Tribological Properties of PTFE and PTFE Composites at Different Temperatures

The friction and wear properties of polytetrafluoroethylene (PTFE) and its composites with fillers such as bronze, glass fiber, carbon fiber, carbon, graphite, and polymer were studied at ambient temperature and high temperature. The wear resistance and hardness were enhanced by the fillers. Results showed that the wear resistance of all composites was much higher than that of pure PTFE. Pure PTFE has the lowest friction coefficient at ambient temperature (temperature: 23 ± 2°C, humidity: 50 ± 10%) but highest friction coefficient at high temperature (above 100°C). The PTFE composite filled with bronze showed the best wear resistance at ambient temperature but the poorest wear resistance at high temperature. The carbon-graphite- or polymer-filled PTFE composite showed a lower friction coefficient and moderate wear resistance at both ambient and high temperature.     

Effects of filler crystal structure and shape on the tribological properties of PTFE composites

In this paper, effects of filler crystal structure and shape on the friction and wear properties of potassium titanate whisker (K₂Ti₄O₉ whisker, K₂Ti₆O₁₃ whisker), TiO₂ whisker and TiO₂ particle filled polytetrafluoroethylene (PTFE) composites under dry friction conditions were studied. Meanwhile the influence of filler content, sliding duration, test speed and load were also investigated. Experimental results show that the friction coefficients of various PTFE-based composites are weakly dependent on filler shape but they are more strongly dependent on filler crystal structure. However, for improving the anti-wear property of PTFE, filler crystal structure has less importance than filler shape in the wear-reducing action of PTFE-based composites, and whisker-like filler is better than particle-like filler.     

聚四氟乙烯工程材料的摩擦磨损性能研究

用MPV-200型摩擦磨损试验机研究了干摩擦条件下磨损时间、滑动速度、载荷、填料等对聚四氟乙烯(PTFE)工程塑料摩擦磨损性能的影响，结果表明：PTFE材料的摩擦因数和磨损率先随速度的增大而减小，然后又随着速度的增大而增大；随磨损时间的增长而降低，最后趋于稳定值；另外，摩擦因数大体上随载荷的增大而减小，磨损量则随载荷的增大而增加；填料可将PTFE的磨损量降低2个数量级，其中石墨使PTFE的摩擦因数降低，玻璃纤维和碳纤维则增大了PTFE的摩擦因数，而MoS2对PTFE摩擦因数的影响较小。对PTFE工程塑料的摩擦磨损特性进行系统分析，为优化设计提供理论基础。     

Tribological Behavior of Carbon-Nanotube-Filled PTFE Composites

Carbon nanotube/polytetrafluoroethylene (CNT/PTFE) composites with different volume fractions were prepared and their friction and wear properties were investigated using a ring-on-block under dry conditions. It was found that CNTs signifi-cantly increased the wear resistance of PTFE composites and decreased their coefficient of friction. PTFE composites with 15–20 vol.% CNTs exhibited very high wear resistance. The significant improvements in the tribological properties of CNT/PTFE composites are attributed to the super-strong mechanical properties and the very high aspect ratio of CNTs. The CNTs greatly reinforce the structure of the PTFE-based composites and thereby greatly reduce the adhesive and plough wear of CNT/PTFE composites. The CNTs are released from the composite during sliding and transferred to the interface of the friction couples. They thus serve as spacers, preventing direct contact between the mating surfaces and thereby reducing both wear rate and friction coefficient.     

纳米ZnO填充的PTFE基复合材料摩擦学性能研究

得胜０００型摩擦磨损试验机研究了不同体积含量的纳米氧化锌（ＺｎＯ）填充的ＰＴＦＥ基复合材料在于摩擦条件下与不风对摩时的摩擦学性能,并利用扫描电子微镜（ＳＥＭ）对ＰＴＦＥ及纳米ＺｎＯ／ＰＴＦＥ复合材料的微观结构、磨损表面和转移膜进行了观察和分析。结果表明,纳米ＺｎＯ／ＰＴＦＥ复合材料的摩擦性能与纯ＰＴＦＥ基本相当,但耐磨性明显优于后者,纳米ＺｎＯ在复合材料中的最佳含量为１５ｖｏｌ．％左右。     

Impact of Viscoelasticity on the Tribological Behavior of PTFE Composites for Valve Seals Application

In this article, we studied and explored the impact of viscoelasticity on the friction and wear behavior of pure polytetrafluoroethylene (PTFE), carbon–graphite PTFE composite, and glass fiber–MoS₂ PTFE composite. Tests were carried out using a specific reciprocating tribometer for valve seal application. The worn surfaces of the PTFE composites and the transfer films formed on the counterface were examined with a scanning electron microscope (SEM). Experimental results revealed that the addition of filler materials was effective in reducing the wear volume in all composites studied. In addition, the friction coefficient and wear resistance showed high sensitivity to the viscoelastic behavior of the PTFE seal. SEM investigation showed that the incorporation of particulate fillers into the PTFE matrix could dramatically reduce and stabilize the transfer films to the counterface, so they largely decreased the wear of the PTFE composites.     

PTFE基耐磨固体润滑涂层的摩擦学性能

采用黏接固体润滑涂层法,以聚四氟乙烯为润滑剂,利用喷涂方式在试样上制备2种PTFE基固体耐磨涂层,并采用HSR-2M型高速往复式摩擦磨损试验机对其摩擦学性能进行研究。研究结果表明,水性全氟涂层的摩擦因数不稳定且明显高于油性全氟;随着固化条件的改变,涂层的摩擦因数和磨损量也出现不同程度的变化;当采用油性全氟为润滑剂,固化温度为260℃,固化时间为30 min时,PTFE基耐磨涂层的摩擦因数和磨损量均最小,此时涂层的摩擦学性能最优。     

Friction and wear properties of metal powder filled PTFE composites under oil lubricated conditions

Four kinds of polytetrafluoroethylene (PTFE)-based composite, pure PTFE, PTFE+30vol.%Cu, PTFE+30vol.%Pb and PTFE+30vol.%Ni composite, were prepared. The friction and wear properties of these metal powder filled PTFE composites sliding against GCr15 bearing steel under both dry and lubricated conditions were studied using an MHK-500 ring-block wear tester. The worn surfaces of the PTFE composites and the transfer films formed on the surface of GCr15 bearing steel were examined using scanning electron microscopy (SEM) and optical microscopy respectively. Experimental results show that the friction and wear properties of the PTFE composites can be greatly improved by liquid paraffin lubrication. The wear of these PTFE composites can be decreased by at least 1 to 2 orders of magnitude compared with that under dry friction conditions, while the friction coefficients can be decreased by 1 order of magnitude, SEM and optical microscopy investigations of the rubbing surfaces show that metal fillers of Cu, Pb and Ni not only raise the load carrying capacity of the PTFE composites, but also promote transfer of the PTFE composites onto the counterfaces, so they greatly reduce the wear of the PTFE composites. However, the transfer of these PTFE composites onto the counterfaces can be greatly reduced by liquid paraffin lubrication, but transfer still takes place.     

聚四氟乙烯填充高岭土基矿物聚合物复合材料的摩擦学性能

研究了PTFE填充量对高岭土基矿物聚合物复合材料的力学性能和摩擦磨损性能的影响,利用XRD、SEM分析了材料的微观结构和磨损表面形貌。结果表明:填充PTFE对矿物聚合物材料的力学性能会有一定程度的降低,但可以有效改善复合材料的摩擦磨损性能,当PTFE体积分数为30%时,摩擦因数和磨损率均达到最低,分别为0.429和1.22×10-5mm3/N·m;当PTFE含量较高时,磨损机理除了磨粒磨损外还有对偶件的粘着转移。     

Friction and sliding wear of UHMWPE modified cotton fibre reinforced polyester composites

Ultrahigh molecular weight polyethylene (UHMWPE) modified polyester-cotton composites were developed and studied for friction and sliding wear behaviour at different applied loads and UHMWPE concentrations. Sliding wear tests were conducted by using pin-on-disc apparatus. Composites in the form of the pin were tested against EN-24 steel disc. The specific wear rate of polyester reduced on reinforcement of cotton and on addition of UHMWPE. The coefficient of friction of polyester resin increased on cotton reinforcement and reduced significantly on addition of UHMWPE in cotton polyester composite. The composites exhibited reductions in specific wear rate against the normal load in the specimens those containing 7.41 or higher volume percent of UHMWPE. The significant reduction in wear rate of UHMWPE modified polyester-cotton composite has been discussed with the help of SEM observations of worn surfaces and coefficient of friction. The addition of 14.19 vol.% UHMWPE in polyester resin brought down the value of μ to nearly half to that of polyester resin and 1/3rd of cotton polyester composite.     

Tribological analysis of hydrocarbon refrigerants applied to the hermetic compressor

This paper describes the tribological impacts of hydrocarbon refrigerants deployed in the domestic refrigerator hermetic compressor. In-use durability is examined from a tribological viewpoint. Experimental tribological information is presented from physical test procedures involving sliding tests to establish wear mechanisms and friction coefficients within critical components. Hydrocarbon refrigerant R600a is compared with hydroflourocarbon R134a using aluminium on steel samples within a novel pressurised micro-friction test rig. The refrigerant R600a is tested for its influence upon the tribological performance of mineral oil (MO) and poly-ol-ester (POE) lubricant, whilst an R134a/POE charge combination is used as a benchmark. Although wear rates were significantly greater for samples utilising POE lubricants than for MO, the friction coefficients were much lower.     

纳米Cu粉填充碳纤维/PTFE复合材料的摩擦磨损性能

考察纳米Cu粉含量、粒径对碳纤维/PTFE复合材料摩擦磨损性能的影响,采用扫描电子显微镜分析磨损面和对偶面转移膜形貌,并探讨其磨损机制。结果表明:纳米Cu粉能提高碳纤维/PTFE复合材料的耐磨性,在高载荷下,纳米Cu粉的增强效果更加明显;纳米Cu粉的粒径越小,复合材料的耐磨性越好;添加质量分数0.3%纳米Cu粉的碳纤维/PTFE复合材料耐磨性最优,1.4 m/s,200 N下实验条件下,其磨损率比未添加时降低了45%;SEM分析显示纳米Cu粉能在对偶面上形成平整致密的转移膜,具有显微增强作用。     

PTFE/7075铝合金镶嵌型自润滑材料的摩擦学行为

采用模压／烧结工艺制备了PTFE／7075铝合金镶嵌型自润滑复合材料,在往复式摩擦磨损试验机上进行了摩擦磨损试验,用扫描电镜观察了复合材料磨损后的表面形貌,并探究了其磨损机理。结果表明:在试验条件下,稳态后摩擦温度为51℃,摩擦因数为0．087,磨损率为0．38×10-3mm3／(Nm),和非镶嵌型PTFE基复合材料相比,导热性和耐磨性大大提高,而摩擦因数无明显增加;稳定磨损阶段主要表现为粘着磨损,同时伴有轻微磨粒磨损,磨损后期局部呈现疲劳特征。     

烧结工艺对PTFE自润滑轴承材料摩擦性能的影响

聚四氟乙烯(PTFE)-铜粉-钢背复合材料是一种广泛应用的三层结构自润滑轴承材料,具有良好的减摩耐磨性能。探讨了烧结工艺对其摩擦磨损特性的影响,试验结果表明:在372±4℃时烧结成形的材料的摩擦系数较小,承载能力较大,磨损量较小,表现出了最佳的摩擦磨损特性。     

Film-forming mechanisms for self-lubricating radial spherical plain bearings with hybrid PTFE/aramid fabric liners modified by ultrasonic

PTFE/aramid woven fabric liners were modified by ultrasonic. With self-made wear tester, tribological properties of the self-lubricating radial spherical plain bearings with modified and unmodified liners over swivel times were investigated. With scanning electron microscope and energy disperse spectroscopy, the film-forming mechanisms were analyzed. Results show: ultrasonic modification can improve tribological performances of the liners. Through ultrasonic modification, continuous and stable PTFE transfer films which had better wear resistance formed in a shorter time. Bearings with modified liners occurred slight adhesive wear, while the bearings with unmodified liners occurred serious adhesive wear and abrasive wear during the test process.     

聚四氟乙烯纤维基层压材料的摩擦学行为研究

以无碱玻璃纤维布作为基材,以浸渍有聚四氟乙烯的棉纤维布为表层,以环氧树脂为黏合剂,经热压制备聚四氟乙烯纤维基层压材料;采用 MRH-03型高速环－块摩擦磨损试验机研究其在空气、纯水、海水介质中的摩擦学行为,利用扫描电镜观察并分析磨损表面的形貌及摩擦形式。结果表明,与基底材料相比,增加聚四氟乙烯棉纤维布后,材料的摩擦性能有明显的改善;加入水作为润滑介质后,由于水膜边界润滑的作用,特别是由于海水作为润滑介质时摩擦产生的淤泥状的 Mg （OH）2和 CaCO3的自润滑作用,摩擦因数和磨损率进一步减小。     

Tribological performance of microwave sintered copper-TiC-graphite hybrid composites

Copper matrix composites are finding many applications due to their inherent properties such as good electrical and thermal conductivity and corrosion resistance. New series of copper-TiC (5-15 vol%)-graphite (5-10 vol%) hybrid composites are fabricated through a novel microwave processing technique. Pin-on-disc is used to evaluate their tribological properties under testing parameters of normal loads 12-48 N and sliding speed of 1.25-2.51 m/s. The formation of mixed smooth layer with higher graphite hybrid composites improves the wear resistance and reduces the friction coefficient. Morphology of worn out surfaces and wear debris were analyzed to understand the wear mechanisms.     

Tribological behaviour of an elastomer aged in different oils

This paper presents the influence of aging the nitrile rubber, the most popular seal material, in various base fluids on sliding friction and abrasive wear. The lubricants used are synthetic esters, natural esters, different types of mineral base oils, poly-α-olefins and very high viscosity index oils. Friction has been studied for two directions of motion with respect to lay on the elastomer sample by using the SRV Optimol test machine. These findings show that as compared to all other lubricant formulations, ageing the elastomer in polyol ester leads to the maximum reduction of friction coefficient especially in perpendicular sliding to the initial lay on the surface. The abrasive wear studies were carried out by using a two-body abrasive wear tester against dry and lubricated elastomer. It was interesting to note that two-body abrasive wear of elastomeric material was higher during rubbing in presence of the fluids as compared to that in dry condition. Further, aging the elastomer in these base fluids especially in ester base fluids, results in more abrasive wear.     

PTFE复合材料高温摩擦磨损性能研究

研究了高温条件下不同填料填充的PTFE复合材料的摩擦磨损性能,并与常温下的摩擦磨损性能进行了比较.结果表明青铜粉、纤维填充的复合材料在高温下表现出与常温相反的摩擦磨损规律;碳类填充复合材料在不同温度下则表现出较为稳定的规律;特种塑料改性的PTFE复合材料,具有极好的综合性能.     

Sliding wear behaviour of PEEK‐PTFE blends

The role of PTFE in tailoring the tribological performance of PEEK is not clear from the literature, and conflicting evidence is reported about its ability to improve friction, wear, or both. Moreover, little has been reported on the optimum composition of such blends for the best possible combination of mechanical and tribological properties. Hence, in this work various blends of PEEK with PTFE have been injection moulded and characterised for their mechanical properties. Their friction and wear behaviour was evaluated using a pin‐on‐disc machine. It was observed that the inclusion of PTFE powder not only removed scuffing problems associated with the friction behaviour of PEEK, but also improved both friction and wear characteristics. A blend with 7.5 wt. % PTFE showed the best wear behaviour, while a blend with 30 wt.% PTFE exhibited the best friction performance. A concentration of 7.5 wt. % PTFE was thought to be the optimum amount for the best possible combination of mechanical and tribological properties.