Fluorine-free Superhydrophobic Coatings Research Articles

Innovative and cost-effective fabrication of fluorine-free superhydrophobic coating: Using polydimethylsiloxane/soil particles for surface modification

In this study, a simple, efficient, and environmentally friendly method was used to create fluorine-free superhydrophobic coatings. The coatings were prepared by modifying soil particles with polydimethylsiloxane. Different from the previously reported methods, the micro-/nanostructures of these coatings were formed using natural soil as the building block. The modified soil particles were analyzed using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy to determine their elemental compositions and functional groups, respectively. The surface topography of the coatings was characterized by scanning electron microscopy and laser scanning confocal microscopy. The resulting superhydrophobic coatings exhibited exceptional wear resistance, with a contact angle of 166.2±2.5° and a sliding angle of 3.6±1.3°. The coatings also had extremely low water adhesion (62 μN) and demonstrated good mechanical, weather-resistant, and self-cleaning properties. These coatings can be applied to various materials such as cement, wood, and sponge, owing to their favorable comprehensive performance. The coatings are anticipated to find widespread application in outdoor industries.

A Single-Step Route to Robust and Fluorine-Free Superhydrophobic Coatings via Aerosol-Assisted Chemical Vapor Deposition.

Robust fluorine-free superhydrophobic films were produced from a mixture of two fatty acids (stearic acid and palmitic acid), SiO2 nanoparticles, and polydimethylsiloxane. These simple and nontoxic compounds were deposited via aerosol-assisted chemical vapor deposition to provide the rough topography required for superhydrophobicity, formed through island growth of the aggregates. The optimum conditions for well-adhered superhydrophobic films produced films with a highly textured morphology, which possessed a water contact angle of 162 ± 2° and a sliding angle of <5°. Superhydrophobicity was maintained after ultraviolet exposure (14 days at 365 nm), heat treatment (5 h at 300 °C and 5 h at 400 °C), 300 tape peel cycles, and exposure to ethanol and toluene (5 h each).

Implementation of endurable superhydrophobic surfaces through dilution rate control of the PDMS coating on micro-nano surface structures

Modifying the wettability of engineering surfaces has been widely practiced for several years because changing the surface properties of materials can induce useful functional properties. Superhydrophobic surfaces with maximized hydrophobicity prevent contamination, freezing, and corrosion, and are usually categorized based on the coating solution used. Among the various coating solutions, polydimethylsiloxane (PDMS) has attracted wide attention because it yields fluorine-free superhydrophobic coatings. Herein, fluorine-free superhydrophobic coatings were fabricated by varying the ratio of PDMS and toluene with respect to their viscosity. The roughness, wettability, and durability of the coatings were measured and described in detail. A simple chemical etching and oxidizing process was used to fabricate micro-nanostructures on the hydrophilic surface before hydrophobic coating. The variance in the morphological structure and surface roughness of the yielded micro-nanostructures in accordance with the viscosity control was analyzed using SEM images and surface roughness values, respectively. To measure the contact angle of the water droplet, coating conditions were derived to realize a superhydrophobic surface with a contact angle of over 150°. Furthermore, these superhydrophobic specimens were tested for durability in saline, acidic, and alkaline solutions. The superhydrophobic specimens showed no sign of degradation in brine for 72 h, and some surfaces showed degradation in HCl and NaOH aqueous solutions.

Large-Scale Spraying Fabrication of Robust Fluorine-Free Superhydrophobic Coatings Based on Dual-Sized Silica Particles for Effective Antipollution and Strong Buoyancy.

With the rapid development of bionic science and manufacturing technology, superhydrophobic surfaces have received extensive attention and research. However, the cumbersome steps, high cost, fluorine pollution, and poor durability greatly restrict its commercial promotion and application. Here, a simple spraying method is used to construct wear-resistant superhydrophobic coatings on various substrates such as glass, filter paper, copper sheets, and polyethylene terephthalate films, using an integrated fluorine-free suspension consisting of silica micropowder, nanofumed silica, epoxy resin, and polydimethylsiloxane. The prepared superhydrophobic coating can withstand 75 sandpaper abrasion cycles and can still maintain good superhydrophobic performance after other physical tests (e.g., hand kneading and tape peeling after knife scraping). In addition, the coating is extremely water-repellent under harsh conditions such as strong UV irradiation and extreme chemical corrosive media. In the buoyancy test, the coated filter paper can bear 39 times its own gravity. This water-repellent interface also has the ability to self-clean in air and oil environments due to its ultralow adhesion to water droplets. Thanks to its simplicity, cheapness, and environmental friendliness, this superhydrophobic coating has promising applications in the fields of construction, chemicals, transportation, and electronics.

Superwetting interfaces for oil/water separation

Superhydrophobic coatings have been applied in various fields. The materials used in the preparation of superhydrophobic coatings have attracted the attention of scholars. Due to the harm of fluorine-containing substances with low surface energy to the environment, fluorine-free superhydrophobic coatings have become a hotspot in the research field. Herein, a fluorine-free superhydrophobic coating with oil/water separation was made by a solution immersion way. The fluorine-free copolymer and polydimethylsiloxane (PDMS)/SiO2 nanoparticles (NPs) were mixed to prepare a composite solution, and the superhydrophobic surface was obtained on the paper by a dipping method. The scanning electron microscope, x-ray photoelectron spectrometer, 1H nuclear magnetic resonance, and Fourier transform infrared were used to study the surface characteristics and structural composition of the superhydrophobic material. The research proved that the copolymer and PDMS/SiO2 NPs were successfully coated on the paper surface, and the rough structure of the superhydrophobic surface was also attributed to the introduction of the copolymer and PDMS/SiO2 NPs. The evaluation of the coating has proved its excellent hydrophobicity, oil/water separation performance, and self-cleaning performance. The coating is a sustainable and environmentally friendly superhydrophobic material that can be used in packaging, construction, petrochemical, and other industries.

Fluorine-Free Transparent Superhydrophobic Nanocomposite Coatings from Mesoporous Silica

In recent decades, there has been a growing interest in the development of functional, fluorine-free superhydrophobic surfaces with improved adhesion for better applicability into real-world problems. Here, we compare two different methods, spin coating and aerosol-assisted chemical vapor deposition (AACVD), for the synthesis of transparent fluorine-free superhydrophobic coatings. The material was made from a nanocomposite of (3-aminopropyl)triethoxysilane (APTES) functional mesoporous silica nanoparticles and titanium cross-linked polydimethylsiloxane with particle concentrations between 9 to 50 wt %. The silane that was used to lower the surface energy consisted of a long hydrocarbon chain without fluorine groups to reduce the environmental impact of the composite coating. Both spin coating and AACVD resulted in the formation of superhydrophobic surfaces with advancing contact angles up to 168°, a hysteresis of 3°, and a transparency of 90% at 550 nm. AACVD has proven to produce more uniform coatings with concentrations as low as 9 wt %, reaching superhydrophobicity. The metal oxide cross-linking improves the adhesion of the coating to the glass. Overall, AACVD was the more optimal method to prepare superhydrophobic coatings compared to spin coating due to higher contact angles, adhesion, and scalability of the fabrication process.

Hexadecyltrimethoxysilane-Modified SiO2 Nanoparticle-Coated Halloysite Nanotubes Embedded in Silicone–Acrylic Polymer Films as Durable Fluorine-Free Superhydrophobic Coatings

Superhydrophobic coatings have received considerable attention owing to their potential applications. There has been an increasing demand for the construction of durable superhydrophobic coatings u...

Effect of fabric texture on the durability of fluorine-free superhydrophobic coatings

Water repellency is a desired feature of fabrics for certain applications in textile industry such as water-repellent garments, tents, and umbrellas. Coating of fabrics with fluorocarbons or silicones followed by heat treatment is the general process to impart hydrophobicity even though the resulted water repellency is limited. In this study, we prepare a fluorine-free superhydrophobic coating from hydrophobic SiO2 nanoparticles that can be easily applied to common fabrics by simply spray coating, leading to superhydrophobic fabrics with a water contact angle of 172° and a sliding angle of 3°. The process to achieve extreme water repellency is simple and only involves a single step, and there is no need for further processes like annealing or heat treatment. The superhydrophobic coated fabrics display durability dependence on the texture of the underlying material, where coated chenille and nonwoven fabrics show robust mechanical durability against water impact, abrasion, and laundering. The ready availability of the coating materials, the simple process of application, and the robust mechanical durability of superhydrophobic fabrics show great potential for real-world applications.

Underwater writable and heat-insulated paper with robust fluorine-free superhydrophobic coatings.

Since its invention invented in China, paper has been widely used in the world for quite a long time. However, some intrinsic defects servely hinder its application in some extreme conditions, such as underwater or in fire. Herein, a bio-inspired durable paper with robust fluorine-free coatings was fabricated via a two-step spray-deposition technique. It not only consisted of modified SiO2 microspheres and nanoparticles, but also contained an epoxy resin, endowing the paper with multifunctional properties. First, this bio-inspired functional paper showed excellent superhydrophobic and self-cleaning properties with a high static water contact angle (WCA) of 162.7 ± 0.5° and a low sliding angle (SA) of 5.7 ± 0.6°. Moreover, it possessed unusual repellent properties toward multiple aqueous-based liquids and heat-insulated properties. Second, this paper could be used for writing underwater and maintained satisfactory superhydrophobic performance for a long time with a WCA of 153.3 ± 1.8°. Besides, its high mechanical robustness was also experimentally confirmed in harsh working conditions, such as strong acid/alkali, boiling water, abrasion, bending, and folding. Compared with conventional paper, it is anticipated that this bio-inspired functional paper would be really competitive and demonstrate great potential in the field of underwater and fire-proof applications.

Fluorine-Free Superhydrophobic Coatings Based on Silicone and Functionalized Colloidal Silica

Recently, fluorine materials have been a serious cause of environmental concern. In response, a novel fluorine-free superhydrophobic coating is presented in this paper. A superhydrophobic coating based on silicone and surface-modified colloidal silica is explored and exploited. First, a superhydrophobic coating, based on silicone resins and fluorine group-modified colloidal silica, is developed. Then, the fluorine group-modified colloidal silica is replaced by octyl-modified colloidal silica, a superhydrophobic coating based on fluorine-free materials, octyl-functionalized colloidal silica, and epoxy-modified silicone. The hydrophobicity and coating integrity were investigated, and the fluorine-free coating shows good superhydrophobicity and coating integrity. The result demonstrates the feasibility of a fluorine-free superhydrophobic coating, thus providing an effective solution to the environmental problems caused by fluorine chemicals.

Fabrication of fluorine-free superhydrophobic coatings from montmorillonite with mechanical durability and chemical stability

In this study, durable superhydrophobic coatings were successfully prepared by modifying montmorillonite with stearic acid and organosiloxane, and this procedure was simple, efficient, and environmentally friendly. Different from the previously reported methods, the micro-/nanostructures of the superhydrophobic coatings were constructed by using the abundant natural montmorillonite as the building blocks. The surface topography of the coating was analyzed with a scanning electron microscope, while element compositions and functional groups were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, respectively. The as-prepared superhydrophobic coatings showed excellent wear resistance, and could maintain their superhydrophobicity after sandpaper abrasion for 180 cm in length. Apart from the superb wear resistance, the obtained superhydrophobic coatings also displayed strong acid resistance and anti-UV properties. In addition, the as-coated fabric not only possessed superhydrophobicity and the ability of oil–water separation, but also exhibited excellent fire resistance because of the thermal stability of MMT particles. Notably, the favorable comprehensive performance of the as-prepared coatings was indicative of their potential applications in oil/water separation and some harsh conditions, and as outdoor protective materials.

Influence of particle size in fluorine free corrosion resistance superhydrophobic coating - Optimization and stabilization of interface by multiscale roughness

Fluorine free superhydrophobic coatings with stabilized air-water interface had been fabricated by utilising different particle sized silica. Coatings were formulated with various composition of different sized nanosilica's along with nanotitania and aluminium stearate embedded in a matrix of silicone resin of Mn ∼1,65,000. The as-prepared coating exhibited higher contact angle (CA) 152.5° along with high mechanical properties like abrasion, adhesion and impact resistance. As particles with different sizes were incorporated in the coating, the interface was stabilized during immersion in water uptake study. In addition most of these coatings also exhibited exceptional corrosion resistance withstanding upto 1000 h of salt spray.

Durable and fluorine-free superhydrophobic coatings from palygorskite-rich spent bleaching earth

Abstract With the increasing consumption of vegetable oils, value-added recycling of spent bleaching earth (SBE) is of wide concern. Here, we report a simple and sustainable method for converting SBE containing palygorskite (PAL) to hybrid carbon materials (PAL/C) with a nanorod-like structure, which can then be used as building blocks for the preparation of durable and fluorine-free superhydrophobic coatings. The PAL/C composites were prepared by calcination of the SBE containing PAL in air. Then, the homogeneous suspensions in ethanol were prepared by hydrolytic condensation of n-hexadecyltrimethoxysilane onto the PAL/C nanorods. Superhydrophobic coatings can be readily prepared by spray-coating the suspensions onto substrates. The PAL/C composites and the superhydrophobic coatings were characterized using a variety of analytical techniques including scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Superhydrophobicity of the coatings depends upon their surface topography, which can be precisely regulated by the calcination temperature of SBE and the concentration of the PAL/C composites in the suspensions. The superhydrophobic coatings show high water contact angle and extremely low sliding angle of 1.2°. The superhydrophobic coatings also feature high mechanical, thermal and chemical durability. This is because the PAL/C nanorods are closely linked and encapsulated together by polysiloxane (POS) among them, forming a highly crosslinked network. We believe that this study will shed light on the value-added recycling of SBE and cost-effective preparation of bioinspired antiwetting coatings.

A fluorine-free superhydrophobic PPS composite coating with high thermal stability, wear resistance, corrosion resistance

Abstract A simple spraying method was used for fabricating stability and wear-resistance fluorine-free superhydrophobic coatings by introducing the silicone rubber (SR) particles and carbon nanotubes (CNTs) into poly(phenylene sulfide) (PPS) matrix. When the weight content of PPS:SR:CNTs = 0.7:0.3:0.015, the water contact angle (WCA) and the slide angle (SA) of the prepared coating were (164 ± 1.5)° and (1 ± 0.8)°, respectively. The WCA of the prepared coating also possessed good durability, which could maintain (141 ± 1)° after 10,000 times of abrasion. It was mainly ascribed to the internal micro/nano-structure designed by combining SR particles with CNTs and low surface free energy groups Si-CH3 of SR. Moreover, the prepared coating exhibited excellent wear resistance, which was 2 times higher than pure PPS coating. The adhesive ability of the prepared coating corresponded with Grade 4 according to ASTM D3359 due to the synergy of SR particles and CNTs. The test results of thermogravimetric (TG) indicated the outstanding thermal stability of the prepared coating with weight loss less than 10% under 478 °C. Furthermore, the corrosion resistance of the aluminum could be effectively enhanced by the prepared superhydrophobic coating with performance of higher corrosion potential −756.69 mV and lower corrosion current 4.97 × 10−8 A/m2 after 15 days immersion in 3.5 wt.% NaCl solution. Therefore, it is believed that the prepared coating with excellent thermal-stability, wear-resistance and corrosion-resistance might have a huge potential in large-scale industrial application.

Highly transparent fluorine-free superhydrophobic silica nanotube coatings

Transparent coatings with self-cleaning properties are required for protection of outdoor optical devices. Highly transparent, fluorine-free superhydrophobic coatings of silica nanotubes (SNT) on glass substrates are fabricated by using poly(dimethylsiloxane) (PDMS) as the silica source and multi-walled carbon nanotubes (MWCNTs) as the sacrificial template, following by hydrophobization through chemical vapor deposition (CVD) of cured PDMS. The influence of surface topography from SNT on the transparency and superhydrophobicity of the coatings is investigated. High transparency and excellent superhydrophobicity of the surface can be achieved by changing the concentration of PDMS (CPDMS) for SNT coatings as well as the amount of the cured PDMS (APDMS) for hydrophobization. The optimum coating has an average transmittance higher than 83% in the visible-light range (400–780nm), a water contact angle (CA) of 165° and a slide angle (SA) lower than 3°. When applied as protective cover, the glass substrate with superhydrophobic coating has little effect on the power generation efficiency of solar cells and has outstanding self-cleaning properties.

Fabrication of durable superhydrophobic coatings on cotton fabrics with photocatalytic activity by fluorine-free chemical modification for dual-functional water purification

Fluorine-free superhydrophobic coatings on cotton fabrics with photocatalytic activity.

Fluorine-Free Superhydrophobic Coatings with pH-induced Wettability Transition for Controllable Oil-Water Separation.

We present a simple, environmentally friendly approach to fabricating superhydrophobic coatings with pH-induced wettability transition. The coatings are prepared from a mixture of silica nanoparticles and decanoic acid-modified TiO2. When the coating is applied on cotton fabric, the fabric turns superhydrophobic in air but superoleophilic in neutral aqueous environment. It is permeable to oil fluids but impermeable to water. However, when the coated fabric is placed in basic aqueous solution or ammonia vapor, it turns hydrophilic but underwater superoleophobic, thus allowing water to penetrate through but blocking oil. Therefore, such a unique, selective water/oil permeation feature makes the treated fabric have capability to separate either oil or water from a water-oil mixture. It may be useful for development of smart oil-water separators, microfluidic valves, and lab-on-a-chip devices.

Spray-Coated Fluorine-Free Superhydrophobic Coatings with Easy Repairability and Applicability

The present paper reports a very simple and low-cost fluorine-free superhydrophobic coating prepared by spray-coating metal alkylcarboxylates, for example, Cu[CH(3)(CH(2))(10)COO](2), onto virtually any substrates. Superhydrophobicity with a static water contact angle of about 160 degrees and a sliding angle of 5 degrees was achieved from the proper precursor concentration. The advantages of the present approach include the cheap and fluorine-free raw materials, environmentally benign solvents, an industrial implementation method, and easy repairability and applicability so as to make a great application potential in practice. The hydrophobicity of coatings and the adhesion to water were found to be dependent on the surface morphology that was governed by the precursor concentrations from which coatings were prepared. The static wetting behavior of water droplets with different sizes gentlly deposited on the coatings was studied in more detail and correlated to theories, i.e., Wenzel's and Cassie's models. The results indicated that nanoribbon-textured coatings prepared from low precursor concentration (0.02 M) exhibited a transition from the metastable Cassie-Baxter state to the Wenzel state with increments in the droplet volume, and eventually droplets firmly stick to the surface even when the droplet was gently deposited on the surface. Surface coatings with dual roughness at both microscale and nanometer scale were formed as the concentration (0.04 M) was increased and conferred a stable Cassie state, even for increased droplet size and increased droplet deposit speed.