Powder coatings, due to the lack of solvents and volatile organic compounds (VOCs), have gained in importance compared to conventional liquid systems. They fulfill key criteria such as effectiveness, economics, energy efficiency, environmental compliance, and excellent surface finish. Recently, low curing temperature and UV-cured systems have been increasingly used. These techniques offer a lot of advantages such as, application of powder coatings on the heat-sensitive materials and energy savings. Acrylic resins are rarely used in powder systems, mainly due to their price. Nevertheless, they are an attractive alternative in low temperature curing or UV-cured systems (free radical or cationic polymerization) thanks to their chemical structure. The review article focuses on the correlation between the chemical structure of the corresponding monomers in the resin and their properties and application in powder coatings. Moreover, the correlation between the structure of acrylic resin and the powder coating formulation process was described.

Polyacrylic resins containing glycidyl methacrylate (GMA), methyl methacrylate (MMA) and n-butyl acrylate (BA) in various molar ratios were obtained. Triaryl sulfonium hexafluorophosphate was used as a photoinitiator and reacted with the epoxy groups of GMA. The relationship between the chemical structure of polyacrylic resins and the parameters of the UV curing reaction and the functional properties of powder coatings was investigated. The appearance and mechanical properties of the coatings were determined based on thickness, gloss, roughness, deformability, scratch resistance, adhesion to steel, hardness, and water contact angle. DMA was used to assess the cross-link density. Powder coatings with good physical and mechanical properties and curing time of 70 s were obtained.

This paper presents studies on the influence of the chemical structure of (meth)acrylic monomers on the properties of powder coatings based on polyacrylate resins. For this purpose, a wide range of monomers were selected—2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), n-butyl acrylate (nBA), tert-butyl acrylate (tBA), dodecyl acrylate (DA), ethyl acrylate (EA) and benzyl acrylate (BAZ)—for the synthesis of the polyacrylate resin. The average molecular mass and molecular mass distribution of the synthesized resins were measured by gel permeation chromatography (GPC). The glass transition temperature (T_g) and viscosity of polyacrylate resins were determined by using differential scanning calorimetry (DSC) and a Brookfield viscometer. These parameters were necessary to obtain information about storage stability and behavior during the application of powder clear coatings. Additionally, DSC was also used to checked the course of the low-temperature curing reaction between the hydroxyl group contained in the polyacrylate resin and the blocked polyisocyanate group derived from a commercial agent such as Vestanat B 1358/100. The properties of the cured powder clear coatings were tested, such as: roughness, gloss, adhesion to the steel surface, hardness, cupping, scratch resistance, impact resistance and water contact angle. The best powder clear coating based on the polyacrylate resin L_HEMA/6MMA/0.5nBA/0.5DA was characterized as having good scratch resistance (550 g) and adhesion to the steel surface, a high water contact angle (93.53 deg.) and excellent cupping (13.38 mm). Moreover, its crosslinking density (CD) and its thermal stability was checked by using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA).

This work focused on obtaining a low-temperature powder coating characterized by self-healing properties. To achieve this, acrylic resin, blocked polyisocyanates (bPICs) with 1,2,4-triazole, and unsaturated commercial resin were used. The synthesis of bPICs with triazole enabled the low-temperature curing and reversible Diels–Alder (DA) reaction at 160 °C. The chemical structure of bPICs was confirmed using ¹H-NMR. The occurrence of the DA and retro-DA (rDA) reactions in the crosslinked polymer, at temperatures of 60–85 °C and 90–130 °C, respectively, was confirmed using Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and FT-IR spectroscopy. The self-healing properties of the powder coating were examined using polarized optical microscopy. Additionally, the occurrence of the DA and rDA reactions between triazole and unsaturated polyester resin was investigated through repeated self-healing tests.

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.

Magnesium alloys, because of their excellent strength-to-weight ratio, are increasingly used in many industries. When used in external elements, the key factor is to provide adequate anticorrosion protection. High-temperature, cured-powder coatings are widely used to protect most metals, but their use on magnesium alloys is difficult as a result of the instability of the magnesium substrate at elevated temperatures. Another problem is ensuring the proper adhesion of the organic coating to the magnesium substrate. This paper presents the procedure for the synthesis of a duplex coating on AZ91 magnesium alloy. The topcoat was a powder coating based on acrylic resin, the main ingredient of which was glycidyl methacrylate. Because of the presence of epoxy groups, the coating was cured using ultraviolet (UV) radiation (low-temperature technology). The conversion subcoating was produced by plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte. The synthesized coating system was tested, among others, for microscopic (SEM), adhesive (mesh of cuts), and anticorrosion (EIS). The duplex PEO/UV-curable powder coating showed very good adhesion to the metal and increased the anticorrosion properties of the magnesium substrate, compared to the powder coating produced directly on the magnesium alloy and on an alternative conversion coating (synthesized in the process of chemical zircon phosphating).