Oil Repellency Research Articles

Preparation and characterization of superhydrophobic and highly oleophobic FEVE-SiO2 nanocomposite coatings

Here, an excellent superhydrophobic and highly oleophobic nanocomposite coating composed of fluoroethylene-vinyl ether (FEVE) resin as a matrix for modified SiO2 nanoparticles was synthesized on a stainless-steel wire mesh substrate via a facile sol-gel method. The surface morphology, microstructure, composition, and roughness of the coatings were investigated by field emission scanning electron microscopy (FESEM) equipped with energy-dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The most efficient coating with superhydrophobicity and high oleophobicity feature indicates the water and oil repellency with contact angles (CAs) of 152° and 141°, respectively, with the high adhesion to the substrate. The mechanism of amphiphobic behavior of the coating is mainly attributed to the micro-nano hierarchical structure of the coating owing to the increased roughness caused by the presence of SiO2 nanoparticles and their effective embedding into FEVE resin cross-linking with isocyanate and using metallic mesh substrate besides the reduced surface tension due to the using fluoroalkylsilanes (FASs), strong bonding of the film to the substrate via electrostatic and chemical interactions. Moreover, the coating preserves the promising long-term amphiphobicity after 10 days of immersion in water with the water and oil contact angles of 145° and 134°, respectively.

Highly efficient self-cleaning of heavy polyelectrolyte coated electrospun polyacrylonitrile nanofibrous membrane for separation of oil/water emulsions with intermittent pressure

Electrospun polyacrylonitrile fiber membranes (EPFMs) are coated with multilayer films that assembled by layer-by-layer (LBL) technique through alternating deposition of polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA). To obtain the heavy polyelectrolyte (PE) layer consisting of PAH and PAA, single pH value was replaced with alternative pH during LBL processes stabilizing the PAH/PAA layer without significant desorption. The heavy zwitterionic-like LBL coating of PAH/PAA film on the EPFM surface presents complete oil repellency while wetted in water (i.e., underwater superoleophobicity), so that allows to efficiently remove oil stains on dry EPFM by water. Removal of oil staining from a fibrous surface with high contact area demands to build up extremely strong bonding with water in both pristine and oil-wetted states. The PAH/PAA-coated EPFMs exhibit excellent self-cleaning from fibers even already wetted by oil. Generally, there is a maximum permeation volume during oil/water emulsion separation, because the blocked oil accumulates as a hydrophobic layer to block water passing through. These PAH/PAA-coated EPFMs are resilient to oil accumulation with intermittent pressure during the oil/water separation to remain the high permeation flux (over 30,000 L m−2 h−1 bar−1), still an pressing challenge in this area.

Transparent omniphobic polyurethane coatings containing partially acetylated β–cyclodextrin as the polyol

Polyurethane is currently prepared from a polyisocyanate and a polyol derived from depletable and non-sustainable petroleum precursors. This paper reports the partial acetylation of β-cyclodextrin (CD), derived from the renewable starch by enzymatic conversion, and the subsequent use of the acetylated CD as the polyol to produce a greener polyurethane. More importantly, a method for incorporating the low-surface-tension liquid poly(dimethyl siloxane), PDMS, into the new polyurethane formulation is reported. The final polyurethane coating bearing a liquid-like PDMS monolayer on its surface and nanometer-sized PDMS pools in its matrix is transparent and exhibits superior oil and water repellency. On the coating, various test liquids with surface tensions above ~22 mN/m cleanly glide at low substrate tilt angles and complex fluids such as ink and paint samples readily contract. While the green polyurethane coating and its omniphobic or anti-smudge counterpart are promising candidates for practical applications, the approaches used in this study should be adaptable for modifying other biomass-based precursors such as sugars or even possibly starch for preparing green polyurethanes and omniphobic polyureathanes.

Transparent Omniphobic Coating with Glass‐Like Wear Resistance and Polymer‐Like Bendability

AbstractTransparent omniphobic or anti‐smudge coatings with glass‐like wear resistance and polymer‐like bendability have many potential applications but there are no reports of such materials. We Report herein a molecular composite possessing these properties. The composite is prepared via the photo‐initiated ring‐opening polymerization of the epoxide rings of glycidyloxypropyl polyhedral silsesquioxane (GPOSS). While the desired hardness is provided by the silica core, the flexibility is imparted by the glycidyloxypropyl network. Oil and water repellency is achieved without adversely affecting the other properties by incorporating a low‐surface‐tension liquid lubricant poly(dimethyl siloxane). On the final coating, various organic solvents and water readily and cleanly glide, while complex fluids, such as ink and paint facilely contract. These properties are retained after an initially flat coating sample is rolled into a U‐shape 500 times or is abraded with steel wool.

Transparent Omniphobic Coating with Glass-Like Wear Resistance and Polymer-Like Bendability.

Transparent omniphobic or anti-smudge coatings with glass-like wear resistance and polymer-like bendability have many potential applications but there are no reports of such materials. We Report herein a molecular composite possessing these properties. The composite is prepared via the photo-initiated ring-opening polymerization of the epoxide rings of glycidyloxypropyl polyhedral silsesquioxane (GPOSS). While the desired hardness is provided by the silica core, the flexibility is imparted by the glycidyloxypropyl network. Oil and water repellency is achieved without adversely affecting the other properties by incorporating a low-surface-tension liquid lubricant poly(dimethyl siloxane). On the final coating, various organic solvents and water readily and cleanly glide, while complex fluids, such as ink and paint facilely contract. These properties are retained after an initially flat coating sample is rolled into a U-shape 500 times or is abraded with steel wool.

Screening of textile finishing agents available on the Chinese market: An important source of per- and polyfluoroalkyl substances to the environment

Organofluorinated surfactants are widely employed in textile finishing agents (TFAs) to achieve oil, water, and stain repellency. This has been regarded as an important emission source of per-and polyfluoroalkyl substances (PFASs) to the environment. China is the biggest manufacturer of clothes, and thus TFA production is also a relevant industrial activity. Nevertheless, to date, no survey has been conducted on PFAS contents in commercially available TFAs. In the present study, TFA products were investigated by the Kendrick mass defect method. The quantification results demonstrated a significant presence of perfluorooctane sulfonate (0.37 mg/L) in TFAs manufactured by electrochemical fluorination technology. The products obtained by short-chain PFAS-based telomerization were dominated by perfluorooctanoic acid (mean concentration: 0.29 mg/L), whose values exceeded the limits stated in the European Chemical Agency guidelines (0.025 mg/L). Moreover, the total oxidizable precursor assay indicated high levels of indirectly quantified precursors with long alkyl chains (C7-C9). Together, these results suggest that there is currently a certain of environmental and health risks in China that originates from the utilization of TFAs, and a better manufacturing processes are required to reduce such risks.

Synthesis of Dual-Functional and Robust Underwater Superoleophobic Interfaces.

Fish-scale-mimicked super oil-repelling wettability that functions under water has emerged as an important avenue for developing various functional materials. Mainly, polymeric hydrogel, brittle metal oxides, and electrostatic multilayers have been utilized for synthesizing an artificial underwater superoleophobic interface, and most of these reported artificial bioinspired wettabilities are likely to be compromised under practically relevant severe settings. Moreover, a design of a dual-functional fish-scale-mimicked interface that would be capable of separating water-soluble organic pollutants, in addition to the eco-friendly removal of different forms of contaminated oils under severe settings, could be highly useful in addressing globally recognized severe water pollution problems. In this report, a dual-functional underwater superoleophobic membrane is introduced for simultaneous removal of contaminated dyes and oil/oily phase, where graphene oxide (GO) nanosheets were strategically integrated with naturally abundant and environmentally friendly cotton fibers by adopting mussel-inspired chemistry. The synthesized membrane was found to exhibit fish-scale-mimicked nonadhesive underwater superoleophobicity, and this super oil repellency remained unaffected even after prolonged exposures to various practically relevant harsh chemical and physical conditions. Moreover, this material was capable of rapid (within 2 min) adsorption of water-soluble cationic organic dyes with high adsorption capacity (136 mg/g for methylene blue), following linear pseudo-second-order kinetics. The biomimicked extreme oil repellency was exploited for separating different forms (bulk and emulsion) of oil/oily (both sedimenting and floating) contaminants with high separation efficiency (above 98%), and the immobilized GO in the biomimicked membrane parallely allowed cationic organic dyes (methylene blue and crystal violet) to be removed from the aqueous phase through a single-step gravity-driven filtration process. The performance of simultaneous removal of cationic dyes and oil/oily contaminants remained unaffected even under various practically relevant severe settings including extremes of pH, sea water, river water, and so forth. Furthermore, the dual-functional biomimicked membrane was repetitively (10 times) used for successful separation of both the contaminated cationic dye and oil/oily phase from the aqueous phase, without affecting the separation efficiency. This simple approach is likely to provide a facile basis for addressing the problem of water pollution under practically relevant diverse and severe settings.

Solvent-Free Synthesis of a Superamphiphobic Surface by Green Chemistry

A superamphiphobic surface having both water and oil repellence was prepared by applying a solvent-free surface coating method using liquid-CO2 in the scope of “green chemistry”. Poly(perfluoroalkyl ethyl acrylate) homopolymer was synthesized by a free radical polymerization in supercritical CO2 medium. This polymer was dissolved in liquid-CO2 containing hydrophilic nanosilica particles in a stirred stainless steel reactor at room temperature under a low CO2 pressure. The polymer/nanosilica dispersion was used to coat glass slides located horizontally in a stainless steel tube by using the “free meniscus coating” method. A series of superamphiphobic coatings were formed under different coating conditions with the variation of polymer/nanosilica concentrations, the types of nanosilica powders, system pressures, and degassing flow rates. The highest apparent water contact angle was 173° and the hexadecane contact angle was 169° on these superamphiphobic hybrid coatings with roll-off angles that were <7°. Su...

IMPROVEMENT OF MULTIFUNCTIONAL AUTOMOTIVE TEXTILE

In order to improve multifunctional automotive textile, required functionalities that have been expected by the automotive industry were enhanced in this study. For this aim, flame retardant and water-oil repellent effects were achieved on 100 % polyester based automotive fabrics via pad-dry-cure system with performed finishing recipes. After functionalization of the fabrics, polyurethane based foams were laminated to the treated automotive textiles. In order to be able to compare the results of tests and to determine the effects of used chemicals on the functionalities of fabrics, chemical amounts of recipe were optimized and the results were discussed. Flame retardancy, water repellency and oil repellency tests were performed before and after abrasion tests. Color spectrums of treated fabrics were tested after chemical finishing applications. Morphological analyses of samples were tested by SEM and chemical structures of the fabrics were analyzed by FTIR-ATR. According to performance test results, multifunctional automotive textile including flame retardant and water-oil repellent effect was achieved successfully. During the burning test, it was determined that laminated textile structure was self-extinguished whereas 3M water repellency grades were at the highest value before abrasion tests.

Water and oil repellent properties affected by the crystallinity of fluorocarbon chain in fluorine-silicon containing finishing agent

Novel soap free and core-shell typed fluorosilicon containing water and oil-repellent finishing agents were fabricated via semi-continuous seed emulsion polymerization reaction. Notably, a series of non-functional acrylate monomers with different carbon chain lengths, i.e. methyl methacrylate, ethyl methacrylate, butyl methacrylate, iso-Octyl methacrylate and lauryl methacrylate were deployed to tune the crystallinity and ordering of final polymer membranes. Experimental results reveal that the water and oil-repellent properties of treated cotton fabric were significantly affected by the crystallinity of designed products. Physical and chemical characterizations were carried out via infrared spectroscopic analysis, thermogravimetric analysis, X-ray diffraction, scanning electron microscope and transmission electron microscope techniques. The hydrostatic pressure, water contract angle, moisture resistance and oil-repellent rating of cotton fabric treated by best performed finishing agent (adopting lauryl methacrylate as non-functional monomers) were determined to be 2.87 KPa, 144.6°, 4 and 5 grade, respectively.

Evaluation of Oil Repellent Effect by Metamaterial Structure

Evaluation of Oil Repellent Effect by Metamaterial Structure

Synthesis of fluoroalkylsilane-coupling agents and their self-assembled monolayers

In this paper, 3-isocyanatepropyl triethoxysilane (IPTS) was synthesized using one-pot reaction using 3-aminopropyl triethoxysilane (APTES) and triphosgeneas as the raw materials. IPTS was then reacted with three kinds of perfluoroalkyl alcohol to obtain 3-(1H,1H,2H,2H-perfluoroalkoxyamidepropyl)-triethoxysilanes with different fluoroalkyl chain lengths. The silicon wafer was etched to obtain an active and coarse surface followed by coating with self-assembled monolayer (SAMs) using fluoroalkylsilane as materials. AFM were used to reflect the variation of the surface morphologies and roughness of self-assembled films before and after coating. ATR-IR test indicated that a combination of possible bonding forms the SAMs. EDS was used to characterize the distribution of the elements on the SAMs. The result of contact angle testing and surface energy counting showed that the SAMS have good water- and oil repellency, which improved with the increment of fluoroalkyl chain length. XPS were used to characterize the change of surface element content of SAMs before and after heat treatment, which resulted in the microphase separation on the film surfaces and made the fluoroalkyl migrate from the internal of the monolayer to the outermost surface. After heating, the fluoroalkyl accumulated on the surface, which lowered the surface energy further and obtained the better water- and oil repellency.

Nanocrystalline cellulose/fluorinated polyacrylate latex via RAFT‐mediated surfactant‐free emulsion polymerization and its application as waterborne textile finishing agent

ABSTRACTA simple method for nanocrystalline cellulose (NCC)/fluorinated polyacrylate was developed by RAFT‐mediated surfactant‐free emulsion polymerization, in which the nanocomposites formed a core‐shell spherical morphology. The influence of the content of NCC‐g‐(PAA‐b‐PHFBA) (AA was acrylic acid, HFBA was hexafluorobutyl acrylate) on the properties of latex and film were systematically studied. The monomer conversion, the tensile strength, and water–oil repellency of film increased first and then decreased, the latex particle size decreased first and then decreased, when the content of NCC‐g‐(PAA‐b‐PHFBA) increased from 1 to 6 wt %. Elongation at break and thermal stability distinctly decreased when the content of NCC‐g‐(PAA‐b‐PHFBA) gradually increased. XPS showed that the fluorine‐containing groups well concentrated at the film–air interfaces during the annealing process. SEM analysis revealed that the treated fiber had a rugged surface, and the treated fabric had an excellent water repellency. In addition, this green grafting method in water offered a new perspective for the fabrication of exceptional NCC‐based nanocomposites with NCC as the core and also helped to promote the potential applicability of NCC in a range of multipurpose applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1305–1314

Underwater superoleophobicity of Nb2O5 photocatalyst surface

The underwater oil wettability of a flat Nb2O5 photocatalyst surface prepared by a sol-gel based method was investigated. The Nb2O5 surface exhibited photocatalytic oxidation and photo-induced superhydrophilic properties under UV irradiation, and its activity was comparable to those of anatase-type TiO2 surfaces prepared by a sol-gel based method. The surface exhibited excellent underwater superoleophobicity toward n-hexadecane and oleic acid. The underwater oil repellency was superior to that of the TiO2 surface.

Surface chemistry-dominated underwater superoleophobic mesh with mussel-inspired zwitterionic coatings for oil/water separation and self-cleaning

Mussel-inspired surface modification has been received great attention due to the universal adhesive properties of catechols for fabrication of multifunctional coatings, especially for gluing hydrophilic polymers to fabricate underwater-superoleophobic materials utilizing in oil/water separation. Despite the extensive research carried out on this topic, the similarity and discrepancy between catecholamine and catecholic amino acid on surface modification and post functionalization have not been fully addressed yet. In this work, underwater superoleophobic surfaces have been successfully developed by a two-step dip-coating method with mussel-inspired coatings and subsequent zwitterionic sulfobetaine methacrylate (SBMA) grafting onto stainless steel meshes and used in oil/water separation. Here, dopamine and 3,4-dihydroxy-L-phenylalanine were both served as mussel-adhesives. More specifically, small molecule zwitterion rather than polyzwitterion was functionalized onto mussel-inspired coatings to minimize the effect of surface topography on surface wettability. The modified surfaces were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements to observe the surface morphology, estimate the surface roughness, and evaluate the wettability, respectively. It showed that SBMA modified meshes with polydopamine (PDA) or poly(3,4-dihydroxy-L-phenylalanine) (PDOPA) layer possessed quite different surface roughness, while both presented excellent oil repellency in water with underwater oil contact angles of 153°–160°, indicating a less dependence on surface roughness. Although by using the small molecule as the hydrophilic functionalized groups, the as-prepared meshes exhibited good self-cleaning and oil/water separation performance (separation efficiency >98% for hexane and >97% for soybean oil) and outstanding recyclability with 98% separation efficiency after 30 cycles. This method provides insight into different properties of polycatechols and simplifies the fabrication process through the use of small molecule zwitterion rather than zwitterionic polymer. Besides, the modified meshes also exhibited excellent stability for long-term use. The resulting underwater superoleophobicity and robust self-cleaning ability promise an ideal candidate for oil/water separation and oil contamination restriction.

Ultrastable Underwater Anti-Oil Fouling Coatings from Spray Assemblies of Polyelectrolyte Grafted Silica Nanochains.

Surfaces that have superhydrophilic characteristics are known to exhibit extreme oil repellency under water, which is attractive for applications including anti-fogging, water-oil separations, and self-cleaning. However, superhydrophilic surfaces can also be easily fouled and lose their extreme oil repellency, which limits their usage in practical applications. In this work, we create an anti-oil fouling coating by spray coating poly(acrylic acid) (PAA)-grafted SiO2 nanochains (approximately 45 nm wide and 300 nm long) onto solid surfaces, forming a nanoporous film exhibiting superhydrophilicity (water contact angle in air ≈ 0°) and underwater superoleophobicity (dichloroethane contact angle ≥ 165°). The polymer-grafted nanochain assemblies exhibit extremely low contact angle hysteresis (<1°) and small adhesion hysteresis (-0.05 mN m-1), and thus, oil can readily roll off from the surface when the coating is immersed in water. Compared to other superhydrophilic surfaces, we show that both the unique structure of spray-assembled nanochains and the hygroscopic nature of PAA are essential to enable ultrastable anti-oil fouling. Even after the PAA-grafted nanochain coating is purposely fouled by oil, oil can be readily and completely expelled and lifted-off from the coating within 10 s when placed under water. Further, we show that our coating retains underwater superoleophobicity even after being subjected to shearing under water for more than 168 h. Our approach offers a simple yet versatile method to create an ultrastable superhydrophilic and anti-oil fouling coating via a scalable manufacturing method.

Highly fluorinated chemicals in functional textiles can be replaced by re-evaluating liquid repellency and end-user requirements

Ongoing regulation of, and concerns regarding, per- and polyfluoroalkyl substances (also popularly known as “highly fluorinated chemicals”), has driven the textile market to search for sustainable alternative chemistries that can provide similar liquid repellency to per- and polyfluoroalkyl substances in performance textiles. This paper aims to inform the potential substitution of fluorochemicals with more environmentally friendly durable water repellents, taking a case-by-case approach and evaluating protection needs for consumer outdoor clothing and medical protective clothing separately. Recently developed non-fluorinated durable water repellents, some based on green chemistry principles, were evaluated in an in-depth assessment for their functionality against fluorinated short-chain alternatives (with hydro-and oleophobic moieties of carbon chain length of six or less). Repellency towards water and non-polar liquids was evaluated with established standard test methods and by measuring the roll-off angle of liquid droplets with a novel sample holder setup. This improved method allowed an enhanced mechanistic understanding of the droplets’ roll-off processes on woven textiles. The best non-fluorinated alternatives demonstrated high water repellency equal to fluorinated side-chain polymers with 'short' fluorinated carbon chains ≤6 carbons, and should be considered as suitable substitutes for consumer outdoor clothing. These results are supported by a survey of end-use requirements indicating water repellency and durability were the most important purchasing criteria. For polar liquids, with lower surface tensions, the repellency provided by non-fluorinated alternatives was clearly reduced, although they had a moderate repellency towards liquids with intermediate polarity (e.g. red wine or synthetic blood). Only fluorinated side-chain polymers with 'short' fluorinated carbon chains ≤6 carbons were seen to provide sufficient protection to polar liquids with very low surface tension (olive oil or gastric fluid). Since occupational protective clothing (e.g. medical clothing) often must provide protection against liquid of a wider range of polarities (e.g. in the case of medical clothing, to bodily fluids and protect the wearer from the transmission of diseases), current non-fluorinated DWRs do not provide sufficient liquid repellency. This implies that innovations in textile technology are still needed to substitute PFASs in some types of occupational protective clothing and other end uses where oil and stain repellency is essential.

Photopolymerization of maleimide perfluoropolyalkylethers without a photoinitiator

ABSTRACTPerfluoropolyalkylethers derived from hexafluoropropylene oxide were functionalized with maleimide groups. Irradiated by UV‐light, the new maleimide macromonomers demonstrated very fast polymerization kinetics with a curing time as fast as 8 s. The effect on photopolymerization of different features such as the molecular weight of the fluorinated chain and the chain length of the hydrogenated spacer were studied, as well as the influence of the type of photoinitiator and the presence of air. Thermal and surface properties of the UV‐cured polymers were examined and were typical to fluoropolymers in view of water–oil repellent coatings. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 699–707

Preparation and Surface Properties Study of Novel Fluorine-Containing Methacrylate Polymers for Coating.

A new structural fluorine-containing methacrylate monomer CH2=C(CH3)COOC–(CF3)2CF2CF2CF3 (5) was synthesized derived from perfluoro-2-methyl-2-pentene (D2). A homopolymer of 5 and copolymers of 5 and methacrylate with different alkyl chain length (chain length n = 1, 2, 4, 6, 8, 12, 18) were obtained. These new fluorinated acrylate polymers showed excellent water and oil repellency. The contact angle of the films of the homopolymer and part of the copolymers were similar with the corresponding polymers prepared from CH2=CHC(O)OCH(C3F7)(CF(CF3)2), but greater than that of the C6F13(CF3)CHOC(O)CH=CH2 homopolymer. The structure-property relationship research indicated that the copolymers’ hydrophobicity decreased first and then increased with the increase of alkyl chain length. Td of all the polymers were greater than 220 °C and Tg fluctuated within the range of −51~103.8 °C. Contact angle and Tg could be adjusted by controlling the feed ratio of monomer to meet the requirements of technical indicators in the practical applications. The outstanding liquid repellency and thermal stability make monomer 5 a promising alternative to perfluorinated long-chain fluorosurfactants.

Molecular and phenotypic responses of male crucian carp (Carassius auratus) exposed to perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) has long been produced and widely used due to its excellent water and oil repellent properties. However, this trend has facilitated to the ubiquitous existence of PFOA in environmental matrix, and the potential ecotoxicity on aquatic organisms has not been fully elucidated. To study the tissue-specific bioconcentration and the nervous system- and energy-related biochemical effects of PFOA, as well as the phenotypic alterations by this chemical, male crucian carp (Carassius auratus) were exposed to gradient concentrations of PFOA (nominal 0.2, 10, 500 and 25,000 μg/L) in a flow-through apparatus for 7 days. PFOA was enriched in tissues following an order of blood > kidney ≥ liver > gill > brain > muscle. The bioconcentration factors ranged from 0.1 to 60.4. Acetylcholinesterase activity in the fish brain was inhibited, while liver carboxylesterase was induced in most cases and attenuated with time. The acyl-CoA oxidase activity was dose-dependently elevated and accompanied by a decline of ATP contents. PFOA treatments also inhibited the activity of the electron transport system (ETS). At the transcriptional level, ETS component complexes II and IV were concordantly depressed, and ATP synthesis was also downregulated. The mRNA level of peroxisome proliferator activated receptor α was increasingly upregulated, with related downstream genes upregulated in varying degrees. The phenotypes showed patterns of increased liver pathology and reduced swimming activity. In summary, PFOA leads to adverse effects in Carassius auratus related to multiple aspects, which may be associated with the nervous system, fundamental energy metabolism and other unpredictable factors. The results obtained in this study are expected to help clarify the PFOA toxic mechanisms on energy relevance.