Solid Lubricant Filler Research Articles

Experimental investigation on the tribo-mechanical behavior of PMMA reinforced by solid lubricant filler for dental implant applications

This study investigates the enhancement of mechanical and tribological behavior in polymethyl methacrylate (PMMA) composites reinforced with graphene oxide (GO) as a solid lubricant filler for advanced biomedical applications, particularly dental implants. PMMA/GO composites were prepared with varying weight percentages of GO (0, 0.2, 0.5, 0.7, and 1 wt. %) to assess their impact on material performance. A noteworthy improvement in both tensile strength and Young’s modulus was detected, reaching up to 141% and 10.6%, respectively, at optimized GO loadings of 1%. Microstructural analysis utilizing scanning electron microscopy for the worn surface revealed enhanced dispersion and interfacial adhesion between GO and the PMMA matrix, reinforcing mechanical coherence. Tribological properties also demonstrated enhancement, with PMMA composites containing 1 wt. % GO exhibiting optimal mechanical and tribological characteristics compared to lower weight fractions. Moreover, microscopic examination revealed a shift in the wear mechanism of the PMMA-GO composite, which was attributed to the lower friction coefficient obtained by GO integration.

Wear-Resistant Elastomeric Composites Based on Unvulcanized Rubber Compound and Recycled Polytetrafluoroethylene

Advancements in industrial machinery and manufacturing equipment require more reliable and efficient polymer tribo-systems which operate in conditions associated with increasing machine speeds and a lack of cooling oil. The goal of the current research is to improve the tribological properties of elastomeric composites by adding a solid lubricant filler in the form of ultrafine polytetrafluoroethylene (PTFE) with the chemical formula [C2F4]n and recycled polytetrafluoroethylene (r-PTFE) powders. PTFE waste is recycled mechanically by abrasion. The elastomeric composites are prepared by mixing a nitrile butadiene rubber with a phenol-formaldehyde resin and PTFE powders in an extruder followed by rolling. The deformation-strength and tribological tests of r-PTFE elastomeric composites are conducted in comparison with the ultrafine PTFE composites. The latter is based on products of waste fluoropolymer processing using a radiation method. The deformation-strength test shows that the introduction of ultrafine PTFE and r-PTFE powder to the composite leads to a decrease in strength and elongation at break, which is associated with the poor compatibility of additives and the elastomeric matrix. The friction test indicates a decrease in the coefficient of friction of the composite material. It is determined that the 15 wt.% filler added in the elastomeric matrix leads to a reduction in the wear rate by 20%. The results obtained show the possibility of using ultrafine PTFE powder and r-PTFE for creating elastomeric composites with increased tribological properties. These research results are beneficial for rubber products used in many industries, mainly in mechanical engineering.

Evaluating the effect of solid lubricant inclusion on the friction and wear properties of Laser Sintered Polyamide-12 components

The processing of Polyamide-12 (PA12) by Laser Sintering is one of the most well-established Additive Manufacturing (AM) processes for producing functional components for end-use applications. However, its further adoption within industry remains hindered by an incomplete understanding of resultant part quality and the impact this has on component wear. The scope of this research was to investigate the dry sliding behaviour of Laser Sintered Polyamide-12, as well as evaluate whether the inclusion of solid lubricant fillers effect the friction and wear properties of parts produced. Polytetrafluoroethylene (PTFE), Graphite and Molybdenum disulphide (MoS2) were added to Polyamide-12 powder in 1 : 100 mass ratios, respectively, to create three different polymeric composites. Mechanical blending and Laser Sintering then ensued; the latter was performed using identical processing parameters throughout. Tribological performance was evaluated by ball-on-flat uni-directional wear testing. Tensile testing was also carried out to help elucidate what wear mechanisms were active during sliding, as well as identify whether solid lubricant inclusion impacted mechanical performance. Results showed that in all instances solid lubricant inclusion significantly influenced the friction and wear properties of resultant composites, without compromising their mechanical performance when compared with neat-PA12. More specifically, it was demonstrated that the individual additions of PTFE and MoS2 could reduce the coefficient of friction and specific wear rate of Laser Sintered PA12 components by as much as 50% and 78%, respectively.

Role of Testing Conditions in Formation of Tribological Layers at Line Contacts of Antifriction CF-Reinforced PI- and PEI-Based Composites.

High-strength PI and PEI polymers differ by chemical structure and flexibility of the polymer chains that ensure lower cost and higher manufacturability of the latter. The choice of a particular polymer matrix is of actuality at design of antifriction composites on their basis. In this study, a comparative analysis of tribological behavior of PI and PEI- based composites was carried out with linear contact rubbing. The neat materials, as well as the two- and three-component composites reinforced with chopped carbon fibers, were investigated. The third components were typically used, but were different in nature (polymeric and crystalline) being solid lubricant fillers (PTFE, graphite and MoS2) with characteristic dimensions of several microns. The variable parameters were both load and sliding speed, as well as the counterface material. It was shown that an improvement of the tribological properties could be achieved by the tribological layer formation, which protected their wear track surfaces from the cutting and plowing effects of asperities on the surfaces of the metal and ceramic counterparts. The tribological layers were not formed in both neat polymers, while disperse hardening by fractured CF was responsible for the tribological layer formation in both two- and three component PI- and PEI-based composites. The effect of polymer matrix in tribological behavior was mostly evident in two-component composites (PI/CF, PEI/CF) over the entire P⋅V product range, while extra loading with Gr and MoS2 leveled the regularities of tribological layer formation, as well as the time variation in friction coefficients.

Effect of Transfer Film on Tribological Properties of Anti-Friction PEI- and PI-Based Composites at Elevated Temperatures.

The structure, mechanical and tribological properties of the PEI- and PI-based composites reinforced with Chopped Carbon Fibers (CCF) and loaded with commercially available micron-sized solid lubricant fillers of various nature (polymeric-PTFE, and crystalline-Gr and MoS2) were studied in the temperature range of 23–180 (240) °C. It was shown that tribological properties of these ternary composites were determined by the regularities of the transfer film (TF) adherence on their wear track surfaces. The patterns of TFs formation depended on the chemical structure of the polymer matrix (stiffness/flexibility) as well as the tribological test temperatures. Loading with PTFE solid lubricant particles, along with the strengthening effect of CCF, facilitated the formation and fixation of the TF on the sliding surfaces of the more compliant PEI-based composite at room temperature. In this case, a very low coefficient of friction (CoF) value of about 0.05 was observed. For the more rigid identically filled PI-based composite, the CoF value was twice as high under the same conditions. At elevated temperatures, rising both CoF levels and oscillation of their values made it difficult to retain the non-polar PTFE transfer film on the sliding surfaces of the PI-based composite. As a result, friction of the ceramic counterpart proceeded over the composite surface without any protecting TF at T ≥ 180 °C. For the sample with the more flexible PEI matrix, the PTFE-containing TF was retained on its sliding surface, providing a low WR level even under CoF rising and oscillating conditions. A similar analysis was carried out for the less efficient crystalline solid lubricant filler MoS2.

Влияние структуры матрицы на трибологические характеристики твердосмазочных композитов на основе высокотемпературных термопластов полиимида

The structure, mechanical and tribological properties of polyimide (PI) and polyetherimide (PEI) based composites, which differ by the presence of "hinged" oxygen atoms in the polymer’s molecular chain have been studied. The composites were reinforced with chopped carbon fibers and simultaneously loaded with organic (PTFE) and inorganic (MoS2) solid lubricant fillers. Tribological tests were carried out according to the «ball-on-disk» scheme under dry sliding friction on a ceramic counterface in the temperature range of T = 23-180 °C. It has been shown that only the «PEI/10% CF/10% PTFE» composite possesses the highest wear resistance in the entire temperature range studied. At the same time, the loading with PTFE particles ensured the formation and adhering of a stable layer of secondary structures (transfer film layer) on the sliding surface of the polymer composite. Changes in wear intensity and friction coefficient correlated well with each other. When the MoS2 solid lubricant filler were loaded, the transfer film was fixed on the sliding surface of the composite only at the highest testing temperature T = 180 °C. This was ensured by the presence of oxygen atoms in the PEI molecules. In so doing, formation of the transfer film layer gave rise to low coefficient of friction and relatively high wear resistance of the «PEI/10 CF/10 MoS2» ternary composite. A comparative analysis of the tribological properties of two types of polymer matrices have shown that the wear rate of PEI based composites loaded with PTFE was identically low at T = 23°C and 120°C, while at T = 180°C it was 300 times lower in contrast to PI-based ones. We suggest that this was related to the more «rigid» nature of the PI matrix (which does not contain «hinged» units in the macromolecule). Under conditions of a high and oscillating friction coefficient, the PI matrix was not capable of adhering a solid lubricant PTFE-containing transfer films layer. The PEI-based composites are recommended for use in tribounits due to both high manufacturability (processability) governed by the flexibility of the polymer chain, and high wear resistance due to the formation of stable secondary structures on sliding surfaces in the temperature range T = 23-180 °C.

Tribological performance of self-lubricated polyamide6/boric oxide composites after water conditioning

PurposeThis paper aims to investigate the tribological performance, i.e. abrasion resistance, friction coefficient and wear rates, of self-lubricated water conditioned polyamide6/boric oxide composites.Design/methodology/approachPolyamide6 and polyamide6/boric oxide self-lubricated composites were immersed in water for 15 days to analyze the effect of water conditioning on friction, wear and abrasion resistance. Tribological testing on pin-on-disc tribometer and abrasion resistance testing on TABER abrader were performed to see the friction coefficient and wear rates of materials. The scanning electron microscopy (SEM) characterizations were performed to analyze the wear tracks.FindingsTribological testing results revealed the loss in abrasive resistance, but there was an improvement in frictional coefficient and wear rates with steel after water absorption. The SEM images clearly show less depth of wear tracks in water-conditioned materials than dry ones. Water conditioning was found supportive in the formation of smooth lubricating transfer film on steel disc during the tribological testing.Originality/valueThe tribological behaviour of polymer composites is different in dry and in high humidity or water conditions. Experiments were performed to investigate B2O3 solid lubricant filler effectiveness on tribological behaviour of water-conditioned polyamide composites. Bonding between polyamide6 and water molecules plus the formation of orthoboric acid was found advantageous in decreasing the friction coefficient and wear rates of composites.

Effects of solid lubricant fillers on the flexural and shear strength response of carbon fabric-epoxy composites

Multi-layered carbon fabric-epoxy composites (CFEC) encounter certain challenges in expanding their usage mainly due to their low interlaminar shear strength (ILSS) and sensitivity to delamination damage. The present article focuses on evaluating the effectiveness of the fillers molybdenum disulfide (MoS2) and hexagonal boron nitride (h-BN) (2–8 wt%) on the flexural and the shear properties of the CFEC. The filler dispersion in epoxy resin is achieved by ultrasonication and composite fabrication through vacuum-assisted hand lay-up process. The filler surface area, evaluated as per nitrogen adsorption principles, reveals characteristics of hysteresis isotherm and mesoporous structure in both the fillers. Fourier transform infrared analyses on MoS2 reveal the stretch vibration due to molybdenum-sulfur and disulfide bonds whereas, in the h-BN, the transverse stretching and the out-of-plane bending happen due to boron-nitrogen and the boron-nitrogen-boron molecular group, respectively. Further analysis in the atomic force microscope shows more regular filler distribution at the outer surface for 4 and 6 wt% filler loaded CFEC whereas, 8 wt% filler loading results in an uneven particle distribution and attains the minimum surface roughness. The study exhibits the maximum ILSS (43.46 MPa) which is 43% enhancement compared to the neat CFEC for 6 wt% h-BN loaded CFEC. The maximum flexural strength (532 MPa) was noticed in 4 wt% MoS2 loaded CFEC signifying 62% improvement compared to the neat CFEC. The structural property improvements were witnessed because of the regularly distributed filler that strengthens the fiber-matrix interaction zone and reduces the matrix crack. The findings reveal that the proposed enhanced scheme by solid lubricant fillers proves to be more favorable for improving the matrix-dominated properties and the bending stiffness compared to the other particle-reinforced approaches.

Thermomechanical Properties of Carbon Fabric Reinforced Epoxy Laminates with h-BN and MoS2 Fillers

Abstract This work endeavors to investigate thermomechanical performance of carbon fabric reinforced epoxy composite (CEC) with fillers – hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2). The filler of 2, 4, 6, and 8 Wt.% was dispersed precisely in the epoxy resin through magnetic stirring and ultrasonication, prepared the filler loaded CEC using vacuum bag technique and studied the composite behavior at an elevated temperature by dynamic mechanical analysis. The 6 Wt.% MoS2-CEC showed 70% enhancement of storage modulus since the filler in the epoxy networks increased the composite stiffness. The increase in G-band intensity of Raman spectra in the filler loaded composites confirmed the improved matrix-fiber stress transfer. The 4 Wt.% BN-CEC revealed the highest glass-transition temperature 92°C. The thermogravimetric analysis of the composite exhibited a two-step thermal decomposition: epoxy matrix (nearby 260°C) and carbon fibers (beyond 420°C). The 4 Wt.% MoS2-CEC showed the maximum degree of crosslinking, twice the neat CEC, the MoS2 restrained the mobility of the epoxy chains and decreased the thermal decomposition. Both the filler loaded composites have comparable thermal stability and are significantly improved than the neat CEC. Thus, the composite containing solid lubricant filler up to 6 Wt.% shall be used for high-temperature applications.

Friction and Wear Performance of Various Polymer Coatings for Journal Bearings under Stop Start Sliding

Increasing environmental legislation and demands for improved fuel economy performance have resulted in the introduction of various measures to optimize the internal combustion engine. Many of these actions significantly change the operating conditions of the engines and bring with them new challenges that original engine manufacturers (OEMs) have to solve. One example is stop start technology, which changes the operation of many core parts of engines such as journal bearings. Hence, the current paper deals with this topic. In particular, different polymer coated bearings have been studied regarding their friction and wear performance under stop start sliding. Detailed material characterization of the materials was carried out using light microscopy and scanning electron microscopy. Furthermore, tribometric tests were conducted under controlled and similar conditions on a TE92 tribometer using a bearing segment test set up. The results show that the various polymer coated bearings tested provide enhanced friction and wear performance in comparison to other bearing types (e.g., lead-based electroplated) and that friction and wear performance differs also among them. In this regard, a higher amount of solid lubricant fillers and a dense filler structure appears to be beneficial under the given test conditions.

Preparation and wear resistance properties of thermosetting polyimide composites containing solid lubricant fillers

A polyimide (PI) oligomer end-capping with 4-phenylethynyl anhydride was successfully synthesized to prepare a series of thermosetting PI composites containing solid lubricant fillers MoS2, SiO2, Si3N4, or graphite via hot-press-molding technique. Friction and wear tests were carried out under dry friction condition and the effects of friction and wear properties of PI containing difference solid fillers were also investigated. The results indicated that the type and content of the incorporation fillers played an important role in the wear resistance properties of PI composites. Among the prepared composites, PI/MoS2-20 wt% composites showed the lowest friction coefficient (0.11), which was decreased by 47.6% compared to pure PI. While PI/graphite-20 wt% composites showed the least wear loss of 0.864 mg, which was a 90.4% decrease compared to pure PI. Furthermore, the tensile strength of PI/graphite-20 wt% composites showed an increase of 18.7% compared to pure PI. Moreover, the thermal stability and thermal conductivity of PI was improved with the incorporation fillers. The wear type of worn surfaces gradually changed from adhesion wear and fatigue wear of pure PI into abrasive wear of PI composites. The resultant PI composites exhibited good wear resistance, mechanical, thermal conductivity and thermal stability properties, suggesting their potential applications as high-performance friction materials.

On the Role of Solid Lubricant Fillers in the Tribological, Micromechanical, and Morphological Properties of PA66 Composites

Abstract To achieve thermoplastics-based composites with high tribological performances, molybdenum disulfide (MoS2) and graphite (Gr) were incorporated separately to a polyamide 66 (PA66) matrix. Two different development methodologies of composites were used. The morphological features and the micro-mechanical properties of composites were investigated to stress the influence of the filler surface treatment and its dispersion. The friction coefficient was evaluated using a ball on a flat micro-tribometer. The wear mechanisms were also characterized. The best tribological performance was exhibited by 10 wt% of graphite. The surface treatment of the filler inclusions by 3-aminopropyltriethoxysilane (AMPTES) showed an improvement in the morphological aspects of adhesion at the filler/matrix interface.

Solid-Lubricant, Polymer – Polymeric and Functionalized Fiber– and Powder Reinforced Composites of Ultra-High Molecular Weight Polyethylene

Mechanical and tribotechnical characteristics of solid-lubricant and polymer-polymeric composites of UHMWPE were studied for the sake of design extrudable, wear-resistant, self-lubricant polymer mixtures for Additive Manufacturing (AM). Tribotechnical properties of UHMWPE blends with the optimized content of solid lubricant fillers (polytetrafluoroethylene, calcium stearate, molybdenum disulphide, colloidal graphite, boron nitride) were studied under dry sliding friction at different velocities (V = 0.3 and 0.5 m/s) and loads (P = 60 and 140 N). Also, in order to increase strength and wear-resistance of UHMWPE composites they were reinforced with wollastonite microfibers and aluminum metahydroxide AlO (OH) microparticles preliminary treated (functionalized) in polyorganosiloxane. The comparison on measured mechanical and tribotechnical properties are given with interpretation of the mechanisms of observed phenomenon.

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.%).

Enhanced Mechanical and Wear Performance of Epoxy/glass Composites with PTW/Graphite Hybrid Fillers

Epoxy/glass composite containing two different micro-fillers was developed by vacuum bagging technique. The effect of ceramic whisker (7.5 wt%) and solid lubricant filler (2.5 wt%) on mechanical and dry sliding wear behavior of epoxy/glass composites was studied. The mechanical property characterization included evaluations of tensile, flexural and impact properties as per ASTM standards. The dry sliding wear tests were conducted on pin-on-disc arrangement with steel disc as counterface. Experimental results indicated that single incorporation of ceramic whisker can improve stiffness, friction coefficient and anti- wear abilities of epoxy/glass composites significantly. The strength properties of composites were slightly reduced after whisker addition. However, incorporation of solid lubricant as secondary filler resulted in improvement of both mechanical and tribological properties of composites. It was also found that tribological properties of filled epoxy/glass composites were closely related with sliding conditions such as applied load and sliding velocity. The deformation and failure mechanisms under tensile loading and dry sliding were investigated using SEM photographs.

The Tribological Behaviors of Self-Lubricating Composites as Filler in Copper Foam

A copper foam–based (CFB) self-lubricating composite was developed as a friction pair material. The composite consists of copper foam with three-dimensionally interpenetrated pores and solid lubricant fillers (polytetrafluoroethylene [PTFE] and MoS2). The thermal and electrical conductivity, bending strength, and tribological properties of the new composite were investigated. The friction and wear properties were investigated on a M-2000 model ring-on-block test rig. An electric field was imposed between the sample and ring to monitor the tribochemical reaction and formation of transfer film by means of contact resistance. Measurement of friction temperature was carried out by means of three thermocouples embedded in the material. The friction coefficients of the CFB composite decrease slightly, and the wear rate substantially decreased overall compared with that of the homologous polymers. The optical and scanning electron micrographs (SEM) of the frictional surfaces show the worn surface of the CFB composite. The main wear mechanism was three-body abrasion, caused and promoted by plastic deformation, abrasive wear, and fatigue spalling. X-ray photoelectron spectroscopy (XPS) analysis showed that the reactions of MoS2 with Cu accompanied by their respective oxidation reactions are involved in the identifiable copper area.

Mechanical and tribological response of ABS polymer matrix filled with graphite powder

Thermoplastic-based polymer composites containing solid lubricant filler have been developed using a hot compression molding technique. The thermoplastic polymer is Acrylonitrile Butadiene Styrene (ABS) which is of great importance in applications such as bearing and slider material. The solid lubricant employed is graphite powder. Four mass ratios of the graphite particles in the ABS matrix were considered in the range of 0–7.5%. The mechanical properties of ABS composites were investigated using tensile test. The results show that the mechanical properties decrease significantly with the increase of graphite particles amount. Friction experiments were also conducted using a reciprocating tribometer recently developed in our laboratory. For each of the considered mass ratio, evolutions of the friction coefficient, the weight losses and the wear scar micrograph with respect to the number of sliding cycles were analyzed. Severe adhesive wear mechanism is activated for the ABS without graphite particles. Addition of graphite in ABS matrix exhibits lower friction coefficient and weight losses, whose values decrease as the weight fraction of graphite increases in the polymer matrix. Based on scanning electron microscopy (SEM) observations, the worn surface of the filled ABS composites reveals the development of a specific third body which reduces friction and wear. The best friction coefficient and weight loss were obtained with 7.5% in weight (7.5 wt%) of graphite.

Solid lubricants in rolling-contact bearings at elevated temperatures

This article presents data from tests on the solid lubricant packing AFZ-3 at elevated temperatures in a VNIPP-100 tester and a modified TsKB-79 tester. Four Type 208 bearings were tested in the VNIPP-100 machine with an inner race speed of 3000 rpm, a radial load of 500 N on the bearing, and an outer race temperature of 250/sup 0/C. The bearing condition was monitored according to the operating noise. The tests were run to failure, with the four bearings operating for 630, 825, 831, and 931 h respectively. The solid lubricant filler retained its lubricating properties. Rolling-contact bearings packed with the AFZ-3 material were also tested under production conditions. Type 305 bearings with the AFZ-3 material operated in monorail cars in a ceramic plant under conditions of periodic exposure to temperatures of 280-300/sup 0/C for more than five years and remained serviceable. Type 312 bearings packed with the AFZ-3 material were tested in a charge loading machine designed to charge metal to thermal furnaces. The bearings remained serviceable after six months of operation. Includes a table.

フェライトの精密研削 (第2報)

Wheel wear experiments have been carried out in Mn-Zn ferrite grinding by using the wheels which are composed of 6-12μm diamond abrasives, polyoxybenzoyl, thermosetting polyimide and solid lubricant filler. The wheel wear is characterized by a specific grinding wheel wear at a small stock removal rates and by a grinding condition in which rapid increase of wheel wear arises. These characteristics are related to binding force of the bond to abrasives and fillers, and to the thermal resin softening which is caused by the frictional heating. The most excellent wheel, which contains 10 wt% WS2 particles of 0.1μm size, shows 3000 in grinding ratio. Effects of the solid lubricant fillers are concluded as increasing in permissible removal rate, reducing the wheel wear and its periodic change through grinding, and improving surface roughness of the work.

Rolling of powder mixtures with a solid lubricant filler

1. It is shown that sheet material can be successfully rolled from powder containing up to 16 wt.% of graphite. 2. To obtain strip with stable properties from a powder mixture with a solid lubricant filler, it is necessary to add glycerin to the charge. The optimum glycerin content depends on the amount of solid lubricant in the charge and the rolling process parameters.