Sliding Wear of the Hybrid Kevlar/PTFE Fabric Reinforced Phenolic Composite Filled with Nano-titania

The Kevlar/polytetrafluroethylene(Kevlar/PTFE) fabric composite can be used as a self-lubricating liner of the self-lubricating bearing.Many types of nano-particles can improve the tribological performance of the polymer-based composite.Unfortunately,up to now,published work on the effect of nano-particles on the tribological performance of the fabric composite which can be used as a self-lubricating liner is quite scarce.Therefore,for the purpose of exploring a way to significantly improve the tribological performance of the fabric composite,the tribological performance of the Kevlar/PTFE fabric composite filled with nano-titania is evaluated by using the block-on-ring wear tester.The scanning electron microscopy is utilized to observe the morphologies of worn surfaces of the fabric composites and the counterparts.The tensile properties of the composites are evaluated on the universal material testing machine.The test results show that the addition of nano-titania at a proper mass fraction of the matrix resin improves the wear resistance and the tensile strength,decreases the friction coefficient,and makes the wear volume of the composite reach a relative steady state more quickly;plastic deformation and microcutting are important for the wear of the fabric composite;a lubricating layer is formed on the worn surface of the composite during sliding,and the lubricating layer is critical for the tribological performance of the composite;the formation and properties of the lubricating layer are influenced by the nano-titania particles.The proposed study on the effect of nano-titania on the tribological performance of the Kevlar/PTFE fabric composite,especially on the evolution of the worn surface of the composite,provides the basis for further understanding of the influence mechanism of the nano-particles on the tribological performance of the composite and explores a method of improving the tribological performance of the composite.     

Effect of plasma treatment of Kevlar fabric on the tribological behavior of Kevlar fabric/phenolic composites

Pure and plasma-treated Kevlar fabrics were used to prepare Kevlar fabric/phenolic composites by consecutive dipping of the fabric in phenolic adhesive resin. The friction and wear performance of the resulting composites has been evaluated in a pin-on-disk wear tester at various dry-sliding conditions. The surface changes occurring on Kevlar fibers treated with air-plasma were analyzed by using X-ray photoelectron spectroscope (XPS), Fourier transform infrared spectroscope (FT-IR) and scanning electron microscope (SEM). Moreover, the impact of air-plasma treatment time and power on the friction and wear behavior of Kevlar fabric/phenolic composites composed of the air-plasma-treated Kevlar fabrics was systematically studied. It was found that plasma treatment can significantly improve the tribological performance of the prepared Kevlar fabric/phenolic composites; the best performance was after a plasma treatment at 50 W for 15 min. The plasma treatment generates oxygenic and nitrogenous groups on the surface of the fabric, coupled with an increase of the surface roughness, strengthening the bond between the Kevlar fabric and phenolic adhesive resin and hence improving the tribological properties of the Kevlar fabric/phenolic composites.     

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.     

Tribological behavior of spun Kevlar fabric composites filled with fluorinated compounds

The tribological behavior of the spun Kevlar fabric composites filled with polyfluo wax (PFW) and LaF₃ were evaluated using a pin-on-disc friction and wear tester under variable applied load and rotating speed. The worn surface and transfer film of the composites were then examined with SEM. The results indicated that the oxidation of PFW after curing and viscous flow characteristic of PFW in friction process were beneficial to the formation of the compact, uniform and smooth transfer film, corresponding to the excellent wear resistance of the composite filled with 15 wt% PFW. The corresponding wear mechanisms were also discussed.     

Study on the tribological behavior of hybrid PTFE/cotton fabric composites filled with Sb2O3 and melamine cyanurate

The tribological behavior of the hybrid PTFE/cotton fabric composites filled with microsize Sb₂O₃ and melamine cyanurate (MCA) was investigated. It was found that the wear rate of the hybrid PTFE/cotton fabric composites decreased when Sb₂O₃ was used as the filler but increased with MCA filler. It was also observed that hybrid fillers (consists of Sb₂O₃ and MCA) had a wear reduction effect on the hybrid PTFE/cotton fabric composites at lower loads but increased the wear rate at higher loads. The wear behavior of the composites was explained in terms of the topography of worn surfaces and transfer film formed on the counterpart pin.     

Friction and wear behavior of hybrid glass/PTFE fabric composite reinforced with surface modified nanometer ZnO

Nano-ZnO was successfully grafted with 2,4-toluenediisocyanate (TDI) and β-aminoethyltrimethoxylsilane (OB551) to avoid the agglomeration of nano-ZnO in composite. The hybrid glass/PTFE fabric composites reinforced with the untreated, OB551 and TDI modified nano-ZnO, respectively, were prepared by dip-coating of the hybrid fabric in a phenolic adhesive resin containing the nanoparticles to be incorporated and the successive curing. The friction and wear behaviors of various nano-ZnO reinforced hybrid glass/PTFE fabric composites sliding against AISI-1045 steel in a pin-on-disk configuration were evaluated on a Xuanwu-III high-temperature friction and wear tester, with the unfilled one as a reference. The morphologies of the worn surfaces of the composites and of the counterpart pins were analyzed using scanning electron microscopy. In addition, FTIR spectrum was taken to characterize the untreated and treated nano-ZnO. It is found that the untreated and treated nano-ZnO reinforced hybrid glass/PTFE fabric composites exhibit improved wear resistance and friction-reduction in comparison with the unfilled one. The TDI modified nano-ZnO reinforced composite can obtain the best friction and wear performance under different applied load; followed by the OB551 modified nano-ZnO reinforced one. Sliding conditions, such as environmental temperature and lubricating condition, significantly affect the tribo-performances of the unfilled and filled hybrid glass/PTFE fabric composites.     

Effect of surface treatment on the mechanical and tribological performance of Kevlar pulp reinforced epoxy composites

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of Kevlar pulp. The surface characteristics of untreated and treated Kevlar pulp were characterized by Fourier transform infrared (FT-IR) spectroscope. The bend strength and block-on-ring wear behavior of Kevlar pulp/epoxy composites were comparatively investigated. The worn surfaces of the composites were examined by scanning electron microscope (SEM). The results show that surface treatment can effectively improve the interfacial adhesion between Kevlar fiber and epoxy matrix. Thus, the bend strength and wear resistance were significantly improved. The RES surface treatment is superior to ECP grafting treatment in promoting interfacial adhesion between Kevlar fiber and epoxy resin.     

Friction and wear properties of Kevlar pulp reinforced epoxy composites under dry sliding condition

In this work, the friction and wear properties of Kevlar pulp reinforced epoxy composites against GCr15 steel under dry sliding condition were evaluated on a reciprocating ball-on-block UMT-2MT tribometer. The effects of Kevlar pulp content on tribological properties of the composites were investigated. The worn surface morphologies of neat epoxy and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms discussed. The results show that the incorporation of Kevlar pulp into epoxy contributed to improve the friction and wear behavior considerably. The maximum wear reduction was obtained when the content of Kevlar pulp is 40 vol%. The friction coefficient of epoxy and its composites increased with load while increase in the sliding frequency induced a reverse effect. Fatigue wear and scuffing were notable for the neat epoxy. The fatigue cracks were greatly abated when the filler content was 40 vol%. The wear grooves appeared on the worn surface at higher filler content.     

The influence of metal surface composition on the tribological properties of filled PTFE/steel couples

In this paper, the friction and wear behaviors of filled PTFE/steel couples are studied. The stationary specimen was made of filled PTFE. The rotating specimen, made of steels, underwent various treatments. The experimental results showed that the frictional coefficient and wear rate were low when the surface of the steel specimen contained nitrogen. The structure of the transfer film was examined by X-ray photoelectron spectroscopy (XPS). The transfer film containing nitrogen on the steel surface was thick. The authors consider that the hypothesis of the adhesion of the n–p–n structure may explain the characteristics of the different sliding couples in this paper and might be an important way to improve the friction and wear properties of the filled PTFE/metal sliding couples.     

Influence of weave of carbon fabric on abrasive wear performance of polyetherimide composites

Three composites of Polyetherimide (PEI) reinforced with carbon fabric (CF) of three weaves viz. plain, twill and satin-4 H were developed keeping the amount of fabric constant (55% by vol.). Studies on mechanical properties confirmed that the twill weave composite (T) showed the highest strength, modulus (both tensile and flexural) and interlaminar shear strength (ILSS) followed by satin (S) and plain weave (P) composites. The performance order, however, was reverse in the case of toughness and elongation to break. Specific wear rate in a single-pass, unidirectional and un-lubricated abrasive wear mode against SiC paper showed strong influence of weave in mild wear condition (load 10 N). Composite S showed the highest wear resistance (W _R) followed by composites T and P. With increase in load, the difference in performance diminished to the extent that at 40 N, it was almost similar for all the three composites. This was correlated with the difference in the length of the fibers between crossover points which, in turn, allowed the microdisplacement of fibers in the composites during abrasion. This was supported by the SEM.

SiC颗粒增强PTFE基复合材料磨损图的研究

研究了SiC颗粒增强PTFE基复合材料(PTFE／SiCp)在干摩擦条件下的磨损特性。对磨损表面进行了观察分析，建立了复合材料磨损机制转变图，对在不同磨损条件下的磨损机制进行了概括。结果表明，SiC颗粒增强PTFE基复合材料发生轻微磨损的主要机制是显微切削，发生严重磨损的主要机制是粘着磨损。     

A Study on the Sliding Wear of Hybrid PTFE/Kevlar Fabric/Phenolic Composites Filled with Nanoparticles of TiO2 and SiO2

TiO₂ and SiO₂ nanoparticles were introduced into hybrid polytetrafluoroethylene (PTFE)/Kevlar fabric/phenolic composites. The results showed the incorporation of TiO₂ nanoparticles can reduce the wear rate of the fabric/phenolic composite at elevated temperatures, although the wear of hybrid PTFE/Kevlar fabric/phenolic composite did not change much when TiO₂ or SiO₂ nanoparticles were used as filler. The wear behavior was explained in terms of morphology of transfer films and worn surfaces. There was a good correlation between the morphology of transfer film and wear results.     

高能电子辐照对PTFE填充酚酞聚芳醚酮复合材料摩擦磨损性能的影响

用MM-200型摩擦磨损试验机考察了辐照对PTFE填充酚酞聚芳醚酮复合材料的摩擦磨损性能的影响。结果表明：PEK-C复合材料经辐照后其磨擦磨损性能变差。电镜分析表明,辐照样品的磨屑大于未辐照后样品的磨屑。辐照样品的磨损表面梨沟较明显,而未辐照样品的磨损表面无犁沟槽,且表面比较光滑,而电子探针微区分析EPMA表明,辐照样品与钢环对磨后,其摩擦表面较粗糙,钢环表面没有形成连续、均匀的转移膜;而未辐照样品与钢环对磨后,它们的摩擦表面较光滑,钢环表面均形成了较连续、均匀的转移膜。     

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。     

Synthesis and evaluation of mechanical and high temperature tribological properties of in-situ Al-TiC composites

In situ Al-TiC (5, 10 and 15 wt%) composites were produced by using a reaction mixture of K₂TiF₆ and graphite powder with molten metal. The effect of ceramic particulate addition on the high temperature sliding wear resistance of the composites was studied. The sliding wear tests were conducted at room temperature, 120 and 200 °C. The wear rate increases with the increase in applied load and decreases with increase in the weight percentage of TiC. Both monolithic and composites were able to withstand thermal softening effects due to the formation of oxidative protective transfer layer.     

PTFE/芳纶织物衬垫自润滑关节轴承性能试验

对比分析研究了同型号国产与进口PTFE/芳纶织物衬垫自润滑关节轴承的粘结质量、摩擦学性能以及承载性能,研究结果表明:进口轴承的剥离强度、摩擦磨损性能以及承载性能均略优于国产同型号的关节轴承;国内自润滑关节轴承的衬垫粘结质量、摩擦学性能以及承载性能需要进一步提高。     

Effect of aerosil organophilization on tribological properties of low-filled UHMWPE composites

The effect of aerosil on the formation of structure and surface layers of ultrahigh-molecular-weight polyethylene (UHMWPE) and its low-filled composites is studied during friction. Surface modification of aerosil by vinyl triethoxysilane is found to result in elevated crystallinity degree and hardness of the filled polymeric system, and hardening of the composite surface layer under friction. This can be, evidently, attributed to friction-induced grafting of binder macromolecules to the organophilicized aerosil surface. Strengthening of the matrix bonding with the filler is accompanied by worsening of lubricity, growth of wear resistance, and increasing contribution of the adhesive mechanism instead of the abrasive one to the wear of low-filled UHMWPE composites.     

聚四氟乙烯复合材料的摩擦学二次转移行为研究

采用冷压成型、自由烧结工艺分别制备了青铜粉、聚酰亚胺、二硫化钼和石墨填充改性的聚四氟乙烯复合材料,在改装的M-2000型摩擦磨损试验机上考察了材料的二次转移摩擦学性能;用扫描电子显微镜对磨损表面进行观察和分析。结果表明:增加载荷有利于提高转移膜与基底的结合强度;填料种类对PTFE复合材料二次转移膜的摩擦学性能有影响,在本实验条件下(干摩擦、室温、滑动速度为0.42m/s、接触载荷为30N),以PTFE复合材料作为润滑剂提供源使用时,PTFE/MoS2、PTFE/Graphite复合材料形成的二次转移膜最好,PTFE/Bronze复合材料二次转移膜次之,PTFE/PI复合材料形成二次转移膜的能力最差。     

聚四氟乙烯填充含量对钢背超高分子量聚乙烯纤维织物复合材料摩擦学性能的影响

为改善广泛应用于船舶苛刻环境无油/脂润滑摩擦配副材料的摩擦学性能,将聚四氟乙烯（PTFE）按不同质量分数与钢背超高分子量聚乙烯纤维织物复合材料结合,研究它与45钢盘在变转速环环端面干摩擦状态下的摩擦学特性。对试验过程中摩擦因数及磨损量进行测量,利用表面轮廓仪、扫描电子显微镜与超景深显微镜对复合材料及对磨件磨损表面形貌进行了观察与分析。结果表明：所有填充PTFE的复合材料摩擦学性能均表现优异,随着PTFE含量的增加,复合材料摩擦性能变差,其中1 %（质量分数） PTFE填充复合材料综合摩擦性能最好,在试验工况下主要发生磨粒磨损,PTFE填充量较高的复合材料在高速下由于团聚及摩擦热量积聚主要经历黏着磨损与疲劳磨损。     

GF/PTFE自润滑纤维复合材料磨损性能热衰退研究

针对高频摆动关节轴承摩擦热对自润滑纤维复合材料摩擦磨损性能的影响,研制了高频使用条件下的玻璃纤维增强聚四氟乙烯(GF/PTFE)自润滑纤维复合材料,利用MYB～500高频高载摆动摩擦磨损试验机,对其进行不同摩擦温度下的摩擦磨损性能测试,研究摩擦热作用下材料自润滑性能和磨损性能衰退特征,分析磨损产物和摩擦表面以及不同摩擦温度下材料的磨损机理。结果表明,摩擦热对材料自润滑性能影响显著,适当的摩擦温度范围能够保证材料的自润滑性能,摩擦温度和摩擦因数之间互为耦合作用,对材料的磨损性能具有一定的影响;高摩擦热作用于自润滑过程及机理的改变,造成材料的磨损性能衰退现象。因此,不同温度下材料的磨损特征具有明显的差异化,其中低摩擦温度下(60～120℃)材料自润滑性能优异,磨损率很低;140℃摩擦温度条件下材料摩擦磨损性能开始衰退;材料在高摩擦温度下(140～180℃)的磨损初期自润滑性能良好、磨损轻微,而中后期磨损严重。微观分析表明,低摩擦温度下材料的磨损机理以轻微粘着和疲劳磨损为主;高摩擦温度下材料的磨损以片状剥落、纤维剪切破坏为主,且磨损面局部损伤特征明显,磨损严重。