The flexural and tribological properties of UHMWPE composite filled with plasma surface‐treated wood fibers

In this paper, the wear performance of an ultra‐high molecular weight polyethylene composites filled with wood fiber were studied using a pin‐on‐disc method. The effects of surface treatment of wood fiber and sliding load and on the friction and wear of the wood fiber/UHMWPE composite are reported. The test results showed that the sliding load is an important controlling factor; its effect is diminished when the wood fiber is modified.     

Investigation of tribological properties of Al2O3-polyimide nanocomposites

Polyimide (PI) nanocomposites with different proportions of nanoparticle Al₂O₃ were made by compression molding at elevated temperature. The mechanical and tribological properties of the resulting PI-based nanocomposites were investigated. The bending strength and microhardness of the nanocomposite specimens were determined, and the tribological behavior of the nanocomposite blocks in dry sliding against a plain carbon steel ring was evaluated on an M-2000 friction and wear tester. The morphologies of the worn nanocomposite surfaces and transfer films on the counterpart steel ring were observed on a scanning electron microscope. Results indicated that the PI-based nanocomposites with appropriate proportions of nanometer Al₂O₃ exhibited lower friction coefficient and wear volume loss than PI under the same testing conditions. The nanocomposite containing 3.0wt.%–4.0wt.% nanometer Al₂O₃ registered the lowest wear volume loss under a relatively high load. The differences in the friction and wear behaviors of PI and PI–Al₂O₃ nanocomposites were attributed to the differences in their worn surface morphologies, transfer film characteristics, and wear debris features. The agglomerated abrasives on the worn composite and transfer film surfaces contributed to increase the wear volume loss of the nanocomposites of higher mass fractions of nanometer Al₂O₃.     

Microstructure and anti‐ wear and corrosion performances of novel UHMWPE/graphene‐nanosheet composite coatings deposited by flame spraying

Ultra‐high molecular weight polyethylene (UHMWPE)/graphene‐nanosheet (GN, multiple layers of graphene sheets with the thickness of ~5–10 nm) coatings have been deposited by flame spraying. The structure of UHMWPE remained almost intact after the spray processing and addition of GNs resulted in a slightly decreased crystallinity and improved thermal stability of UHMWPE. In addition, the coating containing 1.0 wt.% GNs exhibited a reduction of ~20% in wear rate and 25% in friction coefficient (0.18 versus 0.24). Significantly enhanced anti‐corrosion performances of the UHMWPE–GN coatings were suggested by increased corrosion potential, corrosion current density, and impedance modulus value of the UHMWPE–GN coatings. The very well retained GNs are located mainly at the interfaces between UHMWPE splats and act as bridges connecting the splats, which mainly accounts for the enhanced properties of the composite coatings. The novel UHMWPE–graphene composite coatings show great potential for protecting engineering components for applications against corrosion. Copyright © 2013 John Wiley & Sons, Ltd.     

Enhanced surface free energy of UHMWPE fibers and its interfacial adhesion behavior to PI resins

Mechanical properties of composites made up of ultra‐high‐molecular‐weight polyethylene (UHMWPE) fiber, polyimide (PI), and TiO₂ particles were investigated. The hybrid composite of 20 vol% of UHMWPE fiber with TiO₂ showed tensile strength greater than UHMWPE fiber/PI composite. A positive hybrid effect in tensile strength is obtained. It is observed that addition of small amount of TiO₂ to UHMWPE fiber/PI increased the tensile strength of the composite by 28%. With increase in TiO₂ loading to 1 to 3 vol%, the impact strength of the hybrid composite is increased from 55 KJ/m² to 69 KJ/m². This maximum value is more than one and a half times greater than the impact strength of neat UHMWPE fiber/PI composite.     

Friction and wear behavior of PI and PTFE composites for ultrasonic motors

High‐performance polymer‐based frictional materials have become increasingly important to improve the mechanical output properties of ultrasonic motors. This study discussed the friction and wear behavior of 2 dominating frictional materials of polymer composites for ultrasonic motors, polyimide (PI), and polytetrafluoroethylene (PTFE) filled by aramid fibers (AF) and molybdenum disulfide (MoS₂). To explore the wear mechanisms, the tribo‐pair contact stress was theoretically characterized, and the interface temperature rise was numerically predicted. The predictions showed that the flash temperature on asperity tips could reach the glass transition temperature of the polymer materials. The experimental results indicated that the contact stress and sliding speed have a small effect on the friction of the PI composite but influence considerably the friction of the PTFE composite. A higher contact stress brings about a higher specific wear rate, but a higher sliding speed reduces the wear rate. Compared with AF/MoS₂/PTFE, the AF/MoS₂/PI has much better tribological performance under high loads and speeds.     

Modification effects of short carbon fibers on mechanical properties and fretting wear behavior of UHMWPE composites

The present work comparatively studied the modification effects of short carbon fiber (CF) on the mechanical properties and fretting wear behavior of ultra‐high molecular weight polyethylene (UHMWPE)/CF composites. The interactions between CFs and UHMWPE interface were also investigated in detail. The results showed that, with the increase in fiber content, the compressive modulus and hardness of the composites increased, while its impact strength decreased. It was found that filling of CF can reduce the friction and wear of UHMWPE. In addition, the UHMWPE‐based composites reinforced with nitric acid‐treated CF exhibited better mechanical properties, lower friction coefficient, and higher wear resistance than those of untreated UHMWPE/CF composites. This was attributed to the improvement of interfacial adhesion and compatibility between CF and UHMWPE matrix caused by surface chemical modification of CF. Copyright © 2015 John Wiley & Sons, Ltd.     

The Wear Resistance of Composite Materials Based on Ultra-High-Molecular-Weight Polyethylene with Fillers of Various Types

The tribological properties and wear resistance under different action of composite materials based on of ultra-high-molecular-weight polyethylene (UHMWPE) and fillers of various types such as organomodified montmorillonite (MMT), graphite nanoplates (GNP), molybdenum disulfide, and shungite prepared via polymerization in situ are studied. According to the obtained results, the introduction of these fillers to UHMWPE in the amount of 0.4–7 wt % has almost no effect on the value of the coefficient of sliding friction on steel in the mode of dry friction. Composites with GNP, MoS₂, and shungite are characterized by a significant (two- to threefold) increase in the wear resistance in the case of sliding friction on steel. The abrasive wear of composites in the case of friction on an abrasive paper is substantially affected by the type of filler, the use of MMT was the most effective for increasing the wear resistance of composites. In the case of a highspeed impact effect of water–sand suspensions all the studied composites are characterized by increased wear resistance in comparison with industrial UHMWPE at a low concentration of fillers and by an increase in the wear with the increase of the filler content.     

Tribological behavior of polyurethane-based composite coating reinforced with TiO2 nanotubes

The unmodified and hexamethylene diisocyanate (HDI) modified TiO₂ nanotubes, were used for fabricating TiO₂ nanotubes (TiNTs)/polyurethane (PU) composite coating. The effects of applied load and sliding speed on the tribological behavior of the composite coating were investigated using a block-on-ring wear tester. Compared to the TiO₂ nanotubes filled PU composite coating, the HDI modified TiO₂ nanotubes (TiNTs-HDI) filled one had the lower friction coefficient and higher wear life under various applied loads and sliding speed. Scanning electron microscope (SEM) investigation showed that the TiNTs-HDI filled PU coating had smooth worn surface under given applied load and sliding speed, and a continuous and uniform transfer film formed on the surface of the counterpart ring, which helped to reduce the wear of the coating. The improvement in the tribological properties of TiNTs-HDI/PU composite coating might due to an improvement in interfacial adhesion between TiNTs and PU after HDI treatment. The strong interfacial coupling of the composite coating made TiNTs-HDI not easy to detach from the PU matrix, and prevented the rubbing-off of PU composite coating, accordingly improved the friction and wear properties of the composite coating.     

Study on the friction and wear behavior of surface‐modified carbon nanotube filled carbon fabric composites

The functionalization of multi‐walled carbon nanotubes (MWNTs) was achieved by grafting furfuryl amine (FA) onto the surfaces of MWNTs. Furthermore, the functional MWNTs were incorporated into carbon fabric composites and the tribological properties of the resulting composites were investigated systematically on a model ring‐on‐block test rig. Friction and wear tests revealed that the modified MWNTs filled carbon fabric composite has the highest wear resistance under all different sliding conditions. Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA) revealed that MWNTs were successfully functionalized and the modification led to an improvement in the dispersion of MWNTs, which played an important role on the enhanced tribological properties of carbon fabric composites. It can also be found that the friction and wear behavior of MWNTs filled carbon fabric composites are closely related with the sliding conditions such as sliding speed, load, and lubrication conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Carbon‐ion implantation improves the tribological properties of Co?Cr?Mo alloy against ultra‐high molecular weight polyethylene

Amorphous diamond‐like carbon (DLC) has drawn a great deal of attention for its superior wear properties against ultra‐high molecular weight polyethylene (UHMWPE). Its rate of wear, however, is not necessarily maintained within a specific range. The aim of this study was to evaluate the mechanical features and tribological properties of three types of surfaces: (i) uncoated, (ii) carbon‐ion implantation (CII)‐treated, and (iii) DLC‐film‐coated substrate. The surface alterations were carried out on cobalt–chrome (Co? Cr? Mo) alloy by the plasma‐source ion implantation (PSII) method. The wear properties and friction coefficient were estimated by a pin‐on‐plate wear‐tester. We found, as a result, that the implanted carbon penetrated the substrates in which good adhesion was expected. Though the surface modifications by CII and DLC hardened the surfaces, the surface with DLC was also roughened (R_a = 39 nm). In contrast, the surface modified by CII had a very smooth surface (R_a = 15 nm) and low friction coefficient (ranging from 0.15 to 0.20), resulting in a low rate of wear. Our findings suggest that CII on the Co? Cr? Mo alloy/UHMWPE pair offers potential benefits as a hard coating for artificial total‐joint arthroplasty. Copyright © 2008 John Wiley & Sons, Ltd.     

稀土对玻璃纤维填充金属-塑料多层复合材料抗冲击磨损性能的影响

研究了稀土元素处理玻璃纤维填充金属－塑料多层复合材料在冲击载荷、干摩擦条件下的摩擦和磨损性能，并利用扫描电子显微镜（SEM）对磨损表面进行了观察和分析，结果表明，用稀土表面改性剂处理玻璃纤维表面，可以提高玻璃纤维与聚四氟乙烯之间的界面结合力，改善复合材料的界面性能，并有利于在偶件表面形成分布均匀、结合强度高的转移膜，使复合材料与偶件表面之间的对摩减轻，大幅度地降低了复合材料的磨损，从而使复合材料具有优良的摩擦性能和抗冲击磨损性能。     

Effect of temperature on friction and wear behaviors of polyimide (PI)‐based solid–liquid lubricating materials

The tribological properties of polyimide (PI) under four oils (including two perfluoropolyether oils and two silicon oils) lubricated conditions were comparatively investigated at room temperature in vacuum and Fomblin M30 and chlorine‐containing silicon oil were selected to study the friction and wear behaviors of PI‐based solid–liquid lubricants against steel at different temperatures in vacuum. Significant improvement in tribological performance of PI was found under oil‐lubricated conditions. The friction coefficient increased as the test temperature decreased for the mobility of liquid lubricant was limited at lower temperatures, while the wear rate exhibited distinct rule. Besides, no tribochemical reaction was detected at the contact surface of PI and chlorine‐containing silicon oil. However, the –CF₃ and fluorinated C? O groups were detected on the worn tracks of PI/Fomblin M30 by X‐ray photoelectron spectroscopy, which indicated that tribochemical reaction happened to PI and Fomblin M30 under high temperature as well as the simulation of friction heat. Copyright © 2015 John Wiley & Sons, Ltd.     

稀土元素表面处理对玻璃纤维填充金属—塑料多层复合材料冲击磨损性能的影响

金属 塑料多层复合材料由钢背、烧结多孔青铜中间层和聚四氟乙烯 (ＰＴＦＥ)与填料混合物组成的表层复合而成 ,具有金属和塑料原有的优良性能 ,如高的机械性能、低的热膨胀系数和低的摩擦系数、良好的导热性和优异的减磨性[1～ 3 ] 。众所周知 ,玻璃纤维可用来提高ＰＴＦＥ复合材料的力学性能[4～ 6 ] 。纤维与基体之间的界面结合力起着控制聚合物复合材料力学性能的重要作用 ,并主要受纤维表面处理的影响[7～ 9] 。Ｗａｔａｎａｂｅ[10 ] 认为只填充玻璃纤维的ＰＴＦＥ复合材料在水中的磨损大于其它复合材料 ,玻璃纤维易受磨损且细碎的玻…     

Superior biolubricant from a species of red microalga

The rheological properties of the sulfated polysaccharide of the red microalga Porphyridium sp., a heteropolymer with a molecular weight of 3-5 x 10(6) Da, indicated that this material might be an excellent candidate for lubrication applications: the viscosity of the polysaccharide is stable over a range of temperatures, pH values, and salinities. In this study, various rheological and lubricant properties of the polysaccharide were evaluated in comparison with those of a widely used biolubricant, hyaluronic acid. The viscosity of the Porphyridium sp. polysaccharide remained essentially unchanged in a temperature range of 25-70 degrees C. In tribology tests on a ball-on-flat ceramic pair, the values for the friction coefficient and wear rate for the pair lubricated with polysaccharide were remarkably lower than those for hyaluronic acid, especially at high loads. In a test on a steel ring/ultrahigh-molecular-weight polyethylene (UHMWPE) block pair, the wear tracks on the surface of the UHMWPE were more pronounced for hyaluronic acid than for the polysaccharide. Atomic force microscopy showed that the polysaccharide was effectively adsorbed onto mica surfaces, forming ultrathin coating layers in the nanometer range. As is required for biolubricant applications, the polysaccharide was not degraded by hyaluronidase. The stability of the Porphyridium sp. polysaccharide to heat and to hyaluronidase combined with its ability to reduce friction and wear indicate its potential as an advantageous biolubricant.     

Chemical modification on UHMWPE microparticles to improve the interfacial and tribological properties of UHMWPE/carbon fabric/phenolic laminate in water environment

Carbon fabric (CF)/phenolic laminates filled with pristine and chromic acid treated ultra high molecular weight polyethylene (UHMWPE) microparticles were fabricated. Their interfacial and tribological properties in water environment were comparatively investigated. The interlaminar shear strength (ILSS) of the laminates was tested on a universal testing machine (DY35), and the tribological properties were evaluated by a block‐on‐ring tribo‐tester. The worn surfaces and the interfaces of the laminates were respectively analyzed by scanning electron microscope (SEM) and field emission SEM (FESEM). The change of the chemical composition of UHMWPE microparticles after chromic acid etching was analyzed by Fourier transform infrared spectroscopy (FTIR). The chemical state of carbon fiber surface was examined using X‐ray photoelectron spectroscopy (XPS). The results revealed that the chromic acid treated UHMWPE microparticles had more remarkable effect than the pristine ones on improving not only ILSS and wear resistance of CF/phenolic laminate, but also its immunity to water environment. This should be attributed to the strengthened interfaces in treated UHMWPE/CF/phenolic laminate, which were characterized by the drawn dendritic UHMWPE fibrils firmly clinging on the surfaces of carbon fibers and resin in a Boston ivy‐like manner. Copyright © 2015 John Wiley & Sons, Ltd.     

The effect of surface modification with nitric acid on the mechanical and tribological properties of carbon fiber‐reinforced thermoplastic polyimide composite

Polyacrylamideacrylate (PAN)‐based carbon fibers were submitted to nitric acid oxidation treatments to improve the interfacial adhesion of the carbon fiber (CF)‐reinforced polyimide (CF/PI) composite. The carbon fiber surfaces were characterized by X‐ray photoelectron spectroscopy (XPS). Nitric acid oxidation not only affects the oxygen concentration but also produces an appreciable change in the nature of the chemical functions, namely the conversion of hydroxy‐type oxygen into carboxyl functions. Nitric acid oxidation treatment modifies the element constituting the fiber, the nitrogen concentration being about 1.2 times higher at the fiber external surface compared to the untreated one. The mechanical and tribological properties of the polymide (PI) composites reinforced by the carbon fibers treated with nitric acid oxidation were investigated. Results showed that the tensile strength of the CF/PI composites improved remarkably due to nitric acid treatment along with enhancement in friction and wear performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of maleic anhydride‐grafted polytetrafluoroethylene on the tensile and tribological properties of blending polytetrafluoroethylene with polyamide‐6

Blending polytetrafluoroethylene (PTFE) to polyamide‐6 (PA6) with and without maleic anhydride‐grafted polytetrafluoroethylene (PTFE‐g‐MA) was produced in a corotating twin screw extruder, where PTFE acts as the polymer matrix and PA6 as the dispersed phase. The effect of PTFE‐g‐MA on the tensile properties and tribological propertiesof PTFE/PA6 polymer blends is studied. Results show that the structural stability and morphology of the blends were greatly improved by PTFE‐g‐PA6 grafted copolymers, which were formed by the in situ reaction of anhydride groups with the amino end groups of PA6 during reactive extrusion forming an imidic linkage. The presence of PTFE‐g‐PA6 in the PTFE continuous phase improves the interfacial adhesion, as a result of the creation of an interphase that was formed by the interaction between the formed PTFE‐g‐PA6 copolymer in situ and both phases. Compared with thePTFE/PA6 without PTFE‐g‐MA, the PTFE/PA6 with PTFE‐g‐MAhad the lowest friction coefficient and wear under given applied load and reciprocating sliding frequency. The interfacial compatibility of the composite prevented the rubbing‐off of PA6, accordingly improved the friction and wear properties of the composite. Copyright © 2009 John Wiley & Sons, Ltd.     

Sliding Wear Behavior of Nanoclay Filled Polypropylene/Ultra High Molecular Weight Polyethylene/Carbon Short Fiber Nanocomposites

In the present investigation, authors made an attempt to study the sliding wear behavior of polypropylene/ultrahigh molecular weight polyethylene (PP/UHMWPE, 90/10) blends loaded with 30% carbon short fibers (CSF) as reinforcement and nanoclay as filler material. The nanocomposites have been prepared with varying amounts viz., 0, 1, 2 and 3 wt% of nanoclay. The composites were prepared by melt mixing at 60 rpm extruder speed and compression moulding at 180°C. From all the composites, 6 mm diameter and 25 mm length sliding wear specimens were prepared. Sliding wear loss, specific wear rate and coefficient of friction were investigated by using computerized pin-on–disc machine at normal applied loads of 20, 30 and 40 N; at a sliding velocity of 1.5 m/s and at two abrading distances viz., 200 and 300 m. The wear behavior data reveals that 3 wt% nanoclay filled composite exhibits higher wear resistance and lowest specific wear rate as compared to other nanocomposites. Also morphological study was carried out for wear out surfaces of all the composites using scanning electron microscopy (SEM).     

Ultra-High Molecular Weight Polyethylene with Reduced Fusion Defects and Improved Mechanical Properties by Liquid Paraffin

Products made of ultra-high molecular weight polyethylene (UHMWPE) have a tendency to contain fusion defects, arising during the processing of the reactor powder. These defects have been implicated previously in failures of UHMWPE load-bearing surfaces in knee and hip prostheses. To minimize the fusion defects of UHMWPE products, the low molecular weight substance liquid paraffin (LP) was blended with UHMWPE. Our hypothesis was that the addition of LP could minimize structural defects and thus improve the properties of consolidated UHMWPE. The morphology and property of UHMWPE blends with LP were investigated by SEM, DMA, and stress relaxation. The addition of small amounts of LP improved tensile strength, the elongation at break, and friction and wear properties of UHMWPE, presumably due to structural defect elimination through reducing entanglements and enhancing the chain mobility of UHMWPE.     

Surface modification of ultrahigh‐molecular‐weight polyethylene fibers

To prevent the loss of fiber strength, ultrahigh‐molecular‐weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corona‐discharge treatment. The physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance. The gel contents of the fibers were measured by a standard device. The mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE‐fiber‐reinforced vinyl ester resin composites were investigated with tensile testing. After 20 min or so of ultraviolet radiation based on 6‐kW corona treatment, the T‐peel strength of the treated UHMWPE‐fiber composite was one to two times greater than that of the as‐received UHMWPE‐fiber composite, whereas the tensile strength of the treated UHMWPE fibers was still up to 3.5 GPa. The integrated mechanical properties of the treated UHMWPE fibers were also optimum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 463–472, 2004