Effect of several solid lubricants on the mechanical and tribological properties of phenolic resin‐based composites

The flake graphite, polytetrafluoroethylene, and molybdenum disulfide (MoS₂) filled phenolic resin‐based composites were prepared by hot press molding. The thermal, mechanical, and tribological properties of composites were studied systematically. The morphologies of the worn surfaces and the change of chemical compositions during the sliding process of the composites were analyzed by scanning electron microscopy and X‐ray photoelectron spectroscopy, respectively. It was found that the heat‐resisting performance and the hardness of the composites are less affected by solid lubricants, while the solid lubricants did harm to the flexural strength of the composites. The friction and wear behaviors of composites highly depended on the volume fractions of solid lubricants and the sliding conditions. The wear resistance increases and the coefficient of friction decreases when the filler load increases. In addition, the appropriate content of solid lubricants is beneficial to reducing the sensitivities of the composites to load and sliding speed. POLYM. COMPOS., 36:2203–2211, 2015. © 2014 Society of Plastics Engineers     

Effect of solid lubricants on tribological behavior of glass fiber reinforced polyamide 6

The tribological properties of glass fiber reinforced polyamide 6 (GF/PA6, 15/85 by weight) and its composites filled with solid lubricants were investigated. The main purposes of this article were to study the hybrid effect of solid lubricants with glass fiber as well as the synergism of combined solid lubricants, the wear mechanisms were studied by SEM. The results showed that graphite impaired the tribological properties of GF/PA6, but the tribology behavior of graphite filled GF/PA6 composite could be significantly improved by polytetrafluroethylene (PTFE) or/and ultrahigh molecular weight polyethylene (UHMWPE), and the GF/PA6 composite filled with 5 wt % graphite, 5 wt % PTFE together with 5 wt % UHMWPE exhibited the lowest friction coefficient and wear rate, which was almost a reduction in friction coefficient by 37% and in wear rate by 34% contrast to GF/PA6. The effect of load was also studied, and the results showed that the friction coefficient was virtually not affected by load, while the wear rate all increased with increasing load. POLYM. COMPOS., 34:1783–1793, 2013. © 2013 Society of Plastics Engineers     

Friction and wear behavior of basalt‐fabric‐reinforced/solid‐lubricant‐filled phenolic composites

To improve the tribological properties of basalt‐fabric‐reinforced phenolic composites, solid lubricants of MoS₂ and graphite were incorporated, and the tribological properties of the resulting basalt‐fabric composites were investigated on a model ring‐on‐block test rig under dry sliding conditions. The effects of the filler content, load, and sliding time on the tribological behavior of the basalt‐fabric composites were systematically examined. The morphologies of the worn surfaces and transfer films formed on the counterpart steel rings were analyzed by means of scanning electron microscopy. The experimental results reveal that the incorporation of MoS₂ significantly decreased the friction coefficient, whereas the inclusion of graphite improved the wear resistance remarkably. The results also indicate that the filled basalt‐fabric composites seemed to be more suitable for friction materials serving under higher loads. The transfer films formed on the counterpart surfaces during the friction process made contributions to the reduction of the friction coefficient and wear rate of the basalt‐fabric composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of solid lubricant reinforcement on wear behavior of Kevlar fabric composites

The friction and wear behavior of Kevlar fabric composites reinforced by PTFE or graphite powders was investigated using a Xuanwu‐III friction and wear tester at dry sliding condition, with the unfilled Kevlar fabric composite as a reference. The worn surfaces were analyzed by means of scanning electron microscope, and X‐ray photoelectron spectroscopy. It was found that PTFE or graphite as fillers could significantly improve the tribological behavior of the Kevlar fabric composites, and the Kevlar fabric composites filled with 20% PTFE exhibited the best antiwear and antifriction ability among all evaluated cases. The transfer films established with two lubricants in sliding wear of composites against metallic counterparts made contributions to reducing friction coefficient and wear rate of Kevlar fabric composites. In particular, FeF₂ generated in the sliding of Kevlar fabric composites filled with PTFE against counterpart pin improved the bonding strength between the transfer film and counterpart surface, which accounted for the lowest friction coefficient and wear rate of the Kevlar fabric composites filled with PTFE measured in the testing. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

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。     

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%.     

Role of internal additives in the friction and wear of carbon‐fiber‐reinforced polyimide

Polyimide composites should function in sliding contacts under high temperatures, but the interference of carbon fibers with sliding mechanisms is difficult to predict: they often increase the coefficients of friction and act abrasively but show lubricating properties under other conditions. The friction and wear behavior of thermoplastic polyimides reinforced with short carbon fibers and filled with solid internal lubricant (polytetrafluoroethylene) or silicon oil was investigated in this study with a reciprocating cylinder‐on‐plate tester under 50 N at 0.3 m/s with steel counterfaces that were heated at 23–260°C. We concluded that polytetrafluoroethylene additives effectively reduced the coefficients of friction over the entire temperature range, especially under thermally controlled sliding conditions at 120°C, whereas the internal silicon oil increased the coefficients of friction. The wear rates of the fiber‐reinforced polyimide significantly decreased with respect to those of the thermoplastic polyimide, whereas additional fillers slightly increased the wear rates. We further analyzed the role of internal additives by considering the deformation and maximum polymer surface temperature during sliding. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

碳纤维增强PEEK复合材料的摩擦学性能研究

用磨损试验机对碳纤维增强聚醚醚酮（PEEK）复合材料进行室温干滑动磨损试验。考察了碳纤维的含量，石墨润滑剂，对靡时间及载荷对材料靡损量及摩擦系数的影响，并用电子显微镜对其磨损表面进行了观察与分析，同时对材料的磨损机理进行了探讨，研究结果表明，随着载荷的升高和对磨时间的延长，材料的摩擦系数逐渐降低并趋于稳定，磨损量呈上升趋势，加入碳纤维可以明显地降低材料的摩擦系数和磨损量，当碳纤维含量为5％－10％时复合材料的摩擦系数和磨损量最低；加入适量固体石墨可进一步降低复合材料的摩擦系数和磨损量。     

Friction and wear studies of polyetherimide composites under oscillating sliding condition against steel cylinder

Tribological properties of neat polyetherimide (PEI), glass, carbon fiber, and solid lubricants filled PEI composites are presented in this article. The aim of this study was to investigate the friction and wear properties of these composites under dry oscillating sliding condition at room temperature (RT) as well as at elevated temperature (120°C). The polymer specimens were made to oscillate against steel cylinder as a counterpart. The friction and wear properties of PEI and composites were strongly influenced by the temperature. Incorporation of carbon fiber in the PEI matrix has increased the wear rate at RT, while at elevated temperature this trend was opposite. Abrasive action of carbon fibers has severely damaged the counterpart and resulted in accelerated wear of the composite at RT. Solid lubricants filled (PTFE, MoS₂, graphite) along with glass fiber is beneficial in improving the friction and wear performance of the PEI composite at RT, whereas at elevated temperature wear performance was deteriorated. Tribological performance of neat PEI and glass fiber composite was similar with each other at RT. Scanning electron micrographs and optical micrographs of the worn polymer specimens and the steel cylinders was used to study the possible wear mechanisms. The present test results were also compared with data available on the reciprocating wear of PEI and composites in the literature and trends have been reported. POLYM. COMPOS., 38:48–60, 2017. © 2015 Society of Plastics Engineers     

Sliding Wear Performance of TiO2/Short Carbon Fiber/Polyamide 66 Hybrid Composites

In the present work, polyamide 66 (PA66) based composites filled with hybrid TiO₂ particles and short pitch based carbon fiber were prepared. By evaluating sliding wear properties of the composites as a function of the components concentrations. Both wear rate and friction coefficient of the hybrid composites were significantly lower than those of the pure polyamide 66. The composite with 4 wt.% TiO₂ and 6 wt.% carbon fiber offered the greatest improvement of the tribological performance.     

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     

The Friction and Wear Properties of Short Carbon/CNT/PA6 Hybrid Composites Under Dry Sliding Conditions

The authors present a study of the tribological properties of short carbon/carbon nanotube (CNT)/PA6 hybrid composites. Their specific wear rate and the coefficient of friction were examined as a function of sliding time and distance. In addition, the hybrid composites with varying CNT volume ratio were tested to assess hybrid effects. It was found that the friction and wear rate decreased with sliding distance and then leveled off under dry sliding conditions, showing the effective reinforcing effect of CNT. Worn surfaces were observed by scanning electron microscope and the wear process was governed by the plastic deformation and mechanical microploughing.     

Tribological behavior of polyetheretherketone composites containing short carbon fibers and potassium titanate whiskers in dry sliding against steel

Polyetheretherketone (PEEK) composites reinforced by short carbon fibers (SCF) and potassium titanate whiskers (PTW) were prepared using twin‐screw extrusion compounding and injection molding. The tribological properties of hybrid composites were investigated in dry sliding condition against steel. The effects of filler contents on the wear behavior were studied. It was found that the hybrid composite showed an excellent tribological property in dry sliding condition. Applied load had great effect on the tribological behavior of the composites. In most cases, the friction coefficient of the composite decreased with the load rising. The composites with higher CF contents showed outstanding tribological performances at low load but could worsen the wear behavior at high load. Because of the positive effect of PTW, high PTW loading composites presented low wear rate at low load. At high loads, the composites with lower PTW contents had better wear resistance. The scanning electron microscopy (SEM) observation revealed that abrasion wear was attributed to the lower wear resistance of the high PTW content composite at high load. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tribological behaviors of polyurethane composites containing self‐lubricating microcapsules and reinforced by short carbon fibers

Self‐lubricating microcapsules containing methyl silicone oil as core materials, were prepared with poly(melamine‐formaldehyde) as shell material by in situ polymerization method. Combining with synergistic effect of the short carbon fibers (SCFs) which were systematically treated by liquid‐phase oxidation and chemical grafting, they were simultaneously adopted as reinforcing additives to improve the tribological and mechanical properties of polyurethane materials. The tribological behaviors and mechanical properties of the polyurethane composites have been investigated by a block‐on‐ring wear tester and electronic universal testing machine, respectively. The results indicate that the friction coefficient and wear rate of polyurethane composites without SCFs significantly decreased with increased self‐lubricating microcapsule concentration from 2.5 to 10 wt % due to the release of methyl silicone oil; meanwhile, the polyurethane composites filled with 10 wt % microcapsule and 15 wt % SCFs not only exhibited the lowest friction and wear behaviors, but also improved mechanical strength and thermal stability of polyurethane composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45331.     

Influence of cenosphere on tribological properties of short carbon fiber reinforced PEEK composites

This investigation focuses on the effects of cenosphere fillers on tribological properties of carbon fiber reinforced PEEK composites. Dry sliding wear behavior of 15 wt % short carbon fiber (SCF) reinforced PEEK composites filled with 5, 10, 15, and 20 wt % cenosphere was reported in this study, pure PEEK and 15 wt % SCF reinforced PEEK composites were also prepared for comparative analysis. Friction and wear experiments were conducted on a ring-on-block apparatus under different loads (100–400 N). The experimental results showed that all the composites exhibited lower coefficient of friction and better wear resistance than the matrix resin under different load conditions. It is noted that 10 wt % of the cenosphere particles filled SCF reinforced PEEK composites show superior tribological properties when compared to the other composites in this study. The morphologies of the worn surface and the fracture surface were analyzed by scanning electron microscopy and the transfer film was observed by optical microscope to understand the dominant wear mechanisms. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47245.     

Tribological properties of PTFE‐filled PMIA

The polytetrafluoroethylene‐filled (PTFE) poly(m‐phenylene isophalamide) (PMIA) composite blocks are prepared by compression molding. The friction and wear of PTFE‐filled PMIA are investigated on a block‐on‐ring machine by running the PMIA composite block against plain carbon steel (AISI 1045 steel ring). The worn surface of PMIA composite and the steel counterface are examined by using electron probe microanalysis (EPMA). It is found that PTFE‐filled PMIA exhibited considerably lower friction coefficient and wear rate than pure PMIA. Furthermore, the lowest wear rate is obtained when the composite contains 20 vol % PTFE. EPMA investigations show that there are some debris that could restrain the wear of the PMIA composites oriented along the sliding track and embedded in the surface of PMIA composite. A kind of stripe transfer film that contains abundant F element should be the main reason for the improvement of the tribological properties of PTFE‐filled PMIA composites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 747–751, 1999     

Tribological behavior of three‐dimensional braided carbon fiber reinforced polyetheretherketone composites

Three‐dimensional (3D) braided carbon fiber reinforced polyetheretherketone (denoted as CF_3D/PEEK) composites with various fiber volume fractions were prepared via hybrid woven plus vacuum heat‐pressing technology and their tribological behaviors against steel counterpart with different normal loads at dry sliding were investigated. Contrast tribological tests with different lubricants (deionized water and sea water) and counterparts made from different materials (epoxy resin, PEEK) were also conducted. The results showed that the incorporation of 3D braided carbon fiber can greatly improve the tribological properties of PEEK over a certain range of carbon fiber volume fraction (V_f) and an optimum fiber loading of ∼54% exists. The friction coefficient of the CF_3D/PEEK composites decreased from 0.195 to 0.173, while the specific wear rate increased from 1.48 × 10⁻⁷ to 1.78 × 10⁻⁷ mm³ Nm⁻¹ with the normal load increasing from 50 to 150 N. Abrasive mechanism was dominated when the composites sliding with GCr15 steel counterpart under dry and aqueous lubrication conditions. Deionized water and sea water lubricants both significantly reduced the wear of the CF_3D/PEEK composites. When sliding with neat PEEK counterpart, the CF_3D/PEEK composites possess lower friction coefficient than those against epoxy resin and GCr15 steel counterparts. In general, CF_3D/PEEK composites possess excellent tribological properties and comprehensive mechanical performance, which makes it become a potential candidate for special heat‐resisting tribological components. POLYM. COMPOS., 36:2174–2183, 2015. © 2014 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     

Tribological properties of micro‐ and nanoparticles‐filled poly(etherimide) composites

It has been found that nano‐ or microsized inorganic particles in general enhance the tribological properties of polymer materials. In the present study, 5 vol % nano‐TiO₂ or micro‐CaSiO₃ was introduced into a polyetherimide (PEI) matrix composite, which was filled additionally with short carbon fibers (SCF) and graphite flakes. The influence of these inorganic particles on the sliding behavior was investigated with a pin‐on‐disc testing rig at room temperature and 150°C. Experimental results showed that both particles could reduce the wear rate and the frictional coefficient (μ) of the PEI composites under the applied testing conditions. At room temperature, the microparticles‐filled composites exhibited a lower wear rate and μ, while the nano‐TiO₂‐filled composites possessed the lowest wear rate and μ at elevated temperature. Enhancement in tribological properties with the addition of the nano‐particles was attributed to the formation of transfer layers on both sliding surfaces together with the reinforcing effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1678–1686, 2006     

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。