PTFE Coatings Research Articles

Fabrication and Tribology Properties of PTFE-Coated Cemented Carbide Under Dry Friction Conditions

PTFE coatings were deposited on YT15 carbide substrates using spray technology. A series of examinations were conducted, including the use of surface and cross-section micrographs to analyze the structural integrity of the coatings. The surface roughness, the adhesion force between the PTFE coatings and the carbide substrate, and the micro-hardness of the coated carbide were also evaluated. Additionally, the friction and wear behaviors were assessed through dry sliding friction tests against WC/Co balls. The test results indicated that while the PTFE-coated carbide exhibited a rougher surface and reduced micro-hardness, it also demonstrated a significant reduction in surface friction and adhesive wear. These findings suggest that the PTFE coatings enhance the overall wear resistance of the carbides. The lower surface hardness and shear strength of the coatings influenced the friction performance, leading to specific wear failure mechanisms, such as abrasion wear, coating delamination, and flaking. Overall, the deposition of PTFE coatings on carbide substrates presents a promising strategy to enhance their friction and wear performance. This approach not only improves the durability of carbide materials but also offers potential applications in industries where reduced friction and wear are critical for performance.

Rubber-like PTFE Thin Coatings Deposited by Pulsed Electron Beam Deposition (PED) Method.

PTFE coatings were manufactured using the pulsed electron beam deposition (PED) technique and deposited on Si substrates. The deposition was carried out at constant parameters: temperature 24 °C, discharge voltages 12 kV, and 5000 electron pulses with a pulse frequency of 5 Hz. Nitrogen was used as the background gas. The gas pressure varied from 3 to 11 mTorr. The coating adhesion was evaluated using micro scratch testing and the residual scratch morphology was characterized by atomic force microscopy. Detailed studies of the chemical and physical structure were conducted using infrared spectroscopy and X-ray diffraction. These analyses were then correlated with the mechanical response of the coatings observed during the scratch tests. Drawing upon a review of the literature concerning energetic beam interactions with PTFE material, hypotheses were posed to explain why only specific conditions of the PED process yielded PTFE coatings with rubber-like properties.

Enhancing cavitation erosion resistance of VC+TiC coatings with PTFE in marine environments via lasso regression optimization

This research explores the mechanical properties and erosion mechanisms of SS316, VC+TiC, and PTFE coatings to study cavitation erosion resistance. Microhardness analysis revealed that VC+TiC showed the highest resilience due to its hardness, while PTFE, despite lower hardness, displayed potential with formulation adjustments. Lasso Regression models effectively predicted mass loss under various testing conditions, indicating strong relationships between independent variables and erosion responses. Scanning Electron Microscopy (SEM) analysis uncovered distinct erosion mechanisms for each coating, with SS316 showing plastic deformation, VC+TiC exhibiting crater formation, and PTFE displaying torn splats. The development of superhydrophobic surfaces from VC+TiC and PTFE coatings offers promising applications in mitigating cavitation erosion, providing valuable material-specific insights into this phenomenon.

Fabrication of Superhydrophobic Coatings by Using Spraying and Analysis of Their Anti-Icing Properties

Ice accumulation on glass insulators is likely to cause faults such as flashover, tripping and power failure, which interfere with the normal operation of the power grid. Accordingly, superhydrophobic coatings with great anti-icing potential have received much attention. In this study, three superhydrophobic coatings (PTFE, Al2O3 and SiO2) were successfully prepared on glass surfaces by using one-step spraying. The microscopic morphology, wettability, anti-icing and anti-glaze icing properties of the superhydrophobic coatings were comparatively analyzed. The results indicated that the PTFE coating had a densely distributed rough structure, showing a contact angle of 165.5° and a sliding angle of 3.1°. The water droplets on the surface could rebound five times. Compared with the Al2O3 and SiO2 coatings, the anti-icing performance of the PTFE coating was significantly improved. The freezing time was far more than 16 times that of glass (4898.7 s), and the ice adhesion strength was 9 times lower than that of glass (27.5 kPa). The glaze icing test in the artificial climate chamber showed that the icing weight of the PTFE coating was 1.38 g, which was about 32% lower than that of the glass. In addition, the icing/melting and abrasion cycles destroyed the low-surface-energy substances and nanostructures on the surface, leading to the degradation of the anti-icing durability of the PTFE coatings. However, the PTFE coating still maintained excellent hydrophobicity and anti-icing properties after UV irradiation for up to 624 h. The superhydrophobic coatings prepared in this work have promising development prospects and offer experimental guidance for the application of anti-icing coatings on glass insulators.

Hydrophobic, anti-ice, wear- and corrosion-resistant C-(Ti)-PTFE coatings on Ti obtained by electrospark deposition using PTFE-impregnated graphite electrode

Titanium parts for marine and coastal infrastructure require protection from aggressive environment that lead to increased wear, corrosion and icing. To address these important issues, graphite-based coatings reinforced with titanium carbide and containing PTFE have been developed. Composite coatings were obtained by vacuum electrospark deposition using either a pure graphite (G) electrode or a porous graphite electrode impregnated with PTFE powder using both cathodic and anodic polarity. At cathodic polarity, the upper coating layer consists of mixtures of G + TiC (G electrode) and G + TiC + CF2 (G / PTFE electrode) phases. When changing polarity, coatings are obtained based on mixtures of Ti + TiC (G electrode) and Ti + TiF3 + −CF − (G + PTFE electrode) phases with a small amount of amorphous carbon on the surface. The as-deposited coatings were tested under conditions of simultaneous wear and corrosion in artificial seawater. The combination of G and TiC resulted in a hydrophobic (water contact angle (WCA) of 99°) corrosion-resistant (open circle potential (OCP) of 0.2 V versus −0.8 V for Ti) coating with a low coefficient of friction (0.1) and relatively low wear (2 × 10−5 mm3/Nm). The addition of PTFE increases hydrophobicity (WCA = 130°), significantly increases the freezing time of a water drop from 23 to 65 s, and reduces the ice adhesion strength from 0.52 to 0.38 MPa while maintaining tribocorrosion characteristics. The results obtained are important for the further development of wear-, corrosion-resistant, and anti-ice protective coatings.

Analysis of Wear Phenomena Produced by Erosion with Abrasive Particles against Fluoropolymeric Coatings.

To date, PTFE, PFA, and FEP-based fluoropolymer coatings have proven unbeatable in many services due to their excellent chemical inertness, very low wettability, thermal resistance, high non-stick properties, and good applicability. In use, these coatings usually suffer service cycles with consequent deterioration, and it is of great interest to determine the intensity and type of wear caused in addition to the deterioration that occurs in their properties. In this work, the response of three polymeric coatings of interest applied to aluminum substrates, after being subjected to the action of abrasive particles of aluminum corundum, glass, and plastic projected under pressure, has been studied. During the application of a given wear cycle, the hardness, surface roughness, surface texture, and thickness of the coating have been measured, in addition to the slip angle and surface transmittance to analyze the evolution of each type of coating. The results allowed a concise evaluation of the performance of three fluoropolymeric coatings of great interest, differentiating the induced erosive wear phenomena and contributing complete information to facilitate the correct selection for users with practical application purposes and as a basis for future research work focused on advancements in this field.

Paper-based ZnO ultraviolet photodetector with enhanced stability and detectivity by PTFE coatings

Paper-based ZnO ultraviolet photodetector with enhanced stability and detectivity by PTFE coatings

Fabrication of stable and versatile superhydrophobic PTFE coating by simple electrodeposition on metal surface

Superhydrophobic coating has attracted increasing attention due to its exceptional performance, yet fabricating a stable superhydrophobic coating on metal surfaces remains challenging. In this study, a superhydrophobic PTFE coating on the stainless-steel surface with a high stability and versatile performance was fabricated by the simple electrodeposition and high-temperature curing. This approach allowed the superhydrophobic PTFE coating on any metal surfaces to be fabricated in a few minutes. It was found that the addition of water in the solution played a key role in the coating stability, which was speculated that a stable structure of MgO-MgCl2-H2O formed as an adhesive underlayer for the PTFE coating. Furthermore, the surface morphology and hydrophobicity of the coating could be controlled by the bubbles formation on samples surfaces by varying water contents during the electrodeposition. The coating exhibited a maximum water contact angle of 158 ± 2°, and the performance tests indicated that the superhydrophobic PTFE coating exhibits the outstanding stability, self-cleaning property, anti-condensation, corrosion resistance and anti-scale ability. The scale inhibiting rate of the coated surface was up to 80.75 % after 12-hour immersion in the CaCO3 solution. The optimized parameters for the electrodeposition route are highly desirable for the development of the advanced superhydrophobic PTFE coatings for various applications.

Organic/polymeric antibiofilm coatings for surface modification of medical devices

Infections arising from implanted medical devices cause considerable challenges for medicinal specialists and patients. These infections usually arise from the accumulation of biofilm on the device, which is difficult to eliminate and typically needs antibiotic treatment and removal of the device. In this regard, efforts have been made to design the devices or functional polymer coatings that have anti-fouling or antimicrobial properties to limit the formation of biofilm and following infection by preventing or killing bacteria near the device surface or by restricting the initial binding of proteins and bacteria. Herein, the extent of device-related infections, the biofilm formation mechanism, the role of biofilm construction in human pathogenesis, and the key strategies for the progress of antibiofilm coatings are discussed. The most promising antibiofilm coating approaches, comprising the surface topography modifications as well as the PEG, hydrogel, polyzwitterion, Benign bacterial biofilm, enzyme, cationic polymer, PTFE, and smart coatings, etc., were also summarized to avoid the biofilm formation and bacteria proliferation via controlling the antibiofilm mechanisms.

Hydrophobicity, water moisture transfer and breathability of PTFE-coated viscose fabrics prepared by electrospraying technology and sintering process

Coating of PTFE on the fabrics is one facial method to obtain the hydrophobic/superhydrophobic property. However, the breathability of the PTFE-coated fabrics prepared by traditional methods (e.g., sputtering) is significantly affected. Electrospraying technology was able to create the pure PTFE coating layer on any substrates and the following sintering process is necessary to obtain the hydrophobic/superhydrophobic property. In this work, the PTFE-coated viscose fabrics were firstly prepared via electrospraying technology and then stabilized after 10 min sintering process with different temperatures ranging from 150 °C to 210 °C. The morphology, hydrophobicity, breathability, and water moisture transfer of the PTFE-coated viscose fabrics as well as the chemical compatibility between PTFE microparticles and viscose fabric were investigated. With increased sintering temperature, the PTFE coating layer on the viscose fabric became physically denser, which corresponded to the reduced breathability. Only when sintering temperature was equal to or higher than 190 °C, the stable hydrophobicity of PTFE-coated viscose fabric was found. When sintering temperature was increased from 190 °C to 210 °C, the contact angle hysteresis of the hydrophobic PTFE-coated viscose fabric decreased from 9.2° to 3.4° and the one-way water moisture transfer was enhanced.

An experimental study on the detrimental effects of deicing fluids on the performance of icephobic coatings for aircraft icing mitigation

An experimental investigation was conducted to examine the detrimental effects induced by deicing fluids used for aircraft ground deicing on the performance of icephobic coatings for aircraft inflight icing mitigation. Commonly used superhydrophobic surface (SHS) and polytetrafluoroethylene (PTFE or Teflon®) were selected as the representative icephobic coatings in the present study. Test plates and airfoil/wing models coated with SHS and PTFE coatings were immersed into two kinds of deicing fluids (i.e., Type-I and Type-IV deicing fluids) to simulate the scenario of spraying deicing fluids onto aircraft surfaces for ground deicing at airports. Then, the deicing fluids were drained off from the icephobic coated surfaces to imitate their shedding off from airframe surfaces after aircraft takeoff. Variations of the surface wettability and ice adhesion characteristics on the icephobic coated surfaces were examined before and after immersion into the deicing fluids. Advanced diagnostic systems, including scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDS), were used to reveal the changes in the surface topology and chemistry characteristics to elucidate the underlying physical and chemical “contaminations” induced by the deicing fluids to the icephobic coatings. An icing tunnel testing campaign was also conducted to demonstrate the detrimental effects induced by the contaminations of the deicing fluids on the dynamic ice accretion processes on icephobic coated airfoil/wing models. It was revealed that spraying Type-1 deicing fluid for ground deicing would have only very minor (i.e., to the SHS) or no effect (i.e., to the PTFE) on the performance of the icephobic coatings. However, spraying Type-IV deicing fluid onto airframe surfaces would degrade the performance of the icephobic coatings significantly and totally deteriorate the effectiveness of the icephobic coatings for aircraft inflight icing mitigation.

A study of the wear damage of a PTFE coating: The effects of temperature and environment on its mechanical and tribological properties

In this study, a methodology was set up to obtain a measure of the durability of PTFE coatings. Tribological tests to study the effect of both temperature (from 25 °C to 180 °C) and environment (dry, in water, and in oil) on the mechanical and tribological properties of PTFE were carried out. Interactions between the effects of temperature and environment were also investigated. As expected, the experimental results showed that the wear resistance of PTFE significantly decreases with an increase in temperature. Measurements of the mechanical properties of the coatings by nanoindentation at different temperatures confirmed a change in the mechanical properties of the PTFE coatings with increasing temperature. The tribological properties were evaluated through the evolution of the coefficient of friction as a function of temperature and the morphological study of wear debris by scanning electron microscopy (SEM). In addition, the coefficient of friction exhibits no significant difference as a function of the environment. Examination of transfer film formed under various conditions helped us understand the various wear mechanisms occurring during these tests and indicated that the formation of an adhered and persistent transfer film was directly linked to the wear performance of the PTFE coating. In particular, higher wear observed in the oil environment could be attributed to a different tribological behavior of the transfer film on the abrasive counterface, namely poor adhesion, resulting in an ease of removal and replenishment with successive rubbing cycles.

Improved Load-Bearing Capacity and Tribological Properties of PTFE Coatings Induced by Surface Texturing and the Addition of GO

The PTFE coatings with excellent corrosion-resistance and lubrication properties often stop functioning under high load conditions. In this study, a composite coating of PTFE filled with silane coupling agent modified graphene oxide (mGO/PTFE) was prepared by a simple spin-coating process on textured stainless steel (SS) substrate to protect the substrate from failure under high load rubbing. The grafting reaction between GO and silane coupling agent was analyzed by FTIR, Raman, XRD, TGA, and XPS. The morphologies and tribological properties of the mGO/PTFE coatings on the untextured and textured SS substrates were characterized by SEM and UMT tribometer. The results showed that GO surfaces were successfully grafted by silane coupling agent, resulting in that the composite coating of mGO/PTFE was denser than the pure PTFE coating. The tribo-test results confirmed that the groove texture processed by laser surface texture technology greatly improved the load-bearing capacity and anti-wear life of the PTFE coatings. The PTFE coating on the untextured SS surface fails within half an hour of rubbing at the applied load of 10 N, while the one on the groove-textured surface can maintain low and stable friction coefficient for a long time even under the load of 50 N. In addition, the results showed that the loading of mGO further improve the friction reduction and wear resistance of the PTFE coating on the textured SS surface. The wear scar width and the friction coefficient are significantly reduced by 70% and 30%, respectively, as the PTFE coating was filled by 1.0 wt% mGO. Finally, the mechanisms for achieving outstanding properties of the composite coating of mGO/PTFE on the textured SS surface were illustrated by analyzing the wear surfaces of the coating and the counterpart balls by SEM and EDS.

Nucleation, first growth stages and structure of nano-sized polymer coatings deposited from active gas phase

This paper presents an analysis of the structural-morphological, kinetic patterns of the initial growth stages of single-component and composite (polymer-polymer and metal-polymer) nanoscale coatings based on the products of electron-beam dispersion of polymers. The main features of the deposition processes from the active gas phase occurring on the substrate surface and the established size dependences of the structure and molecular composition are explained on the basis of the adsorption-polymerization mechanism for the formation of coatings. It was established that among the most important features of the deposition process from the active gas phase is the simultaneous flow of polymerization and structure formation of adsorbed molecular fragments of the polymer under the conditions of exposure of the active components of the plasma, dispersive filler, and the substrate surface. This feature has a decisive influence on the nucleation of polymer particles, the molecular structure and morphology of nanoscale layers, as well as the dependence of their properties on thickness. Using the PTFE and PE coatings, it was shown that the orientation and ordering of the formed layers changes during the coating growth: at the initial stages of deposition in the layer up to 150 nm, the molecules are oriented predominantly parallel, and in thicker layers due to the bulk structure formation perpendicularly substrate surface. When deposited on the surface subjected to plasma treatment, the growth rate of the formed coating at the initial stages of growth increases by more than 5 times. At the same time, such layers contain predominantly linear molecules with a relatively lower molecular weight. The introduction of micro-and nanoscale polymer coatings in the process of their growth of the formed silver or copper nanoclusters leads to the formation of highly oriented, continuous, highly dispersed layers already at the initial stages of growth. The orientation of the macromolecules of the matrix with the maintenance of Ag or Cu nanoclusters in it has parameters characteristic of single-component coatings. In PTFE+Mo coatings, a linear dependence of molecular orientation on the layer thickness appears. In composite coatings containing silver nanoclusters, the effect of selective plasmon absorption was established.

Friction behavior of PTFE-coated Si3N4/TiC ceramics fabricated by spray technique under dry friction

PTFE coatings were deposited on the Si3N4/TiC ceramic substrate by using spray technology. The surface and cross-section micrographs, adhesive force of coatings with substrate, surface roughness and micro-hardness of the coated ceramics were examined. The friction and wear behaviors of ceramic samples with and without coatings were investigated through carrying out dry sliding friction tests against WC/Co ball. The test results indicated that the coated ceramics exhibited rougher surface and lower micro-hardness, and the PTFE coatings can significantly reduce the surface friction and adhesive wear of ceramics. The friction performance of PTFE-coated sample was affected by applied load due to the lower surface hardness and shear strength of coatings, and the main wear failure mechanisms were abrasion wear, coating delamination and flaking. It can be considered that deposition of PTFE coatings is a promising approach to improve the friction and wear behavior of ceramic substrate.

Electrophoretic deposition of materials using lithocholic acid as a dispersant

Lithocholic acid (LCA) was used as an anionic biosurfactant for the dispersion and electrophoretic deposition (EPD) of electrically neutral materials, such as poly(tetrafluoroethylene) (PTFE) and diamond from suspensions in ethanol. The steroid structure of LCA facilitated its adsorption on PTFE and diamond, which allowed for particle charging and deposition by anodic EPD. LCA was used as a co-dispersant for the fabrication of composite PTFE-diamond coatings. PTFE coatings provided corrosion protection of stainless steel in 3% NaCl solutions. Potentiodynamic studies revealed increased corrosion potential and decreased corrosion current of coated steel in comparison with uncoated steel. Impedance spectroscopy studies and analysis of the equivalent circuit showed that PTFE coating acted a barrier for electrolyte diffusion. LCA is a promising surfactant for EPD of other hydrophobic electrically neutral materials.

Polysilazane‐Based Coatings with Anti‐Adherent Properties for Easy Release of Plastics and Composites from Metal Molds

AbstractPolysilazanes are excellent coating materials, because of their self‐crosslinking in air at low temperatures, high chemical and thermal stability, elevated hardness, and excellent adhesion to many different substrates. Therefore, coatings of two chemically different polysilazanes (crosslinked Durazane 1800 (HTTS)/perhydropolysilazane (PHPS)) are deposited by either dip or spray coating and crosslinked at 200 or 300 °C in air to investigate the chemical composition, surface energy, and coating adhesion in dependency on the precursor type and crosslinking temperature. The silazane HTTS possesses a higher amount of nonpolar organic groups resulting in a lower surface free energy. The anti‐adherence properties are investigated by using a phenolic resin via pull‐off adhesion, which is slightly reduced from 13 MPa for uncoated aluminum to less than 10 MPa for HTTS coated substrates. The addition of different amounts of poly(tetrafluoroethylene) (PTFE) particles causes a remarkable reduction of the surface free energy leading to a strongly reduced pull‐off adhesion of less than 4 MPa of the phenolic resin from the HTTS/PTFE coated substrates. The anti‐adherent properties remain even after repeated pull‐off tests. Because of the excellent properties, the HTTS/PTFE coatings are a very suitable system for easy mold release of plastic parts from metal molds and to replace commercial nonstick PTFE coatings.

Innovative Perfluoropolyether‐Functionalized Gas Diffusion Layers with Enhanced Performance in Polymer Electrolyte Membrane Fuel Cells

AbstractIn this work, perfluoropolyether (PFPE) functionalization was used as hydrophizing treatment for gas diffusion layers (GDLs) in polymer electrolyte membrane fuel cells (PEMFCs), instead of standard PTFE coatings, aiming to enhance the hydrophobicity of the gas diffusion media and to reduce the mass transfer limitations in the final device. Carbon cloth diffusion layers and carbon black were functionalized by decomposition of a PFPE peroxide. PFPE‐functionalized carbon black was employed in the preparation of an ink suitable for obtaining microporous layers (MPLs) by deposition onto macroporous backing layers. Dual‐layer gas diffusion media showing superhydrophobic behavior due to different hydrophobizing treatments were compared with conventional PTFE‐based materials, by testing in a single PEMFC working at two different temperatures and at low and high relative humidity conditions. Such tests demonstrated improved performances over conventional GDLs for pure PFPE‐based samples in terms of both overall electrical performance and reduced diffusive limitations in high current density conditions. The maximum output power achieved with the novel PFPE‐based compounds was 460 mW cm−2 at 80 °C and relative humidity (RH) 100% while the best improvement (10%) with respect to conventional GDLs was realized at 80 °C and RH 60%.

Effect of PEEK and PTFE coatings in fatigue performance of dental implant retaining screw joint: An in vitro study

ObjectivesMechanical complications play a key role in failure of dental implants. Retaining screw loosening was one of the most commonly encountered. This study investigated the effect of PEEK and PTFE coatings on dental implant screw thread joint. MethodsRetaining screws were coated with PEEK and PTFE in thickness of 30 μm and 60 μm. Friction coefficient and clamping force of screw thread pair were measured, single load-to-fracture (SLF) test and dynamic fatigue life (DFL) test were done to test the stability of implant thread connection. After that, screw fracture mode and erosion morphology of screw surface and implant internal thread were observed. ResultsThe results showed that both PEEK and PTFE coatings could reduce friction coefficient, and consequently increase clamping force, especially PTFE coatings. PEEK coatings had no significant effect on fracture load, while 30 μm PTFE coating reduced fracture load. PEEK coatings also elongated fatigue life and improved the anti-loosening property under dynamic load, while 30 μm PTFE coating shortened fatigue life. Most of the screw fracture happened at the first thread of the retaining screws. The fracture-end of PEEK coated screws were loosed and could easily remove, but fracture-end of PTFE screws could not. Internal thread observation showed that both PEEK and PTFE coatings could reduce wear of implant internal thread. ConclusionPEEK coatings could effectively improve the stability of implant threaded connection, and reduce wear of implant internal thread. PEEK coating may be a suitable way to prevent screw loosening.

Microhardness and Nano-hardness Measurement of Composite Coatings Applied to Aluminium Substrate

In recent years, significant success has been achieved in surface treatment research, particularly in the field of physics, which deals with the surface properties of metals and their alloys, as well as new methods of coating preparation and thin films. These coatings and layers can modify material properties, i.e. increase oxidation and corrosion resistance, and improve frictional surface characteristics and other physical properties (e.g. electronics and optics). This article focuses on the mechanical properties of the coating, in particular on the hardness of composite PTFE coatings with WC micro and nano particles. In the experiment, samples of different concentrations of WC particles in the PTFE matrix were prepared, followed by a Vickers and Nanoindentation test. The difficulty in measuring the hardness of these layers is their small thickness. It is therefore difficult to measure the hardness by conventional methods, for example, Brinell or Vickers. The applicability of the individual methods (according to Vickers, nanoindentation test) we have experimentally verified and drawn the relevant conclusions and recommendations. Part of the contribution is also SEM documentation of created coatings. An important parameter is the coating technology itself when making these composite coatings. The technology can influence the distribution of particles in the matrix, which results in the homogeneity of the coating and the associated mechanical properties or tribological properties.