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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



Impedance sensor for the early failure diagnosis of organic coatings

Abstract

A miniature impedance sensor used for field diagnosis of the early failure of coatings has been developed based on microelectronics and electrochemical impedance spectroscopy (EIS). The aging process of polyurethane-based coatings in salt spray test chamber was studied using the impedance sensor. Several critical indexes related to EIS such as phase angle (θ10Hz, θ15kHz), breakpoint frequency (fb), specific capacitance (C10Hz, C15kHz), and impedance modulus (Z0.1Hz) were proposed to evaluate the severity of coating degradation. The results indicated that the impedance sensor could accurately monitor the degradation process of coatings, and once Z0.1Hz < 106 Ω cm2, fb > 100 Hz, or θ10Hz < 20°, the coating may be regarded as completely degraded and fails to protect the metal substrate.


Datum: 24.04.2018


Synergistic effects of aluminum hydroxide on improving the flame retardancy and smoke suppression properties of transparent intumescent fire-retardant coatings

Abstract

A series of novel aluminum phosphate ester (APEA) flame retardants were synthesized by the salification of cyclic phosphate ester acid (PEA) with different mass ratios of aluminum hydroxide (ATH) and thoroughly characterized by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance spectroscopy. The PEA and APEAs were thoroughly mixed with melamine formaldehyde resin to produce five kinds of transparent fire-retardant coatings. The synergistic effects of ATH on the thermal stability, flame retardancy, and smoke suppression properties of the coatings were investigated by different analytical instruments. The results show that the incorporation of ATH greatly decreases the weight loss, char index, flame spread rating, heat release rate, total heat release, smoke production rate, total smoke release and specific optical density in the coatings applied to plywood boards, which is ascribed to a more compact and intumescent char formed during burning, as determined from digital photographs and scanning electron microscopy images. The synergistic effects of ATH in the coatings depend on the content of ATH, and an excessive amount of ATH diminishes the synergistic effects on the flame retardancy and smoke suppression properties based on fire protection tests and cone calorimeter test. Thermo-gravimetric analysis reveals that the thermal stability and char-forming ability of the coatings gradually improve with increasing loading of ATH. FTIR analysis demonstrates that the incorporation of ATH forms a more phosphorus-rich crosslinked char and aromatic char during burning, thus effectively reducing the mass loss, heat release, and smoke production and exhibiting excellent synergistic flame retardant and smoke suppression effects in the coatings.


Datum: 24.04.2018


Preparation of an ionic/nonionic polyurethane-silicone dispersion (PUSD) with a high solid content and low viscosity using complex soft segments

Abstract

A series of ionic/nonionic polyurethane-silicone dispersions (PUSDs) with a high solid content and low viscosity were prepared using isophorone diisocyanate as the hard segment, polytetrahydrofuran polyether diol (PTMG) and polysiloxane diol (PESI) as the complex soft segments and an ionic/nonionic low molecular weight polyether diol (DPSA) as the hydrophilic, chain-extending agent. The morphologies and rheological properties of the ionic/nonionic PUSD were examined using particle-size, TEM, and viscosity analyses. The hydrophobic and mechanical properties of the dispersions were also tested. It was found that under the conditions of a constant NCO/OH ratio (2/1) and weight percentage of DPDA (6%), the PUSD dispersions with higher PESI contents possessed higher average particle diameters and wider particle-size distributions. Particles in the PUSD dispersions are generally spherical and have a typical core–shell structure due to the use of complex soft segments. However, the solid content of the ionic/nonionic PUSD increased first and then decreased as the weight ratio of PESI to PTMG increased. When the ratio ranged from 4/10 to 6/10, the max solid content of the ionic/nonionic PUSD reached up to 58%, but the viscosity of the PUSD was less than 400 mPa.s−1. Meanwhile, the water contact angle of the films increased due to the formation of a crosslinking structure on the side of the PUSD macromolecule, and when the weight ratio of PESI to PTMG varied from 3/10 to 7/10, the water contact angle of the films increased from 48.3° to 72.3°. In addition, both the freeze-thaw and thermal stabilities of the PUSD dispersions were enhanced as the weight ratio of PESI to PTMG increased. The PUSD coating had good mechanical properties as well.


Datum: 23.04.2018


Comparative study of the dynamic hydrophobicity of fluoroalkylsilane coatings tilted at acute and obtuse angles

Abstract

The relation between surface homogeneity and internal fluidity for a droplet sliding on a surface tilted at acute and obtuse angles was investigated using two hydrophobic fluoroalkylsilane (FAS) coatings with different roughness. The coatings (FAS-smooth and FAS-rough) were prepared on an Si substrate using chemical vapor deposition or soaking methods and were tilted at 35° or 145°. Sliding velocity of water droplets on the surface tilted at 145° was greater than that tilted at 35° for both coatings. For 35° tilting, the dominant mode of the sliding velocity was slipping for FAS-smooth, whereas rolling governed the entire sliding velocity for FAS-rough. The slipping mode was more important than the rolling one for both coatings when they were tilted at 145°. The change of slipping velocity was more remarkable than that of rolling one for both coatings between 35° and 145° tilting. Results show that the difference in gravity direction and contact area of the droplets contributed to this tilt angle dependence of the sliding velocity. When a droplet slid down with acceleration on FAS-smooth surface, the coefficient of the viscous drag force correlated with the velocity ratio (Utotal/Uslip).


Datum: 23.04.2018


Surface topography and tribological properties of coatings prepared from microparticle size polyurethane dispersions studied by atomic force microscopy

Abstract

The surface topography and mechanical properties of coatings prepared using large particle size polyurethane dispersions (PUD) are investigated using atomic force microscopy (AFM) imaging, AFM-based force measurements, and friction force microscopy. PUD coatings, which are prepared from dispersions containing particles of micron size, have surface roughness of 250–300 nm and waviness of 2.5–3 μm resulting from the particle size. The surface moduli of the PUD coatings are varied by tuning the ratio of hard-to-soft segmentation in the polyurethanes and are found to be between 40 and 100 MPa. The friction coefficient obtained in the study is found to be correlated with both the surface modulus of the coatings and the adhesion between the probe and the samples and is well in line with the perceived feel of an experienced human panel. The data are very well behaved and clearly show the utility of this technique in characterizing these types of surfaces.


Datum: 23.04.2018


Shaping characteristics in alginate hydrogel encapsulation via a two-fluid spraying method

Abstract

Recently, an alginate hydrogel containing amphiphilic liposomes was suggested for application to an antifouling coating. In this study, we investigate the shaping characteristics of the alginate hydrogel by a spraying method for application to the coating. Sodium alginate droplets from the spraying nozzle are known to be differently shaped by several external forces during the encapsulation process when such a droplet impacts onto the surfaces of liquid containing calcium ions. We adopted a two-fluid spraying method for fast alginate droplets with a scalable size suitable for mass production. Various shapes, such as mushroom, petal, sphere, and thin-sheet alginate hydrogel shapes containing liposomes, were obtained via this experimental approach. Supported by a theoretical analysis, we determined regimes for the various shapes depending on the droplet size and the concentration of the sodium alginate solution. Alginate hydrogel of different shapes based on the regimes will be used for the coating throughout a different post-processing.


Datum: 11.04.2018


Mesoscopic structure and swelling properties of crosslinked polyethylene glycol in water

Abstract

In this paper, we present our efforts in modeling and simulation of polyethylene glycol crosslinked with an isocyanate tHDI. The polymer, by its nature, is hydrophilic and has strong hydrogen bond interactions with water. The simulations are performed at coarse-grained scale by using a dissipative particle dynamics (DPD) simulation method. The effect of hydrogen bond between water and polymer beads on the structure of the crosslinked hydrophilic polymer structure is studied. The polymer is observed to phase separate with water in the absence of hydrogen bonds in DPD simulations. In the reverse case, where hydrogen bonds are explicitly included in DPD simulations, polymer mixes with water. This behavior is investigated by plotting the density profiles. Moreover, the volumetric swelling behavior in mixtures with different water contents is estimated from simulations and extrapolated by a polynomial fit to compare with experiments. It is observed that the predicted swelling ratio is in good agreement with the experimental measurements.


Datum: 11.04.2018


Preparation and characterization of waterborne polyurethane/polyacrylate emulsions containing sulfonate groups

Abstract

Polyurethane/polyacrylate emulsions (SDPUA) with high solid content were obtained by using carboxyl groups and sulfonate groups as hydrophilic chain-extenders and internal emulsifiers through surfactant-free emulsion polymerization. Polyurethane/polyacrylate emulsions with ethylene diamine (EDA) as chain-extender (EDPUA) were also prepared. The influence of the different 2,4-diamino-benzenesulfonic acid sodium salt (DABS) content on the properties of the SDPUA products was investigated. The main properties of EDPUA were also discussed compared with the SDPUA samples. Dynamic light scattering results showed that when DABS/DMPA molar ratios increased from 1/4.7 to 1/2.28, the particle size increased from 72.2 to 99.7 nm. The particle size of EDPUA emulsion was larger. The steady rheological measurements illustrated that the viscosity decreased with the shear rate increase and the emulsions were displayed as pseudoplastic behavior. Attenuated total reflection Fourier transform infrared results demonstrated the SDPUA products were successfully prepared. As the function of DABS groups, the thermal stability was enhanced. With the increment in DABS/DMPA molar ratio, the contact angles on SDPUA membranes decreased, and the surface free energies increased. The T-peel strength increased to 88.2 N/mm and DABS/DMPA molar ratio increased to 1/2.28, and it was larger than the EDPUA samples. The compatibility of the dual phases was enhanced.


Datum: 10.04.2018


Sonochemically sol–gel derived coating of textiles using heterojunction SnO 2 /ZnO/chitosan bionanocomposites: in vitro antibacterial evaluation

Abstract

The cellulose-based textiles currently used in hospitals are good conducive materials for cross-infection or transmission of diseases caused by microorganisms. Thus, great interest has been recently found in the antibacterial finishing of fabrics for practical applications to prevent the infection incidence. In this work, we developed novel SnO2/ZnO/chitosan bionanocomposites by one-step simultaneous sonochemical/sol–gel deposition to prepare an antibacterial textile as a model for combating bacterial infections. The different prepared samples were characterized using transmission electron microscope, X-ray diffraction, and scanning electron microscopy (SEM) indicating the embedded SnO2 and ZnO nanoparticles in treated fabrics. The treated fabrics were used to evaluate antibacterial activities against Escherichia coli and Streptococcus aureus as a model for Gram-negative and Gram-positive bacteria, respectively, using disk diffusion method in dark conditions as an in vitro model for treatment of bacterial wound infection. The procedure was more developed in terms of SnO2/ZnO molar ratio and using chitosan and citric acid to improve the antibacterial properties of the fabrics and their wash durability, respectively. The highest antibacterial activity of the fabrics was attained in a 50 min sonochemical coating process using SnO2/ZnO 1:2 molar ratio in initial sol and simultaneously deposited chitosan and citric acid. The presence of chitosan as complexing agent, citric acid as crosslink agent, and SnO2–ZnO heterojunction as important influencing parameters synergistically enhanced both the antimicrobial efficiency and maintenance of modified cotton durability after performing several washing cycles.


Datum: 09.04.2018


Effect of upstream meniscus shape on dynamic wetting and operating limits of Newtonian coating liquids in slot coating bead flows

Abstract

The coating bead flow and operability window for Newtonian coating liquids are theoretically and experimentally investigated in the slot coating process, with a focus on the shape of the upstream meniscus and contact angles. From the flow visualization in the coating bead region, the contact angles of the upstream meniscus were measured by changing the flow rate and web speed under uniform operating conditions. It was confirmed that the dynamic contact angle is closely related to the capillary number in this process, based on the Hoffman–Voinov–Tanner model. The viscocapillary and two-dimensional Navier–Stokes models using the experimentally observed contact angles accurately predicted the coating bead dynamics and operability windows for two Newtonian liquids.


Datum: 04.04.2018


High-performance one-pack ambient cross-linking latex binders containing low-generation PAMAM dendrimers and ZnO nanoparticles

Abstract

This study focuses on ambient-temperature self-crosslinking acrylic latex coating compositions containing poly(amidoamine) (PAMAM) dendrimers and ZnO nanoparticles in the role of inter-particle cross-linking agents and flash rust inhibitors. Low-generation amine-terminated PAMAM dendrimers as aqueous solutions were added into latices containing diacetone acrylamide repeat units in their polymer structure. The incorporation of ZnO nanoparticles (without any surface treatment) was performed during the synthesis of a polymer dispersion carried out by the semi-continuous emulsion polymerization technique. The latex storage stability and coating performance with respect to zinc oxide and PAMAM presence were evaluated and compared with a conventional zinc oxide-free coating composition containing adipic acid dihydrazide as the cross-linking agent. It was found that the novel latices containing both PAMAM dendrimers and ZnO nanoparticles exhibited a long-term storage stability and provided crosslinked transparent coating films of high gloss, enhanced mechanical properties, solvent resistance and excellent water whitening resistance. Moreover, the latex compositions containing PAMAM dendrimers as the inter-particle cross-linkers were shown to provide flash rust resistance.


Datum: 02.04.2018


Mathematical and empirical evaluation of accuracy of the Kubelka–Munk model for color match prediction of opaque and translucent surface coatings

Abstract

Attempts were made to evaluate mathematically and empirically the accuracy of the Kubelka–Munk model for color match prediction of opaque and translucent surface coatings in the color using industries. To this end, an innovative inversed mathematical evaluation procedure was concocted which comprised of plotting the absorption and scattering constants of the Kubelka–Munk model or any of its various modified form or replacements theories against the intrinsic optical coefficients of the respective exact radiation transfer theories, namely Chandrasekhar for opaque and van de Hulst for translucent media. The results prove mathematically that the Kubelka–Munk model for opaque media is a sound theory and its various suggested modifications or replacements do not improve the color match prediction of opaque surface coating media. This mathematical conclusion was further confirmed by color match prediction of actual opaque paint samples. On the other hand, the mathematical prediction for translucent media illustrated a completely different picture, depicting nonlinearity between the optical constants and the respective concentrations of colorants. This implies that much further work has to be carried out to derive invertible new equations to enforce linearity to such situations or make use of alternative artificial intelligent procedures which are designed especially for nonlinearity.


Datum: 28.03.2018


Evaluation of the ASTM D7869-13 test method to predict the gloss and color retention of premium architectural finishes-I

Abstract

A recently developed xenon arc-based accelerated weathering cycle, ASTM D7869-13, has been validated for automotive and aerospace coatings, but its ability to predict the gloss and color retention of premium architectural finishes has not yet been evaluated. We review new weathering data comparing the performance of poly(vinylidene fluoride) (PVDF) architectural finishes in south Florida exposure as well as several accelerated exposure methods including ASTM D7869-13. ASTM D7869 accurately reproduced Florida rank order gloss and color retention trends for coatings made with PVDF-acrylic blends and inorganic pigments, as well as the gloss and color changes seen in Florida for 70% PVDF masstone coatings made with a number of single organic pigments. However, the D7869 cycle has difficulty predicting the rank order of rutile TiO2 grades for the gloss retention of PVDF coatings in Florida, as well as the magnitude and direction of color fade from organic pigment degradation in organic pigment/inorganic pigment blends. One open question that remains is whether the ASTM D7869 cycle might have some utility for industry standard or specification purposes, if the test is limited to specific reference colors or more ideally to specific reference pigments.


Datum: 27.03.2018


Corrosion protection performance of nanocomposite coatings under static, UV, and dynamic conditions

Abstract

Silicone-modified epoxy polymeric matrix was successfully fabricated and reinforced with 1–2 wt% SiO2, TiO2, and TiSiO4 nanoparticles. Fourier-transform infrared spectroscopy, contact angle measurements, differential scanning calorimetry, and field-emission scanning electron microscopy together with energy-dispersive X-ray spectroscopy were employed to investigate different characteristics of the prepared coatings. To simulate operating conditions, all samples were characterized via electrochemical impedance spectroscopy (EIS) after being subjected to different conditions. Corrosion under static conditions, in which the samples were exposed to a static electrolyte without further change in other parameters, was investigated. Furthermore, to study the effects of ultraviolet (UV) radiation in accelerating the degradation of the coatings, samples were characterized after being subjected to UV while immersed statically in the electrolyte. Additionally, the corrosion protection performance was investigated after subjecting the coated substrates to dynamic conditions involving continuous movement of the sample in the electrolyte, simulating continuous wear of the coated surfaces. Compared with the static condition, the EIS results revealed the vital role of the silicone resin and nanoparticles in improving the stability of the coating film against corrosion degradation in the presence of UV radiation, while poor performance in dynamic condition was recorded for all the coating systems.


Datum: 27.03.2018


Synthesis of Fe 3 O 4 nanoparticles with tunable sizes for the removal of Cr(VI) from aqueous solution

Abstract

In this study, size-tunable magnetite (Fe3O4) nanocrystal spheres were promptly synthesized by a facile one-pot solvothermal process with the presence of triethanolamine as an additive. The as-synthesized Fe3O4 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and vibrating sample magnetometer. The results showed that the synthesized nanoparticles were in the size range of 30–350 nm, had well-defined Fe3O4 crystal phase, and had favorable saturation magnetization. The effects of various important parameters, such as initial Cr(VI) concentration, temperature, and pH, on the adsorption properties of the as-obtained Fe3O4 particles for the removal of Cr(VI) in aqueous solution were deeply analyzed and studied. The results confirmed that the adsorption efficiency was highly pH dependent, decreased with the increasing of initial concentration of Cr(VI), and increased with increasing temperature. The adsorption data were well fitted with the Langmuir isotherm. The maximum adsorption capacity calculated from the Langmuir isotherm was 56.625 mg g−1 at temperature of 35°C and pH of 2.0.


Datum: 26.03.2018


Drag resistance of ship hulls: effects of surface roughness of newly applied fouling control coatings, coating water absorption, and welding seams

Abstract

Fouling control coatings (FCCs) and irregularities (e.g., welding seams) on ship hull surfaces have significant effects on the overall drag performance of ships. In this work, skin frictions of four newly applied FCCs were compared using a pilot-scale rotary setup. Particular attention was given to the effects of coating water absorption on skin friction. Furthermore, to investigate the effects of welding seam height and density (number of welding seams per five meters of ship side) on drag resistance, a new flexible rotor was designed and used for experimentation. It was found, under the conditions selected, that a so-called fouling release (FR) coating caused approximately 5.6% less skin friction (torque) over time than traditional biocide-based antifouling (AF) coatings at a tangential speed of 12 knots. Furthermore, results of immersion experiments and supporting “standard” water absorption experiments showed that water absorption of the FR coating did not result in any significant impacts on skin friction. On the other hand, water absorption was found to actually lower the skin friction of AF coatings. This may be attributed to a smoothening of the coating surface. The effects of welding seam height and density on drag resistance were found to be substantial when welding seam height is above 5 mm, especially at high tangential speeds (above 15 knots). Using an interpolation approach, the pilot-scale welding seam drag data could be used to estimate the drag resistance at approximated full-scale conditions, equivalent to about one welding seam per five meters of ship side. It was shown, in this case, that the contribution of welding seams to ship skin friction could very well be less significant than those of FCCs when the welding seam height is below 5 mm, a representative value for full-scale welding seam height.


Datum: 26.03.2018


Deposition of a PMMA coating with an atmospheric pressure plasma jet

Abstract

Atmospheric pressure plasma jet polymerization of methyl methacrylate (MMA) was performed in order to deposit a PMMA-like coating on ultrahigh molecular weight polyethylene (UHMWPE). This study is a first step in the transfer from MMA plasma polymerization experiments previously performed in a dielectric barrier discharge (DBD) reactor to a newly designed atmospheric pressure plasma jet. In this novel plasma setup, the substrate is not directly exposed to the plasma region, but placed in the plasma jet afterglow. The effect of several plasma jet process parameters on the coating properties was investigated using different surface characterization techniques such as XPS, FTIR, AFM, and OPS. Results show that the stationary deposition of PMMA-like thin films results in a radial gradient in surface chemistry, surface morphology, and coating thickness. Additionally, the coating properties were found to significantly depend on the monomer-containing gas flow rate. This observation is also confirmed by CFD modeling, which shows that the monomer-containing gas flow rate strongly influences the gas flow pattern of the plasma afterglow and therefore the final properties of the deposited PMMA-like film.


Datum: 21.03.2018


Influence of vinyl-terminated hyperbranched polyester on performance of films obtained by UV-initiated thiol–ene click reaction of A 2  + B 3 system

Abstract

UV curing technology has become an efficient method to fabricate films with desirable properties, although it is susceptible to oxygen inhibition, resulting in low conversion of double bonds and poor mechanical performance. Thiol–ene click reaction can overcome the shortcomings of common UV curing techniques. In this paper, the vinyl-terminated hyperbranched polyester (VTDP) was incorporated into the curing system of di-ene (A2) and trithiol (B3). Trithiols, including 1,3,5-tris(2-hydroxyethyl)isocyanurate tris(3-mercaptopropionate) (THMP) and trimethylolpropane tris(3-mercaptopropionate) (TMMP), were synthesized by an esterification between 3-mercaptopropionic acid and 1,3,5-tris(2-hydroxyethyl) isocyanurate, and tri(hydroxymethyl)propane, respectively. The UV-initiated thiol–ene click reaction between 1,4-butanediol diacrylate (BDDA) and trithiols (TMMP and THMP) was researched by adjusting different VTDP content. FTIR spectral analysis showed that the thiol–ene reactions proceeded smoothly and the conversion degree of acrylic groups was higher than that of thiol groups. The pencil hardness and abrasion resistance of the cured film increased first and then decreased with the increase in VTDP content, but both their flexibility and adhesion had little change. Their glass transition temperatures increased slightly with the increase in VTDP content. THMP has better positive effect than TMMP on the pencil hardness, abrasion resistance and thermal performance of the cured film.


Datum: 21.03.2018


Improved corrosion resistance based on APTES-grafted reduced sulfonated graphene/waterborne polyurethane coatings

Abstract

In this work, reduced sulfonated graphene (RSG) containing free amine groups was prepared and modified by 3-aminopropyltriethoxysilane (APTES) and reduction by diethanolamine (DEA). In addition, waterborne polyurethane (WPU) composite coatings were prepared by adding RSG as an anticorrosive filler to WPU. From the results of Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM), it can be found that sulfonated graphene was modified with APTES and successfully reduced by DEA. The SEM images illustrated that RSG was uniformly doped in the WPU. With increasing RSG content, the hydrophobicity of the RSG/WPU films increased due to the strong covalent interaction between RSG and WPU. Finally, the corrosion resistance of the coating was characterized by polarization curves and salt spray tests.


Datum: 19.03.2018


Recent progress in synthesis of antifogging agents and their application to agricultural films: a review

Abstract

Antifogging agents are very important for use on agricultural films. Fogging reduces crop yield and causes other negative effects. To overcome fogging problems on agricultural films, several approaches including surface coating and reactive extrusion methods have been used. To date, researchers have designed a variety of agents to prepare antifogging films. The mechanism and rules for the composition of such agents have also been reported. However, reported antifogging films do not exhibit satisfactory results. Therefore, antifogging methods require further improvement. In this review, different preparation methods for antifogging agents and films are summarized, along with the advantages and disadvantages of each method. Moreover, test methods for antifogging performance are introduced.


Datum: 19.03.2018


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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