Transparent Coatings Research Articles

Nonfluorinated, transparent, and antireflective hydrophobic coating with self-cleaning function

Transparent coatings with self-cleaning function have great promise for outdoor applications, such as solar cells, windshields, and lenses. However, their applications are limited by the low transmittance and fluorinated materials. Therefore, it is critical to develop highly transparent and non-fluorinated coatings with low-cost. Herein, we report a transparent, antireflective, and fluorine-free highly-hydrophobic coating. A transmittance of 95.0% was obtained for the coated glass across the broad wavelength range of 394–804 nm, and with a maximum value of 99.5% around 553.5 nm, much better than the bare glass (91.1%). The water contact angle (WCA) of 142.0° and a sliding angle < 10° enable a great self-cleaning function of the coating, which exhibits an impressive thermal stability at − 25–550 ℃, an outstanding resistance to sand ablation and long-term UVA radiation. Therefore, this work may provide not only promising coating but also great inspiration for the development of coating that owns high transmittance and self-cleaning function.

Transparent and Sprayable Surface Coatings that Kill Drug-Resistant Bacteria Within Minutes and Inactivate SARS-CoV-2 Virus.

Antimicrobial coatings are one method to reduce the spread of microbial diseases. Transparent coatings preserve the visual properties of surfaces and are strictly necessary for applications such as antimicrobial cell phone screens. This work describes transparent coatings that inactivate microbes within minutes. The coatings are based on a polydopamine (PDA) adhesive, which has the useful property that the monomer can be sprayed, and then the monomer polymerizes in a conformal film at room temperature. Two coatings are described (1) a coating where PDA is deposited first and then a thin layer of copper is grown on the PDA by electroless deposition (PDA/Cu) and (2) a coating where a suspension of Cu2O particles in a PDA solution is deposited in a single step (PDA/Cu2O). In the second coating, PDA menisci bind Cu2O particles to the solid surface. Both coatings are transparent and are highly efficient in inactivating microbes. PDA/Cu kills >99.99% of Pseudomonas aeruginosa and 99.18% of methicillin-resistant Staphylococcus aureus (MRSA) in only 10 min and inactivates 99.98% of SARS-CoV-2 virus in 1 h. PDA/Cu2O kills 99.94% of P. aeruginosa and 96.82% of MRSA within 10 min and inactivates 99.88% of SARS-CoV-2 in 1 h.

Transparent Polymeric Formulations Effective against SARS-CoV-2 Infection.

The main route of the transmission of the SARS-CoV-2 virus is through airborne small aerosol particles containing viable virus as well as through droplets transmitted between people within close proximity. Transmission via contaminated surfaces has also been recognized as an important route for the spread of SARS-CoV-2 coronavirus. Among a variety of antimicrobial agents currently in use, polymers represent a class of biocides that have become increasingly important as an alternative to existing biocidal approaches. Two transparent polymeric compounds, containing silver and benzalkonium ions electrostatically bound to a polystyrene sulfonate backbone, were synthesized, through simple procedures, and evaluated for their antimicrobial properties against Gram-positive and Gram-negative bacteria and Candida albicans (ISO EN 1276) and for their antiviral activity toward 229E and SARS-CoV-2 coronaviruses (ISO UNI EN 14476:2019). The results showed that the two tested formulations are able to inhibit the growth of (1.5–5.5) × 1011 CFU of Gram-positive bacteria, Gram-negative bacteria, and of the fungal species Candida albicans. Both compounds were able to control the 229E and SARS-CoV-2 infection of a target cell in a time contact of 5 min, with a virucidal effect from 24 to 72 h postinfection, according to the European Medicines Agency (EMA) guidelines, where a product is considered virucidal upon achieving a reduction of 4 logarithms. This study observed a decrease of more than 5 logarithms, which implies that these formulations are likely ideal candidates for the realization of transparent surface coatings that are capable of maintaining remarkable antibacterial activity and SARS-CoV-2 antiviral properties over time.

Introducing Polyhydroxyurethane Hydrogels and Coatings for Formaldehyde Capture.

Formaldehyde (FA) is a harmful chemical product largely used for producing resins found in our living spaces. Residual FA that leaches out the resin contributes to our indoor air pollution and causes some important health issues. Systems able to capture this volatile organic compound are highly desirable; however, traditional adsorbents are most often restricted to air filtration systems. Herein, we report novel waterborne coatings that are acting as a FA sponge for indoor air decontamination. These coatings, of the poly(hydroxyurethane) (PHU) type, rich in primary amine groups, are prepared by the polyaddition of a hydrosoluble dicyclic carbonate to a polyamine in water at room temperature under catalyst-free conditions. We highlight the importance of the choice of the polyamine on the curing rate of the formulation and on the FA capture ability of PHU. The excellent FA capturing ability of the best candidate is rationalized by investigating the action mode of the polyamine used to construct PHUs. With poly(vinyl amine), FA is covalently and permanently bound to PHU, with no release over time. The performance of the coating in FA abatement is impressive, with more than 90% of captured FA after one day of contact. The facility to prepare these transparent and colorless coatings from waterborne formulations gives access to new efficient indoor air depolluting solutions, potentially applicable to various surfaces of our living spaces (wall, ceiling, etc.).

Synthesis and Applications of Functional Nanomaterials

The unique physical and chemical properties and variable application potential of nanomaterials are continuously devoted to stimulating scientists’ studying enthusiasm. Extremely fine grains bring quantities excellent properties such as low density, low elastic modulus, high resistance and low thermal conductivity to nanomaterials, which has extensive use in the photoelectric field, environment, bioengineering and other fields. The research progress of graphene quantum dots, transparent reflective coatings and self-assembled nanotubes are mainly demonstrated. This paper shows the role of graphene quantum dots in solar cells, summarizes the synthesis methods of self-assembled nanotubes and their applications in bioengineering, and describes the development of transparent thermal reflective coatings for energy-saving glass attributed to providing relevant reference and basis for the development and research of nanomaterials.

Aluminium Nitride Doping for Solar Mirrors Self-Cleaning Coatings

Soiling severely reduces solar mirror performance, requiring dispendious water consumption for cleaning operations and causing an increase in the levelized cost of energy (LCOE). An emerging technology for facing this problem consists of developing transparent self-cleaning coatings, able to be washed with a small amount of water by virtue of the modulation of surficial wetting properties. Nevertheless, the beneficial effects of coatings decrease in the first year, and coated mirrors show even higher soiling than non-coated ones. Moreover, it is important that coating production processes are economically convenient, consistent with the intended reduction of overall costs. The aim of this work is the research and development of a cheap and scalable solution, compatible with mirror fabrication steps and, in such a sense, economically advantageous. It involves the substitution of the alumina last layer of solar mirrors with more hydrophobic, potentially auxetic aluminum compounds, such as nitrides. In particular, 2D inorganic aluminum nitride thin films doped with metals (such as aluminum and silver) and non-metals have been fabricated by means of reactive sputtering deposition and characterized for the purpose of studying their self-cleaning behavior, finding a trade-off between wetting properties, optical clarity, and stability.

One-step fabrication of transparent Barite colloid with dual superhydrophilicity for anti-crude oil fouling and anti-fogging

HypothesisTransparent superhydrophilic coatings are very promising in various scenarios. Appropriate fabrication of colloid coatings with superhydrophilicity both in air and under oil would enlarge their application potential in anti-oil fouling and facilitate anti-fogging of transparent surfaces. ExperimentsThe Barite colloid was obtained from a one-step precipitation method and was transferred onto glasses to prepare transparent coatings with different thicknesses simply by dip-coating. Then, the impact of thickness on wettability and property was studied through the investigation of wettability in various phase, anti-crude oil fouling performance and anti-fogging ability. FindingsSimilar surface morphology and roughness of these coatings were achieved and all the coated surfaces showed ultra-hydrophilicity both in air and under oil. Moreover, the hydrophilicity in air and under oil was found to deteriorate with the decrease of coatings’ thickness and dual superhydrophilicity could be achieved on thick coatings. More importantly, excellent anti-crude oil fouling property and durable anti-fogging ability were realized on these transparent coatings with dual superhydrophilicity.

Imparting Strong Antifouling Properties to the Transparent PVB Coating through the Zwitterionic Compound Condensation

Fouling is a ubiquitous and longstanding challenge that causes both economic and environmental problems, especially for underwater detection equipment, as fouling directly limits the normal services and functions of such equipment. Therefore, it is necessary to develop coatings with high transparency and good antifouling performance. Herein, a novel zwitterion compound was synthesized, and an antifouling coating with excellent comprehensive properties was prepared by integrating 3-[[3-(triethoxysilyl)-propyl] amino] propane-1-sulfonic acid (TPAPS) into polyvinyl butyral (PVB) polymer, which possesses excellent mechanical properties and transparency. The physical and chemical, mechanical, and antifouling properties, and the light transmittance of the coating were characterized by the SEM, FT-IR, XPS, UV-VIS. The results show that the coating had good mechanical properties and adhesion to the substrate, and the strong hydration ability of TPAPS endowed the coating with excellent resistance to oil stains and biofouling. More importantly, the structure of the coating was homogenous and its surface roughness was very little, which imparted the coating with high transmittance. This research provides a facile approach for synthesizing high-transparency materials with excellent antifouling and mechanical properties.

Mo/W/Al doped tin oxide thin films: exploring optical and mechanical properties for transparent protective coating applications

For the last few years research has been intensified in exploring and improving mechanical properties of tin oxide thin films besides the optical and electrical ones that enhances the film's functionality and broadens its application purview. The present investigation reports a comprehensive study on the effect of Mo, W, and Al doping on optoelectronic and mechanical properties of tin oxide thin films. The films exhibited an optical transparency over 350–400 nm with an average transmission of 85–98% at 550 nm and mechanical hardness spanning over 2–8 GPa, and electrically resistivity in the range 900–200 Ωm, based on the dopant used and its content. Compared to bare tin oxide film, the doped films exhibited a decrease in optical transparency with an improvement in the hardness. 10 wt.% Mo doped tin oxide film exhibited good average optical transparency 72% at 550 nm, highest elastic recovery of 70%, highest hardness 8.0 ± 0.5 GPa and reduced-modulus of 89 ± 0.5 GPa of all the films. The investigation demonstrates a simple technique of producing mechanically hard tin oxide thin films useful as transparent protective coatings.

Liquid-like transparent and flexible coatings for anti-graffiti applications

Transparent, durable and smooth coatings with anti-fouling properties are highly desirable for many applications e.g. windows and touch screens. However, most of smooth anti-fouling coatings are limited by complicated preparation and application conditions such as synthesis at high temperatures or curing under ultraviolet irradiation. In this paper, two kinds of siloxane were cross-linked to form a highly transparent anti-fouling coating, which can be rapidly applied on different substrates by a facile brushing process (~3 min for curing) at room temperature. This coating has excellent anti-graffiti properties for liquids with complex components such as water-based and oil-based inks, furthermore, it also exhibits good flexibility, anti-reflection and anti-corrosion properties. The durability test shows that the performance of the coating remains unchanged under various harsh environments. This work would provide a pathway for developing solid and smooth anti-fouling coating, which is expected to be quickly applied in practice due to its simple principle and rapid preparation.

Effects of UV-curing epoxy acrylate and urethane acrylate coatings incorporated with ZnO nanoparticles on weathering resistance of thermally modified timber

ABSTRACT In this study, the effects of two transparent UV curing coatings (i.e. epoxy acrylate and urethane acrylate) modified by zero, 0.2, and 0.5 loading percent of zinc oxide nanoparticles (ZN) on the weathering resistance of thermally modified timber were investigated. Both coatings improved the weathering resistance of the modified wood; however, epoxy acrylate showed much better performance compared to urethane acrylate. ATR-FTIR results showed no considerable oxidation or chain scission in the epoxy acrylate-coated specimens after six months of weathering, while significant chemical changes occurred in the urethane acrylate-coated specimens. The addition of the nanoparticles reduced the discoloration of both coatings; however, the contact angle and roughness were not significantly affected. Results also showed that the adhesion strength was reduced for both coatings as a result of weathering with the urethane acrylate coating having a lower adhesion strength than the epoxy acrylate. The addition of the ZN, particularly at the higher content, reduced the adhesion strength of the urethane acrylate coating. Generally, the method of fast and simple UV-cured coating of epoxy acrylate alone or coupled with zinc oxide nanoparticles was found to be effective for the protection of thermally modified timber against weathering in outdoor applications.

Hybrid nanoparticles embedded polyvinyl butyral nanocomposites for improved mechanical, thermal and microwave absorption performance

Polymer-based nanocomposites have been broadly investigated to improve its specific properties such as thermal and mechanical properties to use in different application areas. In this study, we aimed to ameliorate the desired physical properties of polyvinyl butyral (PVB) by introducing various amounts of silver (Ag) and cobalt (Co) nanoparticles (NPs) in the polymer matrix. The arc-discharge method submerged in liquid nitrogen was performed to synthesize the metal NPs. To produce hybrid nanocomposites, we demonstrated embedding Ag:Co nanoparticles in the PVB matrix via easy/low-cost solution casting process without any additional materials. In the results of analysis for nanocomposites, it was observed that there were improvements in thermal, mechanical and microwave absorption characteristics of the PVB polymer with interaction of NPs with the polymer. As a result of these interactions, the hybridization of PVB with the metal NPs resulted in the improved thermal stability since the glass transition temperature was increased from 45.6 to 55.1 °C. Besides, while the tensile strength (σ) of the bare PVB film was calculated as 20.52 MPa, the strength of the corresponding tensile strength (σ) of 1.0 wt.% Ag:Co nanocomposite film was improved to 43.41 MPa. Moreover, in order to determine the effect of these changes on the radar absorption feature of nanocomposites, one-dimensional A-Scan measurements were performed on 2–18 GHz frequency band. In the results, it was observed that 1.0%.wt Ag:Co nanocomposite film absorbed approximately 90% of the incoming energy. The characterization results revealed that a positive synergetic effect raised in the case of the modification of the PVB matrix with both Ag and Co NPs. In the light of these data, it was understood that the characteristics of PVB were improved with the NPs combining, and the usage area of that will also increase thanks to this improvement. These regenerated properties made the hybrid nanocomposite a promising substrate material with considerable potential applications for various transparent, flexible, and portable surface coatings.

Fabrication of high transparent, mechanical strong, and flame retardant waterborne polyurethane composites by incorporating phosphorus‐silicon functionalized cellulose nanocrystals

AbstractTo manufacture transparent waterborne polyurethane composite coatings that possess desirable mechanical and flame retardancy properties is still a challenge. Herein, we first synthesized phosphorus‐silicon functionalized cellulose nanocrystals (FCNC) filler, and further introduced it into waterborne polyurethane (WPU) matrix to prepare composite. The phosphorus‐silicon‐containing components were grafted covalently on the surface of FCNC, and the FCNC showed good dispersion level in water and WPU matrix. Moreover, the inserted FCNC could not only maintain the high transparency of WPU‐FCNCs composites, but also remarkably enhancing the mechanical and flame retardancy performances. Noticeably, the WPU‐FCNC3 composite containing 3 wt% of FCNC showed balanced mechanical (σb = 16.7 MPa, εb = 557.5%), limiting oxygen index (22.9%), and a UL‐94 rating of V‐2 among prepared films. Additionally, WPU‐FCNC3 composite exhibited significantly reductions in heat release during combustion, and also showed a high transmittance of 92.2%. The present research supplies promising way for developing transparent, toughness, and flame retardant composite coatings.

Preparation of Surface-Modified Nano Zinc Sulfide/Polyurethane Inorganic-Organic Transparent Coating and Its Application in Resin Lens

The surface modified hydrophilic zinc sulfide nano powder was prepared by hydrothermal method, and the corresponding zinc sulfide/polyurethane organic-inorganic composite transparent coating via in-situ polymerization. The structure of ZnS Nanoparticles and organic-inorganic composite coating were characterized by Infrared Spectroscopy, X-Ray Diffraction, Laser Particle Size Analyzer and Scanning Electron Microscopy. The optical properties were measured by Ultraviolet-Visible spectrophotometer and ellipsometry. The results show that the monodisperse hydrophilic nano zinc sulfide powder with a particle size of about 70 nm can be obtained by thioglycolic acid (TGA) modification, which has good compatibility with waterborne polyurethane. Nano zinc sulfide increased the refractive index of the coating significantly and the refractive index of the coatings could be controlled in the region of 1.46–1.71 organic-inorganic composite coating by adding ZnS. When the amount of nano ZnS added was 30%, the refractive index of the hybrid coating can reach 1.71, and the transmittance was more than 90%. The cured coatings were smooth and no agglomeration between nano ZnS particles could be found. After application on the surfaces of resin lens, the coatings presented better impact resistance, which indicated that the coating has application prospects in the field of fine processing of lens’ surfaces.

Zirconia nanotube coatings - UV-resistant superhydrophobic surfaces

Surface modifications influence material interactions such as wettability, imparting hydrophobicity or hydrophilicity. Mainstream research focused on enhancing product shelf-life directs attention towards superhydrophobic surfaces (SHS). SHS offer several benefits for out-door applications such as self-cleaning, anti-soiling, anti-mist etc. Recently, such surfaces were created by hydrophobization of anodized titania, which although effective lacked a long-term stability of their hydrophobic modifications due to it being susceptible to UV-mitigated degradation. In light of this situation, ZrO2-nanotubes are evaluated with regard to their application as transparent UV-stable superhydrophobic coatings. Nanostructured oxide surfaces are created via single-step electrochemical anodization. The absence of HF acid-based pre-etching steps offer a safe and alternatively a green synthesis route. Anodized oxides are modified using octadecylphosphonic acid (OPA) self-assembled monolayers, demonstrate superhydrophobicity and are at par with conventionally employed coatings such as PTFE, PFDPA and PTES. The OPA-coatings are evaluated for their mechanical stability under a jet of water, chemical stability under indirect sunlight irradiation in air/water and direct UV exposure. Zirconia nanotubular films were evaluated for optical transparency using light microscopy and surface wettability of the different zirconia-composites was compared to the model system - titania. Structural and compositional differences of the SAM layer upon time dependent decay were analyzed with X-ray photoelectron spectroscopy.

Design of highly transparent conductive optical coatings optimized for oblique angle light incidence

Design of highly transparent conductive optical coatings optimized for oblique angle light incidence

UV-Shielding TiO2 thin film deposition on flexible and heat-labile substrate using an open-air hybrid CVD/Plasma method

In this work, compact scratch resistant transparent amorphous TiO2 thin films are deposited at low temperature, i.e. as low as 50 °C, by a scalable hybrid method combining atmospheric pressure chemical vapor deposition and plasma treatment in open air. Thin film morphology, chemical composition and scratch resistance properties are investigated. The role of the plasma in the process is investigated through comparison with coatings deposited without plasma ignition. The versatile method enables film deposition on polymer film and shows good UV protection. This method, operating in open air shows promising results for the simple, large scale deposition of low carbon containing transparent TiO2 coatings at low temperature.

Highly transparent coatings for self-cleaning applications

Highly transparent coatings for self-cleaning applications

Estimation of surface roughness for transparent superhydrophobic coating through image processing and machine learning

In the current era, superhydrophobic surfaces/coatings have gained significant attention worldwide due to their exclusive features such as self-cleaning, anti-corrosion, anti-adhesion, anti-reflection, and anti-icing, etc. The idea of the self-cleaning mechanism of superhydrophobic coatings has emerged from the self-cleaning effect of lotus plant leaves. The superhydrophobic surfaces have a great ability to eliminate dust, bacteria, and viruses due to the very large contact angle (> 150°) between the surface and the water droplets. The present study is based on the surface roughness estimation of field emission scanning electron microscope (FESEM) images of the developed superhydrophobic coatings via image processing and machine learning approach. Transparent superhydrophobic coatings of functionalized SiO2 nanoparticles embedded polystyrene (PS) and dual functionalized ZnO nanoparticles embedded PS were prepared using a modified sol-gel approach. The superhydrophobicity of the synthesized coatings was realized by the large contact angles of more than 150° between water droplets and the coatings. The FSESM images of the superhydrophobic coatings were processed using MATLAB 2018 image processing and machine learning tool to compute the roughness by computational algorithms. The discrete wavelet processing was used for image segmentation, and k-means clustering was applied for predicting the roughness score against different compositions of the coatings. The computational methods exhibited ∼ 91.70% accuracy of the surface roughness estimation of the coatings.

Preface

Analytical Review of the Reports Presented at the 15th International Conference on Films and Coatings (ICFC2021)