Synthesis of fluoroalkyl‐modified polyester and its application in improving the hydrophobicity and oleophobicity of cured polyester coatings

The fluoroalkyl‐modified polyester (PE‐F_n) was synthesized by the reaction of polyester resin (PE) and fluorinated isocyanate, and the structure of the synthesized product was characterized by proton nuclear magnetic resonance (¹H‐NMR) and fluorine nuclear magnetic resonance (¹⁹F‐NMR). The water and oil wettability of the cured PE coatings with PE‐F_n as additives was investigated by contact angle meter. The results showed that the introduction of an extremely low concentration of PE‐F_n into PE led to the increase in contact angle of water and diiodomethane on cured PE coatings, and the decrease in the surface free energy. The X‐ray photoelectron spectroscopic (XPS) analysis showed that the F/C molar ratio in the outer few nanometers was significantly higher than that in the bulk, indicating that the fluoroalkyl groups in PE‐F_n had enriched on the coating surface. It was also found that longer fluoroalkyl groups and fluoroalkyl groups with ? CF₃ at its end had the higher tendency to aggregate on the coating surface. The topological structures of the cured coatings were recorded by an atomic force microscope under tapping mode and the results revealed that there was a strong surface segregation of fluorinated species. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39812.     

Synthesis and characterization of fluorine-containing polyester based on phthalic anhydride and tetrafluoropropyl glycidyl ether

Fluorine-containing polyester (FPE) was synthesized by the reaction of phthalic anhydride, epichlorohydrin, and 2,2,3,3-tetrafluoropropyl glycidyl ether (TFGE) at the catalysis of tetraethylammonium bromide using 1,4-butanediol as the initiator. The structure of FPE was characterized by ¹H NMR and ¹⁹F NMR, and the result showed that the fluorine in TFGE was introduced into FPE. Fluorine content in FPE was determined by oxygen-flask combustion and fluoride selective electrode. It was found that fluorine content in FPEs increased with the increase of TFGE content. The wettability of water and oil on the cured coating based on FPE was investigated by contact angle meter. Contact angles of water and diiodomethane on the cured coatings first increased with the increase of the fluorine content in FPEs and then remained constant. The X-ray photoelectron spectroscopic analysis showed that the F/C molar ratio on the coatings surface was much higher than the overall F/C molar ratio, which indicated that fluoroalkyl groups in FPEs had enriched on the coatings surface. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication of two sites hydrophobicity on cotton surface – a fluoropolymerization approach

Cotton fabric on both surfaces was coated with polymerization of fluoromonomer followed by adsorption of fluorosurfactant by a new technique admicellar polymerization to obtain durable hydrophobicity. Water repellence properties were determined in terms of simple drop test contact angles. The coating on cotton fabric exhibited the right water contact angle of 137.23° and left contact angle 138.35° (an average value of 137.79°). However, the durability of the coatings was decreased after simple home laundering with a decrease in water contact angle value. The surface morphology was evaluated by scanning electron microscopy before and after polymerization. Beside this chemical composition on the cotton, the surface was evaluated by EDS analysis to determine the number of fluorine moieties deposited on the cotton surface by this technique.     

Effect of titania particles preparation on the properties of Ni–TiO2 electrodeposited composite coatings

In this paper, the effect of titania particles preparation on the properties of Ni–TiO₂ electrocomposite coatings has been addressed. Titania particles were prepared by precipitation method using titanium tetrachloride as the precursor. The titanyl hydroxide precipitate was subjected to two different calcinations temperatures (400 and 900 °C) to obtain anatase and rutile titania particles. These particles along with commercial anatase titania particles were separately dispersed in nickel sulfamate bath and electrodeposited under identical electroplating conditions to obtain composite coatings. The electrodeposited coatings were evaluated for their microhardness, wettability, corrosion resistance, and tribological behavior. The variation of microhardness with current density exhibited a similar trend for all the three composite coatings. The composite coating containing anatase titania particles exhibited higher microhardness and improved wear resistance. However, the corrosion resistance of the composite coating containing commercial titania powder was superior to that of plain nickel, Ni–TiO₂ composite coatings containing anatase and rutile titania particles. The poor corrosion resistance of these composite coatings was attributed to the higher surface roughness of the coatings. This problem was alleviated by incorporating ball-milled titania powders. The composite coatings with higher surface roughness were modified with a low surface energy material like fluoroalkyl silane to impart hydrophobic and superhydrophobic properties to the coatings. Among these coatings, Ni–TiO₂–9C coating exhibited the highest water contact angle of 157°.     

Optimization of amphiphobic structural surface thickness in relation to its functionality on stainless steel plates

Fluorine‐based amphiphobic coatings have been widely used in commercial textiles to provide water‐ and oil‐repelling abilities. However, few reports from the literature survey have discussed the surface structural effects of the coated substrate on amphiphobicity. In this research, various thickness amphiphobic coatings based on mixed epoxy, tetraethylorthosilicate, and a particular alkoxysilane with fluorinated side chains (F‐silane) were deposited on Grade 420 stainless steel plates. Film amphiphobicity is characterized by measuring the water and oil contact angles of the coating. Film morphology is examined using atomic force microscopy. The deposited films free of F‐silane are thinner than 150 nm. The films become thick at high F‐silane volume percentage with the surface cavities, ridges, and granules being masked out. On the addition of F‐silane, the water contact angle of the deposited films increases up to 105° and then reaches a plateau of ～ 107° with increasing F‐silane. In contrast, the oil contact angle increases up to 60° at first and then slowly declines with the F‐silane concentration. The total drop of oil contact angle by ～ 20° was attributed to the masking out of surface features on film thickening. This indicates that the surface oleophobicity depends on surface structures. Therefore, improving surface amphiphobicity correlates with creating more refined multiscale surface structures during the industrial manufacturing process of steel plate, prior to surface modification by F‐silane. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41003.     

Effect of pore content and pH on the corrosion behavior of hydrophobic ceramic coatings

In this paper, superhydrophobic ceramic coatings were successfully prepared on stainless steel substrates (S304) by sol–gel method, and the effects of pore content and pH conditions on the corrosion resistance of hydrophobic ceramic coatings were studied. As the porosity increases, the contact angle of the coating increases. Among them, the contact angles of the coatings with 15% and 20% porosity in different pH solutions are all greater than 150°, achieving superhydrophobic surfaces. The contact angle results before and after corrosion show that the solution with a higher pH has a greater damage to the hydrophobicity of the coating. The corrosion resistance of the coatings was evaluated comparatively from polarization curves and electrochemical impedance spectroscopy. As the hydrophobicity improves, the corrosion resistance of the hydrophobic ceramic coating is enhanced. The impedance moduli at .01 Hz of the coating are 1.04 × 10³ times (pH 4), .13 × 10³ times (pH 7), and .74 × 10³ times (pH 10) of the bare steel, respectively. With the increase of pH, the corrosion resistance of hydrophobic ceramic coatings decreases, because OH⁻ in the corrosion solution is more easily adsorbed on the surface of the coating, thereby destroying the long hydrophobic chains.     

Surface and mechanical properties of an organic-inorganic super- hydrophobic coating using modified nano-SiO2 and mixing polyurethane emulsion as raw materials

A series of organic-inorganic super-hydrophobic coatings were prepared using nano-SiO₂ particles modified by fluorine and silicone coupling agents, and a mixing polyurethane emulsion as main raw materials. The mixing polyurethane emulsion was consisted of the polyurethane emulsion end-terminated by double bond (WPUD) and polyurethane emulsion modified by silicone (WPUS). The influence of content of modified nano-SiO₂ particles and the weight ratio of WPUS to WPUD on microstructure and hydrophobicity of the coating surface were studied. The morphologies of coating surface were examined using SEM and AFM, hydrophobicity of the coating was researched by examining static water contact angle and so on. It was found that modified nano-SiO₂ particle was an indispensable factor during the preparation of super-hydrophobic coating. The roughness and hydrophobicity of the coating surface were enhanced obviously with an increase of the content of the modified nano-SiO₂ particles. When the content of the modified nano-SiO₂ particles increased up to 1.5%, the surface of coating possessed good super-hydrophobicity, and static water contact angle reached 169.1°. It was also noticed that the weight ratio of WPUS to WPUD in the base layer has also an important influence on the hydrophobicity and mechanical property of coating surface. With an increase of the ratio of WPUS to WPUD the hydrophobicity of the coating was enhanced, the tensile strength and peel strength reduced, but the elongation at break increased. When the weight ratio of WPUS to WPUD reaches up to 9/100, the static water contact angle reaches the maximum value of 169.1°.     

Synthesis of UV-curable polysiloxanes containing methacryloxy/fluorinated side groups and the performances of their cured composite coatings

Three novel UV-curable polysiloxanes consisting of polysiloxane backbone with methacryloxy/fluorinated side groups were synthesized, and their structures were characterized by FT-IR, ¹H NMR and ¹³C NMR. A series of UV-cured composite coatings based on the synthesized polysiloxanes and an epoxy methacrylate were obtained through photopolymerization. Their gel content, flexibility, hardness, gloss, contact angle, thermal behavior as well as water absorption ratio were investigated. Results found that the siloxane component could enhance the flexibility and gloss of coatings, while the presence of fluorinated groups could improve the hardness. The combination of silicon and fluorine in the same polymer could increase thermal stability and water resistance of the coatings and decrease their surface energy simultaneously. The observation of the fractured-surface morphology showed that the polysiloxanes could be well dispersed in the epoxy methacrylate to some extent. A suitable addition of such polysiloxane in photocurable coating matrixes may provide excellent properties for the cured coatings and widen their applications.     

Fabrication of fluorine-terminated diamond-like carbon thin film using a hyperthermal atomic fluorine beam

Surface modification of diamond-like carbon (DLC) film was performed using a hyperthermal atomic fluorine beam on the purpose of production of hydrophobic surface by maintaining the high hardness of DLC film. By the irradiation of atomic fluorine beam of a 1.0 × 10²⁰ atoms/cm², the contact angle of a water drop against the DLC surface increased from 73° to 111°. The formation of CF₃, CF₂ and CF bonding on the modified DLC surface was confirmed from the measurements of X-ray photoelectron spectra and near-edge X-ray absorption fine structure spectra. Irradiation of hyperthermal atomic fluorine beam was concluded to produce insulator fluorine-terminated DLC film, which has high F content on the surface, by the taking of the use of neutral atomic beam as a fluorine source.     

短氟碳链含氟硅烷偶联剂及其疏水涂层的构建

以三氟丙基甲基环三硅氧烷(D3F)、二甲基氯硅烷、甲基二氯硅烷、乙烯基三甲氧基硅烷(VTMS)为主要原料,通过阴离子开环聚合和硅氢加成反应合成了一系列短氟碳链含氟硅烷偶联剂。载玻片表面经纳米二氧化硅溶胶涂膜和硅烷偶联剂表面修饰得到疏水涂层。探究了不同硅烷偶联剂对于涂层疏水性、附着力、硬度、透过率等性能的影响。结果表明,同类型含氟硅烷偶联剂中氟含量越大,其修饰的涂层接触角越大;相似相对分子质量及氟含量情况下,直链型含氟硅烷偶联剂修饰的涂层疏水性优于支链型修饰的涂层。经含氟硅烷偶联剂修饰的疏水涂层中,接触角最大的是由聚合度为9的支链型含氟硅烷偶联剂(DF3)修饰的涂层,可达141.6°。疏水涂层的附着力均达1级,硬度均达H,可见光透过率高于82.9%,具有良好的自清洁性能。     

A robust quasi-superhydrophobic ceria coating prepared using air-plasma spraying

Hydrophobic coatings that could survive in harsh environment have a wide range of applications from industry to houseware. However, the state-of-the-art polymer-based coatings cannot meet such requirements due to their low melting point and poor wear resistance. In this study, we reported a plasma sprayed ceramic coating made of ceria with exceptional hydrophobicity, high-temperature stability, and good wear resistance. The coating exhibited a water contact angle (WCA) up to 139°, due to the intrinsic hydrophobicity of ceria and unique surface morphology produced by plasma spraying. The WCA only slightly decreased to 131° after annealing at 773 K. In addition, the polished coating (WCA ~ 116°) was still more hydrophobic than the sintered bulk specimen (WCA ~ 95°) with the same composition and roughness, which can be attributed to the surface chemistry change induced by Ar⁺ ion bombing by plasma. It is believed that such robust hydrophobic coating should have great potential in engineering application.     

Development of a superhydrophobic polyurethane-based coating from a two-step plasma-fluoroalkyl silane treatment

A method of achieving a superhydrophobic surface based upon a highly filled polyurethane (PU) paint coating has been demonstrated through the use of a combined oxygen/argon plasma pretreatment and a fluoroalkyl silane (FAS) final treatment.The combined plasma-FAS treated PU surface has been investigated and characterised using: field emission gun secondary electron microscope (FEG-SEM); X-ray photoelectron spectroscopy (XPS); energy-dispersive X-ray spectroscopy (EDX); water contact angle analysis (WCA); atomic force microscopy (AFM), and; Fourier transform infrared spectroscopy (FTIR).It was found that the oxygen/argon plasma treatment increased both the surface roughness (R_a) and surface free energy (SFE) of the PU paint coating from approximately 60–320 nm, and, from ~52 to ~80 mN/m respectively. It was also found that the plasma process created a multiscale roughened texture through the process of differential ablation between the PU polymer and the barium sulphate solid content, which is present in the paint as an extender, and other additives. In addition, the process also imparted favourable polar groups into the PU surface from the ionised and radical oxygen species in the plasma.When the FAS coating was subsequently applied to the PU without prior plasma treatment, there was a significant increases in water contact angles. This parameter increased from approximately 60° on untreated PU to around 130° with FAS applied. In this case, the SFE decreased to ~7.5 mN/m and showed 42.0 at% fluorine present as indicated by XPS.However, subsequently applying the FAS polymer after plasma pretreatment takes advantage of the known synergistic relationship that exists between surface roughness and low surface free energy coatings. The two processes combined to create superhydrophobicity with a surface that exhibited water contact angles up to 153.1°. With this optimised process, the apparent SFE was 0.84 mN/m with a more highly fluorinated surface present. In this case 47.2 at% surface fluorine was observed by XPS.In addition to changes in SFE, plasma treatment was also observed to alter levels of surface gloss and colour. After exposure to 600 s of plasma gloss levels are shown to reduce from values of from ~50 to ~21 (GU), with small but significant corresponding increases in the lightness and yellowness of the surface.     

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     

Facile fabrication of water repellent coatings from vinyl functionalized SiO2 spheres

Water repellent SiO₂ particulate coatings were prepared by a one-step introduction of vinyl groups on the coating surface. Rough surface structure and low surface energy could be directly obtained. Vinyl functionalized SiO₂ (vinyl-SiO₂) spheres with average diameter of 500 nm were first synthesized by a sol–gel method in aqueous solution using vinyltriethoxysilane as the precursor. The multilayer SiO₂ coating fabricated by dip-coating method was highly hydrophobic with a water contact angle of 145.7° ± 2.3°. The superhydrophobic SiO₂ coating with a water contact angle up to 158° ± 1.7° was prepared by spraying an alcohol mixture suspension of the vinyl-SiO₂ spheres on the glass substrate. In addition, the superhydrophobic SiO₂ coating demonstrated good stability under the acidic condition. However, it lost its hydrophobicity above 200°C because of the oxidation and degradation of vinyl groups.     

The effect of side chains on the reactive rate and surface wettability of pentablock copolymers by ATRP

The reactive rate and surface wettability of three pentablock copolymers PDMS‐b‐(PMMA‐b‐PR)₂ (R = 3FMA, 12FMA, and MPS) obtained via ATRP for coatings are discussed. Poly(dimethylsiloxane) (PDMS) is used as difunctional macroinitiator, poly(methyl methacrylate) (PMMA) as the middle block, while poly(trifluoroethyl methacrylate) (P3FMA), poly(dodecafluoroheptyl methacrylate) (P12FMA) and poly(3‐(trimethoxysilyl)propyl methacrylate) (PMPS) as the end block, respectively. Their reactive rates obtained by gas chromatography (GC) analysis indicate that 3FMA gains 8.053 × 10^?5 s^?1 reactive rate and 75% conversion, higher than 12FMA (4.417 × 10^?5 s^?1, 35%), but MPS has 1.9389 × 10^?4 s^?1 reactive rate and 96% conversion. The wettability of pentablock copolymer films is characterized by water contact angles (WCA) and hexadecane contact angles (HCA). The PDMS‐b‐(PMMA‐b‐P12FMA)₂ film behaves much higher advancing and receding WAC (120° and 116°) and HCA (60° and 56°) than PDMS‐b‐(PMMA‐b‐P3FMA)₂ film (110° and 106° for WAC, 38° and 32° for HAC) because of its fluorine‐rich surface (20.9 wt % F). However, PDMS‐b‐(PMMA‐b‐PMPS)₂ film obtains 8° hysteretic contact angle in WAC (114°–106°) and HAC (32°–24°) due to its higher surface roughness (138 nm). Therefore, the fluorine‐rich and higher roughness surface could produce the lower water and oil wettability, but silicon‐rich surface will produce lower water wettability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40209.     

Antigraffiti polyurethane coating containing fluorocarbon side chains grafted polymethylsiloxane

The novel polymethylsiloxane grafted by fluorocarbon side chains was synthesized via hydrosilylation reaction of polymethylhydrosiloxane (PMHS) with 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) in the presence of Karstedt’s catalyst. The reaction factors of reaction temperature, reaction time, catalyst dosage, solvent dosage, and molar ratio of the reactants were investigated through orthogonal experiments. Under optimal conditions, the grafting ratio of HFBA to PMHS reached 91.6%. The structure of the grafted polymer was characterized by FTIR and ¹H NMR spectra. The synthesized polymer was incorporated into two-component polyurethane coating formulations as an additive to prepare antigraffiti coatings. After curing, the contact angle measurement was performed and the results showed that surface free energy of the coating film decreased dramatically from 30.7 to 21.4 mJ/m². The inks of permanent markers cannot spread readily on the coating film and can be removed easily, indicating that the incorporation of the synthesized polymer endowed the coating with admirable antigraffiti performance. XPS analysis revealed that atomic concentrations of silicon and fluorine near the surface (about 10 nm) were much higher than deeper within the film (about 100 nm), suggesting that these two elements had a strong migration tendency toward the coating–air interface. AFM measurement showed that the inclusion of synthesized polymer in coating did not affect the surface roughness of the film.     

In situ preparation of recoverable superhydrophobic coatings for various environments

A superhydrophobic coating was synthesized by in-situ reaction of fumed silica nanoparticles and a co-precursor which contains methyltrimethoxysilane (MTMS), propyltrimethoxysilane (PTMS), and diphenyldimethoxysilane (DPDS). The superhydrophobic surface was achieved by the spray of above mixtures on the substrates. Micro/nano structure of the surface was controlled by the silica nanoparticles. The wetting behavior of the surface was enhanced after coated and obtained a maximum 154^o static water contact angle and a minimum 1^o sliding angle. The surface retained its superhydrophobicity as well as good corrosive resistance and adhesion at a high temperature of 460?°C. Damage to the superhydrophobic coatings caused by extremely low temperature or mechanical force could be easily repaired through a heat treatment or a new spray.     

Preparation of HMDS-modified silica/polyacrylate hydrophobic hard coatings on PMMA substrates

Colloidal silica nanoparticles synthesized from tetraethoxysiliane via a sol–gel process were surface modified by 3-(trimethoxysilyl)propyl methacrylate (MSMA) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS). MSMA acted both as a C=C provider and a coupling agent, whereas HMDS was used to prevent particle aggregation and engender hydrophobicity. The modified silica particles (HMSiO₂) were UV-cured together with the crosslinking agent, dipentaerythritol hexa-acrylate (DPHA) to form coatings on poly(methyl methacrylate) (PMMA) substrates. Dynamic light scattering of the synthesized sols indicated that the average size of HMSiO₂ was ca. 10 nm, consistent with that obtained from TEM imaging. FTIR spectroscopic analyses demonstrated chemical attachment of HMDS to the silica particles. The cured coatings were characterized in terms of water contact angle, light transmittance, hardness, abrasion resistance, and surface morphology. It was found that hydrophobicity of the coatings increased while light transmittance and hardness decreased with increasing HMDS content. DPHA played the role of providing mechanical strength and adherence; however, the coatings became lightly hazy when the weight ratio of DPHA/silica fell in the range 0.3–0.7. In the optimal case, a hard coating (4H) with water contact angle of 108° and transmittance of ~100% (vs PMMA) had been obtained at the DPHA content of 10 wt%.     

A simple method for the fabrication of silica-based superhydrophobic surfaces

The present article reports on a simple and convenient method for the fabrication of superhydrophobic surfaces based on silica particles by spraying the as-prepared silica suspension containing silica sol and silica microspheres on the substrate. The morphologies of the silica particulate coatings could be controlled by varying the silica microsphere concentration. The silica particulate coatings as prepared were exceptionally rough and superhydrophilic, with water contact angles less than 5°. The surface silanol groups of the hydrophilic coatings could be functionalized using 1H,1H,2H,2H-perfluorodecyltriethoxysilane to form hydrophobic groups. The resulting surface showed excellent superhydrophobic property with water contact angle up to 165.6 ± 0.9° and sliding angle of 3.5 ± 0.4°. In addition, the superhydrophobicity of the coating possessed a good stability after 3 months of exposure in air for a wide range of pH values.     

Surface modification of ceramic coating for enhanced hydrophobicity and wear properties

In this paper, a micro–nano structural ceramic coating with good hydrophobicity and wear resistance was successfully prepared by sol–gel method, which is assisted by pore-forming agent and nanoparticles 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane modified. The surface morphology, hardness, roughness, wettability, and tribological properties of three different surface coatings were characterized. With the complication of the surface structure, the roughness of the coating increases from 1.30 to 2.05 μm. Under the combined effect of roughness and long hydrophobic chains, the contact angles of the coatings before and after modification under saline conditions increased from 56.31 to 140.59° (pH4); from 55.58 to 134.40° (pH7); from 53.80 to 132.26° (pH10). Through the comparison of wear rate and wear morphology, it is found that the micro–nano structure coating has the lowest wear rate (0.705 × 10^–6 mm³·N^–1·s^–1) and the smallest plastic deformation. This means that in addition to the good hydrophobicity and chemical stability, the micro–nano structure on the surface also improves the wear resistance of the coating.