Surface hydrophobization of CNF films by roll-to-roll HMDSO plasma deposition

Cellulosic films are typically sensitive towards moisture which limits their industrial applicability. In this study the films made from cellulose nanofibrils (CNF) were surface silylated with hexamethyldisiloxane (HMDSO) by roll-to-roll plasma deposition. The effects on surface hydrophobicity were clear and indisputable. Water contact angles of non-modified and plasma-deposited CNF films were 23° and 103°, respectively. As a result of surface silylation the relative polarity decreased from 46.8% to 0.6%. Surface hydrophobicity correlated well with the plasma deposition line speeds (0.5, 5, and 10 m/min) and the water vapor barrier properties. Silylation also decreased the oxygen transmission rates both at 50% and 80% relative humidity as compared to non-modified CNF films. All films were completely impermeable to olive oil and intact in contact with castor oil, toluene, and n-heptane or mixtures of them. The developed surface hydrophobization method can be exploited in strengthening the position of cellulosic films in high performance film applications.     

Preparation of a high hydrophobic aluminium surface by double zincating process

In this present study, an efficient method has been proposed to develop a high hydrophobic zincated coating on the eva-core aluminium (Al) alloy surface. The double zincating method (Z2) was utilized to develop the required roughness on the Al surface. To control the surface energy, lauric acid (LA) was coated on the surface using the liquid self-assembled monolayers (L-SAMs) method. Surface morphology, the chemical composition of the treated and untreated Al alloy has been studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), optical microscopy and X-ray diffraction (XRD), respectively. The hydrophobicity of the substrates has also been analysed using a contact angle measurement (CA). AFM micrographs show the surface roughness of the Al alloy has been drastically increased with chemical treatments from 0.071 to 0.32 μm. XRD shows the percentage crystallinity of the Al alloy is decreased with double zincating and LA coating from 56.8 to 22.7%. As a result, a high hydrophobicity of Al alloy was induced with a contact angle of 150° upon the double zincating method and L-SAMs coating.     

Fabrication and characterization of hydrophobic thin polytrifluoroethyl methacrylate adhered coating on cotton surface via amicellar polymerization

In this study, fluorine-based methacrylate ester monomers were polymerized on cotton fabric by admicellar polymerization to make the cotton surface highly rough and also highly hydrophobic with a reliable water contact angle value. The rough micro/nano-textured surface morphology, after surface fluorination, results in hydrophobicity. The hydrophobic character was confirmed by a simple drop test and contact angle measurements. Surface composition was evaluated by SEM and FT IR analysis to confirm the fluoropolymeric layer adhered on the cotton surface.     

Nanoconjugates of methacrylic polymers: Synthesis,characterization, and immobilization to leather

Imparting superhydrophobicity to surfaces has direct implications for developing water-repellent materials. Most hydrophobic materials cannot be applied directly to specific surfaces like leather because of noncompatibility. Although methacrylic polymers are compatible to leather, their inherent hydrophilic characteristics make it challenging to use for introducing hydrophobicity or superhydrophobicity. In this article, we present a strategy of introducing hydrophobicity in various degrees as well as superhydrophobicity to different surfaces, particularly leather and glass surfaces by using conjugates of methacrylic polymers and various carbon nanomaterials. The covalent functionalization of methacrylate polymers with carbon nanotubes and fullerenes was performed by radical polymerization in the presence or absence of chain transfer agents (CTAs). CTA was used during polymerization to introduce carboxylic acid group, necessary for chromium-assisted binding to leather to avoid leaching. A balance between the compatibility of the polymer nanoconjugates with the leather and the amount necessary for coating stabilization was studied by a rheometer. While water contact angle measurement indicated the mild hydrophobicity in most cases, we were delighted to observe superhydrophobicity in one case presumably due to increased roughness because of the presence of specific nanomaterial to overcome inherent hydrophilicity of methacrylic polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48627.     

Hydrophobic coating of silicate phosphor powder using atmospheric pressure dielectric barrier discharge plasma

A stable superhydrophobic coating was successfully deposited on commercial silicate‐based orange phosphor by using atmospheric pressure dielectric barrier discharge plasma with hexamethyldisiloxane (HMDSO) and HMDSO/toluene mixture as precursors. Owning to the good optical properties, the deposited film acts not only as a hydrophobic protective layer but also as an antireflection optical thin film capable of improving the phosphor photoluminescence efficiency. The plasma‐polymerized film based on Si?O?Si backbone containing methyl and phenyl nonpolar functional groups exhibited high‐water‐repellent characteristics. It was found that the water contact angle gradually increased with increasing the aging time and remained unchanged at about 140° after 1‐month aging. Besides, the thermal stability of the coated phosphor under high‐temperature condition was substantially enhanced by the aging. The findings of this work can contribute to improving the durability and reliability of the phosphor, eventually the long‐term stability of phosphor‐based light emitting diodes in practical applications. © 2014 American Institute of Chemical Engineers AIChE J, 60: 829–838, 2014     

Hydrophobicity and Water Vapor Permeability of Ethylene-plasma-coated Whey,Chitosan and Starch Films

Abstract

Water vapor transmission rate was measured on uncoated and ethyfeae-plasma-coated whey (65-93.5% whey protein), on chitosan and starch films and on aluminum-coated chitosan. Surface hydrophobicity was assessed by contact angle measurements, and X-ray photoelectron spectroscopy was used to characterize the coatings. The water vapor transmission rate through the uncoated polymer films was highest for starch and lowest for chitosan. Whey showed intermediate water permeability, with the sample containing 65% whey-protein having the lowest water vapor transmission rate. An improvement in water vapor barrier properties was observed only for the aluminum-coated sample and not for any of the polyethylene-coated samples. It is observed that the penetrating water caused the substrate to swell and the polyethylene coating layer to crack. According to profilometry, the thickness of the polyethylene coating layer was 0.1-1 μm after 15 min exposure time. The coating was hydrophobic and contained almost exclusively carbons typical of linear or crosslinked hydrocarbons. It is suggested that the observed decrease in hydrophobicity with time during the contact angle measurements is due to the reorientation at the surface of carbonyls present in small amounts in the coating.     

Surface biomedical effects of plasma on polyetherurethane

Surface biomedical effects of plasma treatment and plasma polymerization on medical-grade polyetherurethane were studied. N₂ and Ar plasma treatments and hexamethyldisiloxane (HMDS) plasma polymerization were performed at a power of 100 W with exposure times ranging from 1 to 15 min. The results showed that the contact angle of water was decreased from 79° to 62° by N₂ and Ar plasma treatments, and N₂ plasma treatment caused a slight enhancement in anti-coagulability and anti-calcific behavior. HMDS polymerization resulted in a decrease from 79° to 43° in the contact angle and an increase from 30.5 to 37.4 s in the recalcification time. At the same time, the anti-coagulability of polymerized samples for the exposure time of 2-5 min was 2.5 times that of the untreated sample. Results of XPS and ESR analyses showed that HMDS deposited onto the polyetherurethane surface and formed new Si-N bonds, and increased the number of radicals in the sample. XPS analysis also showed that N₂ and Ar plasma treatments broke some of the C-O and C=O bonds at the surface and resulted in oxidation of the surface.     

Stretchable Gold Tracks on Flat Polydimethylsiloxane (PDMS) Rubber Substrate

A process to fabricate stretchable gold tracks on silicone rubber substrates is studied by XPS, static water contact angle measurement, AFM, and SEM. The process involves several steps: removing uncured oligomers by hexane Soxhlet extraction; pre-stretching the substrate; activating the strained silicone surface by an oxygen plasma treatment; coating the strained substrate with 5 nm titanium and 80 nm gold layers; and finally releasing the sample. The plasma treatment creates a thin brittle silica-like layer that temporarily increases the substrate's surface energy. Indeed, the plasma treatment is followed by a hydrophobic recovery. As a consequence, the delay between plasma treatment and metal deposition has to be reduced as much as possible. The silica-like layer can be nicely observed after release. The entire process allows us to obtain stretchable metallized samples that remain conductive even after an excessive deformation leading to electrical failure.     

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.     

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.     

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.     

Hydrophobic and superhydrophobic surfaces fabricated by plasma polymerization of perfluorohexane,perfluoro(2-methylpent-2-ene), and perfluoro(4-methylpent-2-ene)

Fluoropolymer films were deposited on silicon (1 0 0) wafers, glass, epoxy, and hierarchical dual-sized filler epoxy composite surfaces by plasma polymerization of perfluorohexane, perfluoro(2-methylpent-2-ene), and perfluoro(4-methylpent-2-ene). The procedure involved continuous wave plasma-enhanced deposition, followed by a discharge-off period, with the monomer gas feed maintained. Silanization of silicon wafers and glass surfaces with triethoxyvinylsilane was employed to improve plasma fluoropolymer bonding to these substrates. The presence of double bonds in perfluoro(2-methylpent-2-ene) and perfluoro(4-methylpent-2-ene) was found to influence fluoropolymer coating topography, thereby increasing surface roughness in modified glass and epoxy substrates. All fluorocarbons provided a similar level of hydrophobization of flat substrates, exhibited by water contact angles (WCA) of about 110°. Hydrophobization of nanocomposite hierarchical surfaces by plasma polymerization provided superhydrophobic surfaces, with WCA of 160° and contact angle hysteresis below 8°.     

改性SiO2/聚硅氧烷无氟超疏水涂层的制备及性能

为了提高基体材料的防污能力,在基体表面制备了一种无氟超疏水复合涂层。首先,使用十六烷基三甲氧基硅烷(HDTMS)对二氧化硅(SiO_2)微纳米颗粒进行疏水改性,其次,将改性后的SiO_2颗粒与有机硅烷混合,利用硅烷的水解、聚合在基体材料的表面得到一层稳定的无氟超疏水复合涂层。采用FTIR、TGA、SEM、AFM和接触角测量仪对涂层的化学组成、表面微观结构和疏水性能进行表征。结果表明:复合涂层表面具有微纳米尺度的粗糙结构,并具有优异的自清洁性和耐磨损性;未磨损前接触角达151°,磨损100周次后接触角进一步提高至161°。     

Plasma deposition of a silicone-like layer for the corrosion protection of magnesium

Magnesium (Mg) and its alloys are widely used for biodegradable implant materials due to their degradability and mechanical properties similar to bone. However, the high corrosion rate and release of hydrogen gas hinder its clinical application. In this study, plasma-polymerization was used to deposit the hexamethyldisiloxane (HMDSO) polymeric films on Mg surface using low temperature radio frequency discharge plasma. The chemical and physical properties of the HMDSO films were characterized by contact angle measurements, field emission scanning electron microscope, and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Contact angle results show that the contact angle and the plasma discharge powers are strongly correlated. ATR-FTIR results indicate that plasma-polymerized HMDSO films have a chemical structure close to polydimethylsiloxane (PDMS). The weight loss test and electrochemical impedance spectroscopy were performed immersion in 0.9% NaCl solution in order to investigate corrosion protective properties of the coating layer. It was found that HMDSO plasma-polymerized coating layer showed good anti-corrosion properties than that of untreated samples. These results that the polymeric films coated on Mg may be potentially applied for clinical use.     

Atmospheric Plasma Surface Activation of Poly(Ethylene Terephthalate) Film for Roll-To-Roll Application of Transparent Conductive Coating

An effective surface activation is crucial for high-speed roll-to-roll coating of functional films for printed electronics applications. In this article, we report a study of surface treatment of three types of poly(ethylene terephthalate) (PET) films by an argon/oxygen atmospheric pressure plasma and an ambient air atmospheric pressure plasma to obtain the required wettability for subsequent slot die coating of transparent conductive polymer layer using a poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) ink. Prior to plasma treatment, the PET surfaces, which differ in manufacturing process of their preparation, were characterized by X-ray photoelectron spectroscopy. The surface changes after the plasma treatments were characterized by water contact angle measurement and atomic force microscopy. We found that the water contact angles of the three types of untreated PET surfaces were 80.9°, 75.9°, and 66.3°, respectively, and the water contact angles after argon/oxygen plasma treatment at treatment speed of 1 m · min^?1 decreased to 36.2°, 31.9°, and 40.9°, respectively. These conditions were stable from 1 up to 4 days, which are longer than reported values of 15–60 min and sufficient for roll-to-roll coating processes.     

Hydrophobic properties of films grown by torch-type atmospheric pressure plasma in Ar ambient containing C6 hydrocarbon precursor

The direct deposition of polymeric films with a torch-type atmospheric pressure plasma using benzene, n-hexane and cyclohexane in Ar was performed on several substrates. The surface morphologies of the films deposited with n-hexane and cyclohexane were uniformly smooth for all deposition thicknesses, and the typical water contact angle on the films indicating the degree of hydrophobicity was about 85o. However, the films deposited using benzene had a micro-coarse surface morphology and showed a superhydrophobic property with a water contact angle exceeding 150°. Some trace of oxygen incorporation was shown in all films due to the plasma deposition process in an air ambient. The small amount of oxygenated species did not lead to a decrease of hydrophobicity of the films.     

Effect of corona discharge on the stability of the adhesion of thin silicone-organic coating to polyamide fiber surface made by the sol–gel method

This paper presents the effect of pretreatment of polyamide (PA6) nonwoven with corona discharge on the stability of the adhesion of thin hydrophobic silicone-organic coating based on vinyltriethoxysilane, made by the sol–gel method. This pretreatment with corona discharge causes a change in the physicochemical properties of the PA6 fiber surface. These changes include, among others, an increase in the fiber surface roughness, wettability, and surface free energy. At the same time, XPS and EDS investigations have shown an increase in the degree of oxidation and the formation of functional polar groups on the fiber surface (C–O–, C–OH, and O=C–O–). As a result of the changes in the surface properties of pretreated PA6 fibers, a higher degree of the sol deposition was obtained compared with that for untreated nonwoven surface. The assessment of the stability of the adhesion of thin hydrophobic coating to the fiber surface was carried out on the basis of changes in the content of silica deposited on fibers and the kinetics of water contact angle after washing and abrasion processes. In the end, the PA6 nonwoven, pretreated with corona discharge, shows a higher stability of the adherence of the thin silicone-organic coating and a higher degree of hydrophobicity than the untreated nonwoven.     

Room-temperature cured hydrophobic epoxy/graphene composites as corrosion inhibitor for cold-rolled steel

Nanocasting was used to develop epoxy/graphene composites (EGCs) as corrosion inhibitors with hydrophobic surfaces (HEGC). The contact angle of water droplets on a sample surface can be increased from ∼82° (epoxy surface) to ∼127° (hydrophobic epoxy and EGC). It should be noted that EGC coating was found to provide an excellent corrosion protection effect on cold-rolled steel (CRS) electrode. Enhancement of corrosion protection using EGC coatings could be attributed to the following three reasons: (1) epoxy could act as a physical barrier coating, (2) the hydrophobicity repelled the moisture and further reduced the water/corrosive media adsorption on the epoxy surface, preventing the underlying metals from corrosion attack, and (3) the well-dispersed graphene nanosheets (GNSs) embedded in HEGC matrix could prevent corrosion owing to a relatively higher aspect ratio than clay platelets, which enhances the oxygen barrier property of HEGC.     

Oleophilic modification of poly(vinyl alcohol) films by functionalized soybean oil triglycerides

In this study, maleinized (SOMAP) and isocyanated soybean oil (SONCO) triglycerides have been successfully grafted onto one surface of poly(vinyl alcohol)(PVA) films to give films that are hydrophilic on one side and hydrophobic on the other. The surface grafting was accomplished by the reaction of succinic anhydride or isocyanate functionalities of soybean oil derivatives and the hydroxyl groups of PVA films. The reaction was run in toluene, using PVA films on glass slides so that only one side of the film was accessible. After grafting, the films were rinsed with hot toluene to remove ungrafted triglycerides from the surface. The reaction on the surface was confirmed by ATR‐FTIR and ¹H‐NMR spectroscopic techniques. A series of films were prepared at different concentrations of SOMAP or SONCO in toluene. The increase in hydrophobicity with an increase in SOMAP or SONCO concentrations was observed by water contact angle measurements. The contact angles on the grafted side of the film reach their maximum value of 88° and 94° for 26 and 2.5% SOMAP and SONCO concentrations in toluene, respectively, while the ungrafted side gives contact angle of 48°. Surface morphologies of PVA‐g‐SOMAP and PVA‐g‐SONCO films were investigated by atomic force microscopy, whereas optical microscopy and staining was used to determine the homogeneity of the films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrophobic recovery of repeatedly plasma-treated silicone rubber. Part 1. Storage in air

Silicone rubber is used for a wide variety of biomedical and industrial applications due to its good mechanical properties, combined with a hydrophobic surface. Frequently, however, it is desirable to alter the surface hydrophobicity of silicone rubber. Often this is done by plasma treatments but the effects are usually transient. In this study, surfaces of medical grade silicone rubber have been repeatedly modified by means of oxygen, argon, carbon dioxide, and ammonia RF plasma treatments with a 24 h time interval in between treatments. Treated samples were stored in air prior to surface characterization by water contact angle measurements, X-ray photoelectron spectroscopy (XPS), streaming potential measurements, and profilometry for surface roughness. The carbon percentage of the surfaces decreased after plasma treatment, while the silicon and oxygen percentages increased irrespective of the plasma used. The formation of Si-O-Si bridges between siloxane chains after plasma treatment was demonstrated by the appearance of a new component in the Si_2p peak but the degree to which this occurred differed per gas. Streaming potential measurements in a 10 mM potassium phosphate buffer indicated a more negatively charged surface for treated samples compared to untreated samples (-23.3 mV at pH 7.0). Surface roughness increased slightly for repeatedly plasma-treated samples from R_A = 0.35 μm to R_A = 0.46 μm, while scanning electron microscopy showed the presence of several 'cracks' spanning the surface after repeated treatment. Argon, carbon dioxide, and ammonia plasmas significantly reduced the advancing water contact angle from 115° to 58°, 72°, and 85°, respectively, on a more permanent basis (especially when the treatments were repeated after recovery). Oxygen plasma effects on water contact angles generally disappeared within 5 h, also after repeated treatment.