Journal of Coatings Technology and Research最新文献

Polymer-based coatings containing metallic microparticles are a kind of functional material with effective spectral selectivity. The spectral radiative transfer model of polymer-based coatings is built based on geometrical optics, and the spectral radiative characteristics of the coatings were investigated by Monte Carlo ray-tracing method. The coatings consist of aluminum particles with different shapes as fillers and four kinds of polymer resins as binders, respectively. After verifying the reliability of the method, the effect of particle shape and binder on the infrared emission properties in the range of 8–14 μm is systematically investigated. The results demonstrate that adding flake particles into the coating can obtain lowest infrared emissivity, which is at most 86.79% lower than the coating containing spherical particles when the volume fraction is 30%. The mean emissivity of Al/acrylic resin, Al/polyetherimide (PEI), Al/polymethyl methacrylate, and Al/polystyrene (PS) composite coatings is 0.46, 0.48, 0.41, and 0.22, respectively. Al/PS composite coating has the minimum mean infrared emissivity among these four kinds of polymer-based coatings, which is 54.2% lower than Al/PEI composite coating. The method proposed in this work will provide theoretical guidance for experimental research.

A painting tradition of medieval Assam, popularly known as Hengul-Hāitāl, has been studied with an aim of restoring and conserving centuries-old woodcarvings and Sāncipat manuscripts for preserving in ordinary open conditions at villages and Vaishnavite monasteries. The pigments, their combinations for producing various shades and the resulting colors have been characterized using various physicochemical techniques. The study unravels some interesting traditional science, such as, using red Hengul (cinnabar), yellow Hāitāl (yellow orpiment) and blue Nīl (Indigo or Prussian blue) as primary colors to produce any desired shade, inclusion of either or both of Hengul and Hāitāl in every shade to repel fungi and insects, applying Kharimāti (a clay) as a wood-primer for better painting effects, choosing of Bael gum as a robust non-staining natural adhesive and finally varnishing with Lā (a natural lac) to protect the pigments from natural erosion and protect the woodcarving from humidity and contaminating hands touching them. The findings provide clues to develop an appropriate method of restoration of partially worn-out woodcarvings for preserving them in ordinary open conditions, based on the traditional method of preparation.

Membrane distillation (MD) is a promising approach to address water scarcity due to its capacity to achieve high water recovery in desalination. However, high energy consumption and decline in permeate flux are key issues of MD desalination. Nanophotonic materials like carbon black (CB) have been used to improve MD performance and reduce energy consumption in the presence of sunlight. In this article, we investigated different coating procedures for the formation of a uniform layer of CB particles on polytetrafluoroethylene (PTFE) and polyvinylidene fluoride membranes. The coated membranes were manufactured and characterized using Fourier-transform infrared spectroscopy and scanning electron microscopy. Contact angle measurements demonstrated an increase in hydrophilicity after CB was added. Both types of membranes exhibited an increase in permeate flux and salt rejection with the addition of CB, with the PTFE membrane coated with 0.5% of CB having the highest water flux, reaching 14.6 L/m² h (LMH) compared to a commercial control having a flux of 8.0 LMH. The effects of different parameters on the performance of the hydrophilic CB-coated PTFE membrane were examined. The results demonstrated that the CB coating developed can be advantageous to improve the performance of MD membranes.

As replacements for bisphenol-A, new bio-based and reactive epoxy-amine coatings have been investigated in this study. Bio-based precursor, epoxy-functionalized tung oil (ETO) was synthesized using glycidyl methacrylate (GMA) and tung oil via a Diels–Alder reaction according to our previous work. The new ETO-diamine-cured systems were prepared with the equivalent molar ratio at room temperature. ETO was cured with acyclic aliphatic (Jeffamine D400) and cyclic aliphatic (Epicure 3300) amines, at four temperatures ranging from 25 to 150°C. The coatings were then compared in terms of their thermal and mechanical properties. The cured coatings were analyzed by IR, thermogravimetric analysis (TGA), and gel content tests. TGA analysis showed that the epoxide-diamine polymers demonstrated thermal stability up to 170°C. The mechanical properties of the films were investigated by pendulum hardness, pencil hardness, cross-hatch adhesion, pull-off adhesion, impact resistance, reverse resistance, and chemical resistance testing. While all the cured systems exhibited good pencil hardness, cross-hatch adhesion, impact resistance, and reverse resistance properties, the epoxide-acyclic diamine system demonstrated greater pendulum hardness and notable pull-off adhesion at 150°C. The research demonstrates the potential for greener and more reactive tung oil-based epoxide coatings with enhanced properties.

Polytetrafluoroethylene (PTFE) emulsion is widely used as a coating material in the impregnation process for preparing polyphenylene sulfide (PPS) needle felts due to its excellent chemical stability and good mechanical properties. However, the effect of emulsion impregnation coating on the filtration performance of needle felts is still under debate. Moreover, in industrial applications with high temperatures, the service life of needle felts is directly affected by their thermal stability, but the pyrolysis and kinetic properties of PPS needle felt after PTFE emulsion impregnation post-processing have rarely been quantitatively investigated. In this study, the PPS fiber/PTFE emulsion (PPS/PTFE) composite needle felt was fabricated by a direct impregnation process. The pressure drop characteristic and mechanical collection efficiency of PPS needle felt and PPS/PTFE composite needle felt were comprehensively evaluated. It was found that the PTFE emulsion impregnation coating not only increases the pressure drop, but also decreases the collection efficiency. More specifically, for particles having a size below 2.5 μm, the decrement of collection efficiency further increases with the decrease of particle size, but the mechanical collection efficiency of PPS/PTFE composite needle felt for particles having larger size is almost the same as that of PPS needle felt. Three emulsion impregnation coating distribution models were inferred to systematically explain this experimental phenomenon. Additionally, the thermal degradation process of PPS needle felt and PPS/PTFE composite needle felt was analyzed, and several typical pyrolysis kinetic parameters were also determined theoretically. It was confirmed that the PTFE emulsion impregnation coatings can enhance the thermal stability of PPS needle felts. This work provides new insight into the rational application of the direct impregnation process as well as emulsion impregnation coating in the industrial filtration field.

In this study, the electromagnetic interference (EMI) and ultraviolet–infrared (UV–IR) shielding behavior of wool (WO) and cotton/elastane (CO/EL) nanocomposite fabrics have been investigated. The study aims to investigate the EMI and UV–IR shielding performance of the CO/EL and wool-based fabrics coated with carbon (C), graphite (Gr), and indium (In) nanocomposite layers. To produce nanocomposite fabric samples, these three materials were used in different compositions and the coating processes were carried out by electron cyclotron resonance (ECR) and thermal evaporation methods. Subsequently, the EMI and UV–IR measurements were performed for the coated fabric samples, and the results have been analyzed. In this study, it has been proven for the first time that the ECR coating method can be used for coating fabrics as a textile material. Finally, it is found that the C+Gr(grid filled)+In wool sample and the carbon-coated CO/EL sample have widely exhibited a significant positive effect on increasing the EMI shielding performance in the range of 18–43 and 12–18 GHz frequencies, respectively. In addition, the results show that the C+Gr(grid)+C-coated CO/EL fabric has significant potential to increase the UV–IR shielding performance.

Phosphate has been used as a coating agent in various fields, such as electrical steel (ES), because of its excellent electrical insulation and corrosion resistance. Although the insulating properties of a phosphate coating can significantly improve the iron loss of the ES sheet, a new coating material to enhance the performance of the ES sheet further should be developed. In this study, we synthesized organic–inorganic hybrid coating agents with superior insulation compared to that of the conventional phosphate coating agent. Inorganic particles with excellent insulating properties (SiO₂, TiO₂, and Cr₂O₃) and silane coupling agents were used as starting materials. The good surface modification of inorganic particles by silane coupling agents with appropriate solvent content in the coating agent led to good dispersion stability of the coating agent. Homogeneous dispersion of the coating agent was attributed to the good surface roughness of the hybrid materials coated on the ES. Finally, when the hybrid coating agent with optimized composition was applied to the ES, the insulation property of the hybrid coating (< 100 mA) was superior compared to that of the conventional phosphate coating (~ 200 mA), and corrosion resistance was also excellent.

Robotically assisted painting is widely used for spray and dip applications. However, use of robots for coating substrates using a roller applicator has not been systematically investigated. We showed for the first time, a generic robot arm-supported approach to painting engineering substrates using a roller with a constant force at an accurate joint step, while retaining compliance and thus safety. We optimized the robot design such that it is able to coat the substrate using a roller with a performance equivalent to that of a human applicator. To achieve this, we optimized the force, frequency of adjustment, and position control parameters of robotic design. A framework for autonomous coating is available at https://github.com/duyayun/Vision-and-force-control-automonous-painting-with-rollers; users are only required to provide the boundary coordinates of surfaces to be coated. We found that robotically- and human-painted panels showed similar trends in dry film thickness, coating hardness, flexibility, impact resistance, and microscopic properties. Color profile analysis of the coated panels showed non-significant difference in color scheme and is acceptable for architectural paints. Overall, this work shows the potential of robot-assisted coating strategy using roller applicator. This could be a viable option for hazardous area coating, high-altitude architectural paints, germs sanitization, and accelerated household applications.

Developing intumescent fire-retardant coatings (IFRCs) combining superior smoke suppression and water resistance is crucial for their industrial applications. Herein, novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-decorated zirconium phosphate (ZrP-D) nanosheets are synthesized and employed in the IFRCs. The ZrP-D nanosheets feature multifunctionality, which simultaneously improve the fire resistance, smoke suppression, thermal stability and water tolerance of IFRCs. Notably, introducing 3wt% ZrP-D decreases the backside temperature of IFRC from 293.9 to 166.3°C by ~ 43.4% in fire resistance test, followed by 47.9%, 33.5% and 89.4% reductions in peak heat release rate, total heat release and total smoke release. Moreover, this IFRC exhibits improved thermal stability and water tolerance, of which char yield and water contact angle reach up to 64% and 82.7°, respectively. When exposed to high-temperature flame, the ZrP-D nanoplatelets mainly function in condensed phase, which significantly increases the expansion and compactness of residual char due to the barrier and catalytic charring effects, thus suppressing the heat release and smoke diffusion. This work provides a rational design for creating intumescent fire-retardant coatings combining smoke suppression and water resistance, thus possessing broad prospects in industry.

Graphical Abstract

The present study explored chitosan, a biodegradable nontoxic biopolymer, at different dosages for surface treatment of recycled paper to improve various properties relevant to packaging. Chitosan, at all applied concentrations, improved important paper properties like surface, strength and barrier due to which the low strength paper can also be used as a packaging paper. The effects of surface treatment of chitosan solutions of different concentrations on paper were analyzed by measuring breaking length, burst index, tear index, double fold, stiffness, air permeance, water vapor transmission rate (WVTR), wax pick, tensile energy absorption (TEA), and stretch. After surface treatment by 1% solution of chitosan, the breaking length, double fold, TEA, and stretch in machine direction were increased by 53.8%, 243%, 93%, and 75%, respectively, whereas burst index was increased by 38.4% in comparison with the base paper. The WVTR was reduced from 706 to 496 g/m²/24 h, and air passage time was increased from 18 to 65 Gurley s after surface treatment by 1% chitosan solution on the base paper. The chitosan solution at all the concentrations showed antibacterial activity in plate assay therefore reducing the susceptibility of paper to microbial attack.

Graphical abstract