Journal of Coatings Technology and Research最新文献

When paint is applied to a substrate, the formation of paint craters is generally due to dewetting caused by a low surface energy substance present, such as siloxanes or perfluorocarbons, either on the substrate or in the paint that is applied to the substrate. As paint cratering is a surface phenomenon, the causing chemicals can be minimal both in size and quantity, or more precisely, below the detection limit of many analytical techniques. In order to identify the chemical responsible for paint craters, a technique that is extremely surface sensitive, chemically selective and capable of imaging is required. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) perfectly fits all these analysis requirements, and for the past decade we have used ToF-SIMS to identify automotive paint cratering chemicals. This article categorizes the paint cratering chemicals for the past decade and their distributions in terms of the four seasons. The information presented is expected to benefit both painting engineers and defect analysts in understanding possible/potential chemicals causing automotive paint craters, which is a costly failure in car manufacturing.

The present paper describes the design of a superhydrophilic self-cleaning surface using mixed metal oxides. SiO₂/ZnO/TiO₂ layers were deposited on a cleaned glass surface by a dip coating method. The silica layer imparts stability and adhesion to the coating of the glass surface. ZnO was deposited in the form of nanoflowers over silica which was further coated by titania nanoparticles in a multilayer. This renders the exposed titania layer to be superhydrophilic having a contact angle of eight. High surface area combined with superhydrophilicity helps impart enhanced photocatalytic activity of the coating due to increased wetting characteristics of the surface. The surface, therefore, acts as a self-cleaning surface by effectively degrading pollutants. Moreover, the formation of a heterojunction between ZnO/TiO₂ layers reduces the band gap to 2.98 eV from 3.59 eV in TiO₂ thus enabling the degradation of pollutants in the visible range (416.25 nm).

Hybrid yarns, combining stainless steel with glass fibers, are promising for impact-resistant composites. Inside the yarn, the thermoplastics matrix is provided in the form of endless filaments. Thermoplastics gained popularity as composites' matrix due to recyclability. The study emphasizes customizing adhesion between stainless steel and polypropylene for desired properties in the composites. Tailored adhesion is crucial for optimizing the performance of stainless steel/polypropylene composites. Within this contribution, a selection of adhesion promoters and preventers is analyzed to generate adjustable adhesion between polypropylene matrix and stainless steel filaments. The characterization is fulfilled using contact angle measurements on films of coating agents and coated stainless steel filaments. Furthermore, surface free energy is calculated and theoretical adhesion is analyzed between coating agent and stainless steel filaments and coated stainless steel filaments and polypropylene matrix. The results are validated by single fiber pullout tests.

This study presents the synthesis and characterization of novel lanthanide complexes, specifically La (III) and Gd (III), designed as flame-retardant additives for paint formulations. The complexes were synthesized and thoroughly characterized using different spectroscopic techniques, complemented by density functional theory computational calculation insights. The resulting La (III) and Gd (III) complexes were then incorporated into paint formulations, and the physical properties of the modified coatings were systematically evaluated. Ignitability and the minimum oxygen percentage required for sustained combustion were quantified according to standardized procedures. The modified coatings demonstrated enhanced mechanical and ignition properties in comparison to blank samples. The limiting oxygen index (LOI) values were notably higher, underscoring the efficacy of the lanthanide complexes as flame retardant additives. La complex led to an ignition time of 850 s and an LOI of 40, while Gd complex resulted in the same ignition time of 850 s and LOI of 50 compared to the uncoated sample of 550 s and an LOI of 16. The mechanical properties of the painted samples, engineered with the inclusion of these prepared metal complexes, exhibited a significant improvement. This comprehensive investigation provides valuable insights into the potential application of lanthanide complexes as effective flame-retardant additives in coatings, offering a promising avenue for enhancing the safety and performance of various materials.

This study reports the development of anticorrosive bilayer coatings consisting of in situ grown layered double hydroxides (LDH) covered with a polyurethane layer on a steel substrate. This design aims at providing corrosion protection via the controlled release of gluconate from LDH near the substrate, while at the same time contributing to the improvement of the polyurethane layer coating adhesion. The CaAl-LDH thin film was initially grown directly on AISI 1080/1010 carbon steel and modified with environmentally friendly gluconate molecules through an ion-exchange reaction. The effect of polyurethane treatments on the LDHs thin film was systematically explored: gluconate is either intercalated in LDHs or dispersed in polyurethane coatings, and the two systems are studied to understand the role of inhibitors in bilayer coating systems at defined conditions. The structural characteristics of the developed coatings were evaluated by scanning electrochemical microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (ATR-FTIR), and glow discharge optical microscopy (GDOES). The findings of electrochemical impedance spectroscopy (EIS) measurements on coated carbon steel substrates in NaCl solution demonstrated the significance of the bilayer film design for long-term corrosion protection, by combining active corrosion protection provided by the LDH conversion film with the passive barrier effect against electrolyte species rendered by the organic polyurethane layer. Additionally, improving the polyurethane coating’s wet adhesion to the substrate when applied onto CaAl-LDH opens new directions toward the co-development of surface treatments with organic coatings.

Ultraviolet curable composite coatings are an eco-friendly option with the absence of volatile organic compound emissions. Achieving a better interface between epoxy acrylate (EA) and mica is essential for the enhanced mechanical and barrier properties of composite coatings. This paper presents a strategy for modifying mica through in situ grafting with various silane coupling agents (KH550, KH560, and KH570) and preparing composite coatings of EA/mica using a blending method. The results indicate that the silane-modified mica exhibited enhanced compatibility with EA coatings. The mechanical properties, thermal stability, and corrosion resistance of epoxy acrylate/silane-modified mica coatings were improved compared to epoxy acrylate/unmodified mica composite coatings. KH570 was found to be the most effective modifier for enhancing these properties of the coatings. Relative to EA/unmodified mica composite coating, the impact resistance of EA/KH570-modified mica composite coatings doubled, with increases in T₅ and T₁₀ by 49.7°C and 9.7°C, respectively. During the 9 day monitoring period using electrochemical impedance spectroscopy, the total impedance modulus |Z|_f=0.01 Hz of EA/KH570-modified mica composite coatings was discovered to be 6–9 times higher than that of unmodified mica coatings, with the R_t value higher by two orders of magnitude.

The inherent combustibility of waterborne polyurethane (WPU) with a limiting oxygen index (LOI) of only 18.0% has impeded its versatile applications in the automotive industry, furniture coatings, leather, and other domains. Therefore, enhancing the fire safety of WPU is imperative. This work reports the synthesis of novel reactive flame retardants and their subsequent chemical grafting onto WPU to ameliorate its flammability weakness. Using the novel flame-retardant intermediate 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and para-hydroxybenzaldehyde as precursors, phosphorus-based flame retardants (DOPOs) were prepared. Hollow glass microspheres (HGB) were modified with a silane coupling agent (KH550) and incorporated into the WPU prepolymerization. Finally, chemical grafting occurred between the hydroxyl groups of DOPOs and the modified HGB to produce dual-component flame retardants involved in the prepolymerization. The addition of 2 wt% synergistic flame retardants to WPU increased its LOI to 26% and eliminated dripping during combustion.

With urbanization and the reduction in forest land, there has been an increase in the temperature around urban areas resulting in the urban heat effect (heat island). As a measure of the urban heat effect, the use of organic polymer thermochromic material (OPTCM) as a building material seems to be a feasible solution. OPTCM is used as a reflective coating that reflects the sunlight, reducing the electricity load on cooling system. The OPTCM easily gets degraded under sunlight and thereby limits its usage in building coating applications. To reduce the photodegradation of OPTCM, it is generally encapsulated with an inorganic metal oxide such as titanium dioxide, zinc oxide, etc. Different methods are discussed and illustrated further to achieve the necessary microencapsulation. It is necessary to study the properties of different inorganic metal oxides as the encapsulating material. The effects of these encapsulating materials on the properties of OPTCM are further discussed in this review paper.

Graphical abstract

A glucose-modified double crosslinked waterborne polyurethane (WPCU) was synthesized by glucose (GLC) and trimethylolpropane (TMP) as crosslinking agents, polycarbonate diol (PCDL) as the functional soft segment material, and isophorone diisocyanate (IPDI) as the hard segment. The effects of GLC and TMP on the structure and material characteristics of WPCU were examined and evaluated using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and other tests. The experimental results demonstrate the favorable comprehensive performance of the modified WPCU. The double-crosslinked polyurethanes exhibited excellent mechanical strength (30.9 MPa for WPCU-0.9 film), a higher water contact angle (82.9° for WPCU-0.3 film), and superior thermal stability compared to single-crosslinked polyurethanes modified solely with GLC. In addition, a new type of double crosslinked waterborne wood paint was formulated by adding various additives. It was subjected to painting experiments on wood panels. The newly developed wood coatings using double crosslinked WPCU emulsions exhibit good chemical resistance (to alcohols, acids, and bases), dry heat resistance, and adhesion (adhesion class I). Paint films achieve a hardness of 2H when the GLC content exceeds or equals 1.2%, exhibiting excellent adhesion resistance, which could contribute to the development of high-stiffness waterborne polyurethanes in the future.