Friction and wear characteristics of PTFE composites filled with metal oxides under lubrication by oil

Four kinds of polytetrafluoroethylene(PTFE)-based composites, such as pure PTFE, PTFE+30%(v)PbO, PTFE+30%(v)Pb₃O₄, and PTFE+30%(v)Cu₂O composite, were prepared. The friction and wear properties of these metal oxides filled PTFE composites sliding against GCr15 bearing steel in both dry and lubricated conditions were studied by using an MHK-500 ring-block wear tester. Then the worn surfaces of these PTFE composites and the transfer films of these PTFE composites formed on the surface of GCr15 bearing steel were examined by using a Scanning Electron Microscope (SEM) and an Optical Microscope, respectively. Experimental results show that the friction and wear properties of these metal oxide-filled PTFE composites can be greatly improved by liquid paraffin lubrication, and the friction coefficients can be decreased by one order of magnitude. Meanwhile, the interactions between liquid paraffin and metal oxide-filled PTFE composites, especially the absorption of liquid paraffin into the surface layers of these PTFE composites, reduce the mechanical strength and the load-carrying capacity of these metal oxide-filled PTFE composites. This leads to the deterioration of the friction and wear properties of these PTFE composites. Investigations of the frictional surfaces show that Pb₃O₄, Cu₂O, and PbO enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, and thus promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel. Therefore, they greatly reduce the wear of the PTFE composites. However, the transfer of these PTFE composites onto the counterfaces can be greatly reduced by lubrication with liquid paraffin. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 85–93, 1997     

不同介质中聚四氟乙烯复合材料的摩擦磨损性能

分别在碱液、水、油和干摩擦条件下考察了碳纤维和玻璃纤维填充聚四氟乙烯复合材料的摩擦磨损性能。利用SEM观察了不同介质中磨损面和对摩面的形貌,并探讨了其磨损机理。结果表明,不同介质中摩擦系数的大小关系是μ干>μ水或油>μ碱,磨损率是W水>W干>W碱或油。水、碱和油都不同程度地阻止了转移膜的形成。碱液和油具有很好的冷却与润滑作用,摩擦系数低,磨损小;然而水分子降低了填料和基体的界面粘接强度,造成犁削和磨粒磨损加重。     

Friction and wear behavior of PTFE composites filled with rare earth compounds under oil‐lubricated conditions

Polytetrafluoroethylene (PTFE)‐based composites, filled with CeO₂, CeF₃, and La₂O₃ in volume contents of 5, 10, 15, 20, and 30%, were prepared. Then, the friction and wear behavior of these PTFE composites sliding against GCr15 bearing steel under both dry and liquid paraffin‐lubricated conditions was evaluated using an MHK‐500 ring‐on‐block wear tester. Finally, the worn surfaces and the transfer films of these PTFE composites were investigated using a scanning electron microscope (SEM) and an optical microscope. Experimental results showed that filling CeO₂, CeF₃, and La₂O₃ into PTFE can reduce the wear of the PTFE composites by 1–2 orders of magnitude. When the content of CeO₂ in PTFE is 15%, the friction and wear properties of the CeO₂‐filled PTFE composite are the best. Meanwhile, when the content of La₂O₃ in PTFE is between 15 and 20%, the PTFE composite filled with La₂O₃ exhibits excellent friction and wear‐reducing properties. However, the friction coefficient of the CeF₃‐filled PTFE composite increases but its wear decreases with increase in the content of CeF₃ from 5 to 30%. The friction and wear‐reducing properties of CeO₂‐, CeF₃‐, and La₂O₃‐filled PTFE composites can be greatly improved by lubrication with liquid paraffin, but the limit loads of the PTFE composites decrease with increase in the content of CeO₂, CeF₃, and La₂O₃ in PTFE (from 5 to 30%) under the same conditions. Investigations of worn surfaces show that the interaction between liquid paraffin and the CeO₂‐, CeF₃‐, and La₂O₃‐filled PTFE composites, especially the absorption of liquid paraffin into the microdefects of the PTFE composites, creates some cracks on the worn surfaces of the PTFE composites and that the creation and development of the cracks reduces the mechanical strength and the load‐supporting capacity of the PTFE composites. However, with increase of the content of CeO₂, CeF₃, and La₂O₃ in the PTFE, the microdefects in the PTFE composites also increase, which would lead to increase in the number of the cracks on the worn surfaces of the PTFE composites under load and, so, in turn, lead to the reduction of the limit loads of the CeO₂‐, CeF₃‐, and La₂O₃‐filled PTFE composites under lubrication with liquid paraffin. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 78: 797–805, 1999     

Friction and wear behavior of the hybrid PTFE/cotton fabric composites filled with TiO2 nanoparticles and modified TiO2 nanoparticles

A chemical grafting method was applied to modify TiO₂ nanoparticles through covalently introducing glycidoxypropyltrimethoxy silicane (KH560) followed by polyoxymethylene onto the particles to overcome the disadvantages generated by the agglomeration of nanoparticles. TiO₂ nanoparticles unmodified and modified were introduced into hybrid polytetrafluoroethylene (PTFE)/cotton fabric composites. Friction and wear test demonstrated that TiO₂ nanoparticles unmodified and modified can significantly increase the wear resistance of hybrid PTFE/cotton fabric composites but cannot reduce the friction coefficient. Fabric composites filled with grafted TiO₂ nanoparticles exhibited a lower wear rate due to the disintegration of agglomeration and the improvement of interfacial adhesion between filler/matrix. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

The friction and wear properties of clay filled PA66

Polyamide 66(PA66)/clay nanocomposites were prepared by direct melt compounding. The mechanical and tribological properties were evaluated. It was found that addition of clay into PA66 increased the bending strength and microhardness of PA66. And also, the incorporation of clay can reduce the friction coefficient of PA66. The nanocomposites which have the mass fraction less than 5% show less wear rate compared with neat PA66. High fraction of clay can cause severe agglomerated abrasives. The differences in the friction and wear behaviors of PA66 and PA66/clay nanocomposites are attributed to the differences in their surface morphologies, transfer film characteristic. The agglomerated abrasives on the worn surface contribute to the increase of wear rate of nanocomposites of higher mass fraction clay. The friction and wear behaviors of PA66 and its nanocomposites under high temperature exhibit similar tendency with those under 25°C. POLYM. ENG. SCI., 48:203–209, 2008. © 2007 Society of Plastics Engineers     

Friction and wear characteristics of metal sulfides and graphite‐filled PTFE composites under dry and oil‐lubricated conditions

Five kinds of polytetrafluoroethylene (PTFE)‐based composites, pure PTFE, PTFE + 30(v)% MoS₂, PTFE + 30(v)% PbS, PTFE + 30(v)% CuS, and PTFE + 30(v)% graphite (GR) composites, were first prepared. Then the friction and wear properties of these PTFE composites, sliding against GCr15‐bearing steel under both dry and liquid paraffin‐lubricated conditions, were studied by using an MHK‐500 ring‐on‐block wear tester. Finally, the worn surfaces and the transfer films of the PTFE composites formed on the surface of GCr15 bearing steel were investigated by using a scanning electron microscope (SEM) and an optical microscope, respectively. Experimental results show that filling with MoS₂, PbS, CuS, or graphite to PTFE can reduce the wear of the PTFE composites by two orders of magnitude compared to that of pure PTFE under dry friction conditions. However, the friction and wear‐reducing properties of these PTFE composites can be greatly improved by lubrication with liquid paraffin. Investigations of transfer films show that MoS₂, PbS, CuS, and graphite promote the transfer of the PTFE composites onto the surface of GCr15‐bearing steel under dry friction conditions, but the transfer of the PTFE composites onto the surface of GCr15‐bearing steel can be greatly reduced by lubrication with liquid paraffin. SEM examinations of worn surfaces show that with lubrication of liquid paraffin, the creation and development of the cracks occurred on the worn surfaces of the PTFE composites under load, which reduces the load‐supporting capacity of the PTFE composites. This would lead to the deterioration of the friction and wear properties of the PTFE composites under higher loads (>600N). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 751–761, 1999     

Study on wear and friction behavior of graphite flake‐filled PTFE composites

The wear rate and coefficient of friction for graphite flake (GF)‐filled polytetrafluoroethylene (PTFE) composites were evaluated on a pin‐on‐disk wear tester under dry conditions. Scanning electron microscopy showed significant reduction in the abrasive wear of the composites. The wear rates of 5 and 10 wt % GF composites were reduced by more than 22 and 245 times, respectively, at sliding speed of 1 m/s. With increasing sliding distance from 1 to 8 km, the wear rate of pure PTFE decreased by 1.4 times whereas that of composites, it decreased up to three times. The significant decreased in wear rate and coefficient of friction might be attributed to the formation of a thin and tenacious transfer film on the counter‐surface. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Friction and wear characteristics of fiber- and whisker-reinforced PTFE composites under oil lubricated conditions

Four kinds of polytetrafluoroethylene (PTFE)-based composites, such as pure PTFE, PTFE + 30(vol.)% carbon fiber, PTFE + 30(vol.)% glass fiber, and PTFE + 30(vol.)% K₂Ti₆O₁₃ whisker composite, were prepared. The friction and wear properties of these fiber- and whisker-reinforced PTFE composites sliding against GCr15-bearing steel (SAE52100 steel) under both dry and liquid paraffin lubricated conditions were studied by using an MHK-500 ring-block wear tester (Timken wear tester). Then the worn surfaces of these PTFE composites and the transfer films formed on the surface of GCr15-bearing steel were investigated by using a Scanning Electron Microscope (SEM) and an Optical Microscope, respectively. Experimental results show that the friction and wear properties of the PTFE composites reinforced with carbon fiber, glass fiber, and a K₂Ti₆O₁₃ whisker can be greatly improved by lubrication with liquid paraffin, and the friction coefficients of these PTFE composites can be decreased by one order of magnitude compared to those under dry friction conditions. Meanwhile, the wear of the fiber- and whisker-reinforced PTFE composites in liquid paraffin lubrication increases with the increase of load, but the friction coefficients of these PTFE composites first decrease with the increase of load, and then increase with the increase of load. The variations of friction coefficients with load for these PTFE composites in liquid paraffin lubrication can be described properly by the Stribeck's curve as given in this article. However, when the load increases to the load limits of the PTFE composites, their friction and wear increase sharply. SEM and optical microscope investigations show that the interactions between liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, create some obvious cracks on the worn surfaces of the PTFE composites. The creation and the development of the cracks reduce the load-carrying capacity of the PTFE composites, and therefore lead to the increase of the friction and wear of the PTFE composites under higher loads. Meanwhile, the transfer of the fiber- and whisker-reinforced PTFE composites onto the counterfaces can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1393–1402, 1998     

Friction and wear properties of NBR/PVC composites

Acrylonitrial butadiene rubber (NBR)/Polyvinyl chloride (PVC) composites with different PVC content were prepared. The effect of PVC content on the mechanical strength and tribological properties of the NBR/PVC composites was investigated. The morphologies of the worn traces and debris of NBR/PVC composites and worn traces of mating ball were observed using a scanning electron microscope (SEM). It was found that the friction and wear of NBR/PVC was lower than that of NBR without PVC. The NBR/PVC composite with 30% PVC content showed the best synthetic mechanical and tribological properties. The inferior elastic properties and the lesser deformation under the applied load of composites with PVC resulted in hysteric force and adhesion force decrease, which leading to a lower friction and wear of NBR/PVC composites. The frictional failure unit of NBR70/PVC30 composite being smaller should be an important reason of the wear of the composite being lowest. The lubricating effect of PVC played an important role in decreasing the friction coefficient and wear of NBR/PVC composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Friction and wear characteristics of copper and its compound-filled PTFE composites under oil-lubricated conditions

Four kinds of polytetrafluoroethylene (PTFE)-based composites, such as pure PTFE, PTFE + 30(v)%Cu, PTFE + 30(v)%Cu₂O, and PTFE + 30(v)%CuS composite, were prepared. Then the friction and wear properties of the PTFE composites filled with Cu, Cu₂O, or CuS sliding against GCr15-bearing steel under both dry and liquid paraffin-lubricated conditions were studied by using an MHK-500 ring-block wear tester. Finally, the worn surfaces and the transfer films of these PTFE composites formed on the surface of GCr15-bearing steel were investigated by using a scanning electron microscope (SEM) and an optical microscope, respectively. Experimental results show that the antiwear properties of these PTFE composites can be greatly improved by filling Cu, Cu₂O, or CuS to PTFE, and the wear of these PTFE composites can be decreased by two orders of magnitude compared to that of pure PTFE under dry friction conditions. Meanwhile, CuS increases the friction coefficient of the PTFE composite, but Cu and Cu₂O reduce the friction coefficients of the PTFE composites. However, the friction and wear properties of Cu, Cu₂O, or CuS-filled PTFE composites can be greatly improved by lubrication with liquid paraffin. The friction coefficients of these PTFE composites can be decreased by one order of magnitude compared to those under dry friction conditions, while the wear of these PTFE composites can be decreased by one to two orders of magnitude. The PTFE + 30(v)%Cu composite exhibits excellent friction and wear-reducing properties under higher loads in liquid paraffin-lubricated conditions, so the PTFE + 30(v)%Cu composite is much more suitable for application under oil-lubricated conditions in practice. Optical microscope investigation of transfer films shows that Cu, Cu₂O, and CuS enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, so they greatly reduce the wear of the PTFE composites. However, the transfer of the PTFE composites onto the surface of GCr15-bearing steel can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. SEM examination of worn surfaces shows that the interaction between liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, creates some cracks on the worn surfaces of Cu₂O or CuS-filled PTFE composites, the creation and development of the cracks reduces the load-carrying capacity of the PTFE composites; this leads to the deterioration of the friction and wear properties of the PTFE composites under higher loads in liquid paraffin lubrication. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1455–1464, 1998     

Friction and wear characteristics of ceramic particle filled polytetrafluoroethylene composites under oil-lubricated conditions

Five kinds of polytetrafluoroethylene (PTFE)-based composites were prepared: PTFE, PTFE + 30 vol % SiC, PTFE + 30 vol % Si₃N₄, PTFE + 30 vol % BN, and PTFE + 30 vol % B₂O₃. The friction and wear properties of these ceramic particle filled PTFE composites sliding against GCr15 bearing steel under both dry and liquid paraffin lubricated conditions were studied by using an MHK-500 ring-block wear tester. The worn surfaces and the transfer films formed on the surface of the GCr15 bearing steel of these PTFE composites were investigated by using a scanning electron microscope (SEM)and an optical microscope, respectively. The experimental results show that the ceramic particles of SiC, Si₃N₄, BN, and B₂O₃ can greatly reduce the wear of the PTFE composites; the wear-reducing action of Si₃N₄ is the most effective, that of SiC is the next most effective, then the BN, and that of B₂O₃ is the worst. We found that B₂O₃ reduces the friction coefficient of the PTFE composite but SiC, Si₃N₄, and BN increase the friction coefficients of the PTFE composites. However, the friction and wear properties of the ceramic particle filled PTFE composites can be greatly improved by lubrication with liquid paraffin, and the friction coefficients of the PTFE composites can be decreased by 1 order of magnitude. Under lubrication of liquid paraffin the friction coefficients of these ceramic particle filled PTFE composites decrease with an increase of load, but the wear of the PTFE composites increases with a load increase. The variations of the friction coefficients with load for these ceramic particle filled PTFE composites under lubrication of liquid paraffin can be properly described by the relationship between the friction coefficient (μ) and the simplified Sommerfeld variable N/P as given here. The investigations of the frictional surfaces show that the ceramic particles SiC, Si₃N₄, BN, and B₂O₃ enhance the adhesion of the transfer films of the PTFE composites to the surface of GCr15 bearing steel, so they greatly reduce the wear of the PTFE composites. However, the transfer of the PTFE composites onto the surface of the GCr15 bearing steel can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. Meanwhile, the interactions between the liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, create some cracks on the worn surfaces of the ceramic particle filled PTFE composites; the creation and development of these cracks reduces the load-supporting capacity of the PTFE composites. This leads to the deterioration of the friction and wear properties of the PTFE composites under higher loads in liquid paraffin lubrication. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2611–2619, 1999     

Friction and wear properties of basalt fiber reinforced/solid lubricants filled polyimide composites under different sliding conditions

Short basalt fibers (BFs)‐reinforced polyimide (PI) composites filled with MoS₂ and graphite were fabricated by means of hot‐press molding technique. The tribological properties of the resulting composites sliding against GCr15 steel ring were investigated on a model ring‐on‐block test rig. The wear mechanisms were also comparatively discussed, based on scanning electron microscopic examination of the worn surface of the PI composites and the transfer film formed on the counterpart. Experimental results revealed that MoS₂ and graphite as fillers significantly improved the wear resistance of the BFs‐reinforced polyimide (BFs/PI) composites. For the best combination of friction coefficient and wear rate, the optimal volume content of MoS₂ and graphite in the composites appears to be 40 and 35%, respectively. It was also found that the tribological properties of the filled BFs/PI composites were closely related with the sliding conditions such as sliding speed and applied load. Research results show that the BF/PI composites exhibited better tribological properties under higher PV product. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

The mechanical and tribological properties of PTFE filled with PTFE waste powders

Polytetrafluoroethylene (PTFE) composites filled with PTFE waste offer interesting combination of tribological properties and low cost. PTFE composites waste was mechanically cut and sieved into powders. PTFE composites filled with PTFE waste powders were prepared by compression molding. Friction and wear experiments were carried out in a reciprocating sliding tribotester at a reciprocating frequency of 1.0 Hz, a contact pressure of 5.5 MPa, and a relative humidity of (60 ± 5)%. PTFE materials slid against a 45 carbon steel track. Results showed that a PTFE composite (B) filled with 20 wt % PTFE waste exhibited a coefficient of steady‐state friction slightly higher than that of unfilled PTFE (A), while wear resistance over two orders of magnitude higher than that of unfilled PTFE (A). Another PTFE composite filled with PTFE waste and alumina nanoparticles exhibited the highest wear resistance among the three PTFE materials. This behavior originates from the effective reinforcement of PTFE waste as a filler. It was experimentally confirmed that the low cost recycling of PTFE waste without by‐products is feasible. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1035–1041, 2007     

沥青炭基C/C复合材料的载流摩擦磨损性能

通过对纯沥青炭基C/C复合材料、含炭黑沥青炭基C/C复合材料和添加氯化铁的沥青炭基C/C复合材料的载流摩擦磨损实验,发现含炭黑沥青炭基C/C复合材料的摩擦系数和磨损量最大,纯沥青炭基C/C复合材料的摩擦系数和磨损量次之,添加氯化铁的沥青炭基C/C复合材料的摩擦系数和磨损量最小,并对3种沥青炭基C/C复合材料的摩擦磨损机理进行了讨论。     

A study of tribological and mechanical properties of PTFE composites filled with surface treated K2Ti6O13 whisker

K₂Ti₆O₁₃ whisker was modified with n‐octadecyltrichlorosilane (OTS), fluorosurfactant (FSK), and silane coupling agent (KH‐550), respectively. The surface energy of K₂Ti₆O₁₃ whisker was calculated based on Van Oss‐Chaudhury‐Good function. Then the influence of surface modification on the tribological and mechanical properties of K₂Ti₆O₁₃ whisker filled polytetrafluoroethylene (PTFE) composites was studied. Surface energy calculation shows that the surface energy of OTS‐treated K₂Ti₆O₁₃ whisker is only 29.0 mJ/m², which is the closest to the value of pure PTFE. Among all samples, the PTFE composite filled with OTS‐treated K₂Ti₆O₁₃ whisker shows the best antiwear property, tensile strength, and impact strength, which is about 19 to 33%, 15 and 55% higher than that of untreated K₂Ti₆O₁₃ whisker filled PTFE, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

PA66/PTFE复合材料的摩擦磨损性能

采用机械共混的方法制备了PA66/PTFE复合材料,研究了聚四氟乙烯(PTFE)改性尼龙66( PA66)复合材料的摩擦磨损性能,并采用扫描电镜( SEM)观察了材料的磨损表面.结果表明:PTFE的加入可以有效改善尼龙66的摩擦性能,当PTFE质量分数为9％时,摩擦系数为纯PA66的57％左右,磨损量为纯PA66的43％左右,综合耐磨性最好.磨损面的扫描电镜观察发现,材料的磨损以黏着磨损和磨粒磨损为主,PTFE在共混体系中形成了微纤结构.     

Friction and wear properties of scrap tire/potassium hexatitanate whisker composites

As a way of solving the environmental problem of waste tires, we developed a new type of friction material made of scrap tire composites with potassium hexatitanate in which rubber formed a continuous phase. The tribological behaviors of the scrap tire rubber composites were investigated by a friction and wear tester under dry conditions. According to the results, the optimum amounts of potassium hexatitanate were 5 phr in terms of the friction and wear properties up to 200 °C. The specimen containing other ingredients showed 0.72 of friction coefficient and 1.03 of wear rate which are highly compatible to those of the commercial ‘Sonata’ motor brake pad when it contains 5, 20, 10, 20, 10 phr of potassium hexatitanate, phenol, cashew, barium sulfate, and copper, respectively.     

表面处理对CF/PA66复合材料磨损性能的影响

采用电化学氧化法和氨气法分别对碳纤维(CF)进行表面处理后,用双螺杆挤出机共混造粒和注塑成型制备CF/PA66复合材料,研究了表面处理对CF/PA66复合材料磨损性能的影向。结果表明:随着CF含量的增加,CF/PA66复合材料的耐磨损性能提高;对CF进行表面处理,可提高CF/PA66复合材料的耐磨损性能,氨气法得到的CF/PA66复合材料的耐磨损性能优于电化学氧化法,当添加CF质量分数为15%时,其体积磨损速率比电化学氧化法的约降低48%。