Progress in Organic Coatings最新文献

Due to electronic product miniaturization and acceleration, electromagnetic radiation and thermal accumulation issues are prominent, posing risks to nearby devices and individuals. Developing thin polymer films to block electromagnetic radiation and prevent fires is crucial for smaller, faster electronics. In this study, we successfully fabricated a unique self-supporting ultra-thin sandwich-structured film named ANFs-PVA/AgNWs (APAg), which exhibited exceptional performance in both electromagnetic interference (EMI) shielding and flame retardancy. The introduction of inner AgNWs layer resulted in significant EMI shielding effectiveness (SE) at X-band frequencies, achieving an impressive 47.01 dB with a loading of only 0.10 mg/cm², effectively blocking 99.99 % of electromagnetic waves (EMWs). The ANFs-PVA layers were adopted as the flexible outer layer, endowing the films with excellent flame retardance and good mechanical support due to the high heat resistance of aramid nanofibers (ANFs) as well as the strong hydrogen bonding interaction between ANFs and PVA. The film demonstrated self-extinguishing behavior in vertical burning tests, achieving a flame-retardant rating of V-0. Furthermore, the sandwich structure provides high durability for the EMI shielding performance of the films under different conditions. This study presents a novel approach for fabricating high-performance polymer-based EMI shielding films that hold great potential for applications in electronics and communication technologies.

Wood is becoming increasingly popular again due to an increased environmental awareness. However, wood generally needs protection from a number of external influences such as moisture, UV, stains, and also fire. The latter is a particular challenge for building materials because once ignited, untreated wood usually burns down completely without the need for a continuous external heat supply. We have recently developed a sustainable coating based on polymerised chitosan itaconate, which protects wood against moisture, UV, and stains. Free-standing chitosan itaconate films were now found to be non-flammable and do not melt when exposed to fire. Thermogravimetric analyses of these films underscore the importance of polymerisation to increase the thermal stability. When applied to wood surfaces, the coating delays the ignition and the spreading of flames. A single application already reduces the burning rate by one third. With multiple layers of the coating, the samples extinguish as soon as the external flame is removed.

While organic coatings effectively prevent metal corrosion, they are prone to micro-porosity and micro-cracking during curing and can be degraded by environmental factors, reducing their protective capacity and the substrate's lifespan. Inspired by the polymer confinement effect, this study synthesizes BNNSs-PDA-TiO₂ nanocomposites to enhance the mechanical and protective properties of silicone epoxy (SE) coatings. FTIR, TGA, XPS, and TEM/EDS analyses confirm the successful growth of TiO₂ on PDA-modified BNNSs. The incorporation of these nanofillers significantly restricts polymer chain mobility, leading to notable improvements in the composite coating's mechanical and protective performance. Compared to pure SE, the tensile strength and Young's modulus of the 1 % BNNSs-PDA-TiO₂/SE composite coating increased by 91 % and 83 %, respectively. Electrochemical impedance spectroscopy (EIS) revealed that, after 6 cycles of accelerated cathodic polarization in 3.5 wt% NaCl solution, the low-frequency impedance modulus and coating resistance of the 1 % BNNSs-PDA-TiO₂/SE composite coating were three orders of magnitude higher than those of pure SE. This enhanced corrosion resistance is attributed to a dual protection mechanism: an improved passive barrier effect (strong interface and restricted polymer chains increased coating density) and the corrosion-inhibiting action of PDA and TiO₂. This study introduces the concept of polymer confinement, offering a new perspective for designing high-performance organic coatings reinforced with 2D nanocomposite fillers.

Hexagonal boron nitride (h-BN) as an ideal two-dimensional nanofiller is often utilized to enhance the thermal conductivity and anticorrosion in the polymer matrix composites. However, the poor compatibility and dispersibility severely restrict its further application. To address this issue, herein, a novel h-BN (FBN) filler with excellent compatibility and dispersibility performances was prepared using a bio-based quercetin modifier by a non-covalent modification method. Leveraging the good compatibility between quercetin and epoxy resin (EP), FBN exhibits good dispersion in the EP. Results from thermogravimetric analysis (TG), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) analyses prove that the addition of FBN not only significantly improves the thermal conductivity but also evidently enhances the thermal stability of the polymer matrix composite. When the mass ratio of micro-FBN to nano-FBN is 2:1, the optimized FBN/EP composite coating can further enhance the thermal conductivity with 2.385 W m⁻¹ K⁻¹. Additionally, electrochemical impedance spectroscopy (EIS) and neutral salt spray (NSS) analyses demonstrate the superior long-term corrosion protection capability of the FBN composite coating, much better than pure EP and h-BN coatings. This is attributable to that the better dispersion and compatibility of FBN in the composite coating further enhances its barrier effect.

Nanofillers of various nano dimensions, ranging from 0D (such as SiO₂) to 1D (such as carbon nanotubes) and 2D (such as graphene), are commonly added to epoxy resin matrices to enhance their tribological properties, making them more suitable for various applications such as protective coatings, composites, and adhesives. Beyond solely utilizing single-nano-dimension fillers, 0D/2D multi-dimensional designed materials are more effective fillers for high-performance epoxy coatings due to their rich morphologies and chemistry. In this work, a highly anti-corrosive epoxy-based coating with multi-dimensional fillers of 2D hexagonal boron nitride (h-BN) and 0D mesoporous silica particles (mSi) is prepared and reported. The approach initially involved the sol-gel condensation reaction coating of h-BN sheets with mesoporous silica to obtain hBN@mSi multi-dimensional fillers. This was followed by the introduction of benzotriazole (BTA) as the corrosion inhibitor to hBN@mSi, forming BTA-hBN@mSi, which was later added to the epoxy resin to obtain the composite coating with improved performance. The underlying mechanism for the improved corrosion behavior in the modified epoxy was then explored using various methods. The results show that the increased specific surface area and pore volume of 0D/2D multi-dimensional fillers of hBN@mSi significantly increased in comparison to their single dimensions. This played a critical role in the BTA loading capacity in the filler and hence the anticorrosion performance of the modified epoxy coating. Furthermore, the modified epoxy coating exhibited good thermal conductivity and mechanical properties, making it suitable for various applications where corrosion resistance, thermal conductivity, and mechanical strength are key, such as in the construction of heat exchangers for various industries including chemical processing, oil refining, power generation, and HVAC systems.

Barrier coatings on dry formed pulp were studied in this article, which were derived from Kraft lignin, stearic acid, and combinations thereof. Coating layers were applied by spray-coating with a solution of lignin or stearoyl chloride and subsequent heat treatment. Alternatively, lignin was esterified with stearoyl chloride on beforehand or combinations of lignin and stearoyl chloride on the air-laid mat were done. Since the treatments were applied prior to thermopressing, the coating agents permeated the top layers of each substrate. As our results show, coatings with lignin could improve the tensile strength and stiffness of the substrate. Grafting with stearic acid, on the other hand, affected the tensile properties negatively, which was argued to arise from worse binding of the cellulose fibers and degradation due to the presence of acid moieties. All treatments improved the barrier properties, as noted by a reduction in air permeation and water-vapor transmission rate (WVTR). The effect of spray coated lignin on WVTR was best, albeit showing less effect on the water absorption as measured by COBB₁₈₀₀. Stearic acid grafting yielded the opposite trend, i.e., reducing water absorption to a greater extent, while affecting WVTR less. Combinations of stearoyl chloride and lignin showed synergies and additive effects to some extent. In conclusion, various treatments for dry formed fibers were implemented and tested, which may promote the development of new barrier solutions for cellulose-based materials.

Fluorosilicone polymers with a high fluorinated group content are shielded from their interactions with crosslinking agents and solvents by their closely arranged fluorinated groups on their surface. Herein, a series of poly(dimethyl-methylphenyl-methyltrifluoropropyl)siloxanes (PDPFSs) were synthesized using the hydrolysis–polycondensation method to reduce the shielding effect of the fluorinated groups. Dimethyl dimethoxy silane, phenyl methyl dimethoxy silane, and 3,3,3-trifluoropropyl methyl dimethoxy silane (TFMDS) were the main raw materials. The chemical structure of PDPFS and the thermal stability, surface properties, mechanical properties, and antifouling properties of the PDPFS coating were characterized. When the TFMDS content increased from 0 to 40 wt%, the number average molecular weight of PDPFS decreased from 43,380 to 38,433 g/mol and the chemical crosslinking rate of the PDPFS coating decreased from 81.25 % to 68.09 %. An analysis of the surface properties of the PDPFS coating revealed a decrease in surface free energy from 24.22 to 13.19 mJ/m² and an increase in roughness from 0.013 to 0.048 μm. The mechanical properties were examined, indicating that the Young's modulus of the PDPFS coating increased from 0.10 to 0.46 MPa and the average molecular weight between crosslinking points increased from 24,795 to 3285 g/mol. Experimental results revealed that the anti-adhesion efficiency and removal efficiency of the PDPFS coatings was mainly related to the TFMDS content. The anti-adhesion efficiency and removal efficiency were proportional to roughness, Young's modulus, and crosslinking density and inversely proportional to number average molecular weight and surface free energy. Further analysis of the comprehensive antifouling ability of the PDPFS coatings revealed that the antifouling efficiency of the PDPFS coating gradually increased from 16.83 % to 62.12 % with increasing TFMDS content. However, the 3,3,3-trifluoropropyl group exhibited an adverse effect on the hydrolysis–polycondensation and crosslinking reactions when the TFMDS content exceeded 35 wt%. Hence, PDPFS with a TFMDS content of 35 wt% was selected for further research.

The emerging of flexible package market compels us to develop printing inks that are eco-savvy and suitable for polymer films. Owing to the advantages of low toxicity, environmental-friendly and cost-effective, water-based inks growingly occur to researchers and the studies on binders for water-based inks unprecedentedly flourish. Notwithstanding, the adhesion on polymer films and the slower dryness rate constrain the water-based inks to be the mainstream in the field of flexible package printing. In this work, a crosslinkable polyacrylate emulsion for water-based inks binders was successfully synthesized via semi-continuous seed emulsion polymerization to improve the adhesion and dryness rate of ink films. Particularly, crosslinkable monomer allyl acetoacetate (AAA) was utilized as crosslinkable monomers, hexamethylenediamine (HDA) was added as a crosslinker. Isobornyl methacrylate (IBOMA) was employed to endow the emulsion with desirable adhesion for water-based inks. The viscosity, surface tension, water contact angle, particle size distribution and glass-transition temperature (Tg) were evaluated to research the influence of the AAA and HDA crosslinkable system. Performances of the acrylate emulsion and the latex films, with emphasis on resistance to Ca²⁺ and thermal stability were obviously superior to other polyacrylate emulsions synthesized in this paper. The 100 % adhesion ratio on polyvinyl chloride (PVC) and polyethylene (PE) films and 80.08 % adhesion ratio on biaxially oriented polypropylene (BOPP) was attained with AAA-HDA crosslinkable polyacrylate emulsion. The dryness rate was accelerated from 23 mm/30 s to 40 mm/30 s. This work provides ideas and inspiration for design of the water-based inks that served in flexible package.

Waterborne epoxy (EP) is considered a promising environmentally friendly anticorrosive technology with extensive potential applications. However, its limited anticorrosive ability poses significant challenges in practical usage. In this study, we use dopamine (DA) polymerization to load 2-mercaptobenzimidazole (MBI) onto the surface of g-C₃N₄ (CN) nanosheets, resulting in the synthesis of MBI-PDA@g-C₃N₄ (MBI-PDA@CN) nanosheet composites. The MBI-PDA@CN composite exhibits favorable hydrophilicity and high loading capacity of 35.8 %, enabling the formation of compact bonding layer at the interface with the EP. Simultaneously, the MBI-PDA@CN nanosheets exhibit a fully lamellar structure, thereby effectively impeding the infiltration of corrosive agents. Electrochemical tests show that the coating resistance (R_p) of MBI-PDA@CN/EP coating (8.5 × 10⁷ Ω cm²) exhibited a significantly higher magnitude compared to that of the EP (2.6 × 10⁶ Ω cm²) after being immersed in 3.5 wt% NaCl solution for 30 days. It is worth mentioning that the MBI-PDA@CN nanosheets possess the capability to gradually release MBI-PDA molecules in acidic environments. Given that MBI and PDA function as outstanding metal corrosion inhibitors, they substantially augment the corrosion resistance of the coating in acidic conditions. This study presents an intriguing approach to fabricating robust corrosion-resistant composite coatings.

As societal awareness of environmental concerns grows, there is a gradual transition towards more environmentally friendly aqueous products, replacing traditional solvent-based ones. However, owing to its short hydrophobic chain segment, polyether defoamer has limitations, including a narrow field of use, poor defoaming ability, and a low defoaming rate. This study employed Fischer esterification to graft tung oil acid (i.e., eleostearic acid) onto 2,5,8,11-tetramethyl-5-decyne-4,7-diol, ethoxylated (TDDE) using p-toluenesulfonic acid as a catalyst. The resulting product, polyether alkynyl alcohol wetting agent (ETDDE), consisted of a tung oil monomer chain (hydrophobic part) and a polyether chain (hydrophilic part). The successful synthesis of ETDDE was confirmed through infrared spectroscopy analysis, gel permeation chromatography testing, and acid value determination. The results showed that the surface tension, defoaming ability, coating gloss, wettability, and water resistance of ETDDE improved with the ratio of eleostearic acid to TDDE.