Mechanical and tribological properties of nitrile rubber filled with modified molybdenum disulphide

In this work, cetyl trimethyl ammonium bromide (CTAB), silane coupling agent (KH570) and polyethylene glycol (PEG) were used to modify the surface property of molybdenum disulphide (MoS₂). MoS₂/nitrile rubber (NBR) composites were directly prepared by mechanical blending. Meanwhile, the effects of loading content of MoS₂, the kinds of modifiers on the mechanical and tribological properties of the composites were evaluated. The dispersion of fillers in rubber matrix and the worn surface of the composites were analysed by SEM. Results showed that the properties of MoS₂/NBR composites prepared by CTAB modified MoS₂ were superior to that of KH570 or PEG modified MoS₂ and unmodified MoS₂ because of strong opposite charges attraction between cetyl trimethyl ammonium cation and MoS₂ surface. When adding 10?phr CTAB modified MoS₂ in rubber matrix, the dispersion of filler was optimum, and the coefficient of friction of composite was the lowest in the prepared composites.     

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     

Improvements in tribological properties of polyoxymethylene by aramid short fiber and polytetrafluoroethylene

In order to improve tribological properties of polyoxymethylene (POM), the effects of aramid short fibers (ASF) and polytetrafluoroethylene (PTFE) solid lubricants, as two classes of additives, were studied. The appropriate composites of the polymer and the additives were prepared by melt mixing process. Distribution of additives in the polymer matrix was characterized by scanning electron microscopy (SEM). Mechanical properties in tension such as modulus of elasticity, yield stress, and stress-at-break as well as the fracture energy in impact test were studied to explore friction and wear mechanisms of the composites against a smooth steel surface. Tribological measurements showed that both additives reduce friction and wear of the POM. However, both additives reduced fracture energy of POM in impact test, which dismisses the role of abrasive mechanism of wear under applied conditions. On the other hand, tensile results showed that addition of ASF mechanically reinforces POM, while PTFE degrades mechanical properties of this polymer, especially yield stress. Considering the role of yield stress in the adhesive mechanism of friction and wear, this property was used to define tribological behavior of samples. Since ASF induces mechanical stiffening to POM, increase in yield stress improves tribological properties. However, PTFE introduces transfer films at the interface, thus reduction of yield stress is in favor of tribological properties of this composite. Finally, it is shown that frictional heating and contact temperature rise has a significant degrading effect on wear resistance.     

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     

表面修饰铁纳米颗粒的制备及其摩擦性能

以次亚磷酸钠为还原剂,双烷氧基二硫代磷酸铵盐为修饰剂,在四氢呋喃-饱和食盐水的两相体系中合成了表面修饰的铁纳米颗粒,采用红外光谱仪、热分析仪等仪器对其进行了结构表征;在透射电子显微镜下观测所制备的铁纳米颗粒的形貌;在四球摩擦试验机上测试了其摩擦性能,并在扫描电子显微镜和能谱分析仪上对钢球表面进行了形貌观测和表层成分分析。结果表明,铁纳米颗粒在低极性有机溶剂中具有良好的分散性,并具有良好的抗磨和承载能力。磨斑的表面分析表明,铁纳米颗粒添加剂在边界润滑下形成了一层含Fe、S、P和O元素的表面膜是其具有良好摩擦学性能的主要原因。     

Mechanical properties and surface morphology of photodegraded polyoxymethylene modified by a core–shell acrylate elastomer with UV stabilization

In order to improve the photostability of polyoxymethylene (POM), a core‐shell acrylate elastomer with UV stabilization, i.e. poly[(methyl methacrylate)‐(butyl acrylate)‐2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxypropoxy)benzophenone] (core‐shell poly(MMA‐BA‐BPMA)), was added into the POM matrix using a melt‐mixing method. The effect of the modification with core‐shell poly(MMA‐BA‐BPMA) on POM was compared with that of poly(MMA‐ co ‐BA‐ co ‐BPMA) copolymer. Scanning electron microscopy, metallographic microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X‐ray diffraction and X‐ray photoelectron spectroscopy were employed to characterize POM blends before and after UV irradiation, and the mechanical properties of the POM blends were investigated. The results showed that core‐shell poly(MMA‐BA‐BPMA) improved well the compatibility with and toughness of the POM matrix, and its light‐stable functional groups could increase the UV resistance of POM blends. During UV aging, the impact strength and elongation at break of POM/core‐shell poly(MMA‐BA‐BPMA) blends were retained, the growth rate of surface cracks of POM was inhibited effectively by core‐shell poly(MMA‐BA‐BPMA) and the degree of photo‐oxidation of POM blend surfaces was improved to a certain extent. Compared with poly(MMA‐ co ‐BA‐ co ‐BPMA), core‐shell poly(MMA‐BA‐BPMA) had a better UV stabilization effect on the POM matrix. Our results indicate that the core‐shell acrylate elastomer with toughening and UV stabilization functions can significantly improve the long‐term UV stability of POM. Copyright © 2012 Society of Chemical Industry     

Structural,thermal, and tribological properties of intercalated polyoxymethylene/molybdenum disulfide nanocomposites

Intercalated polyoxymethylene (POM)/molybdenum disulfide (MoS₂) nanocomposites were prepared by in situ intercalation/polymerization. The structures of the composites were characterized by means of powder X‐ray diffraction (XRD) and transmission electron microscopy. The XRD pattern showed that the polymer was inserted into the MoS₂ galleries. The interlayer spacing of the intercalated phase increased from 6.15 to 11.18 Å. The thermal behavior of the composites was also investigated through thermogravimetric analysis. The results show that the heat resistance of the intercalated composites decreased slightly. The tribological behavior of POM/MoS₂ was investigated on an MQ‐800 end‐face tirbometer under dry friction. The worn surfaces were observed by scanning electron microscopy. The results show that POM/MoS₂ presented better friction reduction and wear resistance, especially under high load. The friction mechanism of the nanocomposites is also discussed in association with X‐ray photoelectron spectroscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study on the tribological characteristics of solid lubricants embedded tin‐bronze bearings

The friction and wear characteristics of graphite, MoS₂, and PTFE embedded tin‐bronze bearings were studied using a pin‐on‐disc tester. The results indicated that solid lubricants decreased and stabilized the friction coefficient, and decreased the wear rate by two to three orders of magnitude. When the content of solid lubricants, PTFE mixed with graphite, was 20–40%, the performance of the solid lubricants embedded bearing (SLEB) was the best. Wear scar was analyzed by means of X‐ray diffraction (XRD), Auger electron spectroscopy (AES), and scanning electron microscopy (SEM). The results show that the transfer films of solid lubricants reduce adhesion between the SLEBs and the mating material, and the wear mechanism of SLEBs changes to fatigue and adhesive wear. The main reason for fatigue wear is microcracks expanding at Pb points in SLEBs. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2394–2399, 2001     

Mechanical and tribological properties of epoxy modified by liquid carboxyl terminated poly(butadiene-co-acrylonitrile) rubber

Diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin was modified using liquid carboxyl-terminated poly(butadiene-co-acrylonitrile) (CTBN) rubber. The liquid CTBN contents used ranged from 2.5 to 20 parts per hundred parts of resin (phr). Mechanical properties of the modified resins were evaluated and the microstructures of the fracture surfaces were examined using SEM technique. The changes in storage modulus and the glass transition temperature were also evaluated using dynamic mechanical analysis (DMA). The tribological tests were performed using a ball-on-disc tribometer. The worn surfaces and the ball counter-mates after tribological tests were investigated using optical microscope technique. The results revealed the influence of liquid CTBN content on mechanical and tribological properties, and also microstructure of the modified epoxy resins. Impact resistance increased whereas the storage modulus and the hardness decreased when the CTBN rubber was introduced to the epoxy network. The coefficient of friction of the CTBN-modified epoxy was lower than that of the neat epoxy. The CTBN content of lower than 10 phr was recommended for improving the wear resistance of epoxy resin. Changes in tribological properties of the CTBN-modified epoxy correspond well to those in mechanical changes, especially the toughness properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A comparative investigation of the tribological behavior and scratch response of polyester powder coatings filled with different solid lubricants

Employing coatings is one of the most effective methods to reduce friction and protect contacting surfaces from wear. The deposition of protective coatings from thermosetting polymer powders has witnessed a rapid growth as an ecological, economic and energy efficient technology. During the last few decades, many new deposition techniques have been developed, and more and more tribological coatings have been made available. In this context, our present investigation tried, firstly to analyze the friction and wear behavior of electrostatically sprayed polyester powder coatings deposited on an aluminum substrate and secondly to focus on the response of these thermosetting coatings to micromechanical deformation under scratch test loading. The effect of graphite and hexagonal boron nitride (hBN) solid lubricant fillers on the friction and wear behavior of polyester composite coatings was evaluated using a reciprocating tribometer under dry friction condition. The experimental findings show that the additions of graphite or hBN are effective in enhancing the wear life of polyester powder coatings. Meanwhile, under the same sliding conditions, the wear results revealed that the polyester coating filled with only 10 wt.% of graphite has a higher anti-wear ability compared to the polyester coating filled with the same weight fraction of hBN. Thus, the two reinforcing polyester matrix fillers play an important role in reducing the plastic deformation of the coatings and enhance the formation of thick third body between the sliding parts as the fraction of solid lubricant increases from 0 wt.% to 10 wt.%. From the scratch analyses, we deduced that coatings scratch behavior is severely affected by the kind and amount of fillers inside the polyester matrix. In fact, the best friction characteristic and scratch resistance are observed in the case of polyester coatings filled with very low amount of hBN (5 wt.%).     

固体润滑剂对丁腈橡胶复合材料性能的影响

将石墨、石墨烯以及两种不同尺寸的二硫化钼分别引入丁腈橡胶复合材料,考察四种固体润滑剂对复合材料性能,尤其是摩擦学性能的影响.结果表明,石墨烯的引入使丁腈橡胶复合材料的硬度及模量明显上升,扯断伸长率下降;而二硫化钼的引入有利于提高材料的撕裂性能.在干摩擦条件下,石墨烯的引入可有效提高材料的耐磨性并降低材料的摩擦系数,这得...     

二氧化钛微球合成、表面修饰及摩擦学性能

通过溶剂热法简便地合成了具有统一形貌和良好结晶度的锐钛矿型二氧化钛微球,并使用硬脂酸对所制备的产品进行表面改性,改性后的产品可以很容易的分散在非极性有机溶剂或者矿物油中形成均匀溶液,且上述溶液在室温环境下可较长时间保存而不出现沉淀。其原因是由于改性后产品表面存在长链羧酸基团,故而在油品中具有良好的分散性。通过 X 射线粉末衍射法 (XRD),扫描电镜 (SEM),红外测试 (FT-IR),热重测试 (TGA) 等检测手段对其晶体结构、晶粒大小以及产品表面形貌进行表征,并且对产品的形成机理进行了探讨。通过四球摩擦试验机考察了修饰后产品作为液体石蜡为基础油润滑添加剂的摩擦学性能。结果表明,经过修饰后的产品拥有良好的抗摩减磨性能并且可以很好的提高液体石蜡载荷能力。     

Mechanical and physical properties of ultraoriented polyoxymethylene produced by microwave heating drawing

The properties of ultra-oriented polyoxymethylene tubes produced by drawing under microwave heating have been assessed by mechanical testing, optical microscopy, scanning electron microscopy, X-ray analysis, birefringence and differential scanning calorimetry. The highest Young's modulus of 58 GPa was obtained at room temperature (77 GPa at ?150°C) at a draw ratio of 33. The maximum tensile strength was 1.7 GPa at a draw ratio of 26. The nonuniformity of Young's modulus in a radial direction has been compared with the nonuniformity of the birefringence and heat of fusion.     

Mechanical properties and deformation mechanism of polyoxymethylene chain in the crystalline state

The true crystallite modulus of polyoxymethylene (POM) was evaluated experimentally and thoeretically as a function of temperature. The mechanical deformation mechanism of POM was lattice-dynamically predicted and confirmed by measuring the stress-induced vibrational frequency shifts of the infrared and Raman spectra, which were interpreted on the basis of anharmonic potential field.     

Mechanical properties and tribological performance of alumina matrix composites reinforced with graphene-family materials

This paper introduce the formation of alumina matrix composites reinforced with multilayered graphene, graphene oxide and nickel-phosphorus coated multilayered graphene. The powder metallurgy technique followed by the Spark Plasma Sintering (SPS) method were utilized to fabricate the specimens. The influence of graphene-family material additions on microstructure was investigated, and correlated with measurements of mechanical properties. The emphasis of the research has been placed on the tribological performance conducted with the use of the ball-on-disc method under loads of 10 N and 30 N. Both the wear tracks of composites and the corresponding counterparts were carefully analysed, to evaluate the combined influence of mechanical properties and tribofilm formation on the measured wear rates. All results were compared to pure alumina as a reference specimen.     

Mechanical and tribological properties of alumina-MWCNTs composites sintered by rapid hot-pressing

Alumina – MWCNTs composites were prepared using a novel approach. This process comprises functionalization of MWCNTs and stabilization of alumina-MWCNTs dispersion with subsequent freezing, which resulted in formation of granulated powders with homogeneous distribution of MWCNTs. The granulated powders were sintered by rapid hot pressing (RHP) at 1550 °C. Relative densities, microstructural analysis, tribological properties, fracture toughness and bending strength of prepared composites were investigated to reveal the effect of MWCNTs. Compared to pure alumina, bending strength and fracture toughness of dense alumina-5 vol.% MWCNTs composites decreased about 37% and 18%, respectively. At higher MWCNT contents, strength remained almost constant and fracture toughness slightly increased. Thus, the positive effect of CNTs on fracture toughness was demonstrated despite their counteracting effect on the refinement of the microstructure.     

Mechanical and tribological properties of short discontinuous UHMWPE fiber reinforced UHMWPE

The tribological properties of Ultra-High Molecular Weight Polyethylene have generated new concern regarding the long-term clinical performance of total joint replacements. To extend the lifetime of artificial joints, it is necessary to decrease the wear rate of UHMWPE. One possible solution is the incorporation of UHMWPE fibers. Mixing of the two components was accomplished by swirling the UHMWPE powder and chopped UHMWPE fibers with compressed nitrogen. During this mixture procedure opposite surface charges will be generated on the UHMWPE powder and UHMWPE fiber. The electrostatic attraction could be responsible for the coherence of the two components, leading a composite with fairly uniformly distributed and randomly oriented fibers was obtained. With this method a fiber volume fraction up to 60 volume percent could be achieved. In this composite the matrix and fibers are of the same chemical nature. The inherent chemical compatibility of the composite components is likely to promote good bonding at the interface, through which a composite with excellent mechanical properties is made. The ultimate stress and modulus of the 60 volume percent composite show an improvement of 160 and 600 percent, respectively, in comparison with the neat UHMWPE. The wear rates were determined with a pin-on-roll apparatus with a nominal contact stress of 3 MPa at a sliding velocity of 0.24 m/s. The volumetric wear rate decreases with the incorporation of the UHMWPE fibers. Received: 28 November 1996/Revised: 20 January 1997/Accepted: 23 January 1997     

Mechanical and tribological properties of injection molded zirconia-alumina for orthopedic implants

Ceramics have gained great attention for hip and knee arthroplasty surgical procedures due to their ability to guarantee long-life performance in patients and are considered an alternative to existing metal systems.In the present study, zirconia toughened alumina (ZTA) for orthopaedic implants has been developed by Ceramic Injection Molding (CIM) process. Microstructural, mechanical and tribological studies have been carried out to establish whether the material is suitable for the purpose. The new CIM ZTA material obtained density up to 99.4%, toughness 6.1 MPa m^1/2, hardness 20 GPa, Young's modulus 320 GPa, and low coefficient of friction ranging between 0.08 and 0.13 under lubricated conditions, and between 0.11 and 0.34 in dry condition. To simulate the performance of the ZTA in vivo, i.e., the influence of material degradation on the ageing properties, accelerated hydrothermal aging was performed in vitro and good mechanical and tribological properties were confirmed for the developed ZTA.     

Effect of oxide and carbide nanoparticles on tribological properties of phenolic-based nanocomposites

The phenolic-based composites and components are widely used because of their excellent thermal, tribological and mechanical behaviors. In the present study, phenolic resin composed of hexamine, novalac, furfural, and furfuryl alcohol has been used. The effects of two carbide nanoparticles (SiC and TiC) and two oxide nanoparticles (TiO₂ and ZrO₂) on the tribological properties of phenolic resin were experimentally investigated. This paper intends to identify the effects of different fillers, fraction of particles and normal load on wear rate and coefficient of friction in dry sliding wear of phenolic-based nanocomposites against hard metal. The proportions of fillers were 0.5, 1 and 2?vol% and experiments were carried out under 40, 50, 60 and 70?N loads and at 0.2?m/s speed. The fillers were mixed with phenolic resin and molded in the form of a cylinder (8.5?mm diameter?×?25?mm height). The samples were cured at 135?°C with a special heating cycle. The wear tests were performed on pin-on-disk testing apparatus at ambient temperature. The composite pins were tested in dry sliding against carbon steel disk. The worn surfaces of samples have been investigated by SEM and the effects of nanometer particles showed different wear mechanisms. Observations showed that carbide particles have better enhancing effect on tribological properties of phenolic resin as compared to the oxide particles. Nanocomposites with SiC particles showed the best tribological properties among the investigated samples. The optimal content of SiC nanoparticles were 1?vol%.     

The mechanical and tribological properties of nitric acid‐treated carbon fiber‐reinforced polyoxymethylene composites

The carbon fibers have been exposed to nitric acid oxidation treatments and introduced into polyoxymethylene composites (POM/CF). The nitric acid treatment increases the number of the flaws, roughness of the surface, and disorder of carbon atoms on fiber, as well as introduces reactive functional groups, which could lead to a better mechanical bonding between fiber and the matrix. It is shown that the impact strength and fiber‐matrix adhesion in composites (POM/mCF) are superior to those for POM/CF composites. Simultaneously, the addition of mCF improves flexural strength and modulus relative to virgin POM significantly. Average friction coefficient values of POM/CF composites are lower than that of POM/mCF composites. As the percentage of fiber increases, the trend of wear ratio of the composites goes down initially and bumps up afterwards. The results indicate that the proper contents of CF and mCF in composites range from 5 wt % to 20 wt %. Scanning electron microscopy of worn surface morphology has revealed that the main wear mechanism of the composites were adhesive wear and ploughing wear. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41812.