study, no extreme heating was provided and the friction flash temperature at GCr15/PPI sliding interface should be lower than that at Al 2 O 3 /PPI interface due to the higher thermal conductivity of GCr15 than Al 2 O 3 . ...
Lubrication failure accompanying with blackening phenomenon significantly reduces the long-running operational reliability of porous polymide (PPI) lubricated with poly-α-olefin (PAO) oil. Here, the effects of lubrication condition and counter-surface chemistry on the blackening failure of PAO impregnated PPI were studied through the comparison of the tribological tests against GCr15 steel ball and Al2O3 ceramic ball with and without PAO oil lubrication. Black products were found to be formed on the PAO impregnated PPI surface slid against steel ball or Al2O3 ball added with iron nano-particles, but be absent under the conditions without iron or PAO oil. Further analysis indicated that the iron-catalyzed splitting of PAO oil into small molecule alkanes and following the formation of black organic matter should be mainly responsible for the blackening phenomenon. Molecular dynamic (MD) simulations demonstrated that the iron facilitated the separation of hydrogen atom and the following broken of C-C bonds in PAO molecules, final resulting in the splitting of PAO oil.
... poor heat dissipation, electrostatic accumulation, and low electrical conductivity. The tribological performance of polymers can be improved by blending with other polymers [5] and nano-fillers. Uniformlydispersed nanomaterials in a polymer matrix improve the thermo-mechanical and physical properties of the composite in terms of dimensional stability [6]. ...
Multifunctional flexible polymer composites have proliferated in different industries. MXenes, as the rising star of 2D materials, offer unique combinations of properties including metallic conductivity, hydrophilicity, high specific capacitance, and solution processability, as well as mechanical flexibility and robustness that accentuate them for the fabrication of multifunctional composites. 2D flake structure and abundant surface terminations of MXene facilitate its integration into polymer matrices to develop high-performance composites. Polyimides (PI) are high-temperature engineering polymers that have rendered their way into aerospace and electronics industries due to their outstanding mechanical strength, high chemical resistance, high thermal stability, excellent electrical and thermal insulation properties. Amalgamating the outstanding characteristics of these two materials, this paper is the first review to summarize advancements in PI/MXene nanocomposites to address the methods of preparation and the effect of MXene loading on the target application e.g., energy conversion and storage, electromagnetic interference shielding, sending, and fire-retardancy. Commencing with a brief introduction on PI and MXene synthetic methods, the nanocomposite fabrication methods are critically discussed. Next, a comprehensive review of the properties and applications of PI/MXene nanocomposites is provided. Lastly, based on the current developments of PI/MXene nanocomposites, this paper is concluded with the prominent characteristics of PI/MXene composites regarding the target application and identifying the gaps and challenges to develop multifunctional composites.
... [3][4][5][6] Compared to metals and ceramics, polymers have the advantages of light weight and easy molding process. Polyether ether ketone (PEEK), 7,8 Polyphenylene sulfide (PPS), 9 Liquid Crystal Polymer (LCP), 10,11 polyethersulfone (PES), polyimide (PI) 12 accessed to a wide range of concerns as matrix resins for polymer-based wear-resistant materials. ...
The synergistic effects of carbon fiber (CF) and polytetrafluoroethylene (PTFE) on the friction and wear behavior of polyarylene ether nitrile (PEN) under dry lubrication condition were studied. According to the scanning electron microscopy (SEM) on the composites' surface after wear, the wear mechanism of the composites under dry sliding condition was analyzed. The research results show that the addition of solid lubricants PTFE and carbon fibers to PEN helps to enhance the properties of friction and wear. The specific wear rate is decreased to 5.7 × 10⁻⁷ mm³/N m at a PTFE composition of 5 wt%, which is optimized by 33.4% more than PEN/CF composites. In addition, wear mechanisms are mainly abrasive wear, accompanied by adhesive wear and plowing of the friction ring.
... The micro pores in PPI material could be used to store lubricating oil [4][5][6]. Oil-impregnated PPI (iPPI) has excellent tribological properties and can keep a high oil content, after centrifugation [7][8][9], which has been widely used in the retainer of micro-oil lubricated bearings used in space [10][11][12][13]. ...
Oil-impregnated porous polyimide (iPPI) materials are usually used as retainer for bearings. In these bearings, balls and rings, balls and retainers are two different kinds of contact. In this paper, the friction and wear properties of iPPI were investigated using steel (disc)—steel (ball)—iPPI (pin) double-contact friction test rig for simulating the actual contact in bearings. The results show that compared with that of iPPI—steel single contact, the friction coefficient of iPPI—steel in double contacts is lower and decreases with the amount of additional oil. The surface of iPPI in single contact suffers more wear compared with that in double contacts. Different from single contact, the worn surfaces of iPPI in double contacts are blackened. The Raman spectra of worn surfaces of balls and discs indicate that α-Fe2O3 and Fe3O4 were formed during rubbing of the double contacts. Many nanoscale iron oxide particles are found on the worn surfaces of iPPI in double contacts; on the contrary, few particles could be found on the surface in single contact. In double-contact friction, the nanoscale wear debris penetrates inside the iPPI material through the process of extruding and recycling of oil, which is the mechanism of the blackening of the iPPI worn surfaces. The studies show that the double-contact friction method is a new and effective method to study the friction in bearings, especially for those with polymer retainer.
... Hard particles either enter the system from the outside or appear inside the system as adhesive wear products [16]. It is possible to prevent abrasive wear or minimize the wear-rate by methods such as hardening the surface of the material [17], removing the particles that cause wear, and lubricating or cooling the part to be subjected to thermal effect by abrasive wear [18,19]. The most economical and easiest measure to be taken against wear is the lubrication of the rubbing surfaces. ...
The application of stainless steel 420 is noted in various industrial applications such as aerospace, automobile etc. The wear mechanism of stainless steel 420 is greatly affected with the use of 100Cr6 balls due to the adhesion and abrasion mechanism generated between the contact surfaces. In this work, the ball-on-flat experiments were performed on stainless steel-420 versus 100cr6 friction pairs under dry, minimum quantity lubrication (MQL) and pool conditions. Then, the wear studies in terms of volume loss, profile tracks, micrographs, coefficient of friction etc. were performed. The results demonstrated that the MQL and pool conditions help to improve the tribological properties of stainless steel 420 alloy against 100Cr6 ball.
... Due to the outstanding properties of low friction coefficient, light weight, chemical stability, low-cost, low noise, and small vibration, PTFE are extensively employed as the matrix of self-lubricating polymer composites [38][39][40][41][42][43][44]. In our previous study, the friction and wear performances of PTFE were significantly improved by the incorporation of PES [45]. ...
Lamellar sodium-montmorillonite (NaMMT)
was used as reinforcing filler to improve the abrasion resistance of polyethersulfone (PES)/polytetrafluoroethylene (PTFE)-based polymers. As filler, the interlayer distance of NaMMT was decreased from 1.523 to 0.995 nm, resulting from the evaporation of interlayer water during the heat treating of composites. The abrasion resistance of PES/PTFE-based composite was effectively improved by introducing NaMMT, attributing to the load bearing of NaMMT on the worn surface. The polymer sample with 20 wt% NaMMT exhibited the best anti-wear performance, which is ascribed to its densification worn morphology. In addition, unlike the pure PTFE transfer films formed for the PTFE and PES/PTFE compounds, NaMMT is also involved in the PTFE transfer film of NaMMT/PES/PTFE compounds. It is inferred that the self-lubricating property of PTFE transfer film is destroyed because of the introduction of NaMMT, leading to that the friction coefficient of NaMMT/PES/PTFE compounds was a little larger than those of PTFE and PES/PTFE compounds.
Purpose
The purpose of this article is to prepare graphene/polyimide composite materials for use as bearing cage materials, improving the friction and wear performance of bearing cages.
Design/methodology/approach
The oil absorption and discharge tests were conducted to evaluate the oil content properties of the materials, while the mechanical properties were analyzed through cross-sectional morphology examination. Investigation into the tribological behavior and wear mechanisms encompassed characterization and analysis of wear trace morphology in PPI-based materials. Consequently, the influence of varied graphene nanoplatelets (GN) concentrations on the oil content, mechanical and tribological properties of PPI-based materials was elucidated.
Findings
The composites exhibit excellent oil-containing properties due to the increased porosity of PPI-GN composites. The robust formation of covalent bonds between GN and PPI amplifies the adhesive potency of the PPI-GN composites, thereby inducing a substantial enhancement in impact strength. Notably, the PPI-GN composites showed enhanced lubrication properties compared to PPI, which was particularly evident at a GN content of 0.5 Wt.%, as evidenced by the minimization of the average coefficient of friction and the width of the abrasion marks.
Practical implications
This paper includes implications for elucidating the wear mechanism of the polyimide composites under frictional wear conditions and then to guide the optimization of oil content and tribological properties of polyimide bearing cage materials.
Originality/value
In this paper, homogeneously dispersed PPI-GN composites were effectively synthesized by introducing GN into a polyimide matrix through in situ polymerization, and the lubrication mechanism of the PPI composites was compared with that of the PPI-GN composites to illustrate the composites’ superiority.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0415
