Research on the tribological performance of Cr2O3 filled with bronze‐based PTFE composites

Enhancement of the wear resistance of bronze‐filled polytetrafluoroethylene (PTFE) composites has been achieved using various fillers, for example, chromic oxide (Cr₂O₃), molybdenum disulfide (MoS₂), graphite, and nanometer aluminum oxide (n‐Al₂O₃), in the present study. The wear resistance was evaluated by a block‐on‐ring wear tester, and the effects of fillers on the wear resistance as well as the mechanism were investigated. The wear rate for the composite where the recipe containing 59% PTFE + 40% bronze + 1% Cr₂O₃ was 0.5 × 10^?5 mm^?3/N m and for the composite in the recipe containing 60% PTFE + 40% bronze was 4.2 × 10^?5 mm^?3/N m, which meant that that Cr₂O₃ increased the wear resistance by approximately 10 times. The differential scanning calorimetry measure analysis showed that Cr₂O₃ had a positive effect on the crystallization of PTFE; the crystallinity of PTFE composites increased from 45% to 52%, which exhibited improved wear resistance. Wear testing and scanning electron microscope analysis had shown that Cr₂O₃ had a positive effect on the formation of transfer film and keeping it stable to exhibit improved wear resistance. X‐ray photoelectron spectroscopy results also showed that Cr₂O₃ was effective in tribochemical reactions during sliding against stainless ring; these maybe responsible for forming transfer film and lowering wear rate of composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41117.     

Effect of SiO2 nanoparticles-decorated SCF on mechanical and tribological properties of cenosphere/SCF/PEEK composites

A silicon oxide (SiO₂) nanoparticles-decorated short carbon fiber (SCF) hybrid (SCF-SiO₂) was designed to improve the weak interfacial bonding between fibers and matrix. Nano-SiO₂ was grafted onto carbon fibers by introducing amino group and epoxy group on the surface of carbon fibers and SiO₂, respectively. The chemical composition of SCF-SiO₂ was analyzed by Fourier transform infrared spectrometer and energy-dispersive spectrometry, the microstructure of SCF-SiO₂ were investigated by scanning electron microscope, and then the hybrid filler was introduced into Poly(ether ether ketone) (PEEK). Due to the strong interfacial interaction between filler and matrix, the mechanical and tribological properties of SCF-SiO₂/PEEK composites were significantly better than SCF/PEEK composites. In order to further improve the tribological properties of the composites, micrometer-sized cenosphere (CS) particles were introduced into the aforementioned system to prepare multicomponent composites. The test results of friction and wear indicate that the CS/SCF-SiO₂/PEEK composites have the optimal tribological properties. Compared with pure PEEK, the friction coefficient of CS/SCF-SiO₂/PEEK composites under 200 N load decreases by 56.4% and the specific wear rate decreases by 87.4%. Meanwhile, the thermal decomposition temperature of CS/SCF-SiO₂/PEEK composites is increased by 40 °C compared to pure PEEK. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48749.     

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.     

Improved tribological and thermo-mechanical properties of epoxy resin with micro-nano structured ZrO2/Ti3C2 particles

Inherent brittleness and poor wear resistance of epoxy resin severely restricts its practical application in many applications. In this present, a micro-nano structured ZrO₂/Ti₃C₂ particle was employed to improve the tribological and thermo-mechanical properties of epoxy resin. The micro-nano structured ZrO₂/Ti₃C₂ particles are synthesized by hydrothermal growth of nano-ZrO₂ onto the surface of accordion-like Ti₃C₂, and the ZrO₂/Ti₃C₂/epoxy composites are fabricated by solution blending and curing reaction. The surface morphology of ZrO₂/Ti₃C₂ particles and the fracture surface of ZrO₂/Ti₃C₂/epoxy composites were investigated. Test results indicated that the wear rate, storage modulus and glass transition temperature of epoxy resin is effectively improved by incorporation of ZrO₂/Ti₃C₂ particles, maybe ascribing to the strong interfacial interaction between micro-nano structured ZrO₂/Ti₃C₂ and epoxy matrix. In addition, the wear mechanism of ZrO₂/Ti₃C₂/epoxy composites were further revealed by analyzing their worn surfaces and wear debris. This work provides a promising strategy for improving the tribological and thermo-mechanical properties of epoxy.     

Mechanical properties study of micro‐ and nano‐hydroxyapatite reinforced ultrahigh molecular weight polyethylene composites

This is a comparative study between ultrahigh molecular weight polyethylene (UHMWPE) reinforced with micro‐ and nano‐hydroxyapatite (HA) under different filler content. The micro‐ and nano‐HA/UHMWPE composites were prepared by hot‐pressing method, and then compression strength, ball indentation hardness, creep resistance, friction, and wear properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, wettability, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results demonstrated that UHMWPE reinforced with micro‐ and nano‐HA would improve the ball indentation hardness, compression strength, creep resistance, wettability, and wear behavior. The mechanical properties for both micro‐ and nano‐HA/UHMWPE composites were comparable with pure UHMWPE. The mechanical properties of nano‐HA/UHMWPE composites are better compared with micro‐HA/UHMWPE composites and pure UHMWPE. The optimum filler quantity of micro‐ and nano‐HA/UHMWPE composites is found to be at 15 wt % and 10 wt %, separately. The micro‐ and nano‐HA/UHMWPE composites exhibit a low friction coefficient and good wear resistance at this content. The worn surface of HA/UHMWPE composites shows the wear mechanisms changed from furrow and scratch to surface rupture and delamination when the weight percent of micro‐ and nano‐HA exceed 15 wt % and 10 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42869.     

Synergetic effect of fly ash cenospheres and multi-walled carbon nanotubes on mechanical and tribological properties of epoxy resin coatings

The multiform wear of friction pair components is the main cause of marine equipment failure and epoxy resin (EP) coatings have been widely used in this field. Fly ash cenospheres (FACs) and multi-walled carbon nanotubes (MWCNTs) were used to reinforce the tribological properties of EP coatings. The synergetic effects of FACs and MWCNTs on the mechanical and tribological properties of EP coatings were studied. Experimental results show that the tensile and flexural properties of FACs-MWCNTs/EP composites are significantly reinforced. The tribological performance of EP composite coatings under seawater conditions is improved by the synergetic effect of FACs and MWCNTs, especially, the 10 wt.% FACs-1 wt.% MWCNTs/EP coatings behave the most excellent tribological properties. It indicates that FACs can increase the hardness of EP coatings and provide a smoother surface for the water film formation, which decreases the friction coefficient and wear volume. MWCNTs can increase the elasticity modulus of EP, and act as a rope to prevent EP matrix and FACs from being desquamated.     

Preparation and tribological behavior of polytetrafluoroethylene/metal mesh composites with sandwich structure

Polytetrafluoroethylene (PTFE) owns an excellent self-lubricating performance, but its wear rate is very high due to the large-scale spalling of the matrix in the friction. In this paper, A new kind of PTFE composites with sandwich structure was prepared by layer-press technology, whose middle layer is filled with metal mesh. The influence of the mesh structure and mesh density of middle metal layer on tribological properties of composites were researched in detail. The results revealled that the metal mesh located in the composites can efficiently prevent the large-scale spalling of PTFE, which induces the sample of PTFE/500# plain woven dutch metal mesh (PTFE-500#PWD) to have a lower wear rate (9 × 10⁻⁵ mm³/Nm) and COF (0.106) under the fixed experimental condition. The prepared PTFE/metal mesh composites reveal excellent anti-friction and anti-wear performance, which can be used to fabricate a new kind of self-lubricating materials.     

Tribological properties of polyimide coatings filled with PTFE and surface‐modified nano‐Si3N4

Polyimide (PI) coatings filled with PTFE and nano‐Si₃N₄ were prepared by a spraying technique and successive curing. Nano‐Si₃N₄ particles were modified by grafting 3‐aminopropyltriethoxysilane to improve their dispersion in the as‐prepared coatings. Friction and wear performances and wear mechanisms of the coatings were evaluated. The results show that the incorporations of PTFE and modified nano‐Si₃N₄ particles greatly improve the friction reduction and wear resistance of PI coating. The friction and wear performance of the composite coating is significantly affected by the filler mass fraction and sliding conditions. PI coating incorporated with 20 wt % PTFE and 5 wt % modified nano‐Si₃N₄ displays the best tribological properties. Its wear rate is more than one order of magnitude lower and its friction coefficient is over two times smaller than that of the unfilled PI coating. Differences in the friction and wear behaviors of the hybrid coatings as a function of filler or sliding condition are attributed to the filler dispersion, the characteristic of transfer film formed on the counterpart ball and the wear mechanism of the coating under different sliding conditions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40410.     

An investigation of thermal and tribological behaviors of PTFE‐based silicon composites filled with AlN and flake graphite particles

The thermal and tribological properties of silicon composites were improved by choosing polytetrafluoroethylene (PTFE) as a thickener and alumina nitride (AlN) and flake graphite (FG) as thermal conductive additives, producing AlN‐modified, FG‐modified, and AlN/FG‐modified PTFE‐based thermal silicon composites (AlN–PTSC, FG–PTSC, and AlN/FG–PTSC, respectively). Three‐dimensional network‐configuration representative volume element models were built to investigate the thermal properties of these composites by applying a Monte Carlo, controllable, spatial distribution algorithm. The composites’ thermal conductivity and volume resistance were also measured. Tribological tests were conducted using a ball‐on‐disk reciprocating friction and wear tester. Scanning electron microscopy and energy dispersive spectroscopy were used to analyze the morphologies and elements of worn surfaces. The results showed that AlN/FG–PTSC possessed the best thermal properties, which were ascribed to a compact thermal conductive network; thermal conductivity was 88.8% and 44.8% greater than the highest value of AlN–PTSC and FG–PTSC, respectively. The numerical values of thermal conductivity were in a good agreement with experimental results. The optimal electrical tribological properties of AlN/FG–PTSC were ascribed to the functions of thermal and electrical properties combined, which could be helpful in abating the arc erosion on friction contacts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45263.     

Hydrophobic and tribological behaviors of a poly(p‐phenylene benzobisoxazole) fabric composite reinforced with nano‐TiO2

1H,1H,2H,2H‐Perfluorooctyl trichlorosilane (PFTS) was used to modify TiO₂ nanoparticles, and hydrophobic PFTS–TiO₂ nanoparticles were obtained by an ultrasonic reaction method. The PFTS–TiO₂ surface morphological and hydrophobic properties were analyzed with scanning electron microscopy (SEM), Fourier transform infrared spectrometry, and contact angle (CA) testing. Then, the poly(p‐phenylene benzobisoxazole) fabric–phenolic composite filled with PFTS–TiO₂ as a lubricant additive was fabricated by a dip‐coating process. The tribological properties of the composite were investigated, and the wear surface morphology was observed by SEM. The experimental results show that the water CA of the composite filled with PFTS–TiO₂ was 158°, and the composite containing 4 wt % PFTS–TiO₂ exhibited excellent antifriction and abrasion resistance. The hydrophobic surface of the composite showed excellent durable performance with a static water CA of 126.7° after abrasion. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45077.     

Study on the tribological properties of porous sweating PEEK composites under ionic liquid lubricated condition

The tribological behaviors of novel porous Polyetheretherketone (PEEK) composites under 1‐hexyl‐3‐methylimidazolium tetrafluoroborate ionic liquid lubricated condition were investigated. The effect of sliding velocity and applied load on the sweating tribological properties and the stability of lubricating oil film was also studied. Results indicated that when the sliding velocity was 0.69 m/s and the applied load was 250 N, the friction coefficient and wear rate of the ionic liquid lubricated porous sweating activated carbon fiber/polytetrafluoroethene/PEEK composites showed the minimum values, were 0.0197 and 4.145 × 10^?15 m³/Nm, respectively. The friction coefficients fluctuated in a narrow range of 0.0162–0.0215. It was found that the porous sweating PEEK composites under ionic liquid lubricated condition showed good low‐friction and antiwear performance, especially under the condition of high sliding velocity and applied load. The formed transfer film due to the tribo‐chemical reaction as well as boundary lubricating film is effective in improving the carrying capacity and antiwear properties of the porous sweating PEEK composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40989.     

Investigation of the relationship between morphology and tribological properties of an epoxy resin based on tetraglycidyl 4,4′‐diaminodiphenylmethane modified with polyetherimide oligomers

In this paper, polyetherimides (PEI) with two different calculated number‐average molecular weights (M_n) of 5000 and 10,000 g/mol were synthesized and used to modify tetraglycidyl 4,4′‐diaminodiphenylmethane. Three different morphologies (separated phase, bi‐continuous phase, and phase inversion structure) were obtained by controlling molecular weights and content of PEI. Thermal and mechanical characterizations showed that addition of PEI resulted in an increase in thermal stability and tensile strength. Tensile strength of samples with bi‐continuous phase was higher than those with separated phase or phase inversion structure. Influence of morphologies on tribology properties were studied by a ring‐on‐block wear tester. Higher wear resistance was achieved from samples with bi‐continuous phase. It was found that wear life of samples with bi‐continuous phase was almost 100% higher than that of samples with separated phase. This is clearly related to the change in thermal and mechanical properties caused by the change of morphologies. Scanning electron microscope observations of worn surfaces and wear debris of the tested samples showed that tribological behaviors and wear mechanisms were heavily dependent on morphologies. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39863.     

Freeze‐drying method prepared UHMWPE/CNTs composites with optimized micromorphologies and improved tribological performance

Uniformly dispersed carbon nanotubes (CNTs) reinforced ultrahigh molecular weight polyethylene (UHMWPE) composites were successfully prepared by freeze‐drying method. Specifically, polymer powders were mixed with CNT aqueous paste, and then freeze‐dried. As a consequence, CNTs covered at the surface of UHMWPE powders evenly when CNT content was not very high, which improved the quantity of crystals and crystallinity of UHMWPE/CNTs composites by providing more nucleation sites during the upcoming compression‐molded process. Furthermore, optimized dispersion state of CNTs and concomitant higher crystallinity made freeze‐drying technique prepared composites display much lower wear rate when compared with pure UHMWPE and UHMWPE/CNTs composites fabricated by common heat‐drying method. In a word, our proposed method of freeze‐drying is simple and effective for mass production of UHMWPE/CNTs composites, and it is promising to be applied to fabricate many kinds of nanofillers modified polymer composites, for example, polymer/graphene material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41885.     

Friction and wear properties of graphene oxide/ultrahigh‐molecular‐weight polyethylene composites under the lubrication of deionized water and normal saline solution

Ultrahigh‐molecular‐weight polyethylene (UHMWPE) and UHMWPE composites reinforced with graphene oxide (GO) were successfully fabricated through a new step of liquid‐phase ultrasonic dispersion, high‐speed ball‐mill mixing, and hot‐pressing molding technology. When the GO/UHMWPE composites were lubricated with deionized water (DW) and normal saline (NS) solution, their friction and wear properties were investigated through sliding against ZrO₂. The worn surface and wear volume losses of these composites were studied with scanning electron microscopy, X‐ray photoelectron spectroscopy, and a Micro‐XAM 3D non‐contact surface profiler. The results show that the microhardness of the GO/UHMWPE composites was improved by 13.80% and the wear rates were decreased by 19.86 and 21.13%, whereas the depths of the scratches were decreased by 22.93 and 23.77% in DW and NS lubricating conditions, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39640.     

Tribological properties of bismaleimide composites with surface‐modified SiO2 nanoparticles

In this article, the surface of SiO₂ nanoparticles was modified by silane coupling agent N‐(2‐aminoethyl)‐γ‐aminopropylmethyl dimethoxy silane. The bismaleimide nanocomposites with surface‐modified SiO₂ nanoparticles or unmodified SiO₂ nanoparticles were prepared by the same casting method. The tribological performance of the nanocomposites was studied on an M‐200 friction and wear tester. The results indicated that the addition of SiO₂ nanoparticles could decrease the frictional coefficient and the wear rate of the composites. The nanocomposites with surface‐modified SiO₂ nanoparticles showed better wear resistance and lower frictional coefficient than that with the unmodified nanoparticles SiO₂. The specific wear rate and the steady frictional coefficient of the composite with 1.0 wt % surface‐modified SiO₂ nanoparticles are only 1.8 × 10^?6 mm³/N m and 0.21, respectively. The dispersion of surface‐modified SiO₂ nanoparticles in resin matrix was observed with transmission electron microscope, and the worn surfaces of pure resin matrix and the nanocomposites were observed with scanning electron microscope. The different tribological behavior of the resin matrix and the filled composites should be dependent on their different mechanical properties and wear mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of a water‐soluble,rubber seed oil–based sulfonate and its tribological properties as a water‐based lubricant additive

A novel, water‐based oleic acid (OA)/2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid (AMPS) copolymer was successfully synthesized as a water‐based lubricant additive. The OA‐AMPS copolymer was characterized by Fourier transform infrared and proton NMR spectroscopies and then used as a lubricant additive in water. The lubrication properties of water‐miscible cutting fluids with the OA‐AMPS copolymer additive were investigated using a four‐ball friction tester. The surface of the wear scars was explored using scanning electron microscopy and X‐ray photoelectron spectroscopy. The addition of the synthesized OA‐AMPS copolymer improved the friction coefficient and wear scar diameter of water. The maximum nonseizure load increased from 95 to 431 N, and the anticorrosion ability on copper was categorized as 1b. Good antiwear and friction‐reducing properties for water were observed and attributed to the absorption and tribochemical films composed of iron oxide and ferrous disulfide. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46119.     

Tribological behaviors of polyurethane composites containing self‐lubricating microcapsules and reinforced by short carbon fibers

Self‐lubricating microcapsules containing methyl silicone oil as core materials, were prepared with poly(melamine‐formaldehyde) as shell material by in situ polymerization method. Combining with synergistic effect of the short carbon fibers (SCFs) which were systematically treated by liquid‐phase oxidation and chemical grafting, they were simultaneously adopted as reinforcing additives to improve the tribological and mechanical properties of polyurethane materials. The tribological behaviors and mechanical properties of the polyurethane composites have been investigated by a block‐on‐ring wear tester and electronic universal testing machine, respectively. The results indicate that the friction coefficient and wear rate of polyurethane composites without SCFs significantly decreased with increased self‐lubricating microcapsule concentration from 2.5 to 10 wt % due to the release of methyl silicone oil; meanwhile, the polyurethane composites filled with 10 wt % microcapsule and 15 wt % SCFs not only exhibited the lowest friction and wear behaviors, but also improved mechanical strength and thermal stability of polyurethane composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45331.     

Enhanced tribological performance of hybrid polytetrafluoroethylene/Kevlar fabric composite filled with milled pitch‐based carbon fibers

As self‐lubricating bearing liner materials, tribological properties of milled pitch‐based carbon fibers (CFs) modified polytetrafluoroethylene (PTFE)/Kevlar fabric composites were investigated, and the microscopic morphology of worn surface was studied. The results show that the appropriate incorporation of CFs can obviously reduce the wear rate of the fabric composite with almost unchanging friction coefficient. The wear rates of 5 wt % CF‐filled PTFE/Kevlar fabric composites are decreased by 30% and 48% for two kinds of composites made with fibers from different producers compared with unfilled fabric composites. Scanning electron microscopy observations show that the appropriate incorporation of CFs obviously improves the interfacial bonding and reduces pull‐out and fracture of Kevlar fiber. Meanwhile, the introduction of CFs at proper fraction is helpful to form smooth and continuous transfer film on the surface of metal counterpart. The improving mechanism of the CF is attributed to increasing mechanical strength, thermal conductivity and self‐lubricating effects. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46269.     

Tribological properties of PBO fabric composites modified by poly (vinyl alcohol)

Friction and wear behaviors of poly (vinyl alcohol) (PVA) modified PBO fabric composites were evaluated in a pin‐on‐disc friction and wear tester, and the relationship between the properties and the structure change resulting from PVA modification were intensively investigated using thermogravimetric analysis (TG) and scanning electronic microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The results indicated that the PVA thin film formed on the fabric surface by chemical crosslinking reaction could improve the antiwear property of the PBO fabric composites efficiently. In argon‐300°C condition, the antiwear property of the PBO fabric composites was improved by 35%, which was due to the improvement of the bonding strength between the fabric and resin and the dispersion of the shear stress induced by the shear creep and plastic deformation of the PVA film in friction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1313‐1320, 2013     

Enhancement of mechanical and tribological properties in ring‐opening metathesis polymerization functionalized molybdenum disulfide/polydicyclopentadiene nanocomposites

This study focuses on the possibility of improving performance properties of polydicyclopentadiene (PDCPD) nanocomposites for engineering applications using nanoparticles. In this article, molybdenum disulfide/polydicyclopentadiene (MoS₂/PDCPD) nanocomposites have been prepared by in situ ring‐opening metathesis polymerization using reaction injecting molding (RIM) process. To enhance the interfacial adhesion between the fillers and PDCPD matrix, the surface modified MoS₂ nanoparticles hybridized with dialkyldithiophosphate (PyDDP) were successfully prepared by in situ surface grafting method. The effect of low MoS₂ loadings (<3 wt %) on the mechanical and tribological behaviors of PDCPD was evaluated. The results indicated that the friction coefficient of the MoS₂/PDCPD nanocomposites was obviously decreased and the wear resistance of nanocomposites was greatly improved by the addition of PyDDP‐hybridized MoS₂ nanoparticles; meanwhile, the mechanical properties were also enhanced. The MoS₂/PDCPD nanocomposites filled with 1 wt % PyDDP‐hybridized MoS₂ exhibited the best mechanical and anti‐wear properties. The friction coefficient was shown to decrease by more than 40% compared to pure PDCPD by incorporating just 1 wt % hybridized MoS₂ nanoparticles, and modest increase in modulus and strength was also observed. The reinforcing and wear‐resistant mechanisms of MoS₂/PDCPD nanocomposites were investigated and discussed by scanning electron microscopy. The well interfacial compatibility between the particle/matrix interfaces played an important role for the improved mechanical and tribological properties of MoS₂/PDCPD nanocomposites in very low MoS₂ loadings. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013