Fabrication of superhydrophobic fiber coatings by DC‐biased AC‐electrospinning

Mesh‐like fiber mats of polystyrene (PS) were deposited using DC‐biased AC‐electrospinning. Superhydrophobic surfaces with water contact angles greater than 150° and gas fraction values of up to 97% were obtained. Rheological study was conducted on these fiber surfaces and showed a decrease in shear stress when compared with a noncoated surface (no slip), making them excellent candidates for applications requiring the reduction of skin‐friction drag in submerged surfaces. We have also shown that addition of a second, low‐surface energy polymer to a solution of PS can be used to control the fiber internal porosity depending on the concentration of the second polymer. Contact‐angle measurements on mats consisting of porous and nonporous fibers have been used to evaluate the role of the larger spaces between the fibers and the pores on individual fibers on superhydrophobicity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication of superhydrophobic unplasticized poly(vinyl chloride)/nanosilica sheets using Taguchi design methodology

This study introduces a relatively simple technique for the manufacture of superhydrophobic coatings on polymeric surfaces. Plastics such as unplasticized poly(vinyl chloride) (UPVC ) do not have a strong hydrophobic nature that is characterized by their low contact angles. Techniques of both increasing surface roughness and lowering surface energy are required to change their hydrophilicity to superhydrophobicity. In the present study, a coating of a low‐surface‐energy thermoplastic polyurethane (TPU ) was spin‐coated with chemically treated nanosilica to reduce the surface energy of UPVC . Nanosilica particles were embedded on the surface using a hot‐press. Taguchi design was used to optimize multiple processing parameters. Samples spin‐coated with 10 g L^?1 nanosilica suspension in ethanol at a rate of 400 rpm for 5 s and then hot‐pressed at 155 °C under 2 atm (203 kPa ) for 4 min had a contact angle of ca 157° and sliding angle of ca 6°, which are characteristic of superhydrophobic surfaces. Atomic force microscopy (AFM) and scanning electron microscopy (SEM ) imaging showed that these superhydrophobic surfaces were highly rough with nanoscale features. Peel test and SEM analysis showed that silica nanoparticles embedded in the TPU coating were more stable than particles immobilized on UPVC sheet without TPU coating, proving that a layer of more flexible coating can improve the longevity of superhydrophobic surfaces manufactured using this facile method. © 2016 Society of Chemical Industry     

Durability enhancement of icephobic fluoropolymer film

An icephobic and superhydrophobic surface was made by the sputtering of fluoropolymer material (PTFE or Teflon^®) on anodized aluminum alloys. The study of this superhydrophobic coating under atmospheric icing conditions showed a 3.5 times reduction of its ice adhesion strength. To evaluate the longevity of such coated surfaces and to assess their potential outdoor applications, their durability was studied after several icing/de-icing cycles. However, these coatings showed weak stability after several icing/de-icing cycles. Plasma argon pretreatment of the anodized aluminum surface was used before sputtering to increase adhesion strength between the anodized aluminum surface and Teflon-like coating. Ice adhesion and contact angle measurements of the pretreated Teflon-like coating indicated clearly that the instability was associated with the low cohesion strength of the Teflon-like film. In order to improve the cohesive strength of the coating, the input power of the discharge was increased during the sputtering process. XPS, SEM, and contact angle analyses showed that an increase in input power renders the Teflon-like coating more stable. The results of ice adhesion measurement showed low variation in ice adhesion strength on such surfaces after 15 icing/de-icing cycles. This coating also showed an excellent stability under UV irradiation and condensation.     

Superhydrophobic durable coating based on UV‐photoreactive silica nanoparticles

Superhydrophobic surfaces can be obtained by tailoring both the chemistry and roughness topography, mimicking the Lotus leaf characteristics. Most of the synthetic superhydrophobic surfaces reported have been composed of micro and nanoparticles (NPs) embedded in polymer‐based coatings. The particles which tailor the topography are bonded to the base polymers by weak secondary forces. Consequently, the topography integrity is highly affected by handling and surface drag making them unsuitable for long term applications. This work is focused on promoting covalent bonding between the NPs and the base polymer to obtain durable superhydrophobic surfaces. The rough topography was achieved by ultraviolet (UV) curing of SiO₂ NPs containing a photoreactive benzophenone moiety in addition to methylated fumed silica NPs which can bind covalently to the polymer base coating, on UV radiation. The hydrophobic chemistry was obtained by fluoroalkylsilane top coating. Coating durability was evaluated using surface air drag and accelerated weathering conditions (UV radiation, humidity and temperature). Results indicated that the proposed approach resulted in superhydrophobic surfaces having high contact angle (>150°) and low sliding angle (<10°) with improved long term durability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41122.     

Preparation and anti‐icing property of a lotus‐leaf‐like superhydrophobic low‐density polyethylene coating with low sliding angle

A lotus‐leaf‐like superhydrophobic low‐density polyethylene (LDPE) coating with low sliding angle was prepared by a facile method. The water contact angle and sliding angle of the as‐prepared superhydrophobic LDPE coating were 156 ± 1.7° and 1°, respectively. The anti‐icing property of the as‐prepared LDPE coating with low sliding angle was investigated in a climatic chamber with a working temperature of ?5°C. The results showed that the superhydrophobic LDPE coating with low sliding angle can largely prevent ice formation on the surface, showing excellent anti‐icing property. The as‐prepared superhydrophobic LDPE coating with good anti‐icing property will be perfectly desirable for outdoor equipments to reduce ice formation on their surfaces in cold seasons. This work will provide a new way to fabricate anti‐icing coating and thus find applications in a variety of fields. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

由无机特殊表面结构构造的超疏水材料

超疏水材料因在自清洁、防腐蚀、防冰附以及减阻等功能上具有广泛的应用，吸引了越来越多的关注。近年来，无机材料因易于构造具有特殊形貌的高比表面结构，在超疏水领域中显示出独特的优势。本文在简要介绍超疏水现象的定义、发展与应用的基础上，综述了超疏水理论的三个经典模型，并对国内外部分已商业化的超疏水材料进行了分析和总结。重点概括了不同种类无机材料构建的超疏水表面的研究进展。最后，本文总结了目前超疏水材料在制备过程中存在的一些问题，针对性地提出该领域未来研究的两个主要趋势：从仿生角度改进材料设计，制备集强附着力与耐久性于一体的多功能复合涂层；降低制备成本以推动产品的规模化和实用化。     

Studies on the controlled morphology and wettability of polystyrene surfaces by electrospinning or electrospraying

Polystyrene (PS) surfaces with various morphologies have been produced by electrospinning or electrospraying, such as beads with different sizes and shapes, bead-on-string structures with different aspect ratios of the beads and fibers with different diameters and shapes. Both the solution properties and the electrospinning conditions affected the PS surface morphology obtained. The results of water contact angle (CA) measurement indicated that the surface morphology could affect the wettability distinctively. It was found that CA values of PS surfaces comprised merely fibers were in the range of 140°-150°. The CA values of PS surfaces comprised bead-on-string structures were usually about 150°. However, the CA values of PS surfaces consisted of particles could reach up to 160°, which shows a superhydrophobic property. A bilayer fibers-on-beads surface was verified to be stable and superhydrophobic.     

Facile fabrication of superhydrophobic polyimide/polytetrafluoroethylene composite coatings with high water adhesion

A facile casting method was used to fabricate superhydrophobic polyimide/polytetrafluoroethylene composite coatings with high water adhesion. The water contact angles of the composite coatings were larger than 150 °, expressing superhydrophobic property. But water droplets pinned tightly on the composite coating, even if it was upside down. The X‐ray photoelectron spectrum analysis indicated that polyimide and polytetrafluoroethylene coexisted in the resulting coating. The observation with scanning electron microscopy showed that the composite coating formed lotus‐like structure with many spherical polyimide papillae randomly bonding on the surface. But the tops of the polyimide papillae were not covered by lance‐shaped Teflon fibres, forming an inhomogenous and discontinuous surface structure. This special surface chemical distribution and lotus‐like structure combined to contribute to the high adhesive superhydrophobicity. This simple method may greatly extend the application range of high adhesive superhydrophobic surfaces in microcontrollable and microfluidic application. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42810.     

A novel composite protective coating with UV and corrosion resistance: Load floating and self-cleaning performance

The research in functional materials has been the focus in studying industrial applications, particularly in the field of superhydrophobic functional bionic material. Although many studies of superhydrophobic surfaces have been published at this stage, the performance remain unsatisfactory, especially in a variety of harsh environments in practical applications, such as extremely cold weather, acidic or alkaline environment, prolonged exposure to light, high temperature, or oily wastewater, etc. The mechanical strength and corrosion resistance of coatings in such environments are all mighty challenges. In this study, we propose a fluoro silane-modified zinc oxide (FAS-ZnO) as a nano-filler. A superhydrophobic and oleophobic composite coating was successfully prepared through a single step by spraying suspensions containing attapulgite (ATP), FAS-ZnO, and carboxylated polyphenylene sulfide (PPS–COOH) onto desired substrates. In addition, stearic acid was added as a binder and used to enhance the bonding strength between the filler and the substrate. The composite coatings were characterized by FE-SEM, XRD and FT-IR on substrates, and the corrosion resistance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) and salt spray chamber experiments. The composite coatings showed excellent corrosion resistance due to the synergistic effect of FAS-ZnO and ATP. It was found that the composite coating had good hydrophobic and oleophobic contact angles of 161 ± 1.5° and 159 ± 1°, respectively, which were mainly attributed to the construction of nano-scale structures. It is worth noting that the composite coating performed excellently in chemical stability, self-cleaning performance, UV resistance, anti-fouling function, mechanical strength, and load-bearing floating ability. The coating maintained its highly hydrophobic surface after being stretched through a universal testing machine. Based on the multiple key properties in the composite coating, it can be expected to be applied to large equipment and instrument surfaces in extreme outdoor environments.     

Prevention of Ice Accretion on Aluminum Surfaces by Enhancing Their Hydrophobic Properties

The accretion of ice on the surfaces of power network systems, aircraft, communication networks, etc., is known to cause serious problems that often lead to costly safety issues. An ideal solution would be to prevent ice from accumulating in the first place, rather than waiting for ice to accrete and then to de-ice which is both time-consuming and expensive. This may be accomplished by depositing coating materials that are icephobic. A low dielectric constant surface is expected to reduce the adhesion of ice due to the screening of mirror charges, thereby eliminating one of the strongest interaction forces — the electrostatic force of attraction — at the ice–surface interface. Superhydrophobic surfaces, which demonstrate high water-repellency due to the negligible contact area of water with these surfaces, are also expected to minimize the contact area of ice. In the present research work, both concepts were studied by producing superhydrophobic nanorough low-ε (dielectric) surfaces on aluminum. Superhydrophobic properties were achieved on surfaces of aluminum by creating a certain nanoroughness using a chemical etch followed by 'passivation' of the surface by a low surface energy coating of rf-sputtered Teflon, providing a water contact angle greater than 160°. The same behavior is reported even when the nanorough substrates were coated with dielectric thin films of ZnO (lower ε) or TiO 2 (higher ε) prior to passivation. It is found that the superhydrophobic nanorough low energy surfaces are also icephobic and the presence of a low dielectric constant surface coating of Teflon (ε = 2) allows a considerable reduction of the ice adhesion strength. Ice adhesion strengths were determined using a centrifugal ice adhesion test apparatus.