Journal of Coatings Technology and Research最新文献

Since ice formation on surfaces at subzero temperatures leads to accidents, increased equipment maintenance costs, and reduced performance, multiple strategies, including superhydrophobic surfaces and coatings, have been explored as means to reduce ice adhesion to solid surfaces. Previous work has correlated the effect of topography of regularly patterned superhydrophobic surfaces with ice adhesion. This work, however, investigated the effect of filtered topography on ice adhesion for random superhydrophobic surfaces. The ice adhesion behavior of superhydrophobic composite coatings, prepared from a mixture of silica nanoparticles and polymer binder and sprayed on glass slides, was determined using a shear strength measurement. The ice adhesion significantly decreased with an increase in particle content up to 40 wt.%, after which the ice adhesion became nearly constant. The present study focuses on the use of a novel filtering method for coating topography evaluation which isolated the asperities contributing to the interface from the roughness profile in the superhydrophobic coating. It showed that the ice adhesion correlated with the filtered asperity height and spacing for these random hydrophobic surfaces. Higher particle contents led to larger asperity distances, smaller solid fractions, and lower ice adhesion. The results and conclusions are based on a static ice adhesion test using still water. In this work, it is demonstrated that ice adhesion can be predicted based on the solid–water–air interface, a correlation that could guide future superhydrophobic coating fabrication to create surfaces with greater reduction in ice adhesion.

Our study decided to use the new and revolutionary approach in the field of pharmaceutical coating processes called the artificial neural network (ANN) by using the neural networks toolbox derived from the Matlab® software. The experiments were performed using tablets of Alfuzosin Chlorhydrate as a model filler, and an aqueous solution of Surelease as a polymer in different contents. The various parameters that can affect coating thickness, weight gain, and the coefficient of variation CV, such as spray rate, air pressure, solid content, speed of the drum, pan loading, and time of coating, were studied. The properties of the coated tablets were evaluated using the ANN, and both the parameters of the coating process and the properties of the coated tablets were used as a basis for optimization, as well as the choice of the optimal structure of the ANN model. It was found that the best neural network architecture had 7 neurons in the hidden layer, with a mean square error of 3.515 and a determination coefficient of nearly 1. The relative importance of each independent variable was quantified using the Garson equation. In this study, spray rate was found to have the highest impact on the properties of tablets.

The search for environmentally friendly coatings has gained relevance in recent years. To circumvent the use of volatile organic compounds, ultraviolet light curing has attracted considerable attention, especially with the recent advances in light emitting diodes (LEDs), wherein one of the most important components is the photoinitiator. Since UV-LED curing has a narrower wavelength spectrum than regular UV curing, the choice of photoinitiator is crucial. In this study, the influence of six types of photoinitiators in the curing of polyester acrylate varnishes was investigated. The post-curing optical, thermal, mechanical, dynamic mechanical, and morphological properties of these varnishes were examined. All varnishes were completely cured, and the resins cured with LED 1711 and diphenyl (acyl) phosphine oxide exhibited the lowest post-curing photoyellowing. Satisfactory mechanical and dynamic mechanical properties were achieved for all samples. However, due to the thickness of the films, more studies are needed to optimize the surface roughness of the varnishes.

Most offshore wind turbines use monopile structures anchored to seabed. In the underwater zone of these structures, water attacks the surface of the steel monopiles which is protected by organic coatings. The influence of applied stresses due to the water flow on the degradation of organic coatings is the focus of this study. For this purpose, an impingement flow chamber was employed to resemble the situation of monopile structures exposed to the shallow water currents in underwater zone. Electrochemical impedance spectroscopy was utilized to measure the changes of barrier properties of coatings exposed to the impingement flow of a 3.5 wt% NaCl solution with a variety of flow rates. Computational fluid dynamics (CFD) modeling as well as the particle image velocimetry measurements were employed to calculate and validate the magnitude of applied stresses on the surface of the coated samples. Thermal activation theory, thermal elasticity laws, and the Fick’s laws were utilized to investigate and analyze the influence of stresses on coating properties. The comparison among the obtained electrochemical parameters under different flow rates shows the direct influence of stresses on the degradation of the coatings. The utilized methods, in addition to the developed analytical procedure, can potentially predict the behavior of organic coatings applied on offshore wind turbines in underwater zone. It was concluded that the applied stresses do not influence the apparent diffusion coefficient of water in coatings, but a higher flow rate increases the volume fraction of water and coating capacitance significantly.

As described herein, a simple one-step hydrosilylation reaction was employed to synthesize alicyclic epoxy silicone prepolymers by using poly(dimethylsiloxane-co-methylhydrosiloxane) (PDMS-PHMS) with different hydrogen contents and 4-vinyl-1-cyclohexene-1,2 epoxide (VCHO) as precursors. The structures of the synthesized epoxy polysiloxane oligomer was characterized by Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy techniques, thus confirming the successful synthesis of the prepolymers. With the addition of an appropriate amount of cationic photoinitiator, the epoxy polysiloxane prepolymers undergo cationic polymerization under ultraviolet light irradiation and were quickly cured to yield series of epoxy polysiloxane resin films. The performances of these cured films were tested and characterized by various techniques such as UV transmittance, thermal weight loss analysis, and contact angle and pencil hardness measurements. The results revealed that the surfaces of these films were uniform and transparent, and these films had excellent heat resistance, acid resistance, hydrophobicity, and ink removal properties. In addition, the influence of the cycloaliphatic epoxy monomer content on the curing behavior and network performance is explored. This study reveals that the curing rate increases as the amount of grafted cycloaliphatic epoxy monomer is increased and that a denser crosslinking network provides the resultant film. Finally, the photocurable silicone material investigated herein is simple to prepare and has excellent performance, and has potential applications in the field of anti-smudge coatings.

A novel organic-inorganic nanohybrid resin was synthesized through sol-gel process using nano magnesium oxide and specially designed acrylic resin. The uniqueness of this process is incorporation as well as dispersion of nano magnesium oxide into acrylic resin matrix where nano magnesium oxide is functional component. Magnesium oxide nanoparticles were successfully synthesized by sol-gel technique using magnesium nitrate as a precursor. Characterization of synthesized magnesium oxide nanoparticles and their distribution in acrylic resin matrix has been confirmed by spectroscopic, X-ray diffraction and SEM analysis. The coating based on such hybrid resin exhibited excellent anti-microbial activity. Such resin system has potential for application in antimicrobial coating.

In civil construction, intumescent coatings are widely used in steel structures, because in a fire, this material loses approximately half of its elastic modulus at 500°C. The use of these paints is essential to ensure the structural safety of the construction as well as that of humans. The phenomenon of intumescence in paints occurs when they are subjected to high temperatures forming a carbonaceous layer that expands on the surface of the coating, with the main purpose of serving as a thermal insulator of the substrate. The development of paints with low impact on the environment has been stimulated due to restrictions on the emission of volatile organic compounds imposed by government agencies. Therefore, the development of water-based intumescent paints has become essential to meet these guidelines. In the present work, intumescent coatings were developed with different water-based resins: epoxy, acrylic and alkyd. The paints were formulated using expandable graphite as a blowing agent and expanded char source, ammonium polyphosphate as an acid source and lignin as a carbon source. The formulations were applied to steel substrates and exposed to burning tests to verify fire resistance, and in addition, the samples were characterized by combustion microcalorimetry, thermogravimetric analysis and pyrolysis coupled with gas chromatography and mass spectrometry. The carbonaceous layers were characterized by optical microscopy, scanning electron microscopy with dispersive energy spectroscopy, X-ray diffraction and Raman spectroscopy. The results of combustion microcalorimetry showed that the formulations containing lignin released less heat than the others. No toxic gases were detected in the pyrolysis of epoxy and acrylic system paints. The X-ray diffraction and Raman analyses proved the formation of thermally stable compounds in the carbonaceous layer.

Water-based anti-corrosion coatings, which are environmentally-friendly replacements for organic solvent-based coatings, do not perform well enough for use in the most challenging corrosion environments. The high water absorption capacity of water-based latex films may reduce barrier performance by contributing to corrosive reactant/product transport. We seek to understand the coupled effects of water absorption and ion transport in hydrated latex films, and to propose mechanisms explaining these effects. Water absorption and ion transport in films immersed in deionized (DI) water were monitored by mass gain and electrical conductivity measurements, respectively. Despite very similar polymer compositions between films, large differences in water absorption and ion transport rates were observed and explained by percolating networks at latex particle boundaries which facilitate transport. A semi-continuum model with three-component diffusion and convection-like elastic relaxation supported the assumptions of the physical mechanisms governing water absorption and ion transport. The evidence of the coupled processes of water absorption and ion transport in hydrated latex films revealed in this study are useful for designing water-based coatings that provide high levels of corrosion resistance.

The anticorrosive properties of hexadecyltrimethoxysilane (HDTMS) functionalized MCM-41 silica particles (MCM-41-HDTMS) incorporated into a methyltriethoxysilane (MTES) sol-gel matrix coatings were studied. The MCM-41 particles were synthesized and functionalized with HDTMS, and added to a sol composed of MTES:methanol:NH₄OH 7M to create a coating. The materials synthesized with and without MCM-41-HDTMS were deposited, by dip coating, on Cu and Fe sheets, and were physically characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle, surface energy using the Owens, Wendt, Rabel, and Kaelble (OWRK) method, and by electrochemical impedance spectroscopy (EIS). The addition of the MCM-41-HDTMS to the MTES matrix induced an increase of the contact angle by about 10 degrees with an augment in its dispersive component, caused by a lofty deposition of long carbon chains from HDTMS over the high surface area of the MCM-41 particles, changing from hydrophobic to superhydrophobic materials with a contact angle of 155° for the Cu-MTES-HDTMS sample. EIS results show that the addition of MCM-41-HDTMS increases the charge transfer resistance providing better protection to metals. The results show that with the addition of MCM-41-HDTMS to an MTES matrix it is possible to synthesize superhydrophobic coatings capable of limiting the corrosion degradation process.

Graphical abstract

In this work, a superhydrophobic and superoleophilic brass mesh had been prepared. The prepared sample displayed a water contact angle (WCA) of 160^o and was characterized by field emission scanning electron microscope (FE-SEM), white light interferometer (WLI), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. Besides, a high-speed camera was used to study the impact process of a droplet on the surface of the prepared sample. The superhydrophobic brass mesh exhibited excellent self-cleaning ability, environmental adaptability, corrosion resistance (η = 98.9%), and delayed icing ability (~ 45 min). Furthermore, the superhydrophobic mesh could be used as a filter to fast and efficiently separate various kinds of oils (light and heavy oils) and oil pollutants in daily life and industry. The superhydrophobic filter could be reused 50 times for oil-water separation without any apparent decrease in its separation capability. Thus, the superhydrophobic brass mesh prepared by a simple method holds promise for various applications in the industrial field of oil-water separation.