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Antibacterial powder coatings have attracted increasing attention with the awakening of people's health awareness. Silver antibacterial agent has been widely used in coating system due to its superior stability and durability. However, silver ions have the problems of excessive release rate and the tendency to cause yellowing of the coating film. The addition of Cu2+ and Zn2+ can effectively alleviate these two phenomena. In this paper, the ternary exchange kinetics of Ag+, Cu2+, and Zn2+ were studied to provide a theoretical basis for the synthesis of LTA-Ag-Cu-Zn. The reaction kinetics study shows that the selectivity and the adsorption capacity of LTA to Ag+ is higher than that of Cu2+ and Zn2+. The thermodynamic analysis discovers that LTA has the highest selectivity for Ag+, and the exchange between the two is spontaneous. In contrast, the selectivity of LTA to Cu2+ and Zn2+ is concentration-dependent. By establishing the three-ion competitive adsorption curve, it is found that the selectivity of Ag+ is the highest, and the selectivity of copper and zinc is similar. These trends result from Ag+ ions' low hydration energy, small hydration radius, and strong electronegativity. This research lays the groundwork for developing high-performance LTA-Ag-Cu-Zn tri-ion exchange antibacterial agents. [ABSTRACT FROM AUTHOR]

Protection against fire and the corrosion of metals is necessary to ensure human safety. Most of the fire and corrosion inhibitors do not meet the ecological requirements. Therefore, effective and ecological methods of protecting metals are currently a challenge for researchers. In this work, the influence of hexakis(4-(hydroxymethyl)phenoxy)cyclotriphosphazene (HHPCP) on the characteristics of powder coatings was examined. The coatings' properties were investigated by measuring the roughness, hardness, adhesion to the steel surface, cupping, gloss, scratch resistance, and water contact angle. The thermal stability was studied by furnace test and TGA analysis. The corrosion resistance test was carried out in a 3.5% NaCl solution. The distribution of phosphazene-derived segments in the coating was examined by GD-EOS analysis. Modified coatings show better corrosion and thermal resistance and can be used for the protection of the steel surface. Their better corrosion resistance is due to the electroactive properties of the phosphazene ring and its higher concentration at the coating surface, confirmed by GD-EOS analysis. The increase in thermal resistance is due to the effect of the formation of phosphoric metaphosphoric and polyphosphoric acids during the decomposition of HHCPC, which remain in the condensed char phase and play a crucial role in surface protection. [ABSTRACT FROM AUTHOR]

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Powder coatings are a green alternative to conventional solvent-borne liquid coatings, but they have the intrinsic drawback of color-matching and adjustment in production with the conventional extrusion process. In this study, an industrially applicable approach to formulate color powder coatings utilizing ultrafine powders, i.e., a powdery blending and pressing method, was invented. This novel method was validated by comparing samples prepared by the Method 1 conventional extrusion method with an extra ultramarine pigment at 3%; Method 2 powdery blending and pressing of the original coatings and the same coating with 6% ultramarine pigment utilizing regular (coarse) powder coatings; and Method 3 utilizing ultrafine powder coatings for the two coatings with the same formulations as Method 2. The coating powders were prepared to have similar particle sizes and particle size distributions, with three commonly used coating binders, namely polyester-epoxy hybrid, polyester/TGIC (triglycidyl isocyanurate), and polyurethane (PU). The powders prepared by Methods 1 and 3 had similar flow abilities in terms of angle of repose (AOR) and avalanche angle (AVA). The performance of the new coatings by Method 3 was close to or better than the ones prepared by Method 1 in terms of the specular gloss, DOI (distinctness-of-image), reflection haze and color values, being superior to Method 2. The coatings via ultrafine powders also exhibited a comparable ultramarine particle distribution in the coating cross-sections as the conventional ones, whereas the ones via regular powders had an inferior pigment dispersion. The new method can greatly enhance the production efficiency and reduce the cost of powder coatings with compound colors, especially for small batch manufacturing.

Today, reducing the use of volatile organic compounds is one of the most important issues for environmental protection. Since the 1950s, powder coatings have been widely considered in the surface coating field, especially pipelines, households, and office appliances, due to their environmental friendliness and excellent performance. These types of coatings are solid and they are applied to the surface in the form of powder using different methods such as electrostatic or fluidized bed and then they are cured by heat. In this study, a brief history of the development of powder coatings is described, and it is continued by full report on the types of powder coatings, their production methods and processes, and the research process, emphasizing the type and characteristics of the resins used in this industry. Considering the importance of powder resins in the formulation of powder coatings, the performance of various thermoplastic and thermosetting resins used in these powder coating systems, including polypropylene, polyethylene, poly(vinyl chloride), fluoropolyethylene, nylon, epoxy, polyester, polyurethane, acrylic, cellulose acetate butyrate, and recycled resins are compared. In addition, the method of application and film formation in electrostatic coatings and the factors affecting them are investigated comprehensively. Furthermore, some of the challenges and problems of this giant industry will be introduced in order to improve its quality and curing methods for to expand the applications. Finally, new technical approaches, aiming to save energy and produce more biocompatible powdered products, using infrared curing technology, curing by ultraviolet radiation, or the ability to coat sensitive-temperature surfaces by powder coating are described.

Powder coatings are a green alternative to conventional solvent-borne liquid coatings, but they have the intrinsic drawback of color-matching and adjustment in production with the conventional extrusion process. In this study, an industrially applicable approach to formulate color powder coatings utilizing ultrafine powders, i.e., a powdery blending and pressing method, was invented. This novel method was validated by comparing samples prepared by the Method 1 conventional extrusion method with an extra ultramarine pigment at 3%; Method 2 powdery blending and pressing of the original coatings and the same coating with 6% ultramarine pigment utilizing regular (coarse) powder coatings; and Method 3 utilizing ultrafine powder coatings for the two coatings with the same formulations as Method 2. The coating powders were prepared to have similar particle sizes and particle size distributions, with three commonly used coating binders, namely polyester-epoxy hybrid, polyester/TGIC (triglycidyl isocyanurate), and polyurethane (PU). The powders prepared by Methods 1 and 3 had similar flow abilities in terms of angle of repose (AOR) and avalanche angle (AVA). The performance of the new coatings by Method 3 was close to or better than the ones prepared by Method 1 in terms of the specular gloss, DOI (distinctness-of-image), reflection haze and color values, being superior to Method 2. The coatings via ultrafine powders also exhibited a comparable ultramarine particle distribution in the coating cross-sections as the conventional ones, whereas the ones via regular powders had an inferior pigment dispersion. The new method can greatly enhance the production efficiency and reduce the cost of powder coatings with compound colors, especially for small batch manufacturing. [ABSTRACT FROM AUTHOR]

The relationship between the elastic modulus and the porosity of powder coatings has been investigated for different methods of their deposition. Porosity is the main means of assessing the quality of coatings and depends on the techniques for their production. A decrease in the elastic modulus of coatings after gas flame spraying is due to the presence of porosity to 30%, and after electric arc spraying – to 20%. The electric contact method of forming coatings makes it possible to reduce porosity to 5-6% and so to bring the value of the elastic modulus of coatings closer to that of compact materials

The morphology and properties of epoxy powder coating with two additives based on allotropic forms of carbon, diamond, and graphene oxide (GO), were studied. The effect of concentrations and preparation methods on the dispersion of GO within the polymer matrix was investigated. Two methods of introducing coating additives were investigated, to the component blend before extrusion and dry-mixed with the sieved powder. The surface roughness, abrasive wear resistance, thickness, as well as glossing of the coating were analysed depending on the type, concentration, and applied method of preparation. The study showed that the quantity of agglomerates in polymer matrix depends on the applied dispersion method. The lowest number of GO agglomerates was obtained by GO sonication before mixing of raw materials. The relationship between the content of GO in the coating and the abrasion resistance was found. The lowest abrasive wear was found for coating with 0.3% GO introduced by extrusion. Both additives, GO and diamond, in various concentrations have an impact on the coating wear resistance.

Powder coatings represent an environmentally friendly VOC-free alternative to widely used solvent-borne zinc-rich coatings, with economic and ecological benefits. In particular, powder coatings have several advantageous properties, such as chemical resistance and mechanical strength. However, the performance and characteristics of polyester-based zinc-containing powder coatings remain unknown. In this study, the corrosion performance of polyester powder coatings containing up to 80% zinc is compared. Electrochemical and salt-spray testing results indicate that coatings formulated with 80% zinc demonstrate superior anti-corrosive properties than coatings with lower zinc dosages. Two distinct behavioral phases of the coating with 80% zinc were observed by measurements of open circuit potential (OCP) and polarization resistance (Rp) during immersion tests—a phase indicative of a barrier effect and a phase consistent with galvanic protection. The evolution of the coating was further characterized and interpreted as five stages by electrochemical impedance spectroscopy (EIS), and the mechanistic details were discussed. This UV-resistant single-layer powder coating has the potential to replace the commonly used high-VOC multi-layer liquid coating systems at a significantly lower cost. [ABSTRACT FROM AUTHOR]

Fluorescent coatings have attracted attention due to their bright colors. However, they have fewer outdoor applications due to low stability, especially the poor weather resistance of the fluorescent pigments. In order to improve their weather resistance and maintain the excellent appearance, this study used polymer binders to coat a light shielding agent nano TiO2 on the surface of the fluorescent pigment to extend the durability. Three organic binders, polyester varnish, polyurethane varnish, and polyvinyl alcohol, were selected. Each binder was dissolved and mixed with pigments and nano TiO2 particles to make a polymer-TiO2 layer on the pigment surface. The effects of binder types and loadings were investigated and evaluated by accelerating weather test of corresponding fluorescent powder coatings. According to SEM and ash test, nano TiO2 was successfully coated on the surface of fluorescent pigments. The modified fluorescent pigment shows a strong ability to absorb ultraviolet rays, and the weather resistance of prepared coatings has been significantly improved compared with the original fluorescent powder coating. When using clear coat PE as a binder and setting the ratio of the binder to the nano TiO2 of 1:2, the UV exposure time of fluorescent powder coatings can be extended by over twelve times compared to the coatings with original pigment for the same color change. This study provides an effective approach to enhance the weather resistance of fluorescent coatings and thus expand their applications. [ABSTRACT FROM AUTHOR]

The investigations of tribo mechanical properties of coatings obtained with electrocontact welding of sintered powder materials and powder-polymer fillers of Russian manufacture are presented. It is proved that the introduction of antifriction components (powders of copper or tin) into filler material at a rate of 5-10 % increases the time to joints seizure by 1.5-2 and decreases by 1.5 the friction ratio. The application of powder-polymer and sintered fillers reinforced with metal grid produces a relief on the operating surface of the coating with the areas possessing minimum hardness. They are worn out more intensely and the forming herewith grooves help to keep lubricating oil on the friction surface. For the friction pair operating in abrasive wear conditions with adhesive wear elements, at welding it is recommended to use powder compositions (by weight): 80-90 % – PG-FBX6-2, 10-20 % of copper powder friction ratio (PMS-N); for wear conditions at adhesive wear: 90 % of iron powder (PZHR 3.200.28), 10 % of tin powder (PO-1); for abrasive wear conditions: 70-80 % – PG-FBX6-2, 30-20 % – VK8.

The investigations of tribo mechanical properties of coatings obtained with electrocontact welding of sintered powder materials and powderpolymer fillers of Russian manufacture are presented. It is proved that the introduction of antifriction components (powders of copper or tin) into filler material at a rate of 5-10% increases the time to joints seizure by 1.5-2 and decreases by 1.5 the friction ratio. The application of powderpolymer and sintered fillers reinforced with metal grid produces a relief on the operating surface of the coating with the areas possessing minimum hardness. They are worn out more intensely and the forming herewith grooves help to keep lubricating oil on the friction surface. For the friction pair operating in abrasive wear conditions with adhesive wear elements, at welding it is recommended to use powder compositions (by weight): 80-90% - PG-FBX6-2, 10-20% of copper powder friction ratio (PMS-N); for wear conditions at adhesive wear: 90% of iron powder (PZHR 3.200.28), 10% of tin powder (PO-1); for abrasive wear conditions: 70-80% - PG-FBX6-2, 30-20% - VK8. [ABSTRACT FROM AUTHOR]

AbstractPolymer coatings have been used for the corrosion protection of metal surfaces acting as a physical barrier against several corroding media. In spite of the good efficiency of these coatings their resistance is limited due to the presence of localized defects which give place to localized corrosion. Aiming to improve the barrier properties of these coatings this work has proposed the use of nanocomposites as powder coatings based on a standard formulation of a commercial powder varnish. Nanocomposites with 2 and 4 wt% contents of organophilic montmorillonite (OMMT) were obtained in the molten state through of a co-rotating twin-screw extruder. The application of the nanocomposite coatings was performed by electrostatic pulverization on mild steel panels. The coatings were characterized to determine their structure using X-ray diffraction (XRD). The morphologies of the coatings were assessed using transmission electron microscopy (TEM). Gloss and adhesion measurements and the flexibility and impact resistance of the coatings were included in the physical assessment of the coatings. The corrosion performance was evaluated by the salt spray test and by electrochemical impedance spectroscopy (EIS). The coatings with clays presented predominantly exfoliated structures, with good dispersion of OMMT in the epoxy matrix. The addition of OMMT reduced the impact resistance, flexibility and gloss but increased the barrier properties of the coatings. The best corrosion performance in NaCl solution was achieved for 4 wt% OMMT.

Protective coatings are the most widely used corrosion protection method for construction materials in different environmental conditions. They isolate metals from aggressive media, making the structure more durable. Today, alongside good anti-corrosive properties, coatings need to be safe for the environment and harmless to those who apply them. The high volatile organic compound (VOC) content in conventional solvent-borne coatings presents a huge ecological problem. A solution for indispensable solvent emission reduction is the application of powder coatings. This study evaluates the corrosion performance and surface morphology of polyester and epoxy-polyester powder coatings. Electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) measurement, salt spray chamber and humidity chamber testing followed by adhesion testing were used to investigate the protective properties of powder coatings. Scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX) was used to analyse the surface morphology and chemical composition, whereas the microstructure and coating uniformity were determined by optical microscope examination. The research revealed a negative influence of coating surface texture on coating thickness and consequently a lack of barrier and adhesion properties. The epoxy-polyester powder coating showed a better performance than the polyester coating. All tested coatings showed uniform structure. [ABSTRACT FROM AUTHOR]