An advanced corrosion protection system, distinguished by multilevel corrosion inhibition, was developed by integrating modified hybrid carriers strategically reinforced within a polyurethane (PU) ...matrix. For this purpose, mesoporous ceria (mCeO2) was synthesized via a hydrothermal hydrolysis process and incorporated with titanium butoxide to synthesize a hybrid core-shell titania mesoporous ceria (TiO2/mCeO2) carrier system. The TiO2/mCeO2 carrier system was modified with sodium benzoate (SB used as a corrosion inhibitor) to develop a modified TiO2/mCeO2-SB system. The synthesized modified particles were then reinforced into the polyurethane-based matrix to study the corrosion inhibition performance. Benefitting the corrosion-inhibiting properties of modified polyurethane-based coatings, the reinforcement of these modified TiO2/mCeO2 particles resulted in a notably improved anti-corrosion performance in the coating after immersion in 3.5 wt. % NaCl solution for four weeks, the impedance was estimated to be 96.65 GΩ.cm2, which is nearly four orders of magnitude than that of blank PU coatings. This is attributed to the synergistic anti-corrosion performance of TiO2 and SB. The protective layer formed due to the interaction of titania and hydroxyl ions resulted in the formation of Ti(OH)4 and SB absorbed on the steel surface, making iron unavailable for further electrochemical reaction. This work reports on the strategy to build a corrosion inhibition coating system, which introduces a new perspective for extending the lifespan of metals.
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•TiO2@mCeO2 composite carrier particles were successfully synthesized.•TiO2@mCeO2 hybrid particles were loaded with SB as corrosion inhibitor.•Loading of SB into TiO2@mCeO2 resulted in exceptional corrosion inhibition efficiency.•Barrier properties of PU-based coatings were improved through the reinforcement of hybrid particles.
Nowadays, nanocomposite coatings have gained much attention from both academic and industrial aspects mainly because of the outstanding properties which they can offer simultaneously. Specifically, ...anti-corrosion properties can make them one of the best choices to solve destructive corrosion problems. Nickel oxide (NiO) nanoparticles have been synthesized to create these outstanding properties in vegetable oil-based polyurethane coatings. To this end, epoxidized soyabean oil was utilized to synthesize polyol and produce polyurethane coatings, and NiO nanoparticles were incorporated into the obtained coatings. The obtained coatings were evaluated through the FTIR, H NMR, and FESEM techniques and their performance in terms of water uptake, anticorrosion and antibacterial properties were investigated. The obtained results clearly showed that the presence of NiO nanoparticles has had an undeniable effect on the performance of the coating in protecting mild steel substrate against corrosion. Moreover, using these nanoparticles has created remarkable antibacterial properties in the coating besides improved mechanical performance compared to pure polyurethane coating.
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•Flower-like Nickel Oxide (NiO) as a multifunctional nanoparticle was developed by a facile hydrothermal technique.•Using the epoxidized soybean oil as a renewable resource to synthesize polyol and polyurethane resin efficiently.•The NiO multifunctional nanoparticle induced anticorrosion properties in polyurethane-based coatings.•PU-based coatings containing flower-like Nickel Oxide nanoparticles could inhibit bacteria growth.•The mechanical properties of polyurethane-based coatings could be improved by adding NiO multifunctional nanoparticles.
The effect of incorporation of silicone oils into a siloxane-polyurethane fouling-release coatings system was explored. Incorporation of phenylmethyl silicone oil has been shown to improve the ...fouling-release performance of silicone-based fouling-release coatings through increased interfacial slippage. The extent of improvement is highly dependent upon the type and composition of silicone oil used. The siloxane-polyurethane (SiPU) coating system is a tough fouling-release solution, which combines the mechanical durability of polyurethane while maintaining comparable fouling-release performance with regard to commercial standards. To further improve the fouling-release performance of the siloxane-PU coating system, the use of phenylmethyl silicones oils was studied. Coatings formulations were prepared incorporating phenylmethyl silicone oils having a range of compositions and viscosities. Contact angle and surface energy measurements were conducted to evaluate the surface wettability of the coatings. X-ray photoelectron spectroscopy (XPS) depth profiling experiments demonstrated self-stratification of silicone oil along with siloxane to the coating-air interface. Several coating formulations displayed improved or comparable fouling-release performance to commercial standards during laboratory biological assay tests for microalgae (Navicula incerta), macroalgae (Ulva linza), adult barnacles (Balanus amphitrite syn. Amphibalanus amphitrite), and mussels (Geukensia demissa). Selected silicone-oil-modified siloxane-PU coatings also demonstrated comparable fouling-release performance in field immersion trials. In general, modifying the siloxane-PU fouling-release coatings with a small amount (1–5 wt % basis) of phenylmethyl silicone oil resulted in improved performance in several laboratory biological assays and in long-term field immersion assessments.
The performance of two bamboo composites namely laminated bamboo lumber (LBL) and bamboo stand lumber (BSL) coated with solvent- and water-based polyurethane (PUS and PUW) surface protectants against ...accelerated UV and natural weathering was evaluated and compared. Thin strips and crushed strands of B. bambos were processed using phenol formaldehyde (PF) adhesive in a hydraulic hot press to prepare the LBL and BSL respectively. The uncoated LBL and BSL exhibited severe darkening of the surfaces on exposure to both weathering regimes. All the polyurethane (PU) coated LBL and BSL showed tendency to undergo photo-yellowing after UV exposure. The roughness, wettability and reduction in glossiness of the coated samples was observed to be increased with increasing exposure period however, the rate of changes in these parameters were lower compared to their uncoated counterparts. The FT-IR spectroscopy results revealed that the lignin present in uncoated LBL and BSL deteriorated rapidly on exposure to UV and natural weathering conditions. It was concluded that the both PUS and PUW coatings on the bamboo composites provided substantial resistance against UV irradiation. The PUS coated LBL exhibited better performance by showing lower colour changes and surface cracking compared to coated BSL on exposure to natural weathering. Overall the performance of PUS coated specimens against natural weathering condition was found to be strongly influenced by the surface properties of the bamboo composites.
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•LBL & BSL coated with Polyurethane exposed to UV and natural weathering.•PUS coated LBL and BSL showed photo-yellowing and reduced glossiness.•Higher colour change, surface roughness and wettability in uncoated LBL and BSL.•Performance of PU was strongly influenced by the surface properties of composites.•PUW coated LBL performed better compared to PUS coated samples.
Corrosion is a major concern for metallic structures, leading to significant economic losses and safety risks. Self-healing coatings have recently emerged as a promising solution to mitigate ...corrosion issues. This research develops a novel self-healing anti-corrosion composite coating using Ni-Al double layer hydroxide (LDHs) modified with phosphate ions as inhibitor. 1 wt% of modified particles were incorporated into the polyurethane (PU) matrix to form a coating (PU-LDH-PO4) and was applied on the carbon steel substrate. Reference coating (PU-LDH-NO3) was also formed for comparison purposes. The LDH serves as a reservoir for the inhibitor, which gradually released in response to corrosion-induced damage. The inhibitor release inhibits the corrosion process and promotes the formation of a protective passive film on the metallic surface. FTIR and FE-SEM coupled with EDS confirmed the successful loading of phosphate ions in the layered structure of Ni-Al LDH. The corrosion resistance of the self-healing composite coating was evaluated by electrochemical impedance spectroscopy (EIS) and salt spray test (SST). These tests demonstrate a higher and more robust inhibition efficiency (98 %) and self-healing effect compared to the reference coating. The enhanced corrosion ability of developed modified coating can be attributed to the effective and controlled release of inhibitor ions as well as the entrapment of aggressive chloride ions (Cl−) through the ion exchange mechanism. This composite coating demonstrated enhanced corrosion resistance and self-healing properties, making it a promising candidate for applications in protecting metallic structures against corrosive environments.
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•Poly(diaminosiloxane) branched polyester/polyether polyurethane.•Dual interpenetrating cross-linked network.•Carbon fiber surface sizing coatings.•Surface free ...energy/wettability.•Interfacial performances.
Carbon fiber (CF) surface sizing coatings with molecularly dual interpenetrating three-dimensional cross-linked network structure were designed by varying the content of poly(diaminosiloxane) groups grafted onto branch chains of cross-linked polyester/polyether waterborne polyurethane (WPU). The synergistic modification of intramolecular cross-linker (TMP) and poly(diaminosiloxane) coupling agent introduced excellent organosiloxane chains into WPU system, and the hydrolytic condensation reaction of polysiloxanes further enhanced cross-linking network density. The hydrophobicity and thermal stability of WPU had been improved by the introduction of polysiloxanes and establishment of cross-linked networks. The temperature of polyurethane at thermal weight loss T5% and Tmax were increased from 219.8 °C and 411.5 °C to 273.2 °C and 430.2 °C, respectively. Compared to untreated CF, the surface free energy and polarity component of WPU treated CF increased by a factor of 1.6 and 3.5, and tensile strength of fiber increased by 20.3 %. The surface migration characteristics of polysiloxanes and the increased density of dual interpenetrating cross-linked network further enhanced effectiveness of WPU coatings in improving surface roughness of fibers and repairing defects. The polysiloxanes with low surface tension and surface energy characteristics as well as polar chains and active groups in WPU collectively enhanced the wettability and chemical reactivity of CF interface. Polysiloxans branched cross-linked polyester/polyether WPU had the potential to optimize the utility of CF in energy vehicle drive shafts and high-speed rail trains vibration damping devices, and contributed to the innovation of environmentally friendly sizing coatings.
•Feedforward comb filtering effect is proposed to extract the phase information of overlapped signals from immersed ultrasonic testing of coatings.•A quantitative relation between the notch frequency ...and interfacial stiffness is obtained from the numerical simulation.•Decimal part of the ratio of notch frequencies to interval frequencies is proposed as a novel index to evaluate the bonding strength of coatings.•A comparative study on bonding strength assessment is conducted based on ultrasonic nondestructive test and destructive cross-cut test.•A baseline-free ultrasonic nondestructive method is proposed for quantitative evaluation of bonding strength of coatings.
Because of the ability to protect and decorate materials, polyurethane coatings (PU) are being applied more and more extensively in the transportation, furniture, automotive, and electronic industries. However, it is difficult to effectively evaluate the bonding quality of coatings by conventional destructive methods for high-volume products in industrial applications. In this work, an ultrasonic nondestructive method based on the feedforward comb filtering effect was proposed to assess the bonding strength of the PU coatings. The coating and substrate interface can be modeled as a distributed spring system. The phase of the reflected ultrasonic wave is highly related to the interfacial stiffness. The superimposed signals can be well analyzed based on the comb filtering effect, and an index called the ratio of notch frequencies to interval frequencies (NIR) was constructed to represent the phase difference. Finite element simulations were conducted to show the index’s construction method and variation with different interfacial stiffnesses. Immersed ultrasonic testing experiments with a transducer of 39.43 MHz were then conducted on PU coatings on two kinds of substrates made of aluminum and magnesium alloys. Each specimen was scanned as a grid to mimic the procedure of the well-known cross-cut test. The notch frequencies of the scanned received signals were applied to obtain the NIR index. To avoid the interference of the thickness of coatings, the decimal part of NIR was further proposed to link with the bonding strength obtained by the cross-cut test. This index changes accordingly with aluminum- and magnesium-based coatings’ bonding strength. The results prove that the proposed ultrasonic method based on the feedforward comb filter effect is high potential to assess the bonding strength of coatings nondestructively.
This study investigates the durability of polyurethane coating containing graphene oxide under UV radiation. In this work, graphene oxide (GO), as an UV absorber, was fabricated by Hummer's method. ...The structure and morphology of GO were characterized by Fourier transform infrared spectroscopy (FT‐IR), Field emission scanning electron microscopy (FESEM) and Ultraviolet‐vision spectroscopy (UV‐Vis). The results showed that GO with layered structure was successfully synthesized. GO was incorporated into polyurethane coating at a concentration of 0.1 wt.%. Gloss measurement, colorimetric measurement and electrochemical techniques were used to evaluate the degradation of polyurethane coating containing GO after exposure to QUV test. The results indicated that presence of GO enhanced the UV durability of polyurethane coating.
FTIR images of (a) Exp. Solvent free acrylic polyol (b) Exp. Solvent free acrylic polyol cured with polyisocyanate, Desmodur N3390.
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•Incorporation of a renewable reactive diluent in ...the acrylic polyol resin synthesis.•Environment friendly Acrylic polyol resin with no solvent in formulation.•Low molecular weight product with excellent cross-link density.•Excellent mechanical and chemical properties of the coating.•VOC of the coating is < 160 g/L.
Solvents play a huge role in the manufacturing of various acrylic resins due to their ability to control the molecular weight, reduce the viscosity and enhance the flow and levelling of the coatings. However, they contribute significantly to volatile organic content (VOC) which is a key parameter in the field of coatings industry. In view to minimise VOC, various polyols have been studied as reactive diluents/solvents to replace conventional solvents in acrylic polyol synthesis. In this manuscript, 1,3-propanediol oligomer, a 100 % bio-based oligomer has been used to completely replace the conventional solvent in the acrylic polyol synthesis. 1,3-propanediol not only acts as a solvent but also takes part in the curing process by reacting with polyurethane (PU) cross-linkers. To achieve the same properties as solvent based acrylic polyol resins, suitable monomers, initiators and reaction conditions were explored. Most of our designs exhibited viscosity in the range of Z6 to Z8 on Gardener scale at 25 °C. A solitary design resulted in a viscosity of Z4-Z5, which was well within our required parameters. This acrylic polyol resin based on 1,3-propanediol was cross-linked with PU cross-linkers in clear coat. The obtained film was then studied using various analytical techniques such as dynamic mechanical analyser (DMA), thermogravimetric analysis (TGA), gel permeation chromatography (GPC) and fourier transform infrared (FTIR) spectroscopy. The advantage with 1,3-propanediol based solvent free acrylic polyol resin is the reduction of VOC from 400 g/L to ∼ 160 g/L. It is observed that the coatings obtained from this acrylic polyol resin exhibited comparable performance in two component (2 K) PU coatings to that of in-house solvent borne acrylic systems having high VOCs.
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