Journal of Coatings Technology and Research最新文献

This study investigates a novel solvent-free, UV LED-curable coating as a robust corrosion protection solution for the inner surface of steel pipelines. The properties of the UV-cured film were characterized in terms of reactivity, thermomechanical properties, and adhesion to metal substrates. The coating was applied to the inside steel pipelines and cured using a patented UV LED lamp designed to fit in confined spaces. Finally, electrochemical impedance spectroscopy characterization and an accelerated cyclic electrochemical technique were performed on the coated pipes to study the corrosion protection properties of the coating, both with and without the addition of inorganic fillers. The results were compared to a commercially available thermally cured coating. It was found that the UV-cured coating confers high barrier properties, effectively preventing liquid penetration even under elevated temperature conditions. Furthermore, the corrosion protection performance in harsh environments was comparable to and, in some cases, higher than standard epoxy linings.

Crosslinking systems play a vital role in the coating industry by significantly improving the wear resistance, chemical resistance, and toughness of the coatings. In particular, polyfunctional aziridines, known for their distinctive nitrogen-containing three-membered ring structures, serve as versatile crosslinkers in automotive coatings and adhesives. These crosslinkers can effectively enhance both the physical and chemical properties of polyurethane coatings. This study focuses on investigating the impact of two different trifunctional aziridines on the thermal curing characteristics of 2K clearcoats containing free-isocyanate crosslinker and polyacrylic resin. The analysis confirmed the ring-opening reaction of the aziridine crosslinker with the carboxyl groups in the resin at room temperature, as evidenced by changes in the –NH stretching frequency in the Fourier transform infrared spectra. To assess the real-time curing performance of aziridines during thermal curing at 80 °C, rheological storage modulus and curing behavior of the formulated 2K clearcoats were measured using a rotational rheometer and a rigid-body pendulum tester. Additionally, nano-indentation and nano-scratch tests were conducted to quantitatively evaluate the surface hardness and scratch resistance of the cured clearcoat films. By examining the relationship between the curing dynamics and the final mechanical properties, this study offers insights into optimizing the amount of aziridines required to enhance the properties of clearcoat films.

Waterborne polyurethane (WPU) has excellent performance because of its special soft and hard segments in polymer chains, but the relatively high cost, poor water vapor permeability, and inferior biocompatibility limit its application. The introduction of biomass materials can improve the performance of WPU. Keratin belongs to natural macro-molecule compounds which contain numerous peptide bonds and hydrophilic groups. It can make up for the shortcomings of WPU materials. In this study, keratin was extracted from the recycled cattle hair waste, and then it was chemically bonded with isocyanates, polyols, and other raw materials to prepare a keratin-modified WPU film which has excellent performance. First, polytetramethylene ether glycol (PTMEG) was reacted with 4.4-dicyclohexylmethane diisocyanate (HMDI) to form a prepolymer, then it was reacted with dimethylol propionic acid (DMPA), neopentyl glycol (NPG) and trimethylolpropane (TMP). The addition of keratin was in the emulsification process, and the structure of keratin-modified WPU was investigated. TG analysis results showed that the addition of keratin can improve the thermal stability of the WPU film with a higher residual carbon content at 600°C. The DMA analysis showed that the mechanical properties of the modified WPU film with a certain amount of keratin added (≤ 0.1%) were significantly improved. The yellowing resistance test showed that the addition of an appropriate amount (≤ 0.1%) of keratin can increase its stability to light, but the addition of an excessive amount of protein (≥ 0.2%) will result in a decrease in the yellowing resistance of the WPU film.

The organosilicon intermediate with three hydroxyl groups was synthesized from isopropanol amine (MIPA) and (3-glycidoxypropyl) trimethoxy silane. Meanwhile, a polyurethane prepolymer, prepared by the polymerization of isophorone diisocyanate with 2, 2-bis(hydroxymethyl) propionic acid and polyethylene glycol (PEG-600) in sequence, was chain extended by the intermediate. Ultimately, methyl ethyl ketone oxime, a conventional isocyanate (NCO) blocking agent, was chosen to inactivate the branched polymers. Thus, a waterborne blocked crosslinker containing siloxane groups was achieved, which was further treated by a mixture of alcohol and water to obtain its hydrolyzed product, i.e., a crosslinker containing silanol groups. The structure and thermal properties of crosslinkers were analyzed by means of ¹H-NMR, FTIR, TG, and DTG, respectively. The gel content, hardness, and adhesion of the cured coatings were also investigated. The results confirm the crosslinker system containing silanol groups performs much better, and when the hardness reaches 0.64 or above, the adhesion can still be maintained above 1.2 MPa.

The preservation of fruits after harvesting has been one of the extensively studied concerns in recent times. In countries with tropical climates, high temperatures, and heavy rainfall like Vietnam, the post-harvest preservation of fruits holds significant practical importance. Avocados are a type of fruit rich in nutritional value and high economic significance. However, avocados have a short shelf life and are susceptible to damage and bruising during harvesting, transportation, and storage. In this study, a coating preservation product for avocados was developed using chitosan in combination with the active compound rutin, encapsulated in a complex with hydroxypropyl-β-cyclodextrin. Research results indicate that a chitosan solution with a concentration of 1.5%, prepared in a 1% acetic acid solution, and supplemented with the rutin–hydroxypropyl-β-cyclodextrin complex at a content of 0.5%, was found to be the most suitable for creating the avocado preservation coating. The utilization of this product extended the preservation period of avocados up to 10 days under room temperature conditions. The biochemical characteristics of the fruit were preserved to the greatest extent, and the ripening process was significantly slowed down compared to control samples.

In this study, a series of photocured epoxied films (SAU-0, SAU-5, SAU-10 and SAU-15) were prepared and applied to the galvanized steel surface for corrosion prevention. These photopolymers were synthesized via cationic photopolymerization using Doublecure®1172 as a cationic photoinitiator. To discuss the crosslinking effect in these photopolymers, various amounts of multifunctional epoxy resin (SU-8) were added into the photoinitiating formulations. The photoreactivity, thermal, mechanical, and morphology properties of all photopolymers were investigated. The results demonstrated that the inclusion of SU-8 epoxy resin not only increased the crosslinking density but also did not sacrifice the interfacial interaction with steel. Finally, the potential dynamic polarization curve of the coated film was studied to realize its corrosion protection performance. As a result, the SAU-15 based photopolymer film, containing the highest amount of SU-8, exhibits the best corrosion protection value (PI = 99.2%) under testing with a 3 M NaCl solution. Furthermore, the SAU-15 based sample demonstrated good long-term storage stability, retaining over 96% of its original corrosion protection value under ambient air atmosphere and room temperature conditions after 28 days. Additionally, all the samples were immersed in 3 M NaCl solution and seawater for long-term stability testing. Once again, the SAU-15 based sample exhibited the best stability after being immersed in the testing solution for 28 days. This paper introduces a concept of SU-8 based photopolymer for corrosion protection and aims to provide a comprehensive understanding of the organic photocured layer technique and its potential for anticorrosion performance.

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Solving the problems of interfacial compatibility and dispersibility between filler and epoxy resin (EP) can greatly improve the anticorrosion performances of epoxy coatings and expand their application field. In this work, carbon nanotubes (CNTs) were modified by poly(sodium 4-styrene sulfonate) and poly(3,4-ethylenedioxythiophene) to form PCNTs hybrids, and the cathodic electrophoretic deposition method was used to form composite epoxy coatings on the surface of sintered NdFeB magnets for enhancing the anticorrosion performance. The corrosion resistance of PCNTs was evaluated by electrochemical and static immersion corrosion tests. Results indicate that PCNTs hybrids possess better distribution and compatibility in epoxy resin than CNTs hybrids, resulting in the anticorrosion performances of higher density of composite epoxy coatings on NdFeB magnets. Optimized EP/PCNTs possess a much higher (left| Z right|)_0.01 Hz of 4.41 × 10⁷ Ω·cm² and a much lower J_corr of 9.648 × 10^− 10 A·cm^− 2 than that of EP (1.34 × 10⁴ Ω·cm² and J_corr 4.436 × 10^− 6 A·cm^− 2), demonstrating superior corrosion resistance.

Large-scale slot die coating technology is crucial for producing perovskite films in perovskite solar cells. Producing high-quality perovskite films requires a stable coating window to ensure that the thickness of the films is uniform and free of defects. This research delves into the production of high-quality perovskite films via slot die coating. It employs a combined approach of theoretical analysis and numerical simulation to define coating limits. Furthermore, it examines the influence of the geometric structure within the internal flow field and the transformation of fluid flow patterns in the external flow field on the overall film quality. We demonstrate that the removal of the edge geometry to the transverse fluid channel in the coating head significantly improves the stability of the internal flow field and enhances the consistency of fluid discharge. Additionally, uniform and stable coating of a perovskite solution can be achieved when the speed of the coating substrate in the downstream coating gap exceeds 0.7 times the maximum velocity of the Poiseuille component of the flow, and the coating flow pattern in the downstream coating gap remains consistent with Couette flow.

Cerbera odollam oil was extracted from the dried Cerbera odollam seeds by the Soxhlet extraction method. Cerbera odollam seed oil-based alkyd resins were synthesized by the alcoholysis–polyesterification process via reaction of the oil with varying amounts of phthalic and maleic anhydride. Standard evaluation methods were used to analyze the physicochemical features of the resins, including acid value, viscosity, and others. Evaluation tests such as drying times, pencil hardness, adhesion, gloss measurement, and chemical inertness were employed to study the film performance of the produced alkyd resins. Mechanical characteristics such as ultimate tensile strength, strength under impact, elastic modulus, surface hardness, and water absorption were evaluated. Further characterization to study the organic architecture of the oil and alkyd resins was carried out by Fourier transform infrared (FTIR) spectroscopy and gas chromatography–mass spectrometry (¹H NMR). The resin with the higher percentage of maleic anhydride showed better surface coating application performance in set-to-touch (88 min), dry-to-touch time (105 min), and pencil hardness (5B) while resin higher in phthalic anhydride shows better results in gloss (92.5) and alkali resistance. On the other hand, the resin with the higher percentage of maleic anhydride showed better mechanical performance in tensile strength, tensile modulus, impact strength, and surface hardness while resin with higher percentage of phthalic anhydride showed better results in water absorption and elongation at break. Overall, the synthesized alkyd resins from the Cerbera odollam seed oil possessed great application potential in both surface coating and polymer composites as matrix.

Chitin nanofibers (ChNFs) with different numbers of carboxyls (i.e., with different degree of substitute, DS) were prepared by adjusting the amount of maleic anhydride used in the acylation treatment prior to mechanical nanofibrillation with ultrasound. Transparent coatings were fabricated by using the obtained ChNFs through casting method and modified via vapor deposition by using 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFDTS). Hydro-oleophobicity and anti-fingerprint capacity of the ChNF coatings were studied. It was found that the ChNF coatings with more carboxyls possessed stronger hydro-oleophobicity as well as anti-fingerprint capacity after the modification of PFDTS deposition. Analysis of X-ray photoelectron spectroscopy suggested that more PFDTS molecules were grafted onto the ChNF coating surface when the ChNFs had more carboxyls (with higher DS). It is the number of carboxyls rather than hydroxyls on ChNF coating surface that determines hydro-oleophobicity and anti-fingerprint capacity of the ChNF coating surface after the modification of the PFDTS deposition.

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