The effect of composition and thermodynamics on the surface morphology of durable superhydrophobic polymer coatings.
ABSTRACT: Durable superhydrophobic coatings were synthesized using a system of silica nanoparticles (NPs) to provide nanoscale roughness, fluorosilane to give hydrophobic chemistry, and three different polymer binders: urethane acrylate, ethyl 2-cyanoacrylate, and epoxy. Coatings composed of different binders incorporating NPs in various concentrations exhibited different superhydrophobic attributes when applied on polycarbonate (PC) and glass substrates and as a function of coating composition. It was found that the substrate surface characteristics and wettability affected the superhydrophobic characteristics of the coatings. Interfacial tension and spreading coefficient parameters (thermodynamics) of the coating components were used to predict the localization of the NPs for the different binders' concentrations. The thermodynamic analysis of the NPs localization was in good agreement with the experimental observations. On the basis of the thermodynamic analysis and the experimental scanning electron microscopy, X-ray photoelectron spectroscopy, profilometry, and atomic force microscopy results, it was concluded that localization of the NPs on the surface was critical to provide the necessary roughness and resulting superhydrophobicity. The durability evaluated by tape testing of the epoxy formulations was the best on both glass and PC. Several coating compositions retained their superhydrophobicity after the tape test. In summary, it was concluded that thermodynamic analysis is a powerful tool to predict the roughness of the coating due to the location of NPs on the surface, and hence can be used in the design of superhydrophobic coatings.
Project description:In this work, we report that superhydrophobic coatings can be prepared by a simple spray-coating technique using readily available materials such as polydimethylsiloxane (PDMS) and hydrophilic and hydrophobic SiO2 nanoparticles. PDMS can combine with the two kinds of SiO2 nanoparticles to form a rough structure, which results in superhydrophobicity of the coatings. The prepared superhydrophobic coating has a water contact angle of 156.4° and a sliding angle of less than 5°. Moreover, the coatings can be applied to various substrates such as glass, paper, and plastic. In addition, the coatings show excellent stability and still remain superhydrophobic after ultraviolet radiation, sand abrasion and water impact, tape peeling, and treatment with a strong alkali/acid solution. Furthermore, the superhydrophobic surfaces are proven to be suitable for antifouling and self-cleaning.
Project description:Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.
Project description:We present a facile and inexpensive approach to superhydrophobic polymer coatings. The method involves the in-situ polymerization of common monomers in the presence of a porogenic solvent to afford superhydrophobic surfaces with the desired combination of micro- and nano-scale roughness. The method is applicable to a variety of substrates and is not limited to small areas or flat surfaces. The polymerized material can be ground into a superhydrophobic powder, which, once applied to a surface, renders it superhydrophobic. The morphology of the porous polymer structure can be efficiently controlled by composition of the polymerization mixture, while surface chemistry can be adjusted by photografting. Morphology control is used to reduce the globule size of the porous architecture from micro down to nanoscale thereby affording a transparent material. The influence of both surface chemistry as well as the length scale of surface roughness on the superhydrophobicity is discussed.
Project description:A family of hybrid organoinorganic silica-based particles with varied chemical natures and morphologies has been synthesized to test their ability to develop coatings with underwater hydrophobicity. The particles were characterized by elemental microanalysis, scanning electron microscopy, and dynamic light scattering to evaluate the organic content, observe the morphology, and estimate the aggregate size, respectively. These morphologies were transferred into surface topographies by spraycoating dispersions made from the particles onto glass supports, resulting in coatings with an ample range of profiles and roughness but all of them being superhydrophobic. Atomic force microscopy and optical profilometry were used to map the coating surfaces and analyze the topography. Then, underwater hydrophobicity endurance was tested by immersion under a 2 cm 20 °C water column perpendicular to circular glass supports coated with the particles. The so-called mirror effect derived from the occurrence of the primary plastron (continuous air layer occluded between the surface and the water) was observed on the surface of all of the coatings tested. Apart from the dependency of plastrons on the water temperature and substrate shape, the plastron quality and lifetime is notably different depending on the particle morphology and thus on the coating topography. These experiments have demonstrated that the most persistent mirror effects, and therefore underwater superhydrophobicity, were produced on coatings that exhibited the smoothest topographies at the micrometric scale. In addition, these particle-only coatings can be made mechanically stable and robust by blending with a polymer matrix.
Project description:Coatings with specific surface wetting properties are of interest for anti-fouling, anti-fogging, anti-icing, self-cleaning, anti-smudge, and oil-water separation applications. Many previous bioinspired surfaces are of limited use due to a lack of mechanical durability. Here, a layer-by-layer technique is utilized to create coatings with four combinations of water and oil repellency and affinity. An adapted layer-by-layer approach is tailored to yield specific surface properties, resulting in a durable, functional coating. This technique provides necessary flexibility to improve substrate adhesion combined with desirable surface chemistry. Polyelectrolyte binder, SiO2 nanoparticles, and silane or fluorosurfactant layers are deposited, combining surface roughness and necessary chemistry to result in four different coatings: superhydrophilic/superoleophilic, superhydrophobic/superoleophilic, superhydrophobic/superoleophobic, and superhydrophilic/superoleophobic. The superoleophobic coatings display hexadecane contact angles >150° with tilt angles <5°, whilst the superhydrophobic coatings display water contact angles >160° with tilt angles <2°. One coating combines both oleophobic and hydrophobic properties, whilst others mix and match oil and water repellency and affinity. Coating durability was examined through the use of micro/macrowear experiments. These coatings display transparency acceptable for some applications. Fabrication via this novel combination of techniques results in durable, functional coatings displaying improved performance compared to existing work where either durability or functionality is compromised.
Project description:A robust, self-healing superhydrophobic poly(ethylene terephthalate) (PET) fabric was fabricated by a convenient solution-dipping method using an easily available material system consisting of polydimethylsiloxane and octadecylamine (ODA). The surface roughness was formed by self-roughening of ODA coating on PET fibers without any lithography steps or adding any nanomaterials. The fabric coating was durable to withstand 120 cycles of laundry and 5000 cycles of abrasion without apparently changing the superhydrophobicity. More interestingly, the fabric can restore its super liquid-repellent property by 72?h at room temperature even after 20000 cycles of abrasion. Meanwhile, after being damaged chemically, the fabric can restore its superhydrophobicity automatically in 12?h at room temperature or by a short-time heating treatment. We envision that this simple but effective coating system may lead to the development of robust protective clothing for various applications.
Project description:Titanium is an inert metal that does not induce osteogenesis and has no antibacterial properties; it is proposed that hydroxyapatite coating can enhance its bioactivity, while zinc can contribute to antibacterial properties and improve osseointegration.A nano-sized hydroxyapatite-zinc coating was deposited on commercially pure titanium using an electro-chemical process, in order to increase its surface roughness and enhance adhesion properties.The hydroxyapatite-zinc coating was attained using an electro-chemical deposition in a solution composed of a naturally derived calcium carbonate, di-ammonium hydrogen phosphate, with a pure zinc metal as the anode and titanium as the cathode. The applied voltage was -2.5 for 2 h at a temperature of 85 °C. The resultant coating was characterized for its surface morphology and chemical composition using a scanning electron microscope (SEM), energy dispersive x-ray spectroscope (EDS), and Fourier transform infrared (FT-IR) spectrometer. The coated specimens were also evaluated for their surface roughness and adhesion quality.Hydroxyapatite-zinc coating had shown rosette-shaped, homogenous structure with nano-size distribution, as confirmed by SEM analysis. FT-IR and EDS proved that coatings are composed of hydroxyapatite (HA) and zinc. The surface roughness assessment revealed that the coating procedure had significantly increased average roughness (Ra) than the control, while the adhesive tape test demonstrated a high-quality adhesive coat with no laceration on tape removal.The developed in vitro electro-chemical method can be employed for the deposition of an even thickness of nano HA-Zn adhered coatings on titanium substrate and increases its surface roughness significantly.
Project description:Zinc oxide nanoparticles (ZnO NPs) were synthesized by a precipitation method, and a new charring-foaming agent (CFA) N-ethanolamine triazine-piperazine, melamine polymer (ETPMP) was synthesized via nucleophilic substitution reaction by using cyanuric chloride, ethanolamine, piperazine, and melamine as precursor molecules. FTIR and energy-dispersive X-ray spectroscopy (EDS) studies were employed to characterize and confirm the synthesized ETPMP structure. New intumescent flame retardant epoxy coating compositions were prepared by adding ammonium polyphosphate (APP), ETPMP, and ZnO NPs into an epoxy resin. APP and ETPMP were fixed in a 2:1 w/w ratio and used as an intumescent flame-retardant (IFR) system. ZnO NPs were loaded as a synergistic agent in different amounts into the IFR coating system. The synergistic effects of ZnO NPs on IFR coatings were systematically evaluated by limited oxygen index (LOI) tests, vertical burning tests (UL-94 V), TGA, cone calorimeter tests, and SEM. The obtained results revealed that a small amount of ZnO NPs significantly increased the LOI values of the IFR coating and these coatings had a V-0 ratings in UL-94 V tests. From the TGA data, it is clear that the addition of ZnO NPs could change the thermal degradation behaviors of coatings with increasing char residue percentage at high temperatures. Cone calorimeter data reported that ZnO NPs could decrease the combustion parameters including peak heat release rates (PHRRs), and total heat release (THR) rates. The SEM results showed that ZnO NPs could enhance the strength and the compactness of the intumescent char, which restricted the flow of heat and oxygen.
Project description:Ultra-hydrophobic bilayer coatings on a glass surface were fabricated by sol-gel process using hexadecyltrimethoxysilane (C16TMS) and tetramethoxysilane (TMOS) (1:4 molar ratio) as precursors. After coating, silica nanoparticles (SiO? NPs) functionalized with different mono-alkoxy derivatives (methoxytrimethylsilane, TMeMS; ethoxydimethylvinylsilane, DMeVES; ethoxydimethylphenylsilane, DMePhES; and methoxydimethyloctylsilane, DMeC?MS) were added, assuring the microscale roughness on the glass surface. Influences of the functionalized SiO? NPs and surface morphology on the hydrophobicity of the hybrid films were discussed. The successful functionalization of SiO? NPs with hydrophobic alkyl groups were confirmed by Fourier transform infrared spectroscopy (FTIR). The thermal stability of hydrophobic SiO? NPs showed that the degradation of the alkyl groups takes place in the 200-400 °C range. Bilayer coating with C16TMS/TMOS and SiO? NPs modified with alkoxysilane substituted with C? alkyl chain (SiO? NP-C?) has micro/nano structure. Hydrophobicity of functionalized SiO? NPs-C? and its higher degree of nanometer-scale roughness gave rise to ultra-hydrophobicity performance for bilayer coating C16TMS/TMOS + SiO? NPs-C? (145°), compared to other similar hybrid structures. Our synthesis method for the functionalization of SiO? NPs is useful for the modification of surface polarity and roughness.
Project description:Superhydrophobic materials have immense applications in the fields of industry and research. However, their durability is still a cause for concern. A facile method for preparing durable superhydrophobic films from carbon nanotubes (CNTs) and the main-chain type polybenzoxazine precursors is reported herein. We used probe ultrasonicator to prepare CNT/polybenzoxazine coatings. Compared with the general sonicating dispersion process, the dispersion time was greatly reduced from a few hours to 5 minutes and the prepared suspension exhibited film-forming characteristics well. The CNT/polybenzoxazine films, which do not contain any fluorinated compounds, exhibit remarkable durability against thermal treatment, organic solvents, corrosive liquids, and sandpaper abrasion, while retaining their superhydrophobicity. Furthermore, these CNT/polybenzoxazine films also showed durable superhydrophobicity after ultraviolet (UV) irradiation for 100 h. This CNT/polybenzoxazine film can be readily used for practical applications to make durable superhydrophobic coatings.