Journal of Coatings Technology and Research最新文献

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.

Graphical abstract

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.

Graphical abstract

Solvent-free epoxy-based intumescent fire-retardant coatings are of significant importance in harsh environments, such as petrochemical facilities, due to their excellent overall protection performance. However, the challenge of low-temperature brittleness and limited intumescence resulting from a highly crosslinked structure still persists. In this study, epoxy-terminated polyester oligomers with an asymmetric structure and low viscosity were synthesized using azelaic acid (AA) and dodecanedioic acid (DA) as dibasic acids with odd and even carbon numbers to address this challenge. The chemical structures of these polyester were thoroughly characterized. Among them, the polyester prepared with a molar ratio of 1:3 for AA and DA (ADE) was optimized as a suitable toughener for solvent-free intumescent fire-retardant coatings based on E-51 epoxy resin. The influence of ADE dosage on thermal stability, fire resistance performance, flexibility, and freeze cracking resistance was investigated in detail. The findings demonstrated that incorporating 50% ADE in ADE/E-51 blends resulted in coating film with an appropriate glass transition temperature and thermal deformation property to match the intumescence behavior of intumescent flame-retardant system. The coating formulated in this way exhibited the best fire protective performance, toughness and freeze cracking resistance.

The increasing demand for effective thermal management has led to a growing need for composite coatings with high thermal conductivity (TC). In this work, we developed a novel approach to enhance the TC of polymer coatings by incorporating hybrid fillers composed of hexagonal boron nitride (h-BN) and graphitic carbon (GC). The process involved the creation of hybrid fibers through wet spinning, combining biomass polysaccharide sodium alginate with bulk h-BN, followed by controlled carbonization at varying temperatures. During carbonization, the in-situ generation of small-molecule compounds facilitated the preparation of BN nanosheets and the formation of a unique BN and graphitic carbon (BN-GC) preassembled  heterostructure. By adjusting the carbonization temperature, the degree of graphitization was controlled in the hybrid fillers. Subsequently, these hybrid fillers were blended with a polymer matrix to create photocurable coatings. Leveraging the intrinsic high thermal conductivity of BN nanosheets and the low interfacial thermal resistance between BN and GC, our composite coatings demonstrated a remarkable enhancement in TC. Notably, with a filler content of 20 wt%, the resulting composite coating exhibited an impressive in-plane and out-of-plane TC of up to 2.34 and 0.41 W/(m K), respectively. This innovative approach holds significant promise for improving the thermal performance of polymer coatings in various applications.

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Polyvinyl alcohol (PVA) coating has attracted intense attention due to its biodegradability and high gas barrier properties. However, the high gas barrier properties deteriorate at elevated humidity. Herein, we aimed to prepare PVA based coating with high water resistance by incorporating nano-SiO₂ (S) and citric acid (CA), and polyethylene (PE) film was selected as a substrate model. The results showed that the PVA/S/CA coated PE films had better water vapor and oxygen barrier performance than the uncoated PE films. With an optimized mass ratio (PVA/S/CA_10%), the coated PE films’ water vapor permeability decreased by 46.53% at 90% RH, and the oxygen permeability decreased by four orders of magnitude at 0% relative humidity (RH). Besides, increased surface roughness and a more hydrophobic surface were observed in the coated PE films. Overall, these coated PE films still retained high transparency and were mechanically robust, making them potential candidates for the flexible food packaging field.

Graphical abstract

Silica from rice husk [SiO₂(rh)] was used as a mineral base for sequential loading of biogenic selenium nanoparticles (SeNPs) and polyhexamethylene guanidine (PHMG) hydrochloride. As result a filler for polymer coatings with a wide spectrum of antifouling activity was obtained. The complex filler was characterized by scanning electron microscopy, energy dispersive X-ray analysis, and transmission electron microscopy. The filler was introduced into epoxy (EP), polydimethylsiloxane (PDMS), and epoxy-siloxane (EP-PDMS) polymer matrices at 3 wt% and 5 wt% to evaluate their antifouling performance and effect on the durability characteristics of coatings. Characterization of the coatings was performed including water contact angle, surface free energy, pseudo-barnacle adhesion strength and modulus of elasticity. The in vitro antimicrobial properties of the prepared samples were evaluated using Staphylococcus aureus and Candida albicans. Antifouling properties were evaluated in field tests for 7 months. The incorporation of a complex filler involving SeNPs and PHMG made it possible to increase the coating resistance to fouling by 2–5 times. The best results were observed for the EP-PDMS sample with 5 wt% SiO₂(rh)-SeNPs-PHMG characterized by low values of surface free energy (10.3 mN/m) and pseudo-barnacle adhesion strength (0.32 MPa) and acceptable rate of biocidal components release. The results indicate the promising use of the new filler for development of effective antifouling coatings.