Tribological properties and corrosion resistance of epoxy resin-polytetrafluoroethylene bonded solid lubricating coating filled with flake aluminum

The aims of this work are to prepare a novel epoxy resin-polytetrafluoroethylene (expressed as EP/PTFE) bonded solid lubricating coating filled with flake aluminum. The focus is to study the effects of two different flake aluminum (floating type and non-floating type) on the tribological performance and anti-corrosion capability of the coating. A CSM friction tester was applied to evaluate the tribological performance of the coating. The electrochemical technique was applied to study the corrosion resistance of the coating. And the experimental results showed that both types of flake aluminum can ameliorate the tribological performance and anti-corrosion properties of the EP/PTFE lubricating coating. Moreover, compared with floating flake aluminum, the incorporation of non-floating flake aluminum significantly improved the tribological properties and corrosion resistance of the EP/PTFE coating due to its good dispersibility, greater enhancement effect on mechanical performance and stronger barrier properties.     

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.     

Application of organosilane coatings for improved anti-adhesive properties enabling facilitated demolding in polymer processing

Easy and residue-free demolding is an everlasting topic in the plastics processing industry. Typically, facile ejection of the produced parts from the mold is provided by separation agents (silicon sprays, surface coatings). In this work, a perfluoroalkyl-based organosilane coating is applied to exchangeable substrates of an injection mold. Besides the simple application, the coating can also be restored easily in a procedure based on flame treatment. Coating and recoating are proven by contact angle measurements with water, while the anti-adhesive effect and the related relief during demolding are evaluated using a special measuring device in an instrumented two-plate injection mold. The results reveal that the organosilane layer reduces the demolding forces and the resulting static friction coefficient by 50%. Furthermore, multiple recoating significantly improves the durability of the anti-adhesive coating. Based on these findings, the easily applicable and renewable organosilane coating represents a suitable alternative to conventional release coatings.     

Oil- and water-resistant paper substrate using blends of chitosan-graft-polydimethylsiloxane and poly(vinyl alcohol)

Reported herein is an economical, plastic- and fluorine-free coating approach for oil and water repellent paper substrates using blends of poly(vinyl alcohol) and chitosan-graft-polydimethylsiloxane copolymer. The obtained coated paper showed good water-resistance, as evidenced by its low Cobb60 values of ~20 ± 2.1 g/m² and high water contact angles of 119 ± 6.3 °. The kit rating of the coated paper was 7.6/12, indicating decent grease-resistant properties as compared to the kit value of 0/12 for the uncoated paper. The coated paper is also repulpable as demonstrated by the complete washing off the coating from the coated paper. Giving the cost-effective nature of the coating materials and good water and oil-resistant properties of the coated paper, the approach developed here is commercially viable, and will offer a multitude of environmental benefits such as the elimination of microplastic- and PFAS problems associated with existing paper coatings.     

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.     

The electrostatic self‐assembly of microgels on polymer brushes and its effects on interfacial friction

In this article, a series of monodisperse poly(N‐isopropylacrylamide‐co‐acrylic acid) [P(NIPAm‐AA)] microgels were prepared with different content of acrylic acid (AA) by surfactant‐free emulsion polymerization, and their electrostatic self‐assemble and tribological behavior on polymer brushes were investigated. The ζ‐potential of microgels became more negative with the increase content of AA, which means a stronger hydration capability. For cationic poly[2‐(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes, negative P(NIPAm‐AA) microgels adsorbed on the surfaces of brushes as a result of the electrostatic interaction, and more AA content means stronger absorption ability. However, compared to the polymer brushes, P(NIPAm‐AA)_2:1 and P(NIPAm‐AA)_5:1 microgels possessed the weaker hydration capability, which led to a concomitant increase in friction of interface. In terms of P(NIPAm‐AA)_10:1 microgels, due to the weak adsorption, they could be sheared off easily, leading to the PMETAC brushes swell again, and thus, a lower friction of interface was obtained. Moreover, the tribological behavior of microgels was significantly affected by the pH, especially the P(NIPAm‐AA)_2:1 microgels exhibited good lubrication property in high pH solution due to high hydration of deprotonated carboxylic acid groups. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44215.     

Elastohydrodynamic lubrication analysis of polymer-on-polymer artificial hip joint of CF/PEEK composite

At present, the main frictional components of artificial hip joint (AHJ) are mainly the combinations of hard materials (metal, ceramic) and soft materials (polymer), such as, metal-on-metal (MoM), ceramic-on-ceramic (CoC), metal-on-polymer (MoP), and ceramic-on-polymer (CoP). As a new type of AHJ, the polymer-on-polymer (PoP) combination has gradually begun to be explored and studied. In this paper, PoP AHJ of CF/PEEK composite are studied, and elastohydrodynamic lubrication analysis based on the solution of the Reynolds equation is performed, and the results are compared with the MoM and MoP AHJs. The comparison shows that under the same steady-state condition, the PoP AHJ has better lubrication performance. The influence of the key structural parameters of the CF/PEEK PoP AHJ is also analyzed in this paper, and the results show that the femoral head size and radial clearance have great influence on the thickness and pressure distribution of the lubricating film. The research results in this paper further confirm the application potential of the PoP AHJ, and are helpful to its practical application and structural design.     

Hybrid polymer matrix composite (UHMWPE-HPMC) as solid particle erosion resistant coating for sharp pipe elbows using numerical simulation and experimental analysis

A hybrid polymer matrix composite coating, resistant to solid particle erosion inside sharp elbows, consisting interlocking chains of molecules with the ability to deflect the surface impact stress and to uniformly distribute stresses along the hard-ceramic reinforcement mixture surface was developed. Formulated mixture of ceramic reinforcement particles mixtures (alumina, tungsten carbide, and silicon carbide) with polymer coupling agents; to increase adhesion to the metal surface, led to 600–700 HVN in ternary and 500–550 HVN in binary mixtures. This behavior coincides with high shear strength of 70–76 MPa, Young's and shear modulus of 8.86 and 13.4 GPa in ternary 15%Al₂O₃-5%WC-10%SiC, respectively. The low erosion weight loss of 0.1% and small coefficient of friction near 0.18 indicates the significant wear resistance of the ternary sample. The electron microscopic micrographs determined the dense smooth coating surfaces with adhesive interfaces with the substrate.     

Tribological and corrosion performance of epoxy resin composite coatings reinforced with graphene oxide and fly ash cenospheres

In this work, a novel graphene oxide (GO)-fly ash cenospheres (FACs) hybrid fillers was introduced to improve the wear and corrosive resistance of epoxy resin (ER) composite coatings. The tribological behavior and the corrosion performance of three kinds of coatings (pure ER, GO/ER and GO-FACs/ER coatings) were studied and the reinforced mechanisms of coatings filled by different fillers were analyzed. The friction coefficient and wear rate of the ER coatings were decreased with the addition of GO-FACs hybrids. The scanning electron microscope images showed that the dispersibility and compatibility of GO-FACs hybrids were effectively improved compared with that of GO sheet. The water contact angle examination indicated that the hydrophobicity of the GO-FACs/ER coatings increased. The electrochemical impedance spectroscopy (EIS) results demonstrated that the GO-FACs/ER coatings have better anticorrosion performance compared with the pure ER coatings and the GO/ER coatings. The hydrophobic surface and the well dispersed fillers constitute the dual barrier to resist the corrosion medium.     

Preventing thermal degradation of PVC insulation by mixtures of cross-linking agents and antioxidants

Poly(vinyl chloride) (PVC) is widely used—in spite of HCl formed from it at elevated temperatures. PVC wire and cable insulation has poor thermal stability, causing the plasticizer to separate from the PVC chains and produce an oily residue, lowering the tensile elongation at break and thus increasing brittleness. One uses cross-linking agents and antioxidants, as well as mixtures of both, to improve the thermal stability of the plasticizer and tensile properties of PVC after thermal exposure. We performed tensile tests, tribological tests, profilometry, scanning electron microscopy (SEM), and water absorption determination before and after thermal exposure at 136 °C for 1 week. After adding the agents, elongation at break increased by 10 to 20% while the wear rate and water absorption were lower than for the control sample. Less voids are seen in the SEM images after adding these two kinds of agents. The thermal resistance of the PVC cable insulation is best enhanced by combinations of cross-linking agents and antioxidants. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48816.     

Graphene oxide/poly(ethylene glycol)/chitosan gel with slow‐release lubrication applied on textured surface

Graphene oxide/poly(ethylene glycol) (GO/PEG) composites that have biocompatibility and biodegradability properties have been prepared to improve the lubrication of artificial joints, but they would be rapidly degraded and absorbed by the human body if injected. To prolong the lubrication effect, GO/PEG lubricants were mixed into a chitosan (CS) sol, and then the GO/PEG/CS sol was added to the dimpled texture of a Co‐Cr‐Mo alloy and transformed into a gel to slowly release GO/PEG lubricants. The results of friction experiments showed that the average friction coefficient of the slow‐release solution is below 0.025, especially when under pressure, and the gel in the texture also has a good lubrication effect. Meanwhile, the FTIR and UV–vis of the slow‐release solution indicated that it is likely to contain GO, PEG, and CS, which are associated with each other via hydrogen bonds and may form a particular structure, leading to good slow‐release lubrication. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45818.     

Improving the antifouling properties of polypropylene surfaces by melt blending with polyethylene glycol diblock copolymers

Protein‐resistant polyethylene‐block‐poly(ethylene glycol) (PE‐b‐PEG) copolymers of different molecular weights at various concentrations were compounded by melt blending with polypropylene (PP) polymers in order to enhance their antifouling properties. Phase separation of the PE‐b‐PEG copolymer and its migration to the surface of the PP blend, was confirmed by attenuated total reflectance–Fourier transform infrared, X‐ray photoelectron spectroscopy, and static water contact angle measurements. Enrichment of PEG chains at the surface of the blends increased with increasing PE‐b‐PEG copolymer concentration and molecular weight. The PP blends compounded with PE‐b‐PEG copolymer having the lowest molecular weight (875 g mol^?1), at the lowest concentration (1 wt %), gave the lowest bovine serum protein adsorption (30% less) compared to that of neat PP. At higher concentrations (5 and 10 wt %), and higher molecular weights (920, 1400, and 2250 g mol^?1), the PE‐b‐PEG copolymers leached‐out resulting in protein adsorption comparable to that of neat PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46122.     

SiAlON–epoxy nanocomposite coatings: Corrosion and wear behavior

In this study, epoxy powder as a matrix was combined with different contents of silicon–aluminum–oxygen–nitrogen (SiAlON) nanoparticles using a planetary ball mill. Pure epoxy and nanocomposite powders were applied on the surface of plain carbon steel components by the electrostatic spraying method. Curing of the coatings was done in an oven or microwave for the appropriate time. The coating structure and morphology of the SiAlON nanoparticles were studied by scanning electron microscopy and transmission electron microscopy, respectively. The corrosion properties of the coatings were assessed by immersion, Tafel polarization, and electrochemical impedance spectroscopy tests in 3.5% NaCl solution. The results show that addition of 10 wt % SiAlON nanoparticles markedly increases the corrosion resistance of epoxy coatings. Thus, it can be inferred that the corrosion rate of these coatings is 15 to 18 times lower than that of pure epoxy samples and 8 to 11 times lower than coatings with 20 wt % SiAlON. The higher corrosion resistance of nanocomposite coatings can be attributed to the barrier properties of SiAlON nanoparticles. The tribological performance of the coatings was studied with the pin‐on‐disk test. The results of wear testing show that the samples containing 10 wt % SiAlON provide about five times more wear resistance than pure ones and about two times more than coatings with 20 wt % SiAlON. However, the coefficient of friction for nanocomposite coatings is reduced about 50% compared to the pure sample. Also, the curing process in either regime (oven or microwave) has the same effect on the corrosion and wear properties, and the coatings are completely crosslinked. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43855.     

Study on the friction properties of nanocopper oxide/fluorosilicone rubber

In order to study the effect of nanocopper oxide (n-CuO) on the friction properties of fluorosilicone rubber (FVMQ), the mechanical blending method was used by adding n-CuO in preparation of FVMQ. Characterization of scanning electron microscopy, X-ray diffraction analysis, energy dispersive spectroscopy, and so on were utilized for studying the mechanism of n-CuO in FVMQ. The experimental test on tensile, tear, and friction performance were performed on n-CuO/FVMQ at both room temperature (RT) and 200°C. In comparison with n-CuO /FVMQ, the wear depth of FVMQ increased by 52.933 and 5.605 μm for RT and 200°C, respectively. Besides, the wear loss of FVMQ increased by 2.9 and 5.3 mg, respectively. The results show that for both at RT or 200°C, the addition of n-CuO changes the friction mechanism of FVMQ. The friction coefficient and wear loss of FVMQ are effectively reduced, so that the friction property of rubber matrix is significantly enhanced. In addition, the tearing property of FVMQ is improved by adding n-CuO to change the crosslinking density of FVMQ.     

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.     

Tribological properties of the polyacrylate/PTFE coating modified by POSS in the space environment

The irradiation conditions in the low earth orbit (LEO) severely inhibit the development of polymeric materials for solid lubrication coatings used on the external surfaces of spacecraft. To solve the problem, octavinyl polyhedral oligomeric silsesquioxanes (OvPOSS) were covalently grafted onto poly(methyl/butyl methacrylate) composites (PMB). The results showed that the appropriate incorporation of OvPOSS (10 wt %) significantly reduced the friction coefficient and improved the wear resistance of the OvPOSS/PMB composite coatings. Furthermore, the impact of OvPOSS on the tribological properties of PMB/polytetrafluoroethylene (PTFE) lubrication coatings in the space environment was investigated. In particular, the degradations, mass losses, surface morphologies, and chemical compositions of POSS/PMB/PTEF composite coatings were characterized under ultraviolet (UV), electric irradiation (EI), and atomic oxygen (AO). The results indicated that OvPOSS provides numerous Si O Si bonds in the polymer matrix that improve the resistance to UV and EI. Besides, a passivating SiO₂ layer was formed to prevent further erosion and degradation of the underlying PMB and PTFE components during AO irradiation. Particularly, the wear resistance of OvPOSS/PMB/PTFE coatings under AO irradiation increased significantly compared with the pristine PMB/PTFE coating. Overall, our results indicate that POSS-containing composites are a good prospective material for space application in the LEO. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48730.     

Effects of ultraviolet aging on the surface properties and tribological performance of polyformaldehyde

Ultraviolet aging restricts the outdoor application of polyformaldehyde as the friction material. In this work, ultraviolet aging processes were applied to polyformaldehyde specimens and effects of the processes on their surface properties and tribological performance were evaluated. Surface morphology results show that a thin layer of white powder and micro‐cracks with further ramifications in other directions were observed on the surfaces after 400 h of ultraviolet exposure, while it is not detectable for the unaged specimens. Analysis of aging surface indicates that ultraviolet leads to the increase of micro‐cracks and the degree of crystallinity. All the tribological test results demonstrate that with the extension of ultraviolet aging time, (i) the process of damage on polyformaldehyde surface induced by ultraviolet aging is first slowly and faster afterward; (ii) the fluctuation of the friction coefficients of polyformaldehyde/GCr15 rubbing pairs increases; and (iii) the wear rate of polyformaldehyde markedly increase after aging test 400 h. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44684.     

Anisotropy of poly(lactic acid)/carbon fiber composites prepared by fused deposition modeling

It is well known that 3D printed parts prepared by fused deposition modeling (FDM) exhibit large anisotropy of mechanical properties. In this article, poly(lactic acid; PLA)/carbon fiber (CF) composites with different built orientations (X, Y, Z) were prepared by FDM. The effects of printing temperature, speed, orientations, and layer thickness on the mechanical properties of the composites were systematically investigated. The mechanical properties of PLA/CF composites show more significant anisotropy. The orientation of the fibers along the printing direction is displayed by scanning electron microscopy. Printing parameters bring almost no effect on mechanical properties of the X-construct oriented specimen, and bring obvious effect on those of the Y-construct oriented specimen and Z-construct oriented specimen. According to the analysis, carbon fiber can amplify this anisotropy from layer fashion, and the key factors from printing parameters are porosity and bond strength between fuses. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48786.     

Photoactive mussels inspired polymer coatings: Preparation and antibacterial activity

In this article we report on the facile preparation of photoactive antibacterial mussel inspired polymer coatings deposited on a stainless steel (SS) substrate from water based precursors. The coating is prepared by the sequential deposition of aqueous based solutions of an anchoring layer based on bio-inspired glue, a cationic polymer bearing pendent catechols, a nanogel decorated by ortho-quinones and a photosensitizer of the aminoacridine type. This latter is grafted to the coating by reaction of its amino group with the o-quinone of the deposited nanogel. The deposition of all layers is followed in-line by Quartz crystal microbalance coupled with dissipation (QCM-D) and AFM shows that the thin polymer film repeated the roughness of the SS substrate. The prepared coatings show good mechanical properties applying nanoindentation techniques. The established antibacterial activity of the prepared photoactive polymer coatings on SS against Gram-negative E. coli strain demonstrate their potential as a power tool for medical applications.     

Synthetic scheme to increase the abrasion resistance of waterborne polyurethane–urea by controlling micro-phase separation

As an environmental-friendly coating material in industry, waterborne polyurethane–urea (WPU) is still not comparable with solvent-based polyurethane (SPU) in mechanical properties, due to the hydrophilic chain-extender. Herein, a synthetic scheme to increase the abrasion resistance of WPU with ether diol, and conventional hydrophilic chain-extender (DMBA, 2,2-bis[hydroxymethyl]butanoic acid) is revealed. This study discuss the degree of micro-phase separation (DPS) with toughness, elongation, abrasion resistance, and compared with the WPU contain various types of diol, such as esters, ether and carbonates, and the ether-based SPU. From the results, the major factor that affect to the abrasion properties of WPU is DPS, which is highly depend on the chemical structure of diol, and hard segment content. WPU film achieve higher toughness with ether-based diol with higher DPS, and better abrasion resistance than SPU. This study demonstrate a strategy for the composition designing, and the synthesis of high-abrasion resistance WPU by controlling the micro-phase separation, and content of DMBA without any inorganic fillers.