Tribological Properties Of Polyimide Composites Research Articles

Tribological Properties of Polyimide Composites Modified with Diamondoid Metal-Organic Frameworks.

In this work, diamondoid metal-organic frameworks (MOFs) were efficiently prepared by sonochemical synthesis and grown on polyimide (PI), aiming to improve the anti-wear performance of the PI matrix. By introducing MOFs into the PI matrix, the free movement of PI molecular chains were restricted, and its hardness and elastic modulus were improved. It was found that the wear rate of the 3 wt.% MOFs/PI composites was reduced by 72.6% compared to pure PI at a load of 4 N after tribological testing by using a ball-on-disk tribometer. This can be attributed to the excellent load-bearing and shear resistance of the fourfold-interpenetrated diamondoid networks, in which the transition metal elements can favor the formation of transfer films. It is worth noting that the 3 wt.% MOFs/PI composites still exhibited great tribological properties under high loads or high speeds. The findings of the present study indicate that diamondoid metal-organic frameworks can be used as efficient modifiers to enhance the tribological properties of PI.

CuO nanowires uniformly grown on carbon cloth to improve mechanical and tribological properties of polyimide composites

The lack of robust interphases bonding between carbon fiber (CF) and polyimide (PI) polymer composites can be tackled by growing homogeneous copper oxide (CuO) nanowires 2 ∼ 3 μm on the surface of the CFC. The CuO nanowires can improve the interface compatibility with PI, and introduce a lubricating phase into PI/CuO@CFC composite to boost its mechanical and tribological performance. Compared to PI/CFC composites, PI/CuO@CFC composites were given a lower friction coefficient (45% lower), as well as a narrower wear width (47% lower), and the tensile strength increased by 43%. The enhancement mechanism is proposed via the analysis of the composite interface and worn surface. Therefore, it is an effective method to grow CuO nanowires for preparing high-performance PI/CFC composites, and has important application prospects in tribology field.

Mesopore silica effect on chemical, thermal and tribological properties of polyimide composites

Abstract In this experimental study, the effects of mesoporous silica filler content on the chemical, thermal and tribological properties of polyimide composites were investigated. For that purpose, Pi/mesoporous silica composites were produced by in situ polymerization with various mesoporous silicas. After fabrication, thermal stability and chemical characterization were determined using TGA and FTIR. Morphological alterations were monitored with a scanning electron microscope (SEM). Texture structure (pore size and pore volume) were determined by the BJH method. Friction and wear properties were investigated by using a pin-on-disc arrangement. At the end of the study, minor shifts of Pi/mesoporous silica composites were observed. Thermal stability, as well as pore size and pore volume, was decreased with mesoporous silica. The coefficient of friction and specific wear rate decreased with the addition of mesoporous silica. Abrasive wear behaviors were seen for both neat Pi and Pi–Si composites. Hence, this study evidenced that the properties of Pi are influenced by mesoporous dimensions and content of Si employed.

Molecular dynamics simulation to enhance the mechanical and tribological properties of polyimide composites by graphene reinforcement

Background: Polyimide is one of the organic polymer materials with the best comprehensive performance. It has outstanding mechanical properties, excellent thermal stability and excellent corrosion resistance, but pure polyimide has high coefficient of friction and wear rate. By combining graphene with polyimide, the mechanical properties of the composite are significantly reformatived, and the friction coefficient and wear rate can be reduced. Objective: The molecular models were developed to study the mechanical and tribological properties of graphene as a reinforced material. Methods: In this paper, the mechanical properties and friction and wear mechanism of materials are studied by molecular dynamics method from the microscopic point of view. The Young’s modulus and hardness of composites were calculated using the strain constant method. Results: Molecular dynamics simulation results expressed that the Young’s modulus and hardness of polymer composites benefited by approximately 115% and 42%, respectively, after the addition of the graphene-reinforced material. The average friction coefficient and wear rate of polymer composites fall by 35% and 48%, respectively. Through the calculation and statistics of the micro-information in the process of friction simulation, the internal mechanism of various situations is revealed in the atomic dimension. Conclusions: Graphene can adsorb on the surface of polymer chain segment, a strong polymer matrix, through van der Waals and electrostatic forces and can effectively resist external loading.

Synergy of core-shell Cu@rGO hybrids for significantly improved thermal and tribological properties of polyimide composites

A facile electrostatic self-assembly way was developed to prepare Cu nanoparticles @ rGO (reduced graphene oxide) nanosheets to enhance the properties of PI (polyimide) composites. Through the electrostatic self-assembly between Cu and rGO, interface compatibility of Cu and PI matrix was improved. Meanwhile, the zero-dimensional Cu and two-dimensional rGO in core-shell Cu@rGO hybrids could integrate the multiple advantages and provide synergistic enhancement for PI composites. As a result, the maximum thermal decomposition temperature of PI/Cu@rGO composites recorded an increase of 12 °C in comparision with that of pure PI. In addition, the Cu@rGO hybrids demonstrated the optimal lubrication properties for PI matrix compared to individual Cu, rGO and Cu/rGO blend. For PI/Cu@rGO-0.5 wt% composites, the specific wear rate and average friction coefficient were decreased by 44.1% and 11.6%. The outstanding tribological performance of PI/Cu@rGO composites can be ascribed to the synergistic enhancement between Cu nanoparticles and rGO nanosheets as well as the formation of high-quality transfer film. Furthermore, the inherent abrasion mechanism of PI/Cu@rGO composites was explored systematically.

Surface modification of YS-20 with polydopamine for improving the tribological properties of polyimide composites

Recently, great effort has been devoted to prepare various reinforce fillers to improve polymer performances, but ignoring the importance of raw polymer powders which are indispensable parts of hot-pressed polymer composites. Herein, we engineer raw polyimide (PI) powders with the assistance of polydopamine (PDA) in aqueous solutions. After the modification, polymer powders change from hydrophobic to hydrophilic, which makes it is possible to further modification of polymer powders in liquid phase. During the curing process of modified polymer powders, the partial dehydration of the catechol groups and crosslinking of PDA via C-O-C bonds are confirmed. Based on the features of PDA, a non-destructive mixing method is utilized to realize homogeneous dispersion of multi-walled carbon nanotubes (MWCNTs) in polymer matrix. In comparison with ball milling method, this way can preserve the integrated innate structure of MWCNTs effectively. Besides, by taking full advantage of the reducing and metal-coordination capability of PDA, Cu2+ is successfully loaded onto the surfaces of polymer powders. The related characterizations demonstrate that Cu2+in situ converts to metallic copper rather than copper oxide during the hot pressing process. The tribological properties of corresponding polymer composites are also studied. These results indicate that modifying polymer powders with PDA is multi-profit and presents practical application prospect.

Growth of ultra-dense MoS2 nanosheets on carbon fibers to improve the mechanical and tribological properties of polyimide composites

To enhance the interface bonding of polyimide (PI)/carbon fiber (CF) composites, CFs were functionalized by introducing a polydopamine (PDA) transition layer, whose active groups provide absorption sites for the growth of molybdenum disulfide (MoS2) nanosheets and improve the bonding strength with PI. Uniform and dense MoS2 nanosheets with thicknesses of 30–40 nm on the surface of the PDA@CF were obtained via a subsequent hydrothermal method. As a result, the interface between the CF and the PI matrix becomes more compact with the help of the PDA transition layer and MoS2 nanosheets. This is beneficial in forming PI/CF-MoS2 composites with better thermal stability, higher tensile strength, and enhanced tribological properties. The lubricating and reinforcing effects of the hybrid CF-MoS2 in the PI composite are discussed in detail. The tensile strength of the PI/CF-MoS2 composite increases by 43%, and the friction coefficient and the wear rate reduce by 57% and 77%, respectively, compared to those of the pure PI. These values are higher than those of the PI/CF composites without MoS2 nanosheets. These results indicate that the CF-MoS2 hybrid material can be used as an additive to improve the mechanical and tribological properties of polymers.

Flexural and Tribological Properties of Polyimide Composites Reinforced by Poly-p-Phenylenebenzobisoxazole Fibers with Different Content

In this paper, the tribological property of polyimide (PI) resin was improved by adding poly-p-phenylenebenzobisoxazole (PBO) fibers. The effects of PBO fiber volume fraction were studied by mechanics and tribology tests. The fracture and wear surfaces of PBO/PI composites were investigated by using scanning electron microscopy (SEM). The measurement showed that the flexural properties of composites reinforced by 10 vol% PBO fibers were lower than pure PI resin. With the increase of PBO fiber content, the flexural strength was first increase and then decrease. The frictional coefficient and wear rate of the PBO/PI composites varied with the variety of fiber content, and the optimum parameter was obtained at 20 vol%. The dominant wear mechanism and friction process were discussed on the basis of microscopic morphology analysis of wear surface of PBO/PI composite and the counterpart.

Tribological properties of polyimide composites reinforced with fibers rubbing against Al2O3

Reinforcing fillers are of great importance in tribological performance and tribofilm formation of polymeric composites. In this study, the tribological properties of aramid particle (AP) and short carbon fiber (SCF) reinforced polyimide (PI) composites were added to hexagonal boron nitride (h-BN), and silica (SiO2) nanoparticles sliding against alumina were comprehensively investigated. When sliding occurred with AP-reinforced PI composites, the tribological properties were not closely depended on the pressure × velocity (p × ν) factors and the nanoparticles. The interactions between AP and its counterpart could not induce tribo-sintering of the transferred wear debris. As such, the tribofilm seemed to be in a viscous state, leading to higher friction and wear. However, the inclusion of hard SCF into the PI matrix changed the interfacial interactions with alumina. A robust tribofilm consisting of a high fraction of silica was generated when the SCF-reinforced PI was added to the SiO2 nanoparticles. It exhibited a high load-carrying capability and was easily sheared. This caused a significant decrease in the friction and wear of the PI composite at 8 MPa·1m/s. Moreover, due to their high melting point, few h-BN nanoparticles were observed in the tribofilm of the SCF-reinforced PI when hexagonal boron nitride was added.

Improved tribological properties of polyimide composites by micro–nano reinforcement

ABSTRACTThe hydroxylate carbon nanotubes (CNTs) were grafted by chemical method on the surface of the oxidized carbon fibers (CF) to improve the mechanical and tribological properties of polyimide (PI). The microstructure and fracture surface of the polyimide composites indicated that CF–CNTs hybrid as a multiscale reinforcement can distribute into the PI matrix homogeneously. Tribo‐tests further showed that CF–CNTs hybrid had a better effect on hardness increment, impact strength enhancement, friction reduction, and wear resistance. Compared to the neat PI, the friction coefficient and wear rate of CF–CNTs/PI composite deceased by 23.2 and 55.9%, respectively. In particular, the loading capacity and high speed resistance of CF–CNTs/PI composite were greatly improved. The corresponding wear mechanisms were also discussed by observing the worn surface of the PI composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47900.

Mechanical and Tribological Properties of Polyimide Composites for Reducing Weight of Ultrasonic Motors

The travelling waves ultrasonic motors (TWUM) with nonmagnetic, large torque, high precision and simple structure was driven by frictional force, which had been applied aerospace, intelligent and precise instruments. In order to reduce the total weight of TWUM, the phosphor bronze stator with the biggest density among the all parts of TWUM (8.89 g/cm3) were substituted with light weight polymer or polymer composites. This study designed and prepared one types of low density polyimide (PI) composite (1.41g/cm3) reinforced with carbon fibers (CF) which can reduce the weight of stator over 85%. Importantly, this PI composite can meet the main requirements of TWUM, such as high elastic modulus, wear resistance, and suitable friction coefficient. The output stalling torque of TWUM with CF/PI stator still have 0.22 N·m (18.3% compared with TWUM with phosphor bronze stator). Moreover, this study systematically investigated the mechanical and tribological properties of CF/PI composite. For comparison, the pure PI, polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) were also analyzed to reveal the wear mechanisms. The experimental results indicated that CF/PI had better wear resistance and lower friction coefficient than other polymer sliding against Si3N4. This light weight polymer composites would be an ideal candidate to reduce the weight of TWUM, which can broaden the lightweight application in the field of aerospace.

Effect of surface roughness and reciprocating time on the tribological properties of the polyimide composites

Novel polyimide (PI) composites were designed and prepared as a frictional material for ultrasonic motors (USM). The effect of roughness and reciprocating time on the tribological properties of PI composites was specially investigated for simulating USM operating condition. These typical PI composites were designed along with the special characteristics of USM by filling proportional solid lubricants and nanoparticles, and prepared using classical hot‐press sintering. The friction and wear behavior of PI composites with different surface roughness polished by SiC sandpaper and various reciprocating time was carried out on a pin‐on‐plate tribo‐meter against GCr15 steel pin. The worn surface was observed by SEM to reveal wear mechanisms. Experimental results indicated that the coefficient of friction and specific wear rate increased with an increase of surface roughness which was detrimental for USM to prolong the service life. The coefficient of friction and wear volume will increase with an increase of reciprocating time due to fatigue wear, but specific wear rate will decrease with the minimum value of 2.1 × 10−6 mm3/N m. This study can provide significant guidance for USM to optimize frictional surface and running‐in time. POLYM. ENG. SCI., 59:483–489, 2019. © 2018 Society of Plastics Engineers

Effect of laser surface texturing on tribological properties of polyimide composites in the application of traveling wave rotary ultrasonic motor

PurposeThe purpose of this paper is to investigate the effect of laser surface texturing on the tribological properties of polyimide composites and the output performance of traveling wave rotary ultrasonic motor.Design/methodology/approachThe surface texturing on polyimide composites specimens were fabricated by laser ablation process of different dimple densities, and then the tribological properties were tested by a flat-on-flat tribometer under dry conditions. Finally, the output performance of the traveling wave rotary ultrasonic motor was tested to verify the effectiveness of dimples surface texturing.FindingsThe results show that surface texturing can greatly enhance the friction coefficient of contact interface, especially the specimen with a dimple density of 7.06 per cent exhibited the highest friction coefficient among the specimens. When the input voltage is 500 V, the output power, locked-rotor torque and output torque of ultrasonic motor with textured PI of 7.06 per cent dimple density as friction material at the speed of 100 r/min increased by 13.8, 19 and 12.8 per cent compared to that of the untextured PTFE, respectively. When the ultrasonic motor reverses, the output performance is increased by 20.9, 40.3 and 17.7 per cent, respectively.Originality/valueSurface texturing is an effective way to improve the friction behavior of polyimide composites and then correspondingly enhance the energy conversion efficiency and output performance of the traveling wave rotary ultrasonic motor.

Effects of rare earth oxide additive on surface and tribological properties of polyimide composites

Rare earth oxide La2O3 microparticles-reinforced polyimide (PI) composites (La-PI-Cs) were fabricated, aiming to improve the tribological property of PI. Surface roughness, surface composition, bulk structure, friction force (Ff) and coefficient of friction (COF) at macro/micro preload, and anti-wear performances of La-PI-Cs were studied and compared with neat PI. With La2O3 microparticles, La-PI-Cs showed larger surface roughness, lower surface energy, and higher hydrophobicity than neat PI, and displayed beneficial layered structure different from the compact structure of PI. Owing to these advantages, La-PI-Cs were found to show a 70% reduction in Ff and COF, and a 30% reduction in wear rate, indicating significantly lowered friction and enhanced anti-wear properties after adding La2O3 microparticles. Our research findings demonstrated an easy and low cost method to fabricate polymer composites with low friction and high wear resistance, and help meet the demanding of polymer composites with high tribological performances in broaden applications.

The preparation and the friction and wear behaviours of TiO2/CNT/PI composite film

Recently, the tribological properties of polyimide composites filled with TiO2 nanoparticles and short pitch-based carbon nanotubes (CNTs) were investigated. Sliding tests were performed on a co-rotating twin-screw extruder under different temperatures and regular pressure and speed. It was found that the composite with 4 wt% TiO2 and 6 wt% CNT could reduce the frictional coefficient and wear rate in the most effective way. Compared to the conventional hybrid composites up to now, the above composite was characterised by relatively lower filler content, which would reduce the manufacturing cost. Therefore, it could be largely processed in practice. Increased surface hardness, lubricating effect of the sheet-like wear debris reinforced by TiO2 and rapidly formed transfer film were believed to be the key issues accounting for the obvious wear-resisting and friction-reducing behaviours.

Effects of Aramid Fiber and Polytetrafluoroethylene on the Mechanical and Tribological Properties of Polyimide Composites in a Vacuum

Polyimide composites filled with aramid fiber (AF) and polytetrafluoroethylene (PTFE) were prepared by hot press molding. The thermal, mechanical, and tribological properties of the composites were studied systematically. The friction and wear behavior, sliding against GCr15 steel balls, were evaluated in a ground-based wear in space simulation facility using a ball-on-disk tribosystem. The morphologies of the worn surfaces during the sliding process of the composites were analyzed by scanning electron microscopy to reveal the wear mechanism. It was found that the heat-resisting performance and the hardness of the composites were minimally affected by the additives. The flexural strength of polyimide/AF/PTFE (PI-3) decreased when PTFE was added. The wear resistance increased and the coefficient of friction decreased due to the effect of both fillers. In vacuum, the friction coefficients of polyimide (PI-1), polyimide/AF (PI-2), and PI-3 increased slightly with sliding velocity, while the opposite results were obtained in air. With the increase of air pressure the friction coefficients of the samples increased.

Microhardness and tribological properties of polyimide composites modified by 200 keV Ar ion implantation

Polyimide/fluorinated ethylene propylene (FI/FEP) laminated composites were implanted with Ar8+ ions of the total energy of 200keV and current density of 5A/cm2. The changes in chemical structures of PI/FEP composites, induced by ion implantation, were analyzed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The microhardness, elastic modulus and tribological properties of PI/FEP composites were measured, respectively. The results demonstrated that during the implantation process the imide structures were partly destroyed; meanwhile, carbon-rich, graphite-like and amorphous structures were formed in the near-surface area of the polyimide layers. The change of chemical structure in the surface layer brought about the enhancement of microhardness, elastic modulus and tribological property. Moreover, the extent of improvement of tribological property depends on the implanted fluence.

Tribological properties of polyimide composites filled with glass fibre and graphite

The glass fibre reinforced polyimide (PI) composites filled with graphite powders were fabricated by means of hot press moulding technique. The friction and wear properties of the resulting composites sliding against GCr15 steel were investigated on a model ring-on-block test rig at dry sliding condition. The wear mechanisms were also discussed, based on scanning electron microscopic examination of the worn surface of the PI composites and the transfer film formed on the counterpart. With the increasing normal loads, the friction coefficient of the composites decreased under the dry sliding, owing to inconsistent influences of shear strength and real contact areas. Experimental results revealed that the incorporation of graphite significantly improve the wear resistance of the glass fibres reinforced PI composites. For best combination of friction coefficient and wear rate, the optimal volume content of graphite in the composites appears to be 30%.

Effect of Solid Lubricant on the Tribological Properties of Polyimide Composites Reinforced with Carbon Fibers

The short carbon fiber reinforced polyimide (PI) composites filled with particulates of graphite were prepared by a heat molding technique. The friction and wear behaviors of PI composites sliding against GCr15 steel rings were evaluated on an M-2000 model ring-on-block test rig. It was found that the filler of graphite can significantly improve the wear resistance and decrease the friction coefficient of the PI composites. It was also found that the tribological properties of the short carbon fiber reinforced PI composites filled with graphite are closely related with the sliding condition such as sliding rate and the applied load.

Effect of carbon fiber surface treatments on the flexural strength and tribological properties of short carbon fiber/polyimide composites

AbstractPitch‐based short carbon fibers (CFs) were treated by air oxidation and cryogenic nitrogen, respectively. Thereafter the treated and untreated CFs were incorporated into polyimide (PI) matrix to form composites. The CFs before and after treatment were examined by XPS and SEM.The flexural strength of the specimen was determined in a three‐point test machine and the tribological properties of PI composites sliding against GCr15 steel rings were evaluated on an M‐2000 model ring‐on‐block test rig. The results show that the surface of the treated CFs became rougher. Lots of active groups formed on the CF surface after air oxidation.The treatment can effectively improve the mechanical and tribological properties in their PI composites due to the enhanced fiber‐matrix interfacial bonding. Copyright © 2008 John Wiley & Sons, Ltd.