酸性溶液中PTW增强PTFE复合材料的耐蚀性和摩擦磨损性能

分别研究了不同含量钛酸钾晶须(PTW)、碳纤(CF)填充聚四氟乙烯(PTFE)复合材料在硫酸溶液中和干摩擦条件下摩擦学性能以及酸中的耐蚀性能,借助SEM等分析探讨了相关机理。结果表明,酸中纯PTFE耐磨性较干摩擦条件下提高了2个数量级,摩擦系数也只有干摩擦的15.3%。与CF/PTFE相比,PTW/PTFE复合材料在酸中显示更好的耐蚀和耐磨性能。PTW可以进一步提高PTFE酸中耐磨性能、降低摩擦系数。含15%（质量）PTW时复合材料具有最低的磨损率,此时比纯PTFE酸中耐磨性提高13.8倍,是相同含量CF/PTFE耐磨性的3.2倍。由于酸溶液的冷却和润滑作用,复合材料的摩擦系数与干条件相比明显降低。然而,酸溶液阻止了转移膜的形成。不管是干摩擦还是在酸性溶液中,当填料含量超过15%（质量）时,犁削和磨粒磨损是PTFE复合材料的主要磨损机理。     

Tribological behavior of carbon nanotube and polytetrafluoroethylene filled polyimide composites under different lubricated conditions

The friction and wear behavior of polyimide (PI) composites reinforced with carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) were comparatively evaluated under dry sliding, water‐, oil‐ or alkali‐lubricated condition. The wear mechanisms of the composites were also discussed. Results indicate that, when comparison with the dry friction situation, PI‐based composites results lower friction coefficients and wear rates under oil‐ or alkali‐lubricated condition. The lowest wear rate of the CNT/PTFE/PI composite is recorded as 1.2 × 10⁻⁶ mm³/Nm during the composite sliding in alkali, which is only about 40% of the value sliding under dry friction condition. The worn surface of neat PI under dry sliding is characterized by severe adhesive wear, whereas abrasive wear is the main character for CNT/PTFE/PI composites. The worn surfaces of CNT/PTFE/PI composites sliding in oil or alkali lubricated condition are smoother than those under dry or water condition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

碱液中晶须增强PEEK复合材料的摩擦磨损性能

研究了不同含量PTW增强PEEK复合材料在碱液中的摩擦磨损性能,并与经典的CF增强PEEK复合材料对比,借助于SEM分析了磨损面和对偶面微观形貌,探讨了相关机理。结果表明,干摩擦时15%(质量)PTW增强PTFE/PEEK复合材料耐磨性是相同含量CF增强时的10.5倍。在碱液中,CF增加了PTFE/PEEK复合材料的摩擦系数、降低了其耐磨性能,而PTW可以进一步降低PTFE/PEEK复合材料的摩擦系数、明显地提高其耐磨性能。含5%PTW可提高PTFE/PEEK复合材料碱液中耐磨性2.36倍。碱液阻止了对偶面转移膜的形成,犁削和磨粒磨损是CF增强PEEK复合材料碱液中的主要磨损机制,而隧道状晶体结构和细微尺寸的纤维态形貌使得PTW在碱液中仍具有显微增强耐磨作用。     

Surface modification of carbon fiber and its effects on the mechanical and tribological properties of the polyurethane composites

To improve the friction and wear behavior of the polyurethane composites, carbon fibers were modified with 2, 4‐diisocyanatotoluene. The mechanical and tribological properties of the reinforced polyurethane composites were studied. Tensile strength of the composites increased with the addition of carbon fibers. The friction and wear experiments were tested on a MRH‐3 model ring‐on‐block test rig at different sliding speeds and loads under dry sliding. Experimental results revealed that carbon fibers with chemical treatment contributed to largely improve the tribological properties of the polyurethane composites. Scanning electron microscopic (SEM) investigations showed that the worn surface of the modified polyurethane composite was smoother than pure polyurethane under given load and sliding speed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Investigation on mechanical and tribological behavior of naturally woven coconut sheath‐reinforced polymer composites

The article presents the results of experimental investigation on mechanical and dry sliding wear behavior of unsaturated polyester resin (USP), reinforced with naturally woven coconut sheath and glass fibers. The mechanical properties of coconut sheath (N) and glass fiber (G) reinforced polyester composites were studied, and the tribological behaviors were tested on pin‐on‐disc sliding wear tester. Mass loss was determined as a function of sliding distance for a sliding velocity of 3.5 m/s and an applied normal load of 40 N. The experimental result revealed that the mechanical properties and wear resistance of the composites depend on the wt% reinforcement of coconut sheath/glass fiber and sliding distance. The hybrid reinforcement (GGN) greatly increased the mechanical properties of USP. At lower sliding distance, the N‐reinforced USP had lower wear loss, whereas at higher sliding distance, the hybrid fiber‐reinforced (GGN) USP composite had lower wear loss. Furthermore, the work showed that the higher sliding distance bring about changes in the worn surface features such as interface separation, inclined fracture of fibers, loss of matrix, and the appearance of debris with the two different fibers. The worn surfaces were also examined by scanning electron microscopy. The study showed differing trends with load for the two types of reinforcements. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Tribological behavior of poly(ether ether ketone) composites filled with potassium titanate whiskers sliding in different media

The friction and wear properties of poly (ether ether ketone) (PEEK) composites filled with potassium titanate whiskers (PTWs) under alkali, water, and dry conditions were investigated. The wear mechanisms in different lubrication situations were studied on the basis of examinations of the worn and counterpart surfaces with scanning electron microscopy and optical microscopy. The results showed that PTWs could obviously increase the wear resistance and reduce the friction coefficient of the PEEK composites under dry sliding conditions. Only when the PTW content was greater than 35 wt % did the wear resistance and friction coefficient deteriorate. Sliding in water caused increases in the wear rate and friction coefficient of the PEEK composites, and the PTW‐filled PEEK composites showed the highest friction coefficient and wear rate under this lubrication condition. On the contrary, sliding in an alkaline solution, the PTW‐filled PEEK composites showed the lowest friction coefficient and almost the same level of wear resistance as that found under the dry condition. Furrows and abrasive wear were the main mechanisms for the PTW‐filled PEEK composites sliding in water. The transfer onto the counterpart rings was significantly hindered with sliding under water and alkali conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of various kinds of fillers on the tribological behavior of polytetrafluoroethylene composites under dry and oil‐lubricated conditions

Polytetrafluoroethylene (PTFE)‐based composites filled with various inorganic fillers in a volume fraction of 30% were prepared. The tribological behavior of the PTFE composites sliding against AISI52100 steel under dry and liquid paraffin‐lubricated conditions was investigated on an MHK‐500 model ring‐on‐block test rig. The morphologies of worn surfaces and wear debris were observed with a scanning electron microscope (SEM) and an optical microscope. As the results, different fillers show different effects on the tribological behavior of the PTFE composites, while the composite shows much different tribological behavior under lubricated conditions as compared with dry sliding. The tribological behavior of the PTFE composites under dry sliding is greatly related to the uniformity and thickness of the transfer films. Only the PTFE composites with a transfer film of good uniformity and proper thickness may have excellent tribological behavior. The PTFE composites show much better tribological behavior under lubrication of liquid paraffin than under dry sliding, namely, the friction coefficients are decreased by 1 order of magnitude and the wear rate by 1–3 orders of magnitude. Observation of the worn composite surfaces with SEM indicates that fatigue cracks were generated under lubrication of liquid paraffin, owing to the absorption and osmosis of liquid paraffin into the microdefects of the PTFE composites. The creation and development of the fatigue cracks led to fatigue wear of the PTFE composites. This would reduce the mechanical strength and load‐supporting capacity of the PTFE composites. Therefore, the tribological behavior of the PTFE composites under lubrication of liquid paraffin is greatly dependent on the compatibility between the PTFE matrix and the inorganic fillers. In other words, the better is the compatibility between PTFE and fillers the better is the tribological behavior of the composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1891–1897, 2001     

混杂填料增强聚四氟乙烯复合材料的摩擦学性能研究

采用MM-200型摩擦磨损试验机对纳米SiC、MoS2和石墨填充聚四氟乙烯(PTFE)复合材料在干摩擦条件下与45#钢对摩时的摩擦磨损性能进行了研究,探讨了MoS2、石墨及纳米SiC的协同效应。认为纳米SiC的加入大大提高了复合材料的承载能力,石墨、MoS2的加入减少PTFE复合材料的摩擦因数。利用扫描电子显微镜(SEM)对PTFE复合材料的摩擦面进行了观察。结果表明:实验中5%nano-SiC和3%MoS2填充PTFE复合材料的摩擦磨损性能最好,且在高载荷下的摩擦磨损性能尤为突出,具有一定的应用价值。     

The Tribological Mechanism of Poly(Vinylidene Fluoride) Composites Reinforced with Carbon Fibers

The current study examines the tribological performance of poly(vinylidene fluoride) (PVDF) and carbon fiber-reinforced poly(vinylidene fluoride) (CF/PVDF) under dry sliding condition. Different contents of carbon fibers were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of carbon fiber content on tribological properties of the composites were investigated. The worn surface morphologies of neat PVDF and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. Moreover, all filled PVDFs have superior tribological characteristics to unfilled PVDFs. The optimum wear reduction was obtained when the content of carbon fiber is 20 vol%.     

Improvement of the tribological behavior of ultra‐high‐molecular‐weight polyethylene by incorporation of poly (phenyl p‐hydroxyzoate)

Ultra‐high‐molecular‐weight polyethylene/poly (phenyl p‐hydroxyzoate) composites (coded as UHMWPE/PPHZ) were prepared by compression molding. The effects of the poly (phenyl p‐hydroxyzoate) on the tribological properties of the UHMWPE/PPHZ composites were investigated, based on the evaluations of the tribological properties of the composites with various compositions and the examinations of the worn steel surfaces and composites structures by means of scanning electron microscopy and transmission electron microscopy. It was found that the incorporation of the PPHZ led to a significant decrease in the wear rate of the composites. The composites with the volume fraction of the PPHZ particulates within 45% ～ 75% showed the best wear resistance. The friction coefficient of the UHMWPE/PPHZ composites decreased with increasing load and sliding velocity, while the wear rates increased with increasing load. This was attributed to the enhanced softening and plastic deformation of the composites at elevated load or sliding velocity. The UHMWPE/PPHZ composites of different compositions had differences in the microstructures and the transfer film characteristics on the counterpart steel surface as well. This accounted for their different friction and wear behaviors. The transfer film of the UHMWPE/PPHZ composites appeared to be thinner and more coherent, which was largely responsible for their better wear resistance of t composite than the UHMWPE matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2336–2343, 2005     

Friction and wear properties of polyimide matrix composites reinforced with short basalt fibers

Short basalt fiber (BF) reinforced polyimide (PI) composites were fabricated by means of compression‐molding technique. The friction and wear properties of the resulting composites sliding against GCr15 steel were investigated on a model ring‐on‐block test rig under dry sliding conditions. The morphologies of the worn surfaces and the transfer films that formed on the counterpart steel rings were analyzed by means of scanning electron microscopy. The influence of the short BF content, load, and sliding speed on the tribological behavior of the PI composites was examined. Experimental results revealed that the low incorporation of BFs could improve the tribological behavior of the PI composites remarkably. The friction coefficient and wear rate decreased with increases in the sliding speed and load, respectively. The transfer film that formed on the counterpart surface during the friction process made contributions to reducing the friction coefficient and wear rate of the BF‐reinforced PI composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of Aluminum Filler on Friction and Wear Characteristics of Glass Epoxy Composites

An experimental study was carried out to investigate the dry sliding friction and wear characteristics of woven glass epoxy composites filled with Al particulates sliding against steel using a pin-on-disc tribometer. The glass fiber weight fraction was kept constant at 60 wt% and Al wt% varied as 0, 5, 10, and 15%. The composite was fabricated by a hand lay-up technique followed by light compression molding. Friction and wear behavior under dry sliding condition are presented as a function of sliding speed varying between 1–5 m/s and normal load ranging between 10–40 N. Friction characteristics of composites depend strongly on a combination of filler content, sliding speed and load. Wear loss increases with both sliding speed and load. Incorporation of a smaller amount of Al filler reduces wear loss compared to un-filled glass epoxy composites. An attempt has also been made to observe the distribution of fiber and Al particles in the composite, and to correlate the wear behavior using Scanning Electron Microscopy (SEM) observations.     

Preparation and tribological properties of carbon fibre reinforced poly(vinylidene fluoride) composites

Abstract

The current study examines the tribological performance of poly(vinylidene fluoride) (PVDF) and carbon fibre reinforced poly(vinylidene fluoride) (CF/PVDF) under dry sliding condition. Different contents of carbon fibres (CFs) were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of CF content on tribological properties of the composites were investigated. The worn surface morphologies of neat PVDF and its composites were examined by scanning electron microscopy and the wear mechanisms were discussed. Moreover, all filled PVDFs have superior tribological characteristics to unfilled PVDFs. The optimum wear reduction was obtained when the content of CF is 20 vol.-%.     

Friction and wear behaviour of silicon carbide/graphene composites under isooctane lubrication

The tribological performance of silicon carbide (SiC)/graphene nanoplatelets (GNPs) composites is analysed under oscillating sliding tests lubricated with isooctane, looking to explore their potential as components for gasoline direct injection (GDI) engines. High graphene filler contents (20?vol.% of GNPs) are required to substantially reduce the friction coefficient of SiC ceramics, attaining decreases on friction up to 30% independently of the applied load. For all materials and testing conditions a mild wear regime is evidenced. SiC/20?vol.% GNPs composite also enhances the wear resistance up to 35% at low load, but the addition of GNPs produces a deleterious effect as the load augments. The tribological behaviour depends on the formation and destabilization of a solid lubricant carbon-based tribofilm and strongly correlates with the mechanical properties of the tested materials.     

Effects of the combination of solid lubricants and short carbon fibers on the sliding performance of poly(ether imide) matrix composites

Solid lubricants, that is, graphite flakes and poly(tetrafluoroethylene) powders, were incorporated with short carbon fibers into a poly(ether imide) matrix to improve the tribological performance. Wear tests were performed with a polymer pin against a mild steel counterpart at a constant sliding speed of 1 m/s under various temperatures and contact pressures. Composites filled with equilibrium contents of solid lubricants and short carbon fibers, that is, 10 vol % of each filler, exhibited the lowest wear rate and friction coefficient. The relatively lower concentration of solid lubricants adversely affected the wear resistance, whereas the friction coefficient did not vary significantly in comparison with the friction coefficient of the composites filled with only short carbon fibers. The improved tribological behavior was attributed to more continuous and effective friction films formed on the material pairs during sliding. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1428–1434, 2004     

Friction and wear behavior of alumina-based graphene and CNFs composites

Alumina – carbon nanofibers (CNF) and alumina – graphene oxide (GO) composites were prepared by spark plasma sintering using freeze-dried powders prepared from optimized suspensions of the mixtures. The tribological behavior was studied using the ball-on-disk technique in dry sliding at ambient conditions and compared to a monolithic alumina used as a reference. At low loads there was little difference between friction and wear behavior, whereas at moderate loads the composites showed a noticeable reduction in wear rate over monolithic alumina, five and 2.5 times for the GO and the CNF composite respectively; the friction coefficient slightly decreased for the alumina – GO material. This behavior is related to the presence of a carbon-rich protecting tribofilm. The film present in the alumina – GO showed better tribological performance due to the absence of coalescence of cracks that led to delamination events in the case of the alumina – CNF composite.     

Tribological properties of SiO2 nanoparticle filled–phthalazine ether sulfone/phthalazine ether ketone (50/50 mol %) copolymer composites

SiO₂ nanoparticle filled–poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions were made by heating compression molding. The tribological behavior of the PPESK composites was investigated using a block‐on‐ring test rig by sliding PPESK‐based composite blocks against a mild carbon steel ring. The morphologies of the worn composite surfaces, wear debris, and the transferred films formed on the counterpart steel surface were examined with a scanning electron microscope, whereas the chemical state of the Fe element in the transfer film was analyzed with X‐ray photoelectron spectroscopy. In addition, IR spectra were taken to characterize the structure of wear debris and PPESK composites. It was found that SiO₂ nanoparticle filled–PPESK composites exhibit good wear resistance and friction‐reduction behavior. The friction and wear behavior of the composites was improved at a volume fraction between 4.2 and 14.5 vol % of the filler SiO₂. The results based on combined SEM, XPS, and IR techniques indicate that SiO₂ nanoparticle filled–PPESK composite is characterized by slight scuffing in dry sliding against steel and polishing action between composite surface and that of the countpart ring, whereas unfilled PPESK is characterized by severe plastic deformation and adhesion wear. In the former case a thin, but not complete, transfer film was formed on the surface of the counterpart steel, whereas in the latter case, a thick and lumpy transfer film was formed on the counterpart steel surface. This accounts for the different friction and wear behavior of unfilled PPESK and SiO₂ nanoparticle filled–PPESK composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2136–2144, 2002     

Durable polytetrafluoroethylene composites in harsh environments: Tribology and corrosion investigation

The tribological properties and mass loss of polytetrafluoroethylene (PTFE) composites filled with carbon fiber (CF) or potassium titanate whisker (PTW) after the immersion in 30% sulfuric acid solution for 5 or 15 days were studied under different temperatures (25, 50, and 75°C). Results show that PTW/PTFE composites exhibit better anticorrosive and antiwear properties than those of CF/PTFE composites. Acid immersion has no obvious effect on the wear rate of the PTW/PTFE composite. The wear rate of CF/PTFE immersed for 15 days is thrice as much that of untreated composites and 3.6 times as much that of PTW/PTFE composites. Results also indicate that the wear rate of PTFE composites increases with the increasing corrosive mass loss rate and is more dependent on the corrosive mass loss rate rather than the friction coefficient. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

High performance PEEK/AlN micro‐ and nanocomposites for tribological applications

The tribological properties of poly(ether–ether–ketone) (PEEK)/aluminum nitride (AlN) composites reinforced with micro‐ and nano‐AlN particles were evaluated under dry sliding conditions. The wear resistance of pure PEEK is 10‐fold higher than mild steel. It was further improved by 2‐fold at 20 wt % micro‐AlN and by more than 4‐fold at 30 wt % nano‐AlN composite compared with pure PEEK. The improvement in wear resistance was attributed to a thin and coherent transfer film. However, it was deteriorated on further increasing micro‐AlN. The coefficient of friction of the composites was increased. Scanning electron microscopy and optical microscopy of worn surfaces and transfer films have been explained in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties and sliding wear behavior of potassium titanate whiskers‐reinforced poly(ether ether ketone) composites under water‐lubricated condition

Polyetheretherketone (PEEK) composites reinforced with potassium titanate whiskers (PTW) were compounded using a twin‐screw extruder followed by injection molding. The effects of PTW on the mechanical properties, crystallization performances and wear behaviors of PEEK under water lubrication have been investigated. It was denoted that the yield strength, Young's modulus, and microhardness of the composites increased with increasing whisker content, but the elongation at break and the impact strength showed decreasing trend. It was revealed that the inclusion of PTW could effectively reduce the friction coefficient and enhance the wear resistance of the PEEK. The DSC tests showed that the crystallinity of the composite slightly decreased with the addition of PTW, which might imply that the crystallinity of PEEK was not the dominant factor that influenced the wear properties of the composites. The enhancement on the wear resistance was attributed to the reinforced effect of PTW on PEEK. The wear mechanism changed from fatigue wear into mild abrasive wear when the PTW was added into PEEK. The lowest wear rate 9.3 × 10^?8 mm³/Nm was achieved at 10 wt % PTW content. However, excessive whiskers would cause severe abrasive wear to the composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010