Search Results (52)

Organic coatings are the most widely utilized corrosion protection strategy for metallic materials. Nevertheless, they can degrade over time through the effects of UV, moisture, and corrosive media, compromising their protective performance. In order to monitor the coating performance for predictive maintenance, an electrochemical sensor was fabricated using 6005A aluminum alloy and coated with four coating systems: (1) epoxy primer, (2) epoxy primer/polyurethane topcoat, (3) epoxy primer/polyurethane topcoat/aluminum-powder-containing polyester resin, and (4) epoxy primer/polyurethane topcoat/aluminum-powder-containing polyester resin/acrylic coat. The sensors and corresponding coupon samples were exposed for 24 months at two sites in Thailand: Pathum Thani (PTI, suburban) and Chon Buri (CBI, mild marine). Electrochemical impedance spectroscopy (EIS) measurements were conducted at a fixed frequency of 117 Hz, synchronized with on-site meteorological monitoring. Impedance data were converted into a coating aging index (AI) to quantitatively assess the coating degradation. Coating deterioration was observed in PTI as early as at 6 months of exposure. Machine learning modeling revealed that cumulative rainfall was the dominant environmental factor influencing coating degradation. The single epoxy primer layer exhibited the poorest durability, while the incorporation of polyurethane, aluminum-pigmented polyester, and acrylic layers significantly prolonged the protective service life of the coating system. Full article

The increasing prevalence of cardiovascular diseases highlights the need to develop vascular grafts that match the mechanics of native vascular tissue and offer functional adaptability. This study reports the development and systematic optimization of a shape-memory polyurethane acrylate (PUA)-based photocurable resin for digital light processing (DLP)-based four-dimensional printing (4DP) applications. Resin formulations were designed by controlling hard/soft segment ratios, reactive diluent content, and crosslink density to position the glass transition temperature (T_g) within the physiological range (25–40 °C). Thermomechanical characterization was performed via dynamic mechanical analysis (DMA) and tensile testing, while a full-factorial Design of Experiments (DoE) approach was applied to optimize DLP process parameters—namely layer thickness, exposure time, and post-curing time. The developed resin formulation yielded a T_g of 38 °C as determined by DMA. Following process optimization, regression models showed high statistical fit (R² > 99%), and experimental validation under optimal conditions (layer thickness: 82.83 µm, exposure time: 11 s, post-curing: 2 min) resulted in an elongation at break of 64.0 ± 3.4%, a Young’s modulus of 10.9 ± 0.1 MPa, and a tensile strength of 6.2 ± 0.3 MPa. The optimized system exhibited thermally triggerable shape memory behavior at near-body temperature, with mechanical properties consistent with natural arterial tissue benchmarks. These findings demonstrate a promising material design strategy for DLP-based 4D-printed vascular structures. Full article

The development of hybrid organic coatings for corrosion protection remains a key research priority. This study focuses on synthesising Layered Double Hydroxide (ZnGa-LDHs) intercalated with environmentally friendly disodium sebacate (SB) corrosion inhibitor, forming ZnGa-SB. To overcome the challenge of limited dispersibility in organic coatings, ZnGa-SB was combined with Graphene Nanoribbons (GNR), produced through the oxidative unzipping of multi-walled carbon nanotubes (MWCNT). The resulting composite, ZnGa-SB/GNR, was synthesised using an in situ hydrothermal method and incorporated into polyurethane (PU) enamel. The synergy between high-barrier GNRs and active ZnGa-SB creates a “labyrinth effect” that effectively inhibits the diffusion of corrosive species. Microstructural analysis, including XRD, FT-IR, Raman, TGA, FE-SEM, and EDS, confirmed the nanofiller structure. The nanofillers were embedded into acrylic resin (AC) for short-term anticorrosive testing in a 0.1 M NaCl solution and then into PU for long-term evaluation in a 3.5 wt% NaCl solution, using electrochemical impedance spectroscopy (EIS). The PU/ZnGa-SB/GNR coating exhibited a high impedance modulus of 5.90 × 10⁷ Ω cm² at |Z|_0.01 Hz, even after 2688 hours of immersion, indicating enhanced corrosion resistance. This coating demonstrated superior performance in cross-cut and pencil hardness tests and sustained less damage in salt spray analysis compared to other coatings. The synergistic effect offers a promising approach for developing next-generation hybrid anti-corrosive coatings. Full article

In response to environmental concerns and the depletion of fossil resources, transitioning coatings toward sustainability is imperative. Bio-based coatings, derived from renewable biomass, represent a highly promising development pathway. This review comprehensively summarizes recent advances, prevailing challenges, and future prospects of bio-based coatings, with a focus on bio-based polymer resins—serving as the primary film-forming materials—and key auxiliary components such as pigments and fillers, additives, and solvents. This review systematically elaborates on the definition of bio-based coatings, their raw material sources, and international standards for bio-based carbon content determination. The core strategies for converting biomass into coating components are critically analyzed, namely direct utilization, physical blending, chemical modification, and biosynthesis. Furthermore, the synthesis, properties, and applications of key bio-based polymer systems—including epoxy, polyurethane, alkyd, and acrylic resins—are critically discussed, with particular emphasis on how molecular engineering enhances their performance and functionality. Despite significant progress, bio-based coatings still face several challenges, such as balancing performance and cost, ensuring the stability of raw material supply chains, and establishing globally unified standards. This review concludes that the integration of chemical modification and biosynthesis technologies, coupled with the establishment of a unified bio-based content standard system, constitutes two core drivers for advancing bio-based coatings from “green alternatives” toward “high-performance dominance” in the future. Full article

Alkyd resins are among the most common coatings used for exterior wood joinery. In Romania, solvent-borne alkyd coatings are widely used to finish wood. The study aims to compare the performance after 7 years of outdoor exposure of two types of alkyd coatings, a semi-transparent brown stain with micronized pigments (Alk1) and an opaque white enamel (Alk2), applied directly on wood or wood pre-treated with three types of resins: acryl-polyurethane (R1), epoxy (R2), and alkyd-polyurethane (R3). Fir (Abies alba) wood served as the substrate. Cracking, coating adhesion, and biological degradation were periodically assessed through visual inspection and microscopy. Additionally, a cross-cut test was performed, and the loss of coating on the directly exposed upper faces was measured using ImageJ. The results indicated that resin pretreatments somewhat reduced cracking but negatively affected coating adhesion after long-term exposure. All samples pretreated with resins and coated with Alk1 lost more than 50% (up to 78%) of the original finishing film by the end of the test. In comparison, coated control samples lost less than 50%. The Alk2 coating exhibited a film loss between 2% and 12%, compared to an average loss of 9% for the coated control. Overall, samples pretreated with alkyd-polyurethane resin (R3) and coated with alkyd enamel (Alk2) demonstrated the best performance in terms of cracking, adhesion, and discoloration. Full article

This review examines the chemical functionalization of Camelina, hemp, and rapeseed oils for the development of sustainable bio-based resins. Key strategies, including epoxidation, acrylation, and click chemistry, are discussed in the context of tailoring molecular structure to enhance reactivity, compatibility, and material performance. Particular emphasis is placed on overcoming the inherent limitations of vegetable oil structures to enable their integration into high-performance polymer systems. The agricultural sustainability and environmental advantages of these feedstocks are also highlighted alongside the technical challenges associated with their chemical modification. Functionalized oils derived from Camelina, hemp, and rapeseed have been successfully applied in various resin systems, including protective coatings, pressure-sensitive adhesives, UV-curable oligomers, and polyurethane foams. These advances demonstrate their growing potential as renewable alternatives to petroleum-based polymers and underline the critical role of structure–property relationships in designing next-generation sustainable materials. Ultimately, the objective of this review is to distill the most effective functionalization pathways and design principles, thereby illustrating how Camelina, hemp, and rapeseed oils could serve as viable substitutes for petrochemical resins in future industrial applications. Full article

With the increasing demand for energy-efficient and sustainable building materials, innovative cooling technologies have become a key focus in the construction industry. This study developed a double-layer cooling coating integrating evaporation and radiation mechanisms. The first layer consists of a TiO₂/PUA radiation layer, where rutile TiO₂ is incorporated into polyurethane acrylate (PUA) resin to enhance solar reflectivity. The second layer is a P(NVP-co-NMA) hydrogel, which evaporates water at high temperatures and absorbs moisture from the air at low temperatures, eliminating the need for additional water supply systems. The TiO₂/PUA@P(NVP-co-NMA) coating demonstrates high solar reflectivity and infrared emissivity, effectively reducing indoor temperatures by dissipating heat through water evaporation and radiative cooling. Testing showed a temperature reduction of approximately 7.6 °C in a small house with this coating under simulated conditions. This material demonstrates favorable properties that may make it suitable for applications on building roofs and exterior walls, potentially addressing some limitations of conventional evaporative or radiative cooling systems. Its observed multi-effect cooling performance indicates promise for contributing to energy savings in sustainable building designs. Full article

Fiber optic sensors are increasingly used to measure dynamic strain fields caused by the propagation of mechanical waves. Their low intrusiveness when embedded within a structure makes them suitable for a wide range of applications. In this paper, the feasibility of integrating fiber Bragg gratings (FBGs) into castable materials for ultrasonic applications is investigated. We employed castable polyurethane resins, which are widely used in industry due to their reproducible and durable mechanical properties. Our study began with an analysis of fiber integration by examining the 1D strain profiles of two polyurethane resins during their polymerization and also the impact of their hardening on the central wavelength value of several FBGs spectra. Subsequently, we assessed the sensitivity of FBGs to ultrasonic waves generated at 100 kHz after resin polymerization. Specifically, we explored how the fiber coating influences the rate of energy transfer from the host material to the fiber core. Our findings demonstrate that the central wavelength shift in the FBG reflectivity spectra, caused by shrinkage during resin polymerization, can reach up to 10 nm. This shift must be considered when selecting FBG wavelengths to prevent the reflectivity spectra from falling outside the permissible range of the interrogation system. We measured exploitable ultrasonic waves propagating in the resin samples. Preliminary observations suggest the presence of early arrivals, which could potentially correspond to crosstalk effects between the FBGs even though they are centered at different wavelengths. Furthermore, we show that in dynamic strain fields caused by ultrasonic wave propagation, both acrylate and polyimide coatings transmit similar amounts of energy to the fiber core. These preliminary results highlight the potential of using FBGs as ultrasonic wave sensors embedded in castable materials such as polyurethane resins. Full article

Coatings can achieve the property of changing color with temperature variations by adding thermochromic microcapsules, which can bring a variable surface to the substrate. Ultraviolet ray (UV)-cured primers have the advantages of a fast curing rate, low-temperature curing, and low pollution. Thermochromic microcapsules can expand the application range of UV primers. Thermochromic microcapsules were synthesized through an orthogonal test, using crystal violet lactone, bisphenol A, and decanol as the core materials in a 1:4:50 mass ratio, with urea formaldehyde resin as the wall material. The effects of the addition of batches of the urea, the mass ratio of the formaldehyde solution to the urea, the hydrophilic–lipophilic balance (HLB) value of the emulsifier, and core-to-wall mass ratio on microcapsules yields, encapsulation rates, thermochromic color differences (ΔE), and formaldehyde releases during synthesis were investigated. The results were normalized, with the thermochromic ΔE as the primary reference for analysis. The results indicate that the HLB value of the emulsifier was the key factor that affected the microcapsule performance. In a single-factor test, the HLB value was adjusted within the range of 6.00 to 10.00. It was found that when the HLB value was 10.00, the microcapsules exhibited the best comprehensive performance, with a yield of 43.29%, an encapsulation rate of 45%, a thermochromic ΔE of 4.60, and a formaldehyde concentration released of 1.310 mg/L. The 11# microcapsules with the optimal morphology and better comprehensive performance were compared with the best 14# microcapsules. Different amounts of these microcapsules were added to the UV primer to investigate the effects of the 11# and 14# microcapsules on the mechanical and optical properties of the UV primer. The main component of the UV primer was polyurethane acrylic resin, propylene glycol diacrylate, and hexanediol diacrylate. When 14# microcapsules were added to the UV primer at a concentration of 10%, the primer exhibited the best comprehensive performance, with a fracture elongation of 17.44%, a roughness of 0.15 μm, and a visible light transmittance of 83%. Microcapsule technology was used to modify UV primers, endowing them with thermochromic properties and expanding the application range of thermochromic microcapsules. Full article

Flexible pressure sensors play an extremely important role in the fields of intelligent medical treatment, humanoid robots, and so on. However, the low sensitivity and the small initial capacitance still limit its application and development. At present, the method of constructing the microstructure of the dielectric layer is commonly used to improve the sensitivity of the sensor, but there are some problems, such as the complex process and inaccurate control of the microstructure. In this work, an ion composite photosensitive resin based on polyurethane acrylate and ionic liquids (ILs) was prepared. The high compatibility of the photosensitive resin and ILs was achieved by adding a chitooligosaccharide (COS) chain extender. The microstructure of the dielectric layer was optimized by digital light processing (DLP) 3D-printing. Due to the introduction of ILs to construct an electric double layer (EDL), the flexible pressure sensor exhibits a high sensitivity of 32.62 kPa⁻¹, which is 12.2 times higher than that without ILs. It also has a wide range of 100 kPa and a fast response time of 51 ms. It has a good pressure response under different pressures and can realize the demonstration application of human health. Full article

Reinforced concrete structures are susceptible to chloride ion attack under different conditions, such as water reservoirs, coastal regions, and industrial locations. The physical and mechanical properties of concrete are known to considerably affect the ion penetration velocity. However, studies addressing the effect of coatings on the chloride ion penetration of reinforced concrete are limited. Thus, the objective of this paper is to evaluate the effects of different surface coatings on chloride ion penetration in concrete elements. Acrylic, polyurethane, and epoxy resin coatings were applied in two layers as recommended by the manufacturers. Natural environment chloride ion exposure was conducted in loco in the city of Torres, Brazil, at two marine locations with different geographical characteristics and distances from the sea. In addition, laboratory tests consisting of salt spray and penetration-by-immersion tests were conducted. The concrete’s characteristics, including its compressive strength, water absorption, and void index, were evaluated. The results indicate higher efficiency with the polyurethane coating, while the acrylic resin had the worst results, with a difference of up to 4.5 mm between them. Full article

UV-curable bio-based resins are widely used in the UV curing field. However, the current UV-curable bio-based resins for the application of nail polish still have the problems of too high viscosity and insufficiently excellent mechanical properties. In this study, a soybean oil-based acrylate photosensitive resin is synthesized by using epoxidized soybean oil as a raw material and reacting it with acrylic acid. The results show that the viscosity of soybean oil-based acrylate can achieve 8.31 Pa∙s, and the UV-cured film prepared by soybean oil-based acrylate and anhydride derivatives can obtain a tensile strength of 35.36 MPa and an elongation at break of 67.8%. In addition, the soybean oil-based acrylate is further reacted with isophorone diisocyanate to obtain soybean oil-based polyurethane acrylate, which can be thermally stable at 90 °C for 7 d. And then, the UV-cured film constructed by soybean oil-based polyurethane acrylate and anhydride derivatives are prepared, and the elongation at the break of the cured films can be up to 320%. This work provides a solvent-free approach by using biomass raw materials to form polyurethane acrylic resins, which have promising potential in the application of nail polish. Full article

Ceramic armor protection with complex shapes is limited by the difficult molding or machining processing, and 3D printing technology provides a feasible method for complex-shaped ceramics. In this study, ZrO₂ ceramics were manufactured by 3D printing accompanied with microwave sintering. In 3D printing, the formula of photosensitive resin was optimized by controlling the content of polyurethane acrylic (PUA) as oligomer, and the photosensitive resin with 50% PUA showed excellent curing performance with a small volume shrinkage of 4.05%, media viscosity of 550 mPa·s, and low critical exposure of 20 mJ/cm². Compared to conventional sintering, microwave sintering was beneficial to dense microstructures with fine grain size, and microwave sintering at 1500 °C was confirmed as an optimized sintering process for the 3D-printed ZrO₂ ceramics, and the obtained ceramics showed a relative density of 98.2% and mean grain size of 2.1 μm. The PUA content further affected the microstructure and mechanical property of the ZrO₂ ceramics. The sample with 10%~40% PUA showed some pores due to the low viscosity and large volume shrinkage of photosensitive resins, and the sample with 60% PUA exhibited an inhomogeneous microstructure with agglomeration, attributed to the high viscosity of photosensitive resins. Finally, the ZrO₂ ceramics via 3D printing with 50% PUA showed superior mechanical properties, whose Vickers hardness was 3.4 GPa, fracture toughness was 7.4 MPa·m^1/2, flexure strength was 1038 MPa, and dynamic strength at 1200 s⁻¹ was 4.9 GPa, conducive to the material’s employment as armor protection ceramics. Full article

A natural extract, i.e., urushiol, was employed to effectively cross-link and modify commercial wet-cured polyurethane acrylic resin. Comprehensive characterization of the paint film was performed using techniques such as FTIR, SEM, and TGA. The results indicated that the incorporation of urushiol significantly increased the cross-linking density of the resin, which in turn enhanced the film-forming properties, mechanical strength, and thermal stability of the paint film. Additionally, the study discovered that under isothermal conditions, the dynamic moduli (G′ and G″) of the paint film are related to the gel point frequency by a power law, aligning with the predictions of percolation theory. The application of the autocatalytic model has provided a novel approach to studying non-isothermal kinetic reactions, offering valuable insights for process optimization and further development of urushiol-based polyurethane. Full article

In this study, the biodegradation properties of leather treated with various finishing chemicals were evaluated in order to enhance the sustainability of leather processing. We applied advanced analytical techniques, including FT-IR, thermogravimetric analysis (TGA), and solid-state NMR spectroscopy. Leather samples treated with different polymers, resins, bio-based materials, and traditional finishing agents were subjected to a composting process under controlled conditions to measure their biodegradability. The findings revealed that bio-based polyurethane finishes and acrylic wax exhibited biodegradability, while traditional chemical finishes like isocyanate and nitrocellulose lacquer showed moderate biodegradation levels. The results indicated significant differences in the biodegradation rates and the impact on plant germination and growth. Some materials, such as black pigment, nitrocellulose lacquer and wax, were beneficial for plant growth, while others, such as polyurethane materials, had adverse effects. These results support the use of eco-friendly finishes to reduce the environmental footprint of leather production. Overall, this study underscores the importance of selecting sustainable finishing chemicals to promote eco-friendly leather-manufacturing practices. Full article