The influence of plasma treatment on the tribological properties of hybrid PTFE/cotton fabric/phenolic composites

In this study, the effects of air‐plasma and N₂‐plasma treatment on the hybrid polytetrafluoroethylene (PTFE)/cotton fabric and a phenolic resin were investigated in detail. The tribological properties of the untreated and plasma‐treated hybrid PTFE/cotton fabric/phenolic composites were investigated. The results indicated that air‐plasma‐treated hybrid PTFE/cotton fabric/phenolic composites exhibited better antiwear and friction reduction properties. The combination of scanning electron microscopy and Fourier transform infrared spectroscopy analysis illustrated that hybrid PTFE/cotton fabric/phenolic composites treated with air‐plasma possessed more integrated structure and more functional groups, which plausibly contributed to the better tribological properties of the hybrid PTFE/cotton fabric/phenolic composites treated with air‐plasma. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

A study on the tribological behavior of hybrid PTFE/Kevlar fabric composites filled with nano‐SiC and/or submicron‐WS2 fillers

The tribological behaviors of hybrid PTFE/Kevlar fabric composites filled with nano‐SiC and/or submicron‐WS₂ fillers were studied. Scanning electron microscopy and energy‐dispersive X‐ray spectrometer were used for analysis of the worn surface, transfer film, and debris of the PTFE/Kevlar fabric composites. In addition, the wear volume loss of the composite was measured by means of a laser microscopic 3D and profile measurement apparatus. The results indicate that although both single fillers and hybrid fillers can reduce the wear rate of composites, but hybrid fillers filled composites could achieve the desired comprehensive tribological properties in dry sliding. The improved tribological performance of filled composites can be attributed to two aspects: the formation of a thin and tenacious transfer film on the counter‐surface, and the restrain the formation of larger debris. Tiny wear debris was easily trapped in the gap of a worn surface and can repair the damaged surface. In addition, the trapped debris could be considered as a secondary source of lubricant. POLYM. COMPOS., 37:2218–2226, 2016. © 2015 Society of Plastics Engineers     

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.     

Enhanced tribological performance of hybrid polytetrafluoroethylene/Kevlar fabric composite filled with milled pitch‐based carbon fibers

As self‐lubricating bearing liner materials, tribological properties of milled pitch‐based carbon fibers (CFs) modified polytetrafluoroethylene (PTFE)/Kevlar fabric composites were investigated, and the microscopic morphology of worn surface was studied. The results show that the appropriate incorporation of CFs can obviously reduce the wear rate of the fabric composite with almost unchanging friction coefficient. The wear rates of 5 wt % CF‐filled PTFE/Kevlar fabric composites are decreased by 30% and 48% for two kinds of composites made with fibers from different producers compared with unfilled fabric composites. Scanning electron microscopy observations show that the appropriate incorporation of CFs obviously improves the interfacial bonding and reduces pull‐out and fracture of Kevlar fiber. Meanwhile, the introduction of CFs at proper fraction is helpful to form smooth and continuous transfer film on the surface of metal counterpart. The improving mechanism of the CF is attributed to increasing mechanical strength, thermal conductivity and self‐lubricating effects. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46269.     

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     

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     

Tribological and mechanical properties of carbon‐nanofiber‐filled polytetrafluoroethylene composites

The effects of various filler concentrations (0.1, 0.5, 1, 1.5, 2, 2.5, and 3 wt %) on the tribological and mechanical properties of carbon‐nanofiber (CNF)‐filled polytetrafluoroethylene (PTFE) composites were studied. Moreover, the influence of various loads (50, 100, 150, and 200 N) and sliding velocities (0.692 and 1.39 m/s) on the friction and wear behaviors of the PTFE composites was investigated. The results showed that the friction coefficients of the PTFE composites decreased initially up to a 0.5 wt % filler concentration and then increased, whereas the antiwear properties of the PTFE composites increased by 1–2 orders of magnitude in comparison with those of pure PTFE. The composite with a 2 wt % filler concentration had the best antiwear properties under all friction conditions. The friction coefficients of the CNF/PTFE composites decreased with increases in the load and sliding velocity, whereas the wear volume loss of the PTFE composites increased. At the same time, the results also indicated that the mechanical properties of the PTFE composites increased first up to a 1 wt % filler concentration and then decreased as the filler concentration was increased above 1 wt %. In comparison with pure PTFE, the impact strength, tensile strength, and elongation to break of the PTFE composites increased by 40, 20, and 70%, respectively, at a 1 wt % filler concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2430–2437, 2007     

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 properties of polyimide fabric‐epoxy composites modified by hollow silica microspheres

The polyimide (PI) fabric/epoxy (EP) composites modified with different content of micro‐SiO₂ hollow spheres were prepared by dip‐coating and subsequently hot‐press process. For comparison, the pure EP and the unmodified PI fabric/EP composite were also fabricated. The differential scanning calorimetry was conducted to investigate the crosslinking reaction of composites. The results indicated that there exhibited a remarkable improvement in the mechanical and tribological properties of PI fabric/EP composites after incorporating the micro‐SiO₂. The best tribological properties were obtained when the content of micro‐SiO₂ was 2 wt%, whose wear rate was 71.9% lower than that of unmodified PI fabric/EP composite. The worn surfaces were observed by a scanning electron microscope to illustrate the friction mechanisms. Note that the skeleton network structure of fabric throughout the whole composites supported the matrix. At the same time, the microparticulates filled in the interstices of fabrics interwoven structure and the gaps between layers of fabrics, which propped up the skeleton network of fabric under the high frictional load and afford excellent interface between fabrics and EP. This ensures the outstanding tribological properties of PI fabric/EP composites. POLYM. COMPOS., 38:2283–2293, 2017. © 2015 Society of Plastics Engineers     

Tribological behaviors of carbon series additions reinforced CF/PTFE composites at high speed

The tribological, mechanical, and thermal properties of carbon series additions reinforced CF/PTFE composites at high speed were investigated. In this work, carbon fiber (CF) filled polytetrafluoroethylene (PTFE) composites, which have excellent tribological properties under normal sliding speed (1.4 m/s), were filled with some carbon materials [graphene (GE), carbon nanotubes (CNTs) and graphite (Gr)] respectively to investigate the tribological properties of CF/PTFE composites at high sliding speed (2.1 and 2.5 m/s). The results reveal that the carbon series additions can improve the friction and anti‐wear performances of CF/PTFE, and GE is the most effective filler. The wear rate of 0.8 wt % GE/CF/PTFE was decreased by 50 ? 55%, 55 ? 60%, 40 ? 45% at 1.4, 2.1, and 2.5 m/s compared with CF/PTFE. SEM study shows GE could be helpful to form smooth and continuous transfer film on the surface of counterparts. Meanwhile, GE can improve its tensile strength and elastic modulus obviously. Thin layer structure of GE could enhance the thermal conductivity, which can be helpful to dissipate heat of CF/PTFE composites wear surface. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43236.     

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     

Effect of compatibilizer on morphology,thermal, and rheological properties of polypropylene/functionalized multi‐walled carbon nanotubes composite

Multi‐walled carbon nanotubes (MWCNTs) filled polypropylene (PP) composites were prepared by a corotating intermeshing twin screw extruder. To improve the dispersion of MWCNTs, the surface of MWCNT was modified with 1,10‐diaminodecane, and maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizer. Micrographs of well dispersed functionalized MWCNTs (diamine‐MWCNT) were observed due to the reaction between MA‐g‐PP and diamine‐MWCNT in PP/MA‐g‐PP/diamine‐MWCNTs composites. The different behaviors in crystallization and melting temperatures of PP/MA‐g‐PP/diamine‐MWCNTs composite were observed compared to PP and PP/neat‐MWCNT. Especially, the decomposition temperature of the composite was increased by 50°C compared to PP. PP/MA‐g‐PP/diamine‐MWCNTs composite showed the highest complex viscosity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of surface modification of carbon nanotube on microstructures and properties of polyamide 66/multiwalled carbon nanotube composites

The melt‐mixing polyamide 66 (PA66) composite samples that incorporated pure, acid‐ and amine‐functionalized multiwalled carbon nanotubes (MWCNTs) were prepared in order to enhance mechanical and frictional properties of PA66 composites. The homogeneous dispersion of amine‐functionalized MWCNTs (D‐MWCNTs) in PA66 matrix was observed from the significantly uniform morphology of tensile fractured surface of the composites. Differential scanning calorimetry measurement indicates that D‐MWCNTs acted as effective nucleation agent for PA66 matrix and the crystallinity of PA66 was increased. The fracture stress and tensile modulus of the composites were significantly improved with the incorporation of D‐MWCNTs, owing to the good dispersion of D‐MWCNTs. Compared with PA66, the PA66 composites with 1.0 wt% D‐MWCNTs were improved considerably in both wear and friction properties owing to the change of the tribological mechanisms. The good dispersion of D‐MWCNTs in PA66 and good interface compatibility between D‐MWCNTs and PA66 favored the formation of a thin layer on the contact surfaces during wear and friction test, which played an important role in reducing wear and friction of the composite and in suppressing the transverse cracks. These results prove the importance of D‐MWCNTs in a positive change of the mechanical and frictional properties of PA66 composites and suggest the applicability prospect of PA66/D‐MWCNTs composites in engineering components.POLYM. COMPOS., 2013. © 2013 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 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     

Tribological behaviors of polytetrafluoroethylene composites under dry sliding and seawater lubrication

The composites of polytetrafluoroethylene (PTFE) filled with expanded graphite (EG), poly(p‐oxybenzoyl) (POB), and basalt fiber (BF) were prepared by heating compression and sintering molding. The tribological behavior of PTFE composites was investigated with a pin‐on‐disk tester under dry conditions and seawater lubrication. The worn surface of PTFE composites and the transfer film on the counterface were observed with a scanning electron microscope. The results indicated that the incorporation of EG and POB improved the hardness of PTFE composites, and addition of BF led to greater load‐carrying capacity. Compared to pure PTFE, the coefficients of friction of PTFE composites slightly increased, but the wear rates were significantly reduced (the wear rate of composite with 3% EG being only 10.38% of pure PTFE). In addition, all the composites exhibited a lower coefficient of friction (decreases of about 0.03–0.07) but more serious wear under seawater lubrication than under dry sliding. The wear mechanism changed from serious abrasive wear of pure PTFE to slight adhesion wear of PTFE composites under both conditions. A transfer film was obviously found on the counterface in seawater, but it was not observed under dry conditions. Among all the materials tested, the PTFE‐based composite containing 20% POB (mass fraction), 2% EG, and 3% BF exhibited the best comprehensive performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2523–2531, 2013     

Tribological properties of porous PPS/PTFE composite filled with mesopore titanium oxide whisker

Nano‐micro hierarchical porous polyphenylene sulfide/polytetrafluoroethylene (PPS/PTFE) composites were prepared by mold‐leaching and vacuum melting process under high temperature condition. The tribological behaviors of porous PPS/PTFE composites and the synergism as a result of incorporation of both micro‐porogen (NaCl) and mesoporous TiO₂ whiskers were investigated. The effects of mesoporous TiO₂ whiskers and nonperforated TiO₂ whiskers on the friction and wear properties of PPS/PTFE composites were comparatively studied, respectively. Results indicated that the wear rate of porous PPS/PTFE composites with 30 wt % NaCl and 7 wt % mesoporous TiO₂ whiskers obtained the lowest values under the load of 100 N. Compared with pure PPS, the wear resistance of nano‐micro porous PPS/PTFE composite was enhanced by 6.45 × 10³ times, showing outstanding wear resistance. During sliding condition, grease could be squeezed through the nano‐micro pores under the coupling effect of load and friction heat, and formed a lubricanting layer on friction surface, providing self‐lubricating effect and high wear resistance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

纤维填充PTFE复合材料的摩擦学研究

在聚四氟乙烯（PTFE）中分别填充碳纤维（CF）、玻璃纤维（GF）及这两种纤维不同配比的混杂纤维（HF），制备了具有不同力学性能和摩擦磨损性能的PTFE基复合材料。探讨了填料组成对复合材料硬度和干摩擦条件下摩擦磨损性能的影响，并研究了PTFE基复合材料磨损表面的形貌学。结果表明，适量填充CF和GF均可提高PTFE的摩擦磨损性能，CF比GF效果更为显著；CF和GF的混杂纤维填充PTFE复合材料．表现出一定的协同性，比填充单种纤维，其效果更显著。     

聚四氟乙烯/聚苯酯复合材料的结晶及摩擦性能研究

采用差示扫描量热仪研究了聚四氟乙烯/聚苯酯(PTFE/POB)复合材料的结晶性能,研究了复合材料在干摩擦条件下和45号钢对磨的摩擦性能,并采用扫描电镜观察了复合材料的磨损表面形貌。探讨了POB含量对复合材料的结晶性能和摩擦性能的影响。结果表明,加入POB后,复合材料的结晶度增加,在POB含量为20 %时结晶度出现峰值。复合材料的结晶速率和摩擦因数均随POB含量的增加而增大,磨痕宽度随POB的含量增加而大幅减小。     

Friction and wear behavior of glass fabric/phenolic resin composites with surface‐modified glass fabric

Untreated, air‐plasma‐bombarded, and β‐aminoethyltrimethoxylsilane‐silanized glass fabric (GF) was used to prepare GF/phenolic composites by dip coating in a phenolic adhesive resin and successive curing. The tribo‐performances of these GF/phenolic composites sliding against AISI‐1045 steel were evaluated with a pin‐on‐disc wear tester. The chemical composition of the untreated and surface‐treated GF was analyzed with Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The interfacial regions between the phenolic resin and GF and the worn surfaces of the composites were analyzed with scanning electron microscopy. The results show that the GF/phenolic composite with β‐aminoethyltrimethoxylsilane‐silanized GF had the highest load‐carrying capacity and best tribo‐performance, and it was followed by the composite with plasma‐treated GF. The improved tribo‐performance of the GF/phenolic composite made of surface‐treated GF was attributed to the strengthened interfacial bonding between the treated GF and the phenolic adhesive resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009