Stable and Durable Conductive Superhydrophobic Coatings Prepared by Double-Layer Spray Coating Method

Nano- and Micro-SiO2 With Integrated Green Chemistry-Based Superhydrophobic Coating for Robust Antifouling and Anticorrosion Properties

With increasing energy demands, the need for coating materials with exceptional superhydrophobic properties has grown substantially. However, the widespread use of fluorinated compounds, solvents, and polymer-based synthetic materials has led to heightened levels of microplastics and pollutants. Here, we used a self-curing, solvent-free, and recyclable polyester polyol polymer material combined with (5 and 6.5 μm) micro- and nanosized SiO2 (μ-SiO2 and n-SiO2) particles to create superhydrophobic coatings with contact angles above 170° and low roll-off angle. They were applied for self-cleaning, antifouling, and anticorrosion purposes and tested for stability in hot water, steam, and ultrasound. Both μ-SiO2 particles mixed with n-SiO2 exhibited excellent improvement in antifouling properties. Furthermore, 5 μm SiO2 incorporated with n-SiO2 demonstrated significantly higher resistance in a 62-cycle sandpaper abrasion test and maintained a contact angle above 150°, whereas this angle was lower for the 6.5 μm SiO2 coating after 30 cycles. These results suggest that 6.5 μm SiO2 offers less resistance to applied force due to its irregular roughness. However, in scenarios with lower forces, such as water drop tests, both coatings easily withstand a drop count of 3000. Additionally, electrochemical polarization curve analysis, AC impedance analysis, and seawater immersion tests confirmed the robust corrosion resistance of the superhydrophobic material.

A review on recent progress and techniques used for fabricating superhydrophobic coatings derived from biobased materials

Superhydrophobic coatings with remarkable water repellence have emerged as an increasingly prominent field of research with the growth of the material engineering and coating industries. Superhydrophobic coatings address the requirements of several application areas with characteristics including corrosion resistance, drag reduction, anti-icing, anti-fogging, and self-cleaning properties. Furthermore, the range of applications for superhydrophobic coatings has been substantially broadened by the inclusion of key performance features such as flame retardancy, thermal insulation, resistance to water penetration, UV resistance, transparency, anti-reflection, and many more. Numerous research endeavours have been focused on biomimetic superhydrophobic materials because of their distinct surface wettability. To develop superhydrophobic coatings with a long lifespan, scientists have refined the processes of material preparation and selection. To accomplish water repellency, superhydrophobic coatings are usually fabricated using harmful fluorinated chemicals or synthetic polymers. Utilising materials derived from biomass offers a sustainable alternative that uses renewable resources in order to eliminate the consumption of these hazardous substances. This paper provides an insight of several researches reported on the construction of superhydrophobic coatings using biomass materials such as lignin, cellulose, chitosan and starch along with the techniques used for the constructing superhydrophobic coatings. This study is a useful resource that offers guidance on the selection of various biobased polymers for superhydrophobic coatings tailored to specific applications. The further part of the paper put a light on different application of superhydrophobic coatings employed in various disciplines and the future perspectives of the superhydrophobic coatings.

Novel Superhydrophobic Copper Mesh-Based Centrifugal Device for Edible Oil-Water Separation

Edible oil is essential for people's daily life but also results in a large amount of oily wastewater simultaneously. Oil-water separation is a practical route that can not only purify wastewater but also recycle valuable edible oil. In this study, the superhydrophobic copper mesh (SCM) was prepared by chemical etching, and a novel oil-water centrifugal device was designed for high-efficiency separation of edible oil wastewater. The kernel is a self-prepared SCM, which has a water contact angle (WCA) of 155.1 ± 1.8° and an oil contact angle (OCA) of 0°. Besides, the separation performance of the SCM for edible oil-water mixtures was studied in this study. The results showed that the SCM exhibited excellent oil/water separation performance, with a separation efficiency of up to 96.7% for sunflower seed oil-water wastewater, 93.3% for corn oil-water wastewater, and 98.3% for peanut oil-water wastewater, respectively. Moreover, the separation efficiency was still over 90% after 18 cycles. A model was established to analyze the oil-water separation mechanism via centrifugation. The oil-water centrifugal separation device has great potential for scale-up applications.

Self-healing system of superhydrophobic surfaces inspired from and beyond nature

Superhydrophobic surfaces show wide prospects in a variety of applications requiring self-cleaning, anti-fog, anti-ice, anti-corrosion and anti-fouling properties, which have attracted the attention of many researchers. However, superhydrophobic surfaces are inevitably affected by chemical corrosion, scratches and wear in practical applications, resulting in the loss of superhydrophobicity. To solve this problem, researchers have developed superhydrophobic surfaces with self-healing properties. In this paper, the research achievements of self-healing superhydrophobic materials in recent years are summarized, and the preparation and repair principle of self-healing superhydrophobic surfaces are introduced from three aspects: surface chemical composition repair, surface roughness repair and double repair. In addition, some multifunctional self-healing superhydrophobic surfaces are introduced, such as conductive, stretchable, antibacterial, etc. Finally, in order to provide a reference for the preparation of widely used long-acting superhydrophobic materials, some existing problems and future development prospects are described in order to attract more researchers' attention and promote the development of this field.

On the Development of Ultradurable Extremely Water-Repellent and Oleophobic Soot-Based Fabrics with Direct Relevance to Sperm Cryopreservation

Nowadays, the tremendous progress of nanotechnologies and materials science facilitates the fabrication of universal and multifunctional superhydrophobic surfaces on a large scale. Yet, integrating icephobic and anti-bioadhesive properties in an individual water-repellent functional coating, for addressing the difficulties faced by cryobiologists, aircraft, and seacraft manufacturers, is quite tricky but feasible if using nonpolar soot nanoparticles, whose fragility, however, impedes their industrial applicability. Here, we advance the current state-of-the-art to an extent, permitting the introduction of economically affordable and ultradurable non-wettable soot-based coatings. The deposition of rapeseed oil soot, cyanoacrylate glue and fluorine compounds onto different fabrics confers the latter with superior tolerance to harsh mechanical and thermal interventions [e.g., scratching, blade scraping, liquid nitrogen immersion (T ∼ -196 °C), torsion and water jetting], while in the meantime retaining water repellency and oleophobicity. The as-prepared soot fabrics can stick continuously to the selected host surface and favor the recovery of ∼60% of the initial motility of human spermatozoa subjected to cryopreservation or being detached and utilized as standalone non-wettable membranes. Our invention may be considered as the first fundamental stage of safely (without any health concerns) transferring the soot in reproductive medicine and developing enhanced cryogenic and antibacterial medical devices.

Effect of Solvent on Superhydrophobicity Behavior of Tiles Coated with Epoxy/PDMS/SS

Superhydrophobic coatings are widely applied in various applications due to their water-repelling characteristics. However, producing a durable superhydrophobic coating with less harmful low surface materials and solvents remains a challenge. Therefore, the aim of this work is to study the effects of three different solvents in preparing a durable and less toxic superhydrophobic coating containing polydimethylsiloxane (PDMS), silica solution (SS), and epoxy resin (DGEBA). A simple sol-gel method was used to prepare a superhydrophobic coating, and a spray-coating technique was employed to apply the superhydrophobic coating on tile substrates. The coated tile substrates were characterized for water contact angle (WCA) and tilting angle (TA) measurements, Field-Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), and Fourier Transform Infrared Spectroscopy (FTIR). Among 3 types of solvent (acetone, hexane, and isopropanol), a tile sample coated with isopropanol-added solution acquires the highest water contact angle of 152 ± 2° with a tilting angle of 7 ± 2° and a surface roughness of 21.80 nm after UV curing for 24 h. The peel off test showed very good adherence of the isopropanol-added solution coating on tiles. A mechanism for reactions that occur in the best optimized solvent is proposed.

A Cleanable Self-Assembled Nano-SiO2/(PTFE/PEI)n/PPS Composite Filter Medium for High-Efficiency Fine Particulate Filtration

A silicon dioxide/polytetrafluoroethylene/polyethyleneimine/polyphenylene sulfide (SiO2/PTFE/PEI/PPS) composite filter medium with three-dimensional network structures was fabricated by using PPS nonwoven as the substrate which was widely employed as a cleanable filter medium. The PTFE/PEI bilayers were firstly coated on the surfaces of the PPS fibers through the layer-by-layer self-assembly technique ten times, followed by the deposition of SiO2 nanoparticles, yielding the SiO2/(PTFE/PEI)10/PPS composite material. The contents of the PTFE component were easily controlled by adjusting the number of self-assembled PTFE/PEI bilayers. As compared with the pure PPS nonwoven, the obtained SiO2/(PTFE/PEI)10/PPS composite material exhibits better mechanical properties and enhanced wear, oxidation and heat resistance. When employed as a filter material, the SiO2/(PTFE/PEI)10/PPS composite filter medium exhibited excellent filtration performance for fine particulate. The PM2.5 (particulate matter less than 2.5 μm) filtration efficiency reached up to 99.55%. The superior filtration efficiency possessed by the SiO2/(PTFE/PEI)10/PPS composite filter medium was due to the uniformly modified PTFE layers, which played a dual role in fine particulate filtration. On the one hand, the PTFE layers not only increase the specific surface area and pore volume of the composite filter material but also narrow the spaces between the fibers, which were conducive to forming the dust cake quickly, resulting in intercepting the fine particles more efficiently than the pure PPS filter medium. On the other hand, the PTFE layers have low surface energy, which is in favor of the detachment of dust cake during pulse-jet cleaning, showing superior reusability. Thanks to the three-dimensional network structures of the SiO2/(PTFE/PEI)10/PPS composite filter medium, the pressure drop during filtration was low.

Nonporous, Strong, Stretchable, and Transparent Electrospun Aromatic Polyurea Nanocomposites as Potential Anticorrosion Coating Films

This study, for the first time, focused on the fabrication of nonporous polyurea thin films (~200 microns) using the electrospinning method as a novel approach for coating applications. Multi-walled carbon nanotubes (MWCNTs) and hydrophilic-fumed nanosilica (HFNS) were added separately into electrospun polyurea films as nano-reinforcing fillers for the enhancement of properties. Neat polyurea films demonstrated a tensile strength of 14 MPa with an elongation of 360%. At a loading of 0.2% of MWCNTs, the highest tensile strength of 21 MPa and elongation of 402% were obtained, while the water contact angle remained almost unchanged (89°). Surface morphology analysis indicated that the production of polyurea fibers during electrospinning bonded together upon curing, leading to a nonporous film. Neat polyurea exhibited high thermal resistance with a degradation temperature of 380 °C. Upon reinforcement with 0.2% of MWCNTs and 0.4% of HFNS, it increased by ~7 °C. The storage modulus increased by 42 MPa with the addition of 0.2% of MWCNTs, implying a superior viscoelasticity of polyurea nanocomposite films. The results were benchmarked with anti-corrosive polymer coatings from the literature, revealing that the production of nonporous polyurea coatings with robust strength, elasticity, and thermal properties was achieved. Electrospun polyurea coatings are promising candidates as flexible anti-corrosive coatings for heat exchanges and electrical wires.