Preparation of Superhydrophobic Coating from Fluorine-Containing Acrylate Polymer and Polysiloxane with Nano-SiO<sub>2</sub>
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Because of the problems caused by icing and snow, it is meaningful to develop coatings for anti-icing. In this paper, a superhydrophobic coating was successfully prepared by compounding fluorine-containing acrylate polymer, polysiloxane and nano-SiO 2 . Results of Fourier transform infrared spectroscopy (FT-IR) showed that epoxy groups in fluorine-containing acrylate polymer were partially cross-linked with silanol groups in polysiloxane, while self-crosslinking of silanols dominates the curing reaction. It was proven that there was a positive correlation between water contact angle (WCA) and nano-SiO 2 amount, exhibiting a maximum WCA value of 153.6°. Nevertheless, the superhydrophobic coating is subject to collapse and the nano-particles could be scrubbed away during icing. As a result, the superhydrophobicity had trivial contribution to deicing in this experiment.Keywords:
Silanol
Superhydrophobic coating
Fluorine
A superhydrophobic coating was prepared on copper (Cu) foam by a one-step chemical deposition technique. The as-prepared coated copper foam displayed excellent superhydrophobicity (water contact angle of ∼153.5° and water sliding angle of ∼1°) with a typical surface micro–nano rough structure at a deposition temperature of 60°C and a deposition time of 20 min. The film was composed of cuprous sulfide (Cu 2 S) and copper tetradecanoate, which revealed the reaction mechanism. The as-prepared superhydrophobic copper foam maintained its superhydrophobicity under harsh environmental conditions (alkaline, weakly acidic, salty, long-term storage and mechanical abrasion). The as-prepared surface was still superhydrophobic after 600 mm abrasion, with a contact angle above 150.2 ± 0.2° and a sliding angle below 10°. Through the method of heat treatment and the modification of myristic acid, the surface achieved a rapid transition in wettability, with the contact angle maintaining stability for 20 cycles. The superhydrophobic film was repeatedly soaked in a mud–water mixture 20 times, and it remained silt-free, indicating excellent self-cleaning and antifouling features. More importantly, the modified copper foam can effectively separate a series of oil–water mixtures with high efficiency (>94%) even after five cycles. Thus, the presented superhydrophobic material with dual functionality is a promising candidate for application in efficient oil–water separation.
Superhydrophobic coating
Abrasion (mechanical)
Deposition
Copper sulfide
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Superhydrophobic surfaces were prepared using a very simple and low-cost method by spray coating. A high static water contact angle of about 154° was obtained by deposition of stearic acid on an aluminium alloy. However, this coating demonstrated a high contact angle hysteresis (~ 30º). On the other hand, superhydrophobic surfaces with a static contact angle of about 162º and 158º, and a low contact angle hysteresis of about 3º and 5º were respectively obtained by incorporating nanoparticles of SiO 2 and CaCO 3 in stearic acid. The excellent resulting hydrophobicity is attributed to the synergistic effects of micro/nanoroughness and low surface energy. A study of the wettability of these surfaces at temperatures ranging from 20 to-10 °C showed that the superhydrophobic surface becomes rather hydrophobic at supercooled temperatures.
Stearic acid
Superhydrophobic coating
Hysteresis
Deposition
Supercooling
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Superhydrophobic coating
Anodizing
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Hydrophobic surface can be achieved by synergistic effect of lowering of surface energy and increase in surface roughness. Present work emphasizes on the development of thin hydrophobic sol-gel coatings on aluminium substrate using a long chain C-16 silane precursor i.e., Hexadecyltrimethoxysilane (HDTMS) crosslinked with Glycidoxypropyltrimethoxysilane (GPTMS) and Tetraethoxyorthosilcate (TEOS), in varying concentrations. Condensation and hydrolysis reactions of all three silane precursors resulted in hydrophobic sol-gel coating with a contact angle greater than 90. This can be attributed to the self assembled, low energy HDTMS groups on the surface. By further, enhancing the surface roughness of the aluminium substrate, before coating application, using various etching solutions, it was possible to achieve enhanced hydrophobicity with contact angle of about 130 and sliding angle of 20. Surface morphology, surface roughness and hydrophobicity of the coating were characterized using SEM, AFM and water contact angle analysis, respectively.
Superhydrophobic coating
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We study the nonwettability and transparency from the assembly of fluorosilane modified silica nanoparticles (F-SiO2 NPs) via one-step spin-coating and dip-coating without any surface postpassivation steps. When spin-coating the hydrophobic NPs (100 nm in diameter) at a concentration ≥0.8 wt % in a fluorinated solvent, the surface exhibited superhydrophobicity with an advancing water contact angle greater than 150° and a water droplet (5 μL) roll-off angle less than 5°. In comparison, superhydrophobicity was not achieved by dip-coating the same hydrophobic NPs. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed that NPs formed a nearly close-packed assembly in the superhydrophobic films, which effectively minimized the exposure of the underlying substrate while offering sufficiently trapped air pockets. In the dip-coated films, however, the surface coverage was rather random and incomplete. Therefore, the underlying substrate was exposed and water was able to impregnate between the NPs, leading to smaller water contact angle and larger water contact angle hysteresis. The spin-coated superhydrophobic film was also highly transparent with greater than 95% transmittance in the visible region. Further, we demonstrated that the one-step coating strategy could be extended to different polymeric substrates, including poly(methyl methacrylate) and polyester fabrics, to achieve superhydrophobicity.
Superhydrophobic coating
Spin Coating
Dip-coating
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We have developed a combination of electro –deposition and spraying methods to prepare water-repellent tin oxide/ polytetrafluoroethylene(SnO2/PTFE) coating. The coating has a high water contact angle. The resulting porous and lowest surface energy hydrophobic groups (－CF3) has a water contact angle of 165° and a sliding angle of 7°, showing super-hydrophobic property. The coating with good adhesion on substrates and the long-term stability can be fabricated on various metal substrates.
Superhydrophobic coating
Polytetrafluoroethylene
Deposition
Tin oxide
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Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q3, Q3/Q4, Q4), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q3 surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q3 surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.
Silanol
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A super hydrophobic coating on the surface of glass substrate has been developed using chemical bath deposition (CBD) process. A water contact angle (WCA) greater than 150° has been achieved. Cobalt Chloride (CoCl2) has been used as the main precursor to investigate optimum composition and high superhydrophobicity. The water droplet has been observed to slide with a sliding angle less than ∼⃒3°. This effect is particularly due to the surface morphology (roughness) and low surface energy that causes water droplet to form a large contact angle thus allowing the surface to show water-repellent properties. Deposition time is the primary parameter affecting the coating properties and a different WCA value has been observed by increasing time. Scanning Electron Microscopy (FE-SEM) images show the presence of a nano flower-like morphology that helps in imparting superhydrophobic behavior. Energy Dispersive X-ray Spectroscopy (EDX) indicate the coating to be composed of cobalt as the main constituent. Contact Angle Measurement confirms the contact angle value to be greater than 170°.
Superhydrophobic coating
Deposition
Characterization
Energy-dispersive X-ray spectroscopy
Morphology
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Polydimethylsiloxane
Superhydrophobic coating
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Polydimethylsiloxane
Superhydrophobic coating
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