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Journal of Coatings Technology and Research

Current research reports and chronological list of recent articles..




The international scientific Journal of Coatings Technology and Research - JCTR - is a forum for the exchange of original research, experience, knowledge and ideas among those with a professional interest in the science, technology and manufacture of functional, protective and decorative coatings including, but not limited to, paints, inks and related coatings and their raw materials.

The publisher is Springer. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

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Additional research articles see Current Chemistry Research Articles.



Journal of Coatings Technology and Research - Abstracts



Atomic force microscopy analysis of cathodic arc ion-plated CrN and CrC coatings

Abstract

Coatings of CrN and CrC were deposited on a YT14 cemented carbide cutting tool using cathodic arc ion plating (CAIP). The surface and interface morphologies of the as-obtained CrN and CrC coatings were analyzed using a field emission scanning electron microscope. The heights, particle diameters and power spectral densities of CrN and CrC coatings were analyzed using atomic force microscopy and the correlated parameters of roughness were obtained. The results show that the roughness of the CrN and CrC coatings is 81.7 × 10−3 and 70.2 × 10−3 nm, respectively, and CAIP has little effect on the CrN and CrC coating roughness. The height of the peak values of CrN and CrC coatings is 0.498 and 0.502 nm, respectively, and the reduction friction of the CrN coating was slightly better than that of the CrC coating. The average particle diameter of the CrN and CrC coatings is 6.575 × 102 and 7.678 × 102 nm, respectively, and the particles are uniformly distributed with no large-scale fluctuations. The power between the cursors of the CrN and CrC coatings is 1.44 × 10−2 and 9 × 10−3 nm2, respectively, with the power spectral density of the CrN coating being the dominant frequency.


Datum: 16.01.2018


Ultra-repellency of Al surfaces: design and evaluation

Abstract

Aluminum (Al) surfaces with ultra-repellency as well as desirable robustness were designed and fabricated. With photolithographic patterning of a thick SU-8 layer and sputtering of a thin Al film, re-entrant micro-pillar textured Al surfaces were prepared. After derivatization with perfluoroalkyl phosphoric acid (FPA), the textured Al surfaces showed ultra-repellency for a wide variety of liquids. The contact angles (CAs) of deionized (DI) water, hexadecane and dodecane were larger than 150°, and those of methanol and ethanol were larger than 100°. The sliding angles (SAs) of DI water, hexadecane and dodecane were 5°, 10°, and 10°, respectively, showing excellent superamphiphobicity. The SAs of methanol and ethanol were in the range of 20°–30°. The robustness of the ultra-repellent Al surface was evaluated by three parameters: robust height (H*), robust angle (T*) and robust factor (A*). For the DI water probing, the values of the parameters are H* ≈ 403, T* ≈ 119 and A* ≈ 92, respectively, indicative of a desirable robustness. We clarified that only re-entrant structures can support composite liquid–solid–vapor interfaces when the corresponding Young’s CAs are smaller than 90°, and the function of the nanometer structures of the hierarchical textures which were widely adopted to fabricate superamphiphobic surfaces is to help construct re-entrant structures. FPA derivatization is effective in lowering the surface energy of Al surfaces, combining with re-entrant textures to provide a simple and high throughput approach to ultra-repellency for a wide variety of liquids.


Datum: 16.01.2018


Synthesis and characterization of solvent-free hybrid alkyd resin with hyperbranched melamine core

Abstract

In this study, a new hybrid alkyd resin was formulated using melamine-based hyperbranched polymer having 24 hydroxyl groups on its structure and relatively low molecular weight alkyd. The alkyd was synthesized using an oil mixture (40% linseed + 60% sunflower). Melamine was used as the core molecule for the hyperbranched polymer due to its excellent properties such as greater hardness, alkali and solvent resistance, and thermal stability. Melamine was first hydroxylated using formaldehyde and changed into hexamethylol melamine. This product was then twice hydroxylated with dimethylol propionic acid to obtain a hyperbranched polymer with 24 hydroxyl end groups. It was then reacted with low molecular weight alkyd resin at different proportions. The product had a low viscosity and could easily flow like oil. It is a solvent-free and water-free liquid. The ‘hyperbranched polymer/alkyd’ ratio affected physical properties of the liquid polymer and also the mechanical properties of the hardened polymer, which can be used for surface coating. The viscosity of the liquid resin decreases from 148 to 8.84 Pa.s as the hyperbranched-polymer-to-alkyd ratio is decreased from 1:3 to 1:24. On the other hand, the hardness of heat-treated resin decreases from 198 Persoz to 43 Persoz, respectively. That is, the increase in the amount of hyperbranched polymer in the resin increases hardness, whereas the increase in the amount of alkyd decreases it. The mechanical tests of hardened resins showed that all specimens passed conical mandrel bending test, and they all depicted high adhesion, and high abrasion and impact resistance. The specimens also had excellent gloss properties.


Datum: 16.01.2018


Self-healing hybrid coating of phytic acid/silane for improving the corrosion resistance of magnesium alloy

Abstract

In order to improve the corrosion resistance of a biodegradable magnesium alloy, a series of phytic acid/3-aminopropyltrimethoxysilane (γ-APS) hybrid coatings was prepared on AZ31 magnesium alloys by dipping the magnesium alloy into the mixing solution of phytic acid and γ-APS. During the preparation of hybrid coatings, the pH values of the mixing solutions greatly affected the uniformity of the coatings and subsequently influenced their corrosion resistance. Electrochemical tests indicated that the hybrid coating prepared in the solution of pH = 8.0 could highly improve corrosion resistance of AZ31 magnesium alloys. Meanwhile, corrosion current density of the hybrid coating coated sample was significantly decreased from the uncoated sample of 138.1 ± 11.9 to 8.5 ± 0.8 μA cm−2. Immersion test in simulated body fluid revealed that the cracks on the surface of the hybrid coating gradually healed up during the lengthy immersion.


Datum: 12.01.2018


Fire-proof silicate coatings with magnesium-containing fire retardant

Abstract

A formula for an environmentally friendly and safe fire-proof paint was developed based on a potassium silicate aqueous solution with addition of a magnesium-containing fire retardant. The predominant use in paint of magnesium-containing fire retardant such as hydromagnesite compared to brucite and magnesite was demonstrated. It was established that a paint containing 5.5 wt% of hydromagnesite provides the first group of fire resistance for a wooden surface. The high fire resistance of the paint with this formula is proven by the high intumescence ratio (150%) and low weight losses (8.4%) after tests in a ceramic tube. When the paint is heated, a gradual loss of weight is detected, which is related to the characteristics of the hydromagnesite structure and helps to obtain an effectively foamed protective layer that prevents the diffusion of combustible gases and flame.


Datum: 12.01.2018


Structure and surface properties of a novel bulk-matte waterborne polyurethane coating composite

Abstract

This paper reports on a novel self-matte or bulk-matte waterborne polyurethane coating composite with inherently extremely low gloss. The coating composite was comprised of a siloxane-containing waterborne polyurethane (SPU) resin and a crosslinked waterborne polyurethane (CPU) resin. The CPU resin was mainly responsible for fabricating the micro-rough surface of the film, which was achieved by a crosslinking reaction between the waterborne polyurethane and bisphenol A-type epoxy E-44 resin. The SPU resin was used to improve the comprehensive properties of the film, which was ascribed to the addition of silane coupling agent KH792. Compared with traditional matte coatings, this coating composite made it possible to avoid high loadings of matting agent and to arrive at highly flexible low-gloss finishes. Gloss levels of as low as a few tenths of a percent, even at high incidence angles, have been achieved with zero loading of extraneous dulling agent. The chemical structures of the SPU and CPU resins were characterized by FTIR-ATR and NMR spectra. The micro-rough topographies and surface rough degrees of the SPU, CPU and their 50%/50% composite films were measured by SEM and MSP, respectively. The particle sizes and particle morphologies of the SPU and CPU resins were imaged by TEM. Finally, the comprehensive properties of the SPU, CPU and their 50%/50% composite resins were evaluated, including the water contact angle, film transparency, tensile strength and storage stability.


Datum: 05.01.2018


Fabrication of UV-curable waterborne fluorinated polyurethane-acrylate and its application for simulated iron cultural relic protection

Abstract

In this study, UV-curable waterborne fluorinated polyurethane-acrylate (UV-WFPUA) coatings were investigated to evaluate their potential application for protecting iron cultural relics. A series of UV-WFPUA materials were synthesized with different contents of hexafluorobutyl methacrylate (HFBMA) and characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. When the content of HFBMA was 10%, the UV-WFPUA-3 material exhibited good mechanical properties and excellent hydrophobicity. The iron sheet was selected to simulate an iron artifact sample in this study. The obtained results indicated that the prepared UV-WFPUA material could provide excellent protective properties for simulated iron artifacts.


Datum: 04.01.2018


Sucrose octaesters as reactive diluents for alkyd coatings

Abstract

Sucrose octasoyate (SS8) was investigated as a reactive diluent for a medium oil alkyd (MOA). SS8, which is derived from sugar and soybean oil, is 100% biobased, nontoxic, and biodegradable. As a result of its unique molecular architecture, it was expected that SS8 would be an excellent reactive diluent for alkyd coatings. The experiment conducted basically involved the incremental replacement of the MOA with SS8, while maintaining essentially equivalent solution viscosity. The properties of cured coatings were determined using industry standard methods. In general, it was found that SS8 could be used to reduce volatile organic compound content of the coatings, while also reducing drying time (i.e., tack-free time), increasing solvent resistance, and increasing impact resistance. Of the properties measured, the only cured film property that was negatively affected by the use of SS8 was the König pendulum hardness. However, the reduction in König pendulum hardness was only observed when the amount of MOA replaced by SS8 was greater than 10 wt%. Overall, these initial results suggest that SS8 is a very good reactive diluent for alkyd coatings.


Datum: 04.01.2018


Superhydrophobic surfaces: a review on fundamentals, applications, and challenges

Abstract

Superhydrophobicity is the tendency of a surface to repel water drops. A surface is qualified as a superhydrophobic surface only if the surface possesses a high apparent contact angle (>150°), low contact angle hysteresis (<10°), low sliding angle (<5°) and high stability of Cassie model state. Efforts have been made to mimic the superhydrophobicity found in nature (for example, lotus leaf), so that artificial superhydrophobic surfaces could be prepared for a variety of applications. Due to their versatile use in many applications, such as water-resistant surfaces, antifogging surfaces, anti-icing surfaces, anticorrosion surfaces etc., many methods have been developed to fabricate them. In this article, the fundamental principles of superhydrophobicity, some of the recent works in the preparation of superhydrophobic surfaces, their potential applications, and the challenges confronted in their new applications are reviewed and discussed.


Datum: 04.01.2018


Study of ionic/nonionic polyurethane dispersions with high solid content and low viscosity using a complex hydrophilic chain-extending agent

Abstract

An ionic/nonionic polyurethane dispersion with high solid content and low viscosity with a complex hydrophilic chain-extending agent was prepared using isophorone diisocyanate as a hard segment and propylene oxide glycol as a soft segment. The complex hydrophilic chain-extending agent consisted of DPSA and BDSA. The effects of the molar ratio of DPSA/BDSA on the properties of the resultant polyurethane dispersions were studied. The morphologies and properties of the ionic/nonionic PU dispersions were examined using particle-size, TEM, and viscosity analyses. It was found that the ionic/nonionic dispersions possessed wide particle-size distributions due to the addition of the complex hydrophilic chain-extending agent. The ionic/nonionic PU dispersions possessed higher solid content than conventional WPU dispersions because the number and volume percentage of the large particles and small particles of the ionic/nonionic dispersions met the requirements for high solid content. It was observed that the solid content of the ionic/nonionic dispersion increased and then decreased with an increasing molar ratio of DPSA/BDSA. When the ratio ranged from 4:10 to 5:10, the solid content of the ionic/nonionic PU dispersion reached up to 55%. It was also noticed that the apparent viscosity of the ionic/nonionic polyurethane dispersion decreased with an increasing molar ratio of DPSA/BDSA. The complex hydrophilic chain-extending agent consisting of DPSA and BDSA enhanced the solid content and decreased the viscosity of the ionic/nonionic dispersions, which are very important for improving the properties and expanding the applications of PU dispersions. In addition, the ionic/nonionic polyurethane dispersion had good electrolyte-resistance properties, stability at both high and low temperatures, and storage stability.


Datum: 01.01.2018


Synthesis and characterization of novel renewable castor oil-based UV-curable polyfunctional polyurethane acrylate

Abstract

In recent years, a lot of interest has been given to renewable resources for their environmental friendliness and potential biodegradability in the synthesis of urethane-derived polymers. In this work, UV-curable castor oil-based polyfunctional polyurethane acrylate (COPUA) was prepared by the reaction of isophorone diisocyanate (IPDI) with castor oil and pentaerythritol triacrylate (PETA). The structures and molecular weights of the targeted IPDI–PETA and COPUA were characterized by FTIR, 1H NMR, and GPC, respectively. In addition, the effect of reactive diluent content on damping properties, thermal stabilities, and mechanical properties of COPUA was characterized by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and universal test machine. DMA revealed the copolymers had a glass transition temperature (T g) from 31.81 to 48.09°C. TGA showed that thermal initial decomposition temperatures were above 344.5°C, indicating the copolymers had certain thermal stability. Finally, some physical properties of curing films were studied by the contact angle and water absorption, and the results showed that the coatings exhibited good hydrophobicity. The COPUA obtained from castor oil can be used as eco-friendly materials and other applications alternative to the use of other petrochemicals in coatings.


Datum: 01.01.2018


Bioinspired metal–polymer thin films with varying hydrophobic properties

Abstract

Nanocomposites involve the inclusion of one material into the layers of another material at a nanoscale level. Inspired by nature, nanocomposites material systems offer functionalities over their bulk forms which in some cases have evolved over millions of years. Here, thin film coatings have been fabricated by PVD sputtering, comprising a soft PTFE phase which is combined with a hard metallic NiTi phase. A series of coatings with PTFE ranging from 10 to 75 vol% have been prepared, and their surface energies and microstructures investigated. The surface energy of the nanocomposite films changes with the PTFE content, falling in the range between PTFE and NiTi with water contact angles between 80° and 102° for a thin film with 25 and 75 vol% of PTFE, respectively. Here, both TEM and EDX reveal PTFE forming along NiTi column boundaries. Coatings with PTFE content greater than 50 vol% failed due to a build-up of intrinsic stress. The degree of hybridization between NiTi and PTFE was found to be dependent on the PTFE layer thickness. SEM analysis of this coating reveals PTFE at the surface embedded within the NiTi matrix.


Datum: 01.01.2018


Evaporation of clearcoat solvents from a rotary bell atomizer and its relationship with bell speed, flow rate, and electrostatic potential

Abstract

The relations between evaporation of clearcoat solvents and various operating parameters of the spray from a rotary bell atomizer were measured using a particle dynamic anemometer (PDA). The robot arm holding the spray applicator was moved relative to the PDA so that the volume flux at different parts of the spray could be measured. The difference in total flux between two planes, perpendicular to the spray axis, was considered to be equal to the evaporation. Evaporation was found to increase with increasing bell speed. Evaporation also increased with increasing coatings flow rate from 100 to 200 cm3/s flow rate, but not for a further increase to 300 cm3/s. Higher electrostatic potential, bell speed, and lower flow rate decrease the mean particle diameter. Particle mean velocity increases with increasing bell speed and flow rate. Coatings flow rate, bell speed, electrostatic potential, and the interaction between flow rate and bell speed were significant factors affecting evaporation rate. Of the former three, coatings flow rate was the most influential.


Datum: 01.01.2018


Synthesis of core–shell-type styrene acrylic latexes with low NMA content and their application in pigment printing pastes

Abstract

In this paper, novel core–shell polymers comprising styrene (St) and butyl acrylate (BA) in both core and shell layers of the polymer particles have been synthesized and employed in pigment printing pastes which were applied on 100% cotton and 65% cotton/35% polyester (PET) fabrics. The aim was to reduce the NMA content and the formation of free formaldehyde from pigment printing pastes by employing newly synthesized core-/shell-type polymers. After five washing cycles, the synthesized core-/shell-type polymer including 1% NMA in the core and 1% NMA in the shell with T g values +30°C and −20°C, respectively, with lowest total NMA content (1.03%) yielded the best result and showed closest ΔE values to the commercially available polymer including 4% NMA. Dry and wet rubbing fastness results showed no significant changes in the absence of NMA when compared with NMA containing samples. The penetration degree of the pigment pastes of the corresponding polymers was relatively higher on 100% cotton fabric for both red- and blue-colored pigments. A negligible decrease in color strength has been observed for all polymers when colored in red.


Datum: 01.01.2018


Fabrication of thermally stable porous films from a cured epoxy resin via the Breath Figures process

Abstract

In the current work, porous films based on epoxy resin have been obtained via the Breath Figures method. It was shown that the use of a low-temperature curing agent and fluoro-containing organosilicon copolymer, compatible with epoxy resin, makes it possible to obtain porous, thermostable, highly hydrophobic coatings with a pore diameter of 3–4 µm. When the epoxy resin/copolymer mixture is homogenous, the modifier prevents water droplet coalescence; otherwise, the mixture becomes heterogeneous, and the positive influence of the modifier is lost. The obtained modified porous films are highly hydrophobic and maintain their porous structure until polymer devitrification occurs. The simplicity of the Breath Figures method shows great potential for the manufacture of water-repellent paint coatings based on epoxy resin for use in a variety of applications.


Datum: 01.01.2018


Synthesis of silica-supported ZnO pigments for thermal control coatings and analysis of their reflection model

Abstract

A spacecraft in orbit undergoes extreme temperature cycling, space radiations, and other extreme conditions that can potentially raise the temperature of spacecraft to harmful levels. Hardware and sensitive detectors utilized in spacecrafts require that temperatures be maintained within specified ranges. Thermal control coatings (TCCs) help to maintain the thermal equilibrium of the spacecraft at a level acceptable for vital components. This is done by employing the diffused reflection of all effective ultraviolet (UV), visible (VIS), and near-IR (NIR) wavelengths of solar radiation and emitting the infrared (IR) energy. The most commonly used TCCs have utilized potassium silicate as the binder and ZnO as the pigment (Z-93), but absorption of UV light by ZnO pigment affects the ideal scheme of these TCCs. In the present study, silica-supported zinc oxide particles with different ZnO contents were synthesized as pigments for white thermal control coatings and the optimized one was selected based on the experimental determination of the optical properties of the prepared coatings. The results revealed that the optimized TCCs containing pigment with the zinc to silicon ratio of 1.91 had better reflection and emission properties in comparison with Z-93, due to the improvement in the refractive index and the dispersion quality of pigment. Then, the scattering properties (S) of the synthesized pigments and ZnO in TCC were investigated based on the reflectance data, according to the Kubelka–Munk analysis. The general trend in scattering coefficients for each formulation showed the same shape, such that with the increase in S values, the zinc to silicon ratio of pigments was raised too. Also, this trend revealed that scattering was more efficient at longer rather than shorter wavelengths. For Z-93, this trend was completely opposite. Also, S values for Z-93 in the wavelength range of 200–400 nm were around zero, while for the prepared coatings, this was not the case. Finally, the statistical nonlinear regression method was utilized to prepare a model for reflectance as a function of the zinc to silicon ratio of pigments and the wavelength of light.


Datum: 01.01.2018


Synthesis of acrylate-based UV/thermal dual-cure coatings for antifogging

Abstract

A dual-cure hydrophilic acrylate polymer was synthesized via radical polymerization with acrylic acid (AA), isophorone diisocyanate (IPDI), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), hydroxyethyl acrylate (HEA), and 3-(trimethoxysilyl)propyl-2-methyl-2-methacrylate (MPS) as monomers, then used as prepolymer for antifog coating with tetraethylorthosilicate (TEOS) as a novel crosslinker. The prepolymer was mixed with crosslinking agent and photoinitiator to form coating formulas. The coating was characterized by nuclear magnetic resonance (NMR), Fourier-transform infrared (FTIR) spectroscopy, and contact angle measurements. The results indicated that the dosage of AMPS and TEOS had great influence on the antifog performance. With an increasing TEOS amount, the hardness, adhesion, water resistance, impact resistance, and thermal stability of the films were improved, at the expense of transparency; with increasing dosage of AMPS, the hydrophilicity of the film increased at the expense of water resistance. Optimum coating properties could be obtained when the amount of AMPS was 7% and that of TEOS was 5.5%. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that some SiO2 microspheres were formed and microphase separation occurred between the macromolecular segments, yielding the excellent coating properties.


Datum: 01.01.2018


One-pot fabrication of robust hydrophobia and superoleophilic cotton fabrics for effective oil-water separation

Abstract

A one-pot sonochemical irradiation method was developed for the fabrication of superhydrophobic and superoleophilic cotton fabric from a solution consisting of branched silica nanoparticles and tetraethoxysilane-dodecyltrimethoxysilane sol. The silica/sol-coated cotton fabric could be wetted by liquids of low surface tension, but was water repellent with a water contact angle of 159 ± 1.2° and water shedding angle of 6 ± 0.8°. The as-prepared cotton fabric could be used as effective materials for the separation of oil from water with separation efficiency as high as 98.2% and maintained separation efficiency above 94% after 30 separation cycles for the kerosene-water mixture. Moreover, the superhydrophobic and superoleophilic cotton fabric could maintain stable superhydrophobicity after treatment with strong acidic and alkali solutions, and harsh mechanical damage. Therefore, this reported robust superhydrophobic cotton fabric exhibits encouraging practical application for oil-water separation.


Datum: 01.01.2018


Fabrication and characterization of polysiloxane/polyacrylate composite latexes with balanced water vapor permeability and mechanical properties: effect of silane coupling agent

Abstract

In order to improve the water vapor permeability and mechanical properties of latex films, polysiloxane/polyacrylate (PSi/PA) composite latexes were fabricated via seeded emulsion polymerization of methyl methacrylate and butyl acrylate onto PSi latex particles, and the effects of the silane coupling agent 3-methacryloyloxypropyl trimethoxysilane (MATS) on the morphologies of the latex particles and films, as well as the microphase separation degree, the water vapor permeability and the mechanical properties of the latex films were investigated. Results indicated that MATS was essential for obtaining the PSi/PA composite latex particles with PSi as core and PA as shell and made a great contribution to restrict the phase separation. The PSi/PA core/shell latex films showed similar tensile strength and elongation with pure PA film, while exhibiting promising water vapor permeability. It was found that the influences of MATS content on the water vapor permeability and mechanical properties were opposite, and on the premise of the requirements for mechanical properties, lower MATS content could provide the PSi/PA core/shell latex films with better water vapor permeability.


Datum: 01.01.2018


Thermal yellowing and photobleaching of automotive topcoats

Abstract

Thermal yellowing and photobleaching are common problems that are seen to some extent in all automotive topcoat systems today. These effects can cause difficulties in the matching of light colors in the assembly plant and then later upon delivery to the customer. Current literature offers no clear mechanism for the thermal yellowing and photobleaching. Based on observed formulation dependencies, a mechanism is proposed based on oxidation of amine compounds. We constructed a model in vitro system using a hydroperoxide to thermally oxidize amines in solution. In this system, a series of amines were tested and both yellowing and photobleaching were reproduced. Loss of basicity confirmed that amine oxidation occurred under these conditions. Both the location of the UV absorption peak and strong amine structure dependence indicate nitrone formation as the yellow chromophore.


Datum: 01.01.2018


 


Category: Current Chemistry Research

Last update: 04.01.2018.






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