Durable Coatings Research Articles

Numerical study of thermomechanical delamination mechanisms in segmented high-temperature coatings

This work addresses the thermomechanical delamination mechanisms in segmented multilayered high-temperature coatings system using computational fracture mechanics approach. A representative unit cell model is presented, where the thermomechanical load is generated by combining uniform temperature changes and boundary-loaded displacements. The model is used to analyze coatings over a broad range of material properties, geometries, and loads. The findings suggest that, for a given coatings system, the mechanical load carried by the top-coat layer is the only force that drives delamination developing along the top-coat/bond-coat interface. The introduced multiple vertical cracks lead to stiffness release over a limited region, resulting in reductions in stress and delamination driving forces within that region. An empirical equation is established using multiple regression analyses to evaluate the delamination driving forces. Accordingly, the importance of the influential factors on the delamination is ranked, and design maps are constructed to facilitate the development of durable coatings.

Largely Enhanced Surface Flashover Voltage of Poly(ether Imide) by Scalable and Durable ZnO Coating: A Gift from In Situ Growth.

Dielectric materials with high surface electric insulation strength are in great demand in a high-power space solar cell array (SSCA). A moderately conductive surface is favorable to inhibit charge accumulation and mitigate electric field distortion, thus improving the surface flashover voltage. Although numerous modification methods have been proposed to achieve this goal, the facile, efficient, scalable, and environmentally friendly modification strategy remains a critical challenge to date. Considering the excellent charge modulation ability of ZnO and its mild preparation conditions, a facile and economical hydrothermal strategy was proposed to fabricate in situ a durable poly(ether imide)/zinc oxide (PEI/ZnO) coating with a high charge decay rate. The blooming flower-like ZnO in the coating is proved to play a key role in enhancing lateral charge dissipation on the surface of PEI, thereby suppressing surface charge accumulation. It was also shown that the shielding effect of ZnO on high-energy photons during flashover and the catalytic effect of Zn2+ on PEI molecular chains during hydrothermal treatment had a facilitating and suppressing effect on outgassing, respectively, and consequently affected the flashover. Excitingly, the synergistic effects of both accelerated charge dissipation and suppressed outgassing helped to improve the flashover voltage of PEI by up to 36.7%. The strategy selected here is efficient, scalable, and facile, and the coating is durable, which makes sense for commercial promotion.

Waterborne polyurethane dispersions based on polypropylene glycol/polycarbonate diol: Evaluation of their use as wood protective coatings

AbstractWhen exposed to the open air, the wood can change its physical and structural properties due to the combined effect of ultraviolet radiation, oxygen, humidity, atmospheric pollutants, and microorganisms. The demand for durable coatings with application to wooden structures or pieces is always a relevant topic. Waterborne polyurethane (WPU) dispersions as wood protective coatings might be attractive, especially outdoors. In this work, WPU dispersions have been synthesized from isophorone diisocyanate and different ratios of polypropylene glycol and polycarbonate (PC) diol. Synthesized polyurethanes were applied to wood surfaces as a coating. The results showed that the partial and total replacement of polypropylene glycol (PPG) by PC influences the mechanical, thermal, and structural properties of the films obtained from aqueous polyurethane dispersions. In addition, a simple and promising methodology based on Fourier‐transform infrared (FTIR) spectra was proposed to determine the polycarbonate content in poly(carbonate‐ether‐urethane). The synthesized coatings reduced water absorption by the wood, especially the one with a 25:75 polycarbonate to PPG ratio. The applied coating does not impact the final color of the wood, allowing a natural aging effect. Polyurethanes are promising for use as coatings for wood.

Fluorinated Polymer Brush-Grafted Silica Nanoparticles: Robust and Durable Self-Cleaning Coating Materials

Fluorinated Polymer Brush-<i>Grafted</i> Silica Nanoparticles: Robust and Durable Self-Cleaning Coating Materials

Progress in Superhydrophobic Structure Optimisation and Performance Enhancement: A Review

background: Superhydrophobic surfaces have broad application prospects in several fields due to their excellent hydrophobic properties, but the traditional methods of manufacturing superhydrophobic surfaces are time-consuming and laborious, the surface wear resistance is poor, and the chemical reagents contain toxic substances, making it difficult to promote the use of superhydrophobicity inexpensively. objective: To solve the problems of high cost, instability, and poor mechanical properties of superhydrophobic structures, we explore the preparation methods of superhydrophobic surface structures to improve the surface superhydrophobicity and reduce manufacturing and usage costs. methods: This paper provides an overview of the literature on preparing superhydrophobic structures and improving superhydrophobic properties. Based on the summary of the research results of other scholars, this paper focuses on the preparation of superhydrophobic surfaces by carbine-co-polymerization covalent grafting chemical reactions and the improvement of superhydrophobic properties by durable opaque coatings with vacuum-deposited layers. results: These two methods are simple to operate and circumvent the problem of oxidative degradation of compounds in the natural environment to produce environmental pollutants. The method I produces a low surface energy stratified micro-nano composite structure on the fiber surface of the fabric by carbon copolymerization covalent grafting reaction. The method II prepares a durable opaque coating with a vacuum-deposited layer, particularly useful on mechanical components or for any other applications not requiring an optically clear coating. conclusion: This paper provides an important basis for optimizing the preparation process of superhydrophobic structures, synthesizing and developing environmentally friendly superhydrophobic materials, extending the service life of superhydrophobic materials, and provides specific guidance for improving the superhydrophobic properties and durability and enhancing the combination of superhydrophobic surfaces with additional functions.

Self-healing icephobic coating with UV shielding and removability based on biobased epoxy and reversible disulfide bonds

Icephobic coatings have attracted wide attention due to low energy consumption, low cost, and high efficiency. However, the icephobic coating is vulnerable to external damage due to long-term exposure, which can result in icephobic properties loss and limit its industrial application. Herein, the novel amphiphilic epoxy self-healing icephobic coating was designed by a compound with multiple hydrophilic groups, polydimethylsiloxane (PDMS) with hydrophobic groups and 4, 4′-diaminodiphenyldisulfide (APD) with reversible bonds. Moreover, considering the resource crisis, the biobased epoxy (GTE) was selected as the compound containing hydrophilic groups. In this study, the GTE will form hydrogen bonds with water molecules to achieve an anti-icing effect, while PDMS mainly play a deicing effect due to low surface energy. Due to the reasonable design, the icephobic coating showed good comprehensive icephobic properties: a 12.5-fold increase in icing delay time (802 s) and a 6.6-fold decrease in ice adhesion strength (32.6 kPa) compared with bare aluminum. Furthermore, the crystallization temperature of water was reduced by about 11 °C. More importantly, the APD with reversible disulfide bonds provides the icephobic coating with self-healing performance, removability, and excellent UV shielding performance. The coating provides a new idea for the preparation of sustainable and durable coatings with comprehensive icephobic performance.

Highly Orientated Sericite Nanosheets in Epoxy Coating for Excellent Corrosion Protection of AZ31B Mg Alloy.

The growing demands for material longevity in marine environments necessitate the development of highly efficient, low-cost, and durable corrosion-protective coatings. Although magnesium alloys are widely used in the automotive and aerospace industries, severe corrosion issues still hinder their long-term service in naval architecture. In the present work, an epoxy composite coating containing sericite nanosheets is prepared on the AZ31B Mg alloy using a one-step electrophoretic deposition method to improve corrosion resistance. Due to the polyetherimide (PEI) modification, positively charged sericite nanosheets can be highly orientated in an epoxy coating under the influence of an electric field. The sericite-incorporated epoxy coating prepared in the emulsion with 4 wt.% sericite exhibits the highest corrosion resistance, with its corrosion current density being 6 orders of magnitude lower than that of the substrate. Electrochemical measurements and immersion tests showed that the highly orientated sericite nanosheets in the epoxy coating have an excellent barrier effect against corrosive media, thus significantly improving the long-term anti-corrosion performance of the epoxy coating. This work provides new insight into the design of lamellar filler/epoxy coatings with superior anticorrosion performance and shows promise in the corrosion protection of magnesium alloys.

Nanolaminate-based antireflection coatings for enhanced scratch and tribological performance.

Developing durable antireflection (AR) coatings with sapphire-like hardness and high transparency faces a significant challenge. Conventionally, achieving these requirements involves depositing thick, high-hardness nitride films. Here, we proposed an alternative approach that combines nanolaminate materials with optical design, overcoming the brittleness of thick nitride films. We selected Ta2O5/Si3N4 nanolaminates with similar refractive indices, improving tribological and optical performance through a unique optomechanical method. Our proposed AR coating exhibited a low reflectance of 0.8% (420-780 nm) and remarkable hardness of 22.8 GPa, and demonstrated the ability to withstand abrasion from steel wool up to 3,000 times on a glass substrate. This work successfully achieves a balance between hardness and toughness, opening new avenues for the development of highly durable coatings.

A durable superhydrophobic coating based on inherent nano/micro-integrated materials

Superhydrophobic coating has been a research focus due to its self-cleaning, anti-fouling, anti-corrosion resistance properties, etc. However, poor durability of superhydrophobic coating affects its service life. In this study, we develop a durable superhydrophobic polyester (PE)/SiO2-perfluorooctyltriethoxysilane (PFOTES) (PSP) coating using a dual-spraying method. Two grades of mesoporous SiO2 particles with inherent nano/micro-integrated (NMI) geometry are successfully embedded into organic PE matrix achieving a stable rough structure under the action of interfacial wetting and chemical-bonding, which greatly reduces the difficulty in constructing hierarchical structure. The micro-scale particles work as both the microstructure important for the superhydrophobic surface and a protective framework for the nanostructure, and thus improve the robustness of superhydrophobic coatings. Significantly, the newly exposed low-surface-energy nanopore feature of PSP coatings are advantageous in maintaining a stable superhydrophobicity after being abraded, and the PSP coatings display good adhesion performance because of dual-interfacial interactions. Moreover, the superhydrophobic coatings possess excellent self-cleaning, anti-fouling and bouncing performances, and they can retain superhydrophobicity after a prolonged exposure to ultraviolet radiation and immersion in strong acid/alkaline solutions. Porous SiO2 particles, taking advantage of its superiority as an NMI structural material, provide a promising candidate for preparing durable superhydrophobic coatings endowing with necessary stable hierarchical roughness.

Mechanical Stability of Liquid‐Infused Surfaces Based on Mussel‐Inspired Polydopamine Chemistry

AbstractLiquid‐infused surfaces exhibit remarkable repellency properties toward water, oils, and complex fluids and are widely applied to maintain clean, operational, and high‐performing surfaces in various fields, from the biomedical sector to marine infrastructure. Polydopamine (PDA) forms an ideal base layer for the development of such coatings as it adheres to virtually any substrate and can be chemically modified via amino‐containing molecules to adjust the surface properties. Here, strategies are explored to increase the mechanical stability of such coatings by i) incorporating imidazole during film formation to increase crosslinking, and ii) formation of a composite consisting of the organic PDA and an inorganic siliceous porous coating by infiltration of a preformed porous silica layer with PDA. Both strategies exhibit improved resistance to tangential shear assessed by a sandpaper abrasion test and to dynamic impact assessed by a sand trickle test. These improved mechanical properties are successfully transferred to liquid‐infused surfaces created from such modified PDA base layers. The most durable coatings retain efficient liquid repellency after 25 abrasion cycles, indicating improved resilience in real‐world applications.

Highly-hydrophobic, transparent, and durable coatings based on ZnO tetrapods with diamond-like carbon nanocomposite

This study investigates the wettability of ZnO tetrapod (ZnO-T) coatings in relation to surface morphology and protective diamond-like carbon nanocomposites with SiOx (DLC:SiOx) film parameters. Randomly distributed ZnO-Ts with different leg lengths were observed to have varying degrees of wettability, which also changed keeping samples in the dark at room temperature. DLC:SiOx films significantly increase the hydrophobicity of ZnO-T coatings, and their thickness influences the surface roughness and hydrophobicity of the coating, moreover DLC:SiOx films show protection not only from the abrasion but also passivate the ZnO-T coatings from light-induced effects. The results indicate that the largest size ZnO-T fraction with a 40 nm thickness of DLC:SiOx film can provide the best hydrophobicity represented by a water contact angle of 148°, while the smallest ZnO-T fraction with a 120 nm thickness of DLC:SiOx film can provide better mechanical durability. We expect that the detailed analysis of ZnO-T coatings with protective DLC:SiOx films conducted in this study will be advantageous for other nanostructures with protective coatings application in wettability control.

One-step rapid synthesis of robust superhydrophobic surfaces through acrylate crosslinking/polymerization

A new synthetic approach is proposed to fabricate highly durable and eco-friendly superhydrophobic surfaces using acrylate click chemistry. This approach does not require complex or time-consuming fabrication processes and can be used for the rapid fabrication of durable anti-fouling materials/coatings. The use of long-chain acrylates provides the surface with extreme water repellency, and the resulting surface exhibits long-term stability under various harsh conditions, including prolonged exposure to chemicals, mechanical stress, and physical abrasions. Unlike existing techniques that suffer from poor durability and stability, the proposed method is facile and uses a temperature-initiated acrylate crosslinking/polymerization chemistry that provides a hierarchical morphology with low surface energy to the surface during the reaction. This technique results in highly robust 3D superhydrophobic surfaces that can be easily molded or sprayed onto various flexible and rigid substrates. These surfaces have potential applications in the fabrication of emerging advanced and functional materials. Furthermore, the superhydrophobic gel materials can be extended in 3D print molding using silicone templates, and the spray coating exhibits self-cleaning performance even after harsh physical abrasion. Overall, this new approach is a promising step towards the development of durable and eco-friendly superhydrophobic materials and coatings that can be used in practical applications.

Mechanically robust superhydrophobic polyurethane coating for anti-icing application

The development of superhydrophobic coatings with excellent mechanical properties is essential for effective anti-icing protection. In this study, we achieved a durable superhydrophobic anti-icing coating by introducing the nanosilica, co-modified with fluoroalkyl silane and aminosilane, into polyurethane through a simple spraying and curing process. The resulting coating had a water contact angle (CA) of up to 162° and a sliding angle (SA) less than 1.5°. We enhanced the mechanical and chemical durability of the coating by reacting amino groups on the silica surface with the isocyanate groups in the curing agent. The coating maintained its superhydrophobicity even after 200 cycles of sandpaper abrasion, 24 h of water impact, or 500 ml of falling sand impact. Additionally, the coating exhibited excellent anti-icing performance, delaying the water-freezing time to 700 s at −15°, and the ice-adhesion strength remained lower than 13 KPa after 25 icing-deicing cycles. These results suggest that the durable superhydrophobic coatings can effectively prevent long-term icing, making them as promising anti-icing candidates for various applications in polar ships.

Novel manufacturing of intelligent hierarchical molybdenum-polydopamine hollow nanocarriers for smart coating

Novel hierarchical molybdenum-polydopamine nanocarriers (SMPDA) for hosting the inhibitors in the redesigned molybdenum-polydopamine-Zn2+ (SMPDA@Zn) form were utilized in the epoxy-based (EP) coating formulation to reinforce the barrier / self-healing functions. In the present study advanced FTIR, Raman, XRD, FESEM-EDS, MAP, TEM, BET, ICP-OES, EIS, PDP, OCP, salt spray, cathodic delamination, and pull-off appraisals techniques were employed to assess the influence of hierarchical nanocarriers in the solution and active / passive properties of epoxy coatings. The conspicuous impermeable hybrid films composed of Fe2+/3+-MoO42−, Fe2+/3+-polydopamine, Fe2+/3+-MoO42−-polydopamine and ZnO / Zn(OH)2 on active sites of mild steel in a saline solution comprising the SMPDA@Zn and SMPDA extract would supply %80 and %57 inhibition efficiency, respectively. Active corrosion protection in reference to Rtotal (Rct + Rf) 44463.1, 41879.3, and 9176.3 KΩ cm2 after 72 h immersion for composite and conventional EP coatings by plugging the polymeric film pores as well as healing the defects, intentionally created on the surface were enhanced interestingly up to 4.8 and 4.5 times. The superiority of the incorporated coatings was also obvious in the pull-off and cathodic disbanding tests so a delamination area reduction of %73 was recorded in the presence of the hierarchical nanocarriers. The present study illuminated new horizons in materials science and engineering on the potential usage of durable self-healing primer epoxy-based EPSZ and EPSM coatings in assorted industries like oil and gas pipelines, marine, and offshore infrastructure industries, refineries, petrochemical plants, non-renewable power plants, sheet metal working of shipbuilding, and subsea equipment.

An Effective Approach to the Disinfection of Pathogens: Cationic Conjugated Polyelectrolytes and Oligomers.

The synthetic cationic conjugated polyelectrolytes and oligomers have demonstrated great effectiveness and versatility as antimicrobial materials. They have the ability to eliminate or render inactive various pathogens, including viruses like SARS-CoV-2, bacteria, and fungi. These pathogens can be rapidly eradicated when the polyelectrolytes and oligomers are applied as sprays, wipes, or coatings on solid surfaces. Inactivation of the pathogens occurs through two distinct processes: a non-light-activated process similar to Quats, and a more efficient and faster process that is triggered by light. These materials possess fluorescence and photosensitizing properties, enabling prolonged protection when coated on surfaces. The level of fluorescence exhibited by samples applied to nonfluorescent surfaces serves as an indicator of the coating's integrity and viability, making it easily detectable. Importantly, these materials demonstrate low toxicity towards mammalian cells and human skin, allowing for their safe use. While they can serve as durable coatings for pathogen protection, extended exposure to visible or ultraviolet light leads to their photochemical degradation. Our research also suggests that these materials act against pathogens through nonspecific mechanisms, minimizing the likelihood of pathogens developing resistance and rendering the materials ineffective.

Durable superhydrophobic coatings for stainless-steel: An effective defense against Escherichia coli and Listeria fouling in the post-harvest environment

Increasing concerns revolve around bacterial cross-contamination of leafy green vegetables via food-contact surfaces. Given that stainless-steel is among the commonly used food-contact surfaces, this study reports a coating strategy enhancing its hygiene and microbiological safety through an antifouling approach via superhydrophobicity. The developed method involves growing a nickel-nanodiamond nanocomposite film on 304 stainless-steel via electroplating and sequential functionalization of the outer surface layer with nonpolar organosilane molecules via polydopamine moieties. The resultant superhydrophobic stainless-steel surfaces had a static water contact angle of 156.3 ± 1.9° with only 2.3 ± 0.5° contact angle hysteresis. Application of the coating to stainless-steel was demonstrated to yield 2.3 ± 0.6 log10 and 2.0 ± 0.9 log10 reductions in the number of adherent gram-negative Escherichia coli O157:H7 and gram-positive Listeria innocua cells, respectively. These population reductions were shown to be statistically significant (α = 0.05). Coated stainless-steel also resisted fouling when contacted with contaminated romaine lettuce leaves and maintained significant non-wetting character when abraded with sand or contacted with high concentration surfactant solutions. The incorporation of superhydrophobic stainless-steel surfaces into food processing equipment used for washing and packaging leafy green vegetables has the potential to mitigate the transmission of pathogenic bacteria within food production facilities.

Development of highly durable Pd coatings with ultra-low photon-stimulated desorption and low resistivity values

Denser Pd coatings were prepared on the inner wall of the Cu tubes and the photon-stimulated desorption (PSD) of gases from the tubes in response to synchrotron radiation was assessed. In comparison with low PSD materials such as TiZrV coatings, the Pd coatings exhibited ultra-low PSD yields. Especially, the initial H2 PSD yield was lower one order. These ultra-low PSD yields could be maintained after several cycles of air exposure and followed heating. In addition, the denser Pd films showed significantly lower resistivities compared to the TiZrV films.

Synthesis, characterization and tribological properties of solid lubricant graphite films produced by PECVD

Graphite, which is one of the mostly used solid lubricants, is commonly used in different industrial applications due to its low friction coefficient. However, the synthesis of graphite films can be a challenging process in some cases, where durable coatings are needed. Therefore, the aim of this study is to obtain graphite films with low friction coefficients and investigate their tribological properties. In order to achieve this, graphite films were synthesized on glass substrates by using Plasma Enhanced Chemical Vapor Deposition (PECVD) technique for different process times (30, 60 and 90 min). Reciprocating wear tests were performed to determine the tribological properties of the obtained graphite films. Afterwards, Raman, FT-IR, SEM and surface wettability analyzes were carried out to characterize the films. The results showed that the graphite film synthesized for 90 min exhibited higher wear resistance and lower friction coefficient than untreated and other treated samples because it had high film thickness and hydrophobicity. Also, it was seen that the thicknesses of the coatings increased depending on the treatment time and the contact angle measurements showed that all the graphite films exhibited hydrophobic behaviour.

Anti-biofouling potential of extremely water-repellent carbon soot coatings immersed in a highly-contaminated seawater swamp

The undesired translocation of marine microorganisms during sailing and the excessive expenditures for ship hull repairment due to biofouling could be circumvented using superhydrophobic coatings. Unfortunately, the combined effect of underwater currents and colonizing activity of multitudinous foulants on the anti-microbial performance of existing non-wettable materials is still at infant stage. The paramount objective here is to evaluate for the first time the potential of two mechanically durable water-repellent soot coatings towards the inhibition of bacterial proliferation in “real-life” outdoor conditions. We demonstrate that upon one-week immersion in a seawater swamp, both specimens lose non-wettability due to dissolution of the trapped gas layer into the water basin, but yet manage to retard the biofilm development, compared to uncoated iron surfaces, and halt the settlement of some Gram-negative and Gram-positive bacterial strains. The noticed selectiveness in the anti-fouling behavior of tested samples is presumably attributed to differences in the cell envelopes, the extent of elicit oxidative stress and soot-mediated formation of toxic ammonia molecules via hydrogen bonding. These unknown so far anti-bacterial mechanisms of the soot expand the horizons of practical applicability beyond the conventional framework and emphasize on its possible future use as a therapeutic agent.

Waterborne robust superamphiphobic coatings based on palygorskite for self-cleaning and anti-fouling

Superamphiphobic coatings have garnered great attention owing to their widespread application potential in self-cleaning, anti-corrosion, anti-fouling and anti-icing, etc. However, environmentally harmful material, complicated preparation methods, and poor mechanical stability significantly hamper their applications. Here, we report preparation of waterborne durable superamphiphobic coatings based on palygorskite. The coatings were prepared by in turn spray-coating a waterborne polyurethane adhesive solution (the primer layer) and a homogenous aqueous suspension of siloxane-modified palygorskite (the top layer) onto substrates. The influences of concentration palygorskite, silane and catalyst on morphology and wettability of the coatings were studied. Because of microstructure of palygorskite and low surface energy of siloxanes, the coatings have a re-entrant hierarchical micro-/nanostructure with low surface energy. Consequently, the coatings exhibit excellent superamphiphobicity and chemical stability. Moreover, the coatings show good mechanical stability because the siloxane-modified palygorskite top layer was firmly affixed on the substrate by the adhesive layer. In addition, the coatings exhibit good anti-fouling and self-cleaning properties. This study demonstrates a new method for the preparation of superamphiphobic coatings and a new application of natural fibrous clay minerals like palygorskite.