Journal of Coatings Technology and Research最新文献

To improve the corrosion resistance and antibacterial adhesion properties of AZ31 magnesium alloy as an orthopedic implant material, superhydrophobic hydroxyapatite/lauric acid composite coatings (HA/LA) were successfully fabricated on AZ31 magnesium alloy utilizing the hydrothermal method and followed by immersion treatment in lauric acid solution. The underlying HA coating synthesized by hydrothermal technique presents a micro-/nanohierarchical structure, appearing superhydrophilic, while the composite coatings (HA/LA) obtained by subsequent treatment with lauric acid exhibited excellent superhydrophobic properties with a contact angle of 152.5 ± 1.2° and a rolling angle of 1.5 ± 0.3°. Electrochemical measurements and long-term corrosion resistance test conducted in simulated body fluid (SBF) indicate a significant enhancement in the corrosion resistance of the HA/LA composite coating. Meanwhile, in vitro bacterial experiments demonstrated that the superhydrophobic composite coating surface was able to reduce the adhesion of adherent Escherichia coli and Staphylococcus aureus by more than 98%, showing excellent antibacterial adhesion properties, indicating that the superhydrophobic HA/LA composite coating in this work grants magnesium alloy with excellent corrosion resistance and antibacterial properties.

Excessive heat build-up of painted surfaces due to solar radiation and the resulting increase in interior temperatures is undesirable and even dangerous for roofing, facades, and other structural elements. One way to reduce surface temperature is to apply suitably pigmented organic coatings exhibiting high solar reflectance properties. The use of high solar reflectance pigments in paints resulted in coatings with high total solar reflectance (TSR) values, and thus with the ability to reduce the temperature of the painted substrate. The coatings were tested under laboratory and outdoor conditions on two livestock farms. It was found that the developed coatings exhibit significantly higher TSR values than commercial coatings of the same colors designed for painting roofs. The TSR values do not change when the coatings are exposed to the weather.

Biofouling release coatings (BRCs) have received attention for their potential to limit the negative impacts of biofouling on marine shipping. The calibrated water jet (CWJ, patent # US 8,984,958 B1) can be used to study the effectiveness of BRCs as a function of ship speed. Using a balance of force and linear momentum, we examined the theory and application of the CWJ for simulating the effect of ship speed on biofilm release for surfaces fouled under (1) laboratory and (2) natural conditions. Greater fouling release corresponded with an increase in CWJ pressure and, therefore, simulated ship speed for the surfaces coated with HullKote. The effectiveness of the CWJ was further confirmed for biofilm release from glass fouled naturally by submersion in flow-through seawater. A scaling analysis confirms that the results of these small-scale experiments are applicable to larger-scale biofouling release from ship hulls. This study is the first to utilize the pressure of a CWJ to quantify biofouling release as a function of simulated ship speed.

Thermal insulating coatings have important potential for energy saving in the field of building thermal management, but they are difficult to apply on a large scale due to the problem of being waterproof and moistureproof. Herein, we design a two-step spray process to fabricate a thermal insulating superhydrophobic composite coating using epoxy resin mixed with hollow glass microsphere as primer coating and fluorine-modified SiO₂ nanocoating as a waterproof layer. The composite coating shows durable superhydrophobicity and low thermal conductivity [0.051 W/(m·k)], which is endowed with excellent thermal insulating properties under light and heat, contact heat conduction (− 20 to 70 °C), and boiling water scouring environment. These multiple key properties that have been integrated into our composite film are expected to provide unique advantages for applications in building thermal management.

In order to increase the concentrations of bio-based alkyd polyols (or fatty acids) in self-crosslinking polyurethane dispersions, herein, a series of novel alkyd polyol-based autoxidizable waterborne polyurethane dispersions (AWPUDs) with different fatty acid contents, long storage stability, and low viscosity were successfully prepared by adding dimethylol propionic acid (DMPA) self-emulsifier in the late stage of their synthesis. They and their corresponding curing films were characterized by Fourier transform infrared spectroscopy (FTIR), particle size analysis, rheology measurement, storage stability evaluation, thermogravimetric analysis, dynamic thermomechanical analysis (DMA), etc. The results showed that the addition process of DMPA played a critical role for the excellent features of AWPUDs. Additionally, the crosslinking density, gel contents, and water contact angles of AWPUD films increased with the enlarged fatty acid contents, whereas their water uptake capability decreased. Moreover, a series of AWPUD coatings were prepared, and their properties like drying times, hardness development, pencil hardness, adhesion capability, impact resistance, flexibility, and water resistances were all effectively improved with the increased fatty acid contents, significantly superior to those of waterborne alkyd coatings and waterborne polyurethane coatings without fatty acids.

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.