Journal of Coatings Technology and Research最新文献

The installations of offshore wind farms, especially the type with monopile structures, increase the number of suspended particles in the surrounding area. The offshore wind structures are usually coated with several layers of coatings, including a thin layer of organic coating as a topcoat. In this study, we aim to investigate the influence of the stresses on the organic coatings due to the kinetic energy of the suspended sand particles. To accomplish the goal, impingement flow jets with particles were applied on coated steel samples for a week in a lab-scale impingement chamber. The working fluid for the experiments was 3.5 wt% NaCl solution with 1 wt% suspended sand particles. Electrochemical impedance spectroscopy (EIS) was conducted to monitor the degradation of organic coatings while exposed to the impingement flow. Computational fluid dynamics (CFD) modeling was utilized to calculate the magnitude of the applied fluid stresses on the coatings. Thermodynamics of electrochemical reactions and the activation theories were utilized to compare with the electrochemical parameters. It was concluded that for the lowest flow rate (Q₁ = 6.31 cm³/s), the added sand particles started to show destructive influence after the first three days of exposure. As the flow rate increased, the destructive influence of sand particles on coating samples appeared earlier at the beginning of the exposure, and the elements of equivalent circuit model showed larger difference between coatings exposed to pure NaCl solution and those exposed to solution with sand particles. For the highest flow rate (Q₃ = 18.93 cm³/s), the destructive influence of sand particles was significant, indicating that for the particulate flows with the velocity of 1 m/s, which is the regular velocity of the underwater zone in shallow sea regions (with a depth of 30 m), the momentum impact of the sand particles plays a vital role in the degradation of the organic coatings.

In this study, a simple one-step sol–gel process was applied to synthesize SiO₂-based superhydrophilic antifogging coatings on glass substrates. In this process, Si(OH)₄ sol was first prepared and then SiO₂ nanoparticles were added to the sol to form coating solutions. The influence of both the Si(OH)₄ sol and SiO₂ nanoparticle contents on the coating properties was investigated. Their contents have significant effects on the coatings’ properties, including hydrophilicity and surface morphology. The water contact angle of the optimum coating is about 3.4°. Besides, as revealed by the steam test and freeze test, the optimum superhydrophilic coating demonstrates good antifogging properties and an adequate level of mechanical strength as well. Compared to other techniques used to fabricate antifogging coating on glass substrate, the sol–gel-based process developed in this study requires no expensive equipment, and the processing time is largely shortened. Thus, such technique has great potential applications in the field of coating industry.

Urushi (oriental lacquer) is a natural material that forms thin films with excellent durability and water resistance. There are two methods for curing urushi: oxidative and thermal polymerizations. Urushi is mainly applied to wood; therefore, the oxidative polymerization method has mainly been used to cure it. Oxidative polymerization requires temperature and humidity control and takes a long time to fully cure urushi. Urushi mixed with pigments has poor coloration. In contrast, the use of a thermal polymerization reaction can achieve curing in a short time. In this study, we focused on the thermal curing reaction of urushi, formed 13 different colored urushi coating films, and investigated their properties and coloration. We observed that urushi coatings produced through thermal polymerization took less time to cure than those produced through oxidative polymerization, and that urushi coatings with better coloration and high water repellency were obtained.

In recent years, most of the coalescing aids commonly used in the market contain volatile organic compounds (VOCs) with low boiling point. Herein, we designed and prepared a novel environmentally friendly coalescing aid, 2-ethylhexanoic acid-3-alkoxy-2-hydroxypropyl ester. Under the action of a catalyst, 2-ethylhexanoic acid and alkyl glycidyl ether were used as raw materials for ring-opening esterification reaction, and 2-ethylhexanoic acid-3-alkoxy-2-hydroxypropyl ester was finally generated. We conducted a single-factor experiment and orthogonal experiment L₉(3⁴) to explore the optimal reaction conditions. The structure of the product was characterized by ¹HNMR and FTIR. The boiling point of the product was determined to be 270–283°C, which was in line with the requirements of the national environmental protection regulations for VOCs. Compared with traditional coalescing aids, the product has low volatility, is not classified as a VOC and is safe and environmentally friendly. The properties of the product were characterized, and the applications of the product in polymer latex and coating were determined. We measured the minimum film-forming temperature (MFFT), atomic force microscopy (AFM), water absorption, scrub resistance, adhesion, color difference, and other properties of the film. The results show that the performance of the new coalescing aid is superior to Texanol (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), which is commonly used in the market, and it has obvious advantages.

Poly(ethylene terephthalate) (PET) films were surface-modified according to microwave plasma activation allowing for dithiol functions grafting (1,6-hexanedithiol) in order to fabricate self-assembled photogenerated silver nanoparticles monolayers. The present study was carried out in constant discharge power conditions and the impact of the plasma treatment on PET wettability properties were reported. PET material modifications were characterized at various stages of the process: plasma activation, dithiol functionalization, and nanosilver grafting according to several experimental techniques: water contact angle measurements and X-ray photoelectron spectroscopy (XPS). The surface topography was studied by atomic force microscopy (AFM). Finally, antibacterial properties of PET material including silver nanoparticles were evaluated to determine the probability to reduce the surface bacterial adhesion of Staphylococcus aureus strain selected as pathogenic bacteria model. Surface grafted with silver nanoparticles was found to be particularly reactive and led to an inhibition of S. aureus adhesion around 96.2% in comparison with the unmodified PET material.

In this study, hydrophobically modified, ethoxylate urethanes (HEURs) and latexes of well-defined structure and composition were used to examine the rheology and phase behavior of HEUR–latex mixtures. The mixtures comprised one of four HEURs that were synthesized with varying molecular weight polyethylene glycols (PEG 35 K, 20 K, 12 K, and 8 K) and end-capped with octadecyl hydrophobes, as well as one of two latexes (butyl acrylate/styrene [BA-Sty] and butyl acrylate/methyl methacrylate [BA-MMA]) that each contained a small amount of methacrylic acid. The two experimental latexes represent compositions commonly used in commercial paint formulations. The polarity of the HEURs decreases as the PEG molecular weight decreases and the surface of the styrene containing latex is less polar than that containing methyl methacrylate. In all HEUR–latex mixtures, the latex polymer volume fraction was maintained constant at 0.25 which provides a dispersed component spatial crowdedness that represents a fully formulated paint. All latex–HEUR mixtures were stable at very low (i.e., below 0.10% by weight) HEUR levels. At critical concentrations dependent on the polarity of thickener and latex, flocculation was accompanied by syneresis for latex-thickener mixtures prepared with all HEURs except the one with the longest PEG spacer. Further increase of HEUR levels revealed another critical concentration above which the mixtures were stable. Effects of the latex polarity diminished for the mixtures prepared with more hydrophobic HEURs.

In this work, a novel bio-based phosphorus-containing reagent was synthesized and characterized. To obtain a flame retardant agent with acid functionality, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and bio-based itaconic acid were first reacted. The synthesized acid then was reacted with glycidyl methacrylate to form a difunctional phosphorus-containing methacrylate flame retardant monomer. The flame retardant monomer was added to a reactive monomer matrix with a photoinitiator to prepare UV-curable coatings. The molecular structure of the flame retardant was confirmed by Fourier-transform infrared-attenuated total reflection spectroscopy and proton nuclear magnetic resonance (¹H NMR) spectroscopy. The flame retardant behavior of coatings was determined using limiting oxygen index. Thermal behaviors of the films were studied by thermal gravimetric analysis. Furthermore, scanning electron microscopy/energy-dispersive spectroscopy was used to determine the elemental composition and to observe the morphology of the coatings. The properties (water adsorption, gel content, etc.) of the coatings were also studied. It was found that the addition of DOPO resulted in a significant improvement in the flame retardant and thermal properties of the coatings.

A mixture of etherified melamine–formaldehyde and acrylic emulsion resin was designed, with the hybrid resin improving the fire retardancy of indoor plywood as well as the CO and CO₂ emissions. The water-based hybrid resin exhibited a single curing peak; the need for solvents was reduced. Compared with pure etherified melamine–formaldehyde resin, the hybrid resin had better flame retardancy and produced less pollution. Scanning electron microscopy and cone calorimetry were conducted, and the analyses revealed that lower binder resin concentrations resulted in improved flame retardancy and better char layer formation. When the binder resin concentrations were increased and CO/CO₂ emissions were continued beyond 300 s, the flame retardancy of the intumescent coating was the same as that of the lower binding resin concentrations. Furthermore, the chemical structure and durability of the phosphocarbonaceous structure were verified through Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance analyses.

In this study, silane coupling agent KH560-FA containing furan groups was synthesized to modify the surface of graphene oxide, and maleimide group-capped waterborne polyurethane was synthesized at the same time. A self-healing material with a microcrosslinking network structure based on polymer/modified graphene oxide was synthesized by Diels–Alder (DA) reaction. The materials obtained can control the formation and fracture of DA chemical bonds under thermal stimulation and repair the damage macroscopically. With the addition of modified graphene oxide from 0 wt% to 0.4 wt%, the tensile strength of the material increased from 3.59 MPa to 15.27 MPa, the repair efficiency reached a maximum of 89.19%, the water contact angle increased from 61° to 77°, and the water absorption decreased from 10.52% to 3.40%. The addition of modified graphene oxide significantly improved the hydrophobicity and mechanical properties of the material. When the addition of KH560-FA-GO was 0.4 wt%, the corrosion resistance of the coating prepared by the emulsion was remarkably improved in deionized water, 5% sodium chloride solution, and 5% sulfuric acid solution. It showed the application potential of materials in the field of coatings.

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.