Polytetrafluoroethylene Coatings Research Articles

Effect of Polytetrafluoroethylene Coating on Corrosion Wear Properties of AZ31 Magnesium Alloy by Electrophoretic Deposition

In this study, we aim to enhance the corrosion and wear resistance of AZ31 magnesium alloy using electrophoretic deposition (EPD) technology to apply a hydrophobic polytetrafluoroethylene (PTFE) coating. Polyethyleneimine (PEI) serves as a charged dispersant, facilitating uniform deposition of PTFE particles on the alloy surface. Results demonstrate a significant reduction in corrosion current density (from 67.5 μA/cm2 to 5.2 μA/cm2) and improved wear resistance (wear volume decreased from 0.24167 mm3 to 0.00167 mm3) in a 3.5 wt% NaCl solution compared to uncoated alloy. Moreover, the friction coefficient of the coated sample decreases. These findings underscore the potential of nano-PTFE coatings prepared via EPD in enhancing AZ31 magnesium alloy’s corrosion and wear resistance, providing a foundation for future protective coating design and optimization.

Fluorinated Polydopamine Shell Decorated Fillers in Polytetrafluoroethylene Composite for Achieving Highly Reduced Coefficient of Thermal Expansion.

The noticeable difference in the coefficient of thermal expansion (CTE) for polytetrafluoroethylene (PTFE) coatings and copper substrates is a major challenge for thermal debonding of the copper-clad laminate (CCL) in high-frequency communications. Theoretically, ceramic fillers with low CTEs in the coating can effectively reduce the gap, and there remains a trade-off between the dispersibility of fillers and the interfacial interactions with the polymeric matrix. Here, we propose a novel approach to prepare a pentafluorobenzoyl chloride (PFBC)-modified polydopamine (PDA) shell on silica particles by using amidation. Such modified particles perform excellent dispersion and exhibit diminished interfacial gaps in the PTFE matrix, which highly reduces CTE to 77 ppm/°C, accounting for only 48.1% of the neat coating. Moreover, the composite exhibits enhanced mechanical strength and toughness, and consequently suppresses thermal debonding in CCL under high-temperature conditions. Therefore, results present a promising potential for its use in the next-generation CCL of high-frequency communication devices.

The Effect of Electroless Nickel–Polytetrafluoroethylene Coating on the Frictional Properties of Orthodontic Wires

In orthodontic treatment, to achieve efficient tooth movement, it is important to reduce the frictional force between the wire and the bracket, especially the binding friction that occurs when the angle between the wire and the bracket is large. Electroless nickel–polytetrafluoroethylene (Ni-PTFE) coating is a coating technology used to deposit PTFE particles with a low coefficient of friction on the coating surface to provide a low-friction surface for metallic materials. The purpose of this study was to investigate the effect of Ni-PTFE-coated orthodontic wires on the frictional force between brackets. The surface morphology, surface roughness, and frictional properties of Ni-PTFE-coated stainless steel wires and Ni-Ti wires were evaluated. The results demonstrate that the Ni-PTFE coating reduced the frictional force between the orthodontic wires and brackets, despite the increased surface roughness. Even when the angle between the wire and bracket was increased, assuming binding friction, the frictional force was reduced by the Ni-PTFE coating. This suggests that the friction between the wire and the bracket was suppressed by the PTFE particles deposited on the wire surface in contact with the bracket.

Triboelectric behaviors mechanism of continuous rotary friction pairs in liquid lubrication and its potential application

Liquid-solid triboelectric behaviors often involve varied liquid-solid and gas-liquid interfaces. However, applications submerged in lubricants haven not been extensively studied. This paper studies the triboelectric behaviors of continuous rotary friction pairs in liquid lubrication. Triboelectric signals are observed from friction pairs made of graphite and stainless-steel with polytetrafluoroethylene (PTFE) coatings. The mechanism lies in the generated streaming current, with constant circumferential velocities and variable radial velocities induced by the variation of film thickness. Pulse signals of electric outputs of 0.26 V are observed as the film thickness changes suddenly. Further discussions about electrode configurations and sealing mediums are conducted for potential applications in film thickness monitoring of mechanical seals. This work expands theories and applications of conventional liquid-solid triboelectric performances.

Research on baking soda media blasting technology for achieving the cleaner production for stripping PTFE coatings in food utensils remanufacturing process: FEM analysis and economic appraisal

The efficient and environment-friendly stripping of damaged Polytetrafluoroethylene (PTFE) coatings is a committed procedure in the remanufacturing process of food utensils. A green and economically valuable baking soda media blasting technology that could meet remanufacturing roughness standards was proposed in this paper, aiming for avoiding the fluorine-containing solid waste disposal challenges and roughness mismatch of existing stripping methods. The compatibility between baking soda media blasting technology (2.0–3.4 μm) and remanufacturing process roughness standards (2.5–4 μm) was confirmed by comparing the stripping ability with other media (alumina, glass bead and walnut shell) at different blasting angles and pressures, and its efficient stripping process parameters (30° and 0.7 MPa), stripping rate (6.81 mm2/s) and cleanliness (The weight percentage of element F was 0.68%) were determined. Based on finite element model (FEM) analysis, the LSTC-dynamics (LS-DYNA) explicit dynamic solver was used to track the process of single particle eroding the coating to explore the extruding-plowing composite stripping mechanism of the stripping coating using the baking soda media blasting technology at the micro level. The discrete phase model (DPM) was used to track the process of particle beam impacting the coating to verify the variation law between the stripping area and blasting process parameters at the macro level. The PXRD and FT-IR test results of the recovered baking soda media and PTFE coatings showed no impurity peaks, confirming the feasibility of the baking soda media recovery project. Based on the economic appraisal by management accounting evaluation method, the introduction of the baking soda media recovery project could significantly reduce the process chain cost by 136852.62 ¥ per year. As a PTFE coating stripping technology that can completely solve the fluorine-containing solid waste disposal problem, the baking soda media blasting technology owns the advantages of non-pollution and low technical cost, which is expected to realize cleaner production of food utensils remanufacturing process in the future.

Electrophoretic deposition of polytetrafluoroethylene (PTFE) as anti-corrosion coatings

Polytetrafluoroethylene (PTFE) is known as the ‘king of plastics’ because of its excellent resistance for both acid and alkali medium, so the coatings composed of PTFE have an attractive application prospect in the field of corrosion protection. In this work, with a solvent of ethanol containing 0.05 g·L−1 PEI + 0.1 mM nitric acid as the dispersion system, the PTFE coatings were successfully prepared onto the Mg-3Al-1Zn (AZ31) alloy sheets by electrophoretic deposition (EPD) strategy. The morphology of the electrophoretic PTFE coating was further reshaped through a sintering post-treatment at 380 °C in argon atmosphere. In 3.5 wt% NaCl solution, the corrosion current density was remarkably reduced (3.92 × 10−6 A·cm−2 for the bare AZ31 vs 1.54 × 10−9 A·cm−2 for the sintered PTFE coating AZ31), and the charge transfer resistance was significant increased (299.92 Ω·cm2 for the bare AZ31 vs 2.79 × 106 Ω·cm2 for the sintered PTFE coating AZ31), which means the electrophoretic-sintered PTFE coating can significantly improve the corrosion resistance of AZ31 alloys. Moreover, it is also suggested that the electrophoretic-sintered PTFE coating may be a general anti-corrosion strategy for a series of metal materials.

Investigation of the Antifreezing, Skid Resistance, and Waterproof Performances of an Acrylic and Polytetrafluoroethylene Coating for Asphalt Pavement

Freezing on asphalt roads affects driving safety. Spraying salt on roadways pollutes the environment. Mechanical deicing requires significant human and financial resources. This paper proposes a new approach to realize autonomous anti-icing of asphalt pavement, an acrylic/polytetrafluoroethylene coating (APC). The contact angle of a water droplet on the APC surface is 155.392°. Moreover, the freezing time of water droplets on the APC-coated asphalt mixture is 1.5 times longer than that of the uncoated asphalt mixture. Moreover, the skid resistance test results show that APC can increase the road friction coefficient, which is 1.2 times that of ordinary pavement. The water permeability test results confirm that APC can prevent water from penetrating into the road surface. In summary, APC improves the anti-icing performance of asphalt pavements and exhibits excellent anti-slip and waterproof properties.

The Development of New Nanocomposite Polytetrafluoroethylene/Fe2O3 NPs to Prevent Bacterial Contamination in Meat Industry.

The bacterial contamination of cutting boards and other equipment in the meat processing industry is one of the key reasons for reducing the shelf life and consumer properties of products. There are two ways to solve this problem. The first option is to create coatings with increased strength in order to prevent the formation of micro damages that are favorable for bacterial growth. The second possibility is to create materials with antimicrobial properties. The use of polytetrafluoroethylene (PTFE) coatings with the addition of metal oxide nanoparticles will allow to the achieving of both strength and bacteriostatic effects at the same time. In the present study, a new coating based on PTFE and Fe2O3 nanoparticles was developed. Fe2O3 nanoparticles were synthesized by laser ablation in water and transferred into acetone using the developed procedures. An acetone-based colloidal solution was mixed with a PTFE-based varnish. Composites with concentrations of Fe2O3 nanoparticles from 0.001-0.1% were synthesized. We studied the effect of the obtained material on the generation of ROS (hydrogen peroxide and hydroxyl radicals), 8-oxoguanine, and long-lived active forms of proteins. It was found that PTFE did not affect the generation of all the studied compounds, and the addition of Fe2O3 nanoparticles increased the generation of H2O2 and hydroxyl radicals by up to 6 and 7 times, respectively. The generation of 8-oxoguanine and long-lived reactive protein species in the presence of PTFE/Fe2O3 NPs at 0.1% increased by 2 and 3 times, respectively. The bacteriostatic and cytotoxic effects of the developed material were studied. PTFE with the addition of Fe2O3 nanoparticles, at a concentration of 0.001% or more, inhibited the growth of E. coli by 2-5 times compared to the control or PTFE without NPs. At the same time, PTFE, even with the addition of 0.1% Fe2O3 nanoparticles, did not significantly impact the survival of eukaryotic cells. It was assumed that the resulting composite material could be used to cover cutting boards and other polymeric surfaces in the meat processing industry.

Laser surface texturing of both thin polytetrafluoroethylene coatings and stainless steel substrates for improving tribological properties

Hilbert curve patterns were laser-textured on both stainless steel substrates and polytetrafluoroethylene (PTFE) thin coatings by applying 15% and 5% of the 2.3-W full laser power, respectively. The nanomechanical and tribological behavior of both smooth and laser-textured PTFE coatings on both smooth and laser-textured stainless steel substrates were studied. It was found that laser-texturing thin PTFE coatings reduced the hardness of PTFE coatings and prevented the coating from tearing under nanoindenter scratches. Furthermore, laser-texturing on both PTFE coatings and the stainless steel substrate improved the coating wear life 29 times compared to the wear life of the control sample without any laser textures.

Evaluation of corrosion performance of superhydrophobic PTFE and nanosilica coatings

Corrosion protection of metals is of paramount importance in different sectors of industry. One of the emerging techniques to prevent or reduce the damaging effects of this phenomenon is to apply superhydrophobic coatings on the susceptible surfaces. In this study, corrosion protection of steel is investigated by fabricating superhydrophobic coatings, using one-step electrodeposition process of nanosilica hybrid film and spraying process of polytetrafluoroethylene (PTFE) on steel surface and also preparation of micro/nano-composite coatings. The anti-corrosion behavior of the nanosilica hybrid film and PTFE coating with two types of microparticles including Al2O3 powder and glass beads in primer layer, and overcoat layer with and without SiO2 nanoparticles is studied. TOEFL polarization and electrochemical impedance spectroscopy (EIS) tests are conducted on coated steel samples to examine their corrosion performance in 3.5 wt% NaCl solution at a temperature of 25 °C. The results showed that the combination of superhydrophobic properties and low conductivity significantly improves the corrosion resistance. Evaluating the effect of adding SiO2 nanoparticles to the overcoat layer in PTFE coating showed that the nanoparticles improve the corrosion resistance of PTFE coatings by sealing up some defects and pores in the coating. Investigation of corrosion resistance of coatings showed that, the corrosion resistance of nanosilica film is lower than that of PTFE coatings. The best sample obtained in this study, namely the PTFE coating with glass beads microparticles in primer layer and SiO2 nanoparticles in overcoat layer, reduced the corrosion rate by nearly 80 times.

Self-Lubricating Pulsed Ion Beam-Assisted PTFE Coating of Titanium in Argon Discharge to Tailor Wear Resistance and Friction

Polytetrafluoroethylene (PTFE) ions were deposited on titanium substrate by using a 1.5 kJ Mather plasma focus device in argon, equipped with a PTFE source. The PTFE and argon ions generated during different number of shots of dense plasma focus (DPF) resulted in deposition of PTFE on the Ti surface. Prepared samples were characterized for structural properties, elemental composition, surface morphology, wear resistance and frictional behavior by X-ray diffraction, energy dispersive X-ray, scanning electron microscope and pin on disc test, respectively. The area of the coherent X-ray scattering region of PTFE coated on Ti estimated by XRD is 9 nm. Both XRD and SEM show that the area of the coherent X-ray scattering region increases with the increase in the number of focus shots. The EDX results confirmed that the concentration of carbon and fluorine on the Ti substrate increases with the increase in energy of ion flux. Finally, the pin on disc test confirms that PTFE ion plasma coating on the Ti surface reduces the friction up to 35% and enhances wear resistance of the Ti surface up to 89%. The above analysis reflects that PTFE coating shows remarkable tribological behavior with low value of friction coefficient and enhanced value of wear resistance. Moreover, this study provides an intuition for organizing the design of self-lubricating and effective wear-resistant coatings.

Corrosion protection properties of Janus PTFE coatings in highly corrosive H2SO4 solutions

To improve the corrosion protection properties of polytetrafluoroethylene (PTFE) in highly corrosive H2SO4 solutions, Janus PTFE coatings (PDA/PEI@PTFE) were constructed. The modified side is achieved by co-deposition of polydopamine (PDA) and polyethyleneimine (PEI) on the sodium naphthalene etched side of PTFE. It not only has a 5-fold increase in interfacial adhesion with substrates via chemical bonds, but also exhibits improved barrier properties due to the coverage of dense PDA/PEI film, with corresponding corrosion resistance increase by ~2–3 orders of magnitude. Meanwhile, the untreated side is hydrophobic pristine PTFE and has good self-cleaning properties and excellent resistance in concentrated H2SO4 solutions.

The friction and wear performance of polytetrafluoroethylene coating reinforced with modified graphene

In order to improve the lubrication performance of polytetrafluoroethylene (PTFE) coating. Modified graphene (RGO) was prepared by Hummers method and ion modification method. RGO/PTFE composites were prepared by solvent-assisted blending. The surface morphology and microstructure of RGO, PTFE and composites with different concentrations were characterized and analyzed by scanning electron microscopy (SEM), Raman spectroscopy (XRD) and X-ray diffraction (XRD). The tribological properties of RGO, PTFE and composite coatings based on 45# steel were studied by ball-disk friction tests. The wear marks were characterized by scanning electron microscope (SEM), energy dispersive instrument (EDS) and 3D profiler. The results show that 5 wt% RGO/ PTFE composite has lower friction coefficient and the best wear resistance. The friction coefficient of the composite is as low as 0.11, which is 37% and 51% lower than that of single-component RGO and PTFE, respectively. The wear resistance of the composite is 155.8% higher than that of single-component RGO and PTFE. The formulations of lubricating coatings in this paper are independently developed and have excellent antiwear effects. The synergistic mechanism of RGO and PTFE is proposed to explain the improvement of friction properties of composite coatings.

Microscale friction and deformation behavior of polydopamine/polytetrafluoroethylene-coated 60NiTi from nanoscratch tests

The scratch behavior of polydopamine (PDA)/polytetrafluoroethylene (PTFE) coatings has traditionally been studied using macro-scale tribometers. However, in this study, a nanoindenter is used to scratch PDA/PTFE coatings on 60NiTi substrate to investigate the nanoscale deformation behavior and failure mechanisms of this coating under various scratch loads. Nanoscratch tests were also performed on the substrate coated only with the adhesive underlayer to study the behavior of PDA under various scratch loads. Scanning electron microscope imaging of the scratches provided further insights to the coating scratch deformation behavior. The study revealed the PDA/PTFE coating failure is strongly correlated with the removal of the PDA particles in the underlayer. The findings also suggest that the compaction of the thin PDA/PTFE coatings could be the main reason for the previously reported large initial wear depth in macro-scale tribology studies.

Thermohydrodynamic behavior of partially coated plain journal bearings with/without considering wall slip

A thermohydrodynamic model was used to study the influence of partial composite coatings on the behavior of plain journal bearings, considering solid elastic deformations and wall slip occurring at the oil film–polytetrafluoroethylene coating interface, and heat conduction between film, coating, interlayer and basement. The purpose is to design partial polytetrafluoroethylene coating to obtain improved bearing behavior based on analyzing the maximum temperature and minimum film thickness in different coating positions (or slip zones). The influences of coating thickness and coating materials (polytetrafluoroethylene, graphite and diamond-like carbon coatings) at different coating positions are also presented. Results show that polytetrafluoroethylene coatings that are completely located in the film convergent region have a small influence on thermal behavior in both nonslip and slip cases. Without slip, a full polytetrafluoroethylene coating can increase the maximum temperature; however, wall slip occurring on a full polytetrafluoroethylene coating surface is helpful in decreasing the maximum temperature when accompanied by a lower minimum film thickness. A thicker polytetrafluoroethylene coating causes bearing seizures more readily. Unlike polytetrafluoroethylene, graphite and diamond-like carbon coatings improve the thermal behavior.

Encapsulation of interdigitated electrodes by PTFE coatings via closed batch initiated chemical vapor deposition

Encapsulation of sensor electrodes is critical for stability and optimum performance of the device. Encapsulation method to be employed should be compatible with the device architecture, provide conformal coatings and be cost effective. In this study, closed batch initiated chemical vapor deposition (CB-iCVD) method is used to deposit Polytetrafluoroethylene (PTFE) encapsulation layers on interdigitated electrodes (IDE). The CB-iCVD method enables deposition of conformal, ultra thin PTFE coatings on patterned surfaces with high precursor consumption efficiencies. The electron microscopy analysis confirms the conformality of the smooth coatings on the IDEs. The encapsulation performance of the coatings in the presence of standard pH solution is demonstrated by the frequency dependent electrochemical impedance spectroscopy (EIS) analysis, which confirms that the PTFE layer can successfully isolate the electrodes from the reactive environment.

Limited Enhancement of Subatmospheric Boiling on Treated Structured Surfaces With Biphilic Pattern

Abstract Boiling heat transfer suffers deteriorations under subatmospheric conditions, which can be attributed to a shortage of viable nucleation sites at declining pressures. In this work, the possibility of enhancing low-pressure saturated boiling of water using a combination of wettability patterning and structural modifications was experimentally explored. The copper test surface, comprised of an array of circular “dimples” (0.3 mm in depth, 0.5 mm in diameter, and 3.0 mm in pitch), was spray-coated by polytetrafluoroethylene (PTFE) coatings so as to form a matching biphilic pattern with the surface cavities. The resulting dimpled biphilic surface showed appreciable heat transfer enhancement—with a maximum 60% increase of the average heat transfer coefficient of nucleate boiling compared with a flat biphilic surface—down to about 9.5 kPa. Further lowering the pressure to 7.8 kPa, however, was found to lead to diminished performance gains. The visualization study of the bubble departure dynamics revealed signs of additional vapor trapping of the hydrophobic-coated cavities, which can induce uninterrupted bubble regeneration with zero waiting time and explain the qualified enhancement of subatmospheric boiling. Thanks to a potential secondary pinning of contact line inside the hydrophobic cavities, incomplete bubble detachment could prevail at somewhat lower pressures than was otherwise possible without the dimple structure, leaving behind significantly more vapor residues. However, the vapor-trapping capacity was found to decrease with pressure, which provided clues with regard to the reduced efficacy of the surface at even lower pressures.

Properties of Polypropylene Yarns with a Polytetrafluoroethylene Coating Containing Stabilized Magnetite Particles

This paper describes an original method for forming a stable coating on a polypropylene yarn. The use of this method provides this yarn with barrier antimicrobial properties, reducing its electrical resistance, increasing its strength, and achieving extremely high chemical resistance, similar to that of fluoropolymer yarns. The method is applied at the melt-spinning stage of polypropylene yarns. It is based on forming an ultrathin, continuous, and uniform coating on the surface of each of the yarn filaments. The coating is formed from polytetrafluoroethylene doped with magnetite nanoparticles stabilized with sodium stearate. The paper presents the results of a study of the effects of such an ultrathin polytetrafluoroethylene coating containing stabilized magnetite particles on the mechanical and electrophysical characteristics of the polypropylene yarn and its barrier antimicrobial properties. It also evaluates the chemical resistance of the polypropylene yarn with a coating based on polytetrafluoroethylene doped with magnetite nanoparticles.

Friction Mechanism and Application of PTFE Coating in Finger Seals

Due to their special flexible structure, finger seals show good wear and leakage characteristics and has a great application prospects. Under the condition of high speed, the sealing and wear performance of finger seals is directly related to the characteristics of the friction pair between the finger foot and rotor. As a kind of high polymer material with a lower friction coefficient, polytetrafluoroethylene (PTFE) has potential application value in finger seals. Therefore, based on the previous theoretical analysis and optimization design, in this study pin-on-disc tests between the metals applied in finger seals and the PTFE coating and bench-scale performance tests of finger seals with the PTFE coating were carried out. The results show that for finger seals made of the cobalt-base alloy GH605, the friction coefficient of finger seals with PTFE coating is only 0.15, which is 50% lower than that without the PTFE coating; after a 50-h durability test, the leakage performance of finger seals with the PTFE coating was more stable, and its leakage rate and wear rate were reduced by 30 and 39%, respectively, compared to without the PTFE coating. The test results in this article indicate that the PTFE coating has excellent wear resistance characteristics and good application potential for finger seals, which provides valuable reference for the design of the friction pair of finger seals.

Effect of Cu nanoparticles on the tribological performance of polydopamine + polytetrafluoroethylene coatings in oil-lubricated condition

The effect of Cu nanoparticles (NPs) on the tribological performance of the thick polydopamine (PDA) + polytetrafluoroethylene (PTFE) coatings in DTE-32 Mobil lubricated condition was investigated. PDA + PTFE + Cu NP coatings with 45 µm thickness were spray-coated with 0.12, 0.25, and 0.50 wt% of Cu NPs in an aqueous PDA + PTFE solution, respectively. The mechanical properties were studied by PeakForce quantitative nanomechanical (PFQNM) characterization and nanoindentation. The Young's modulus increased, and the coefficient of friction (COF) reduced with the addition of Cu NPs compared to PDA + PTFE coating. The PDA + PTFE + 0.25 wt% Cu and PDA + PTFE + 0.50 wt% Cu coatings increased the durability by 52% and 33%, respectively, compared to the coating without Cu NPs. The better tribological performance of the nanocomposite coatings is contributed by the better mechanical properties, better adherence, and enhanced cross-linking between the constituents of the nanocomposite coatings due to the presence of Cu NPs. The addition of 0.25 wt% Cu NPs in PDA + PTFE increased the thermal conductivity by 12%.