Journal of Coatings Technology and Research最新文献

The COVID-19 pandemic refocused scientists the world over to produce technologies that will be able to prevent the spread of such diseases in the future. One area that deservedly receives much attention is the disinfection of health facilities like hospitals, public areas like bathrooms and train stations, and cleaning areas in the food industry. Microorganisms and viruses can attach to and survive on surfaces for a long time in most cases, increasing the risk for infection. One of the most attractive disinfection methods is paints and coatings containing nanoparticles that act as photocatalysts. Of these, titanium dioxide is appealing due to its low cost and photoreactivity. However, on its own, it can only be activated under high-energy UV light due to the high band gap and fast recombination of photogenerated species. The ideal material or coating should be activated under artificial light conditions to impact indoor areas, especially considering wall paints or frequent-touch areas like door handles and elevator buttons. By introducing dopants to TiO₂ NPs, the bandgap can be lowered to a state of visible-light photocatalysis occurring. Naturally, many researchers are exploring this property now. This review article highlights the most recent advancements and research on visible-light activation of TiO₂-doped NPs in coatings and paints. The progress in fighting air pollution and personal protective equipment is also briefly discussed.

Graphical Abstract

Indoor visible-light photocatalytic activation of reactive oxygen species (ROS) over TiO₂ nanoparticles in paint to kill bacteria and coat frequently touched surfaces in the medical and food industries.

Multi-functional textiles have received much attention in the technical textile field for their novel functionalities available in a single substrate. Polyamide 66 (PA66), being an engineering polymer with excellent physio-mechanical properties, exhibits immense possibilities to be developed as a multifunctional textile substrate. In this work, multi-functional polyamide 66 (PA66) textiles equipped with enhanced electro-conductive, hydrophilic and flame-retardant properties were developed via in situ polymerization of pyrrole monomer onto the PA66 fabric surfaces. Meanwhile, various formulations comprised of phytic acid (PA), chitosan (CS), graphene oxide (GO) and Na-metaborate (B) along with the pyrrole also experimented with a goal to study the contribution of each compound onto the desired properties and finally, to come up with a suitable formulation. Among these formulations, only pyrrole containing formulation (i.e., PA66-PPy) demonstrated a significant improvement in all three desired functionalities, namely a noteworthy escalation in electrical conductivity (i.e., about a 43 times increase compared to the pure PA66), a semi-hydrophilic surface (i.e., water contact angle value was lowered from 124.3– 49.9°) and a substantial reduction in the peak heat release rate by 45%. Meanwhile, the formulation comprising both the pyrrole and phytic acid made the polyamide surface a super-hydrophilic one, whereas other formulations exhibited potential efficacy in attaining better flame retardancy, especially in terms of limiting oxygen index (LOI) values, vertical flame test data and char yield%.

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Electrospraying is an effective method of producing functional layers on substrates. By means of electrospraying, it is possible to create uniform and fine droplets that attract to the substrate without being blown away by the electric field formed by the nozzle and the substrate. The uniformity of the coated layer is rarely affected by a fluid drying process (such as Marangoni flow on substrates) as the size of droplets can reach micron/nano-levels and the solvents in the droplets can evaporate quickly. Therefore, the electrospray process is often referred to as ‘dry deposition.’ However, when an electrospray system with multinozzles is considered for the faster process of producing large substrates, the drying process may be completely different than for a single-nozzle system. In addition, crosstalk and nonuniform spray volume from each nozzle can pose an additional problem that needs to be addressed. In this study, we proposed a multinozzle electrospray system and process to average the spray amount heterogeneity and achieve layer uniformity in a fast-drying process. Finally, we demonstrated the effectiveness of our proposed methods by fabricating superhydrophobic layers on a highly insulating substrate.

Acrylic powder coatings are environmentally friendly, solvent-free solid coatings with excellent durability and corrosion resistance that protect substrates from corrosive environments. The curing behavior of acrylic powder coatings affects the coating film properties. In this study, a catalyst was used to control the curing conversion rate, and the curing characteristics and physical properties were compared for coatings with and without the catalyst. Differential scanning calorimetry and an isoconversional method were used to obtain activation energies, and the conversion rate under different isothermal conditions was computed. Notably, complete curing could not be achieved without the catalyst; however, the catalyst-containing coating was entirely cured. With sufficient curing established, the addition of the catalyst was found to increase the adhesion, impact resistance, and corrosion resistance. However, the recoatability was reduced owing to a lack of unreacted monomers on the surface of the catalyst-containing coating film, as verified by Fourier-transform infrared spectroscopy. In general, the addition of a catalyst to acrylic powder coatings enabled complete curing and enhanced most physical properties, offering an improved formulation for applications across high-corrosion environments.

In this study, caffeine-loaded MIL-100 (Fe), caffeine@MIL-100 (Fe), was used as a smart corrosion-inhibiting coating to protect 308L-16 stainless steel (308L-16 SS). For this purpose, a thin film of the smart anticorrosion caffeine@MIL-100 (Fe) coating was deposited on an 308L-16 SS surface using a decanoic acid self-assembled monolayer. A significant encapsulation efficiency for caffeine loading in the MIL-100 (Fe) metal organic framework was obtained as 17.8%. The experimental data indicated that the caffeine@MIL-100 (Fe) coating would release the caffeine very rapidly as the solution became acidified around the corrosion sites and formed a protective layer to prevent from penetrating solution into the substrate. The EIS results and the Tafel plots showed that the proposed smart coating has an excellent performance to protect 308L-16 SS from corrosion in saline media. Based on the results, decreasing the solution pH would cause the MIL-100 (Fe) framework to decompose and subsequently release caffeine at the 308L-16 SS surface.

Marine fouling can cause a series of hazards in the marine industrial field, and the traditional antifouling methods do not fulfill the green antifouling requirement. Herein, a novel DA/PEI/SiO₂/antibacterial peptide antifouling coating was prepared by a multi-modification approach. Initially, the nanocoatings were prepared by depositing DA, PEI, and SiO₂ on the dopamine (DA)-modified 304 stainless steel (SS) surface, and finally, the DA/PEI/SiO₂/AMPs composite coatings were prepared by grafting antimicrobial peptides (AMPs). The surfaces of SS before and after modification were characterized by Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS), field emission scanning electron microscopy (SEM), contact angle measurement, and 3D optical profilometer. SSN-1 cells were used to evaluate the cytocompatibility of the modified surface. The results revealed that the cells cultured on the modified surface still maintained a good adhesion morphology, demonstrating the superior cytocompatibility of the composite coating. The anti-biofilm and antimicrobial properties of the modified samples were evaluated using Vibrio natriegens. The antibacterial efficiency of SS-DA/PEI/SiO₂ surfaces before and after AMPs modification reached 78.39 and 95.90%, and anti-biofilm efficiency of AMPs modified surface achieved 72.87% corresponding to 44.19% of SS-DA/PEI/SiO₂. The successful grafting of AMPs improved the antibacterial and anti-biofilm properties of the modified sample surfaces. Electrochemical and stability tests indicated that the modified sample surfaces exhibited excellent corrosion resistance and antifouling stability properties. This research could provide a novel green anti-fouling and anti-corrosion strategy for the marine industry and other related fields.

Compared with spray gun painting, electrostatic spraying rotating bell (ESRB) painting can provide better film-forming quality and higher adhesion rate, which is more suitable for automobile base coating. However, the complexity of the spray pattern of the ESRB and the automobile surface geometric makes the spray process planning a more challenging problem. This paper aims to provide a new parameterized model of the ESRB to facilitate the thickness calculation and trajectory planning in the off-line painting programming. Firstly, according to the distribution characteristics of paint particles and the force analysis of adhesion process, a new static deposition rate model—offset asymmetric Gaussian model is proposed on the plane. The parameters in the new model have intuitive practical significance and can fully reflect the characteristics of ESRB coating deposition rate. Then based on the analysis of the relationship between the static model and uniform linear spraying deposition, the static model is established by measuring the layer data of corresponding uniform linear spraying. In order to further simulate the paint thickness on curved surfaces, the projection model with variable spraying distance and deposition point normal deflection is also deduced. Finally, a parameterized static model and sampling points library are established which provide efficient and accurate prediction of static deposition result, and is more suitable for off-line programming. Three different groups of simulation proved that the proposed static deposition rate model has high calculation accuracy for different working conditions and fast simulation speed for different spraying parameters.

There is an increase in public awareness of functional textiles, which strive to produce innovative fabrics for specific applications. In this context, acrylic polymer, a significant synthetic fabric used in the textile industry, was selected to provide it with multifunctional characteristics. For this purpose, the acrylic fabric was functionalized with amidoxime groups to serve as ligands for immobilizing silver ions so that it can be further in situ reduced to AgNPs. Polydopamine (PDA) has the advantage of being an ion binding and reducing agent by virtue of its phenolic hydroxyl groups capable of reducing silver ions to AgNPs, and it was exploited in this study for imparting the acrylic fabric with antimicrobial and antioxidant properties. Additionally, glucose as a reducing agent was also used to form AgNPs-loaded amidoximated acrylic fabric. The pristine, amidoximated, PDA-coated AgNPs-loaded amidoximated, and AgNPs-loaded amidoximated acrylic fabrics have been characterized using ATR-FTIR, SEM, EDX, and tensile strength. All fabric samples were assessed as antioxidants using DPPH and FRAP assays. Antimicrobial properties against Pseudomonas Aeruginosa, Staphylococcus aureus, Escherichia coli and Candida albicans were also evaluated using broth assay. An almost complete killing (99.99%) of the pathogenic Gram-negative Escherichia coli was achieved using PDA-coated AgNPs-loaded amidoximated acrylic fabric. The overall results indicated that the composite nanocoating using PDA-AgNPs showed good tensile strength and excellent antioxidant and antimicrobial properties to suggest the viability of PDA-AgNPs coating of fabrics for possible application as biomedical textiles.

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The coating with amphiphilic honeycomb surface containing modified graphene oxide was constructed by a three-step method for improved antifouling properties. Graphene oxide is modified with potassium hydroxide and γ-aminopropyltriethoxysilane, and then the product is dispersed in water and ethanol. Isophorone diisocyanate, polyethylene glycol, and γ-aminopropyltriethoxysilane are used to construct an amphiphilic prepolymer. The honeycomb surface is constructed during the evaporation of water and ethanol and the mixing of the modified graphene oxide and prepolymer. The amphiphilic honeycomb surface gives the coating fouling resistance and fouling release, while the modified graphene oxide gives the coating fouling degradation. The coating’s amphiphilicity, microstructure, and antifouling properties are characterized by the contact angle, confocal laser scanning microscope, scanning electron microscopy, benthic diatom, and bacterial adhesion. The results show that the coatings form an amphiphilic surface with a honeycomb microstructure and exhibit good antifouling properties. The water, diiodomethane, and 1-bromonaphthalene contact angle can be less than 20°. The size and depth of the honeycomb microstructure are about 600 nm and 100–200 nm. Compared with traditional polyurethane and waterborne silicone coatings, the resistance to benthic diatom and bacteria is increased by at least 28 and 400 times, respectively.