Durable Hydrophobicity Research Articles

Mechanical and chemical stability of super-hydrophobic coatings on SMA490BW substrate prepared by HVOF spraying

SMA490BW weathering steel is an important engineering material employed in the bogies of high-speed train. However, the bogies are also subject to ice accumulation, corrosion, sand abrasive, and heterogeneous wear or other hazard. In this paper, the superhydrophobic (SH) surface on SMA490BW steel is fabricated by using High Velocity Oxygen Fuel (HVOF) spraying technology and low surface energy modification. Self-cleaning effect, hydrophobic durability, wear resistance, the weather resistance, PH stability and electrochemical properties were discussed. The results showed that the as prepared coating possesses CA of 154.3 ± 3° and sliding angle of 4.1 ± 0.1°. The CA has no obvious fluctuations after immersing in water for different time and at PH in the range of 1 to 7. The CA is still above 150° after abrasion for 2400 mm. The SH coating possesses higher Ecorr and lower Icorr compared with SMA490BW substrate and HVOF WC-12Co coating. The SH coating has a long-term water repellency towards environmental conditions during weathering. The SH coating possesses excellent mechanical and chemical stability, which is benefit for applying this coating on the high-speed train bogies.

Human Skin-Like, Robust Waterproof, and Highly Breathable Fibrous Membranes with Short Perfluorobutyl Chains for Eco-Friendly Protective Textiles.

Flexible smart membranes with superior waterproofness and extreme breathability are highly desirable for wearable uses. However, present waterproof and breathable materials suffer from limited performance efficiency, alarming environmental risks, and complicated fabrication procedures. We report on eco-friendly fibrous membranes with human skin-like, robust waterproof, and highly breathable capabilities that can be prepared via a facile electrospinning strategy. A novel polyurethane elastomer (C4FPU) possessing double-terminal short perfluorobutyl (-C4F9) chain is synthesized for the first time and incorporated into the polyurethane (PU) fiber matrix, endowing the membrane with mighty and durable hydrophobicity. Additionally, the employment of AgNO3 greatly decreased the maximum pore size ( dmax), contributing to the dramatically enhanced waterproofness. The resulting PU/C4FPU/AgNO3 fibrous membranes exhibit comprehensive properties of exceptional hydrostatic pressure (102.8 kPa), excellent water vapor transmission rate (12.9 kg m-2 d-1), high mechanical property (9.8 MPa), and significant antibacterial efficacy against Escherichia coli and Staphylococcus aureus. The successful synthesis of these intriguing membranes may provide a promising candidate for the new generation of key building blocks of the upscale protective garments.

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.

Correction: Hydrophobic durability characteristics of butterfly wing surface after freezing cycles towards the design of nature inspired anti-icing surfaces.

[This corrects the article DOI: 10.1371/journal.pone.0188775.].

Superhydrophobic ceramic coating: Fabrication by solution precursor plasma spray and investigation of wetting behavior

HypothesisSuperhydrophobic surfaces are often created by fabricating suitable surface structures from low-surface-energy organic materials using processes that are not suitable for large-scale fabrication. Rare earth oxides (REO) exhibit hydrophobic behavior that is unusual among oxides. Solution precursor plasma spray (SPPS) deposition is a rapid, one-step process that can produce ceramic coatings with fine scale columnar structures. Manipulation of the structure of REO coatings through variation in deposition conditions may allow the wetting behavior to be controlled. ExperimentsYb2O3 coatings were fabricated via SPPS. Coating structure was investigated by scanning electron microscopy, digital optical microscopy, and x-ray diffraction. The static water contact angle and roll-off angle were measured, and the dynamic impact of water droplets on the coating surface recorded. FindingsSuperhydrophobic behavior was observed; the best coating exhibited a water contact angle of ∼163°, a roll-off angle of ∼6°, and complete droplet rebound behavior. All coatings were crystalline Yb2O3, with a nano-scale roughness superimposed on a micron-scale columnar structure. The wetting behaviors of coatings deposited at different standoff distances were correlated with the coating microstructures and surface topographies. The self-cleaning, water flushing and water jetting tests were conducted and further demonstrated the excellent and durable hydrophobicity of the coatings.

Hydrophobic durability characteristics of butterfly wing surface after freezing cycles towards the design of nature inspired anti-icing surfaces.

The hydrophobicity and anti-icing performance of the surfaces of some artificial hydrophobic coatings degraded after several icing and de-icing cycles. In this paper, the frost formation on the surfaces of butterfly wings from ten different species was observed, and the contact angles were measured after 0 to 6 frosting/defrosting cycles. The results show that no obvious changes in contact angle for the butterfly wing specimens were not obvious during the frosting/defrosting process. Further, the conclusion was inferred that the topography of the butterfly wing surface forms a special space structure which has a larger space inside that can accommodate more frozen droplets; this behavior prevents destruction of the structure. The findings of this study may provide a basis and new concepts for the design of novel industrially important surfaces to inhibit frost/ice growth, such as durable anti-icing coatings, which may decrease or prevent the socio-economic loss.

Highly compression-tolerant and durably hydrophobic macroporous silicone sponges synthesized by a one-pot click reaction for rapid oil/water separation

Macroporous silicone sponges were first synthesized via a one-pot click reaction, which have controllable porosity, low density, durable hydrophobicity, superoleophilicity, good thermal insulation, and excellent compressibility.

Argon Plasma Treatment of Fluorine‐Free Silane Coatings: A Facile, Environment‐Friendly Method to Prepare Durable, Superhydrophobic Fabrics

A novel method to prepare durable superhydrophobic fabrics through pre‐applying an alkyl silane (alkyl chain longer than C15) onto fabric substrate and by subsequent vacuum plasma treatment in argon is reported. The treated fabrics show a contact angle of 154.2° with low contact angle hysteresis (sliding angle 4.5°). The coatings are durable and can withstand 150 cycles of standard laundries. The argon plasma treatment is found to significantly enhance SiOSi bonding among the silane molecules, leading to a highly crosslinked silica network. The silane coating also shows high optical transparency. Apart from fabrics, other substrates such as filter paper, plastic film, glass slide, silicon wafer, and metal are treated in a similar way, and all the treated surface show durable hydrophobicity, though the contact angle is lower than that of the coated fabrics. Post‐crosslinking of silane through argon plasma treatment may offer a facile but environment‐friendly way to prepare durable superhydrophobic fabrics.

Investigation of Effect of Cellulosic Coating on the Some Properties of Polyester Fabric

Due to the inherent hydrophobic nature of Polyester fibers, fabrics formed entirely from Polyester fibers exhibit relatively poor moisture absorption and release properties introduce an uncomfortable condition to the wearer. The present study focuses on adding enhanced and durable hydrophobicity properties to Polyester fabrics, through coated using a cellulose solvent of NaOH/urea/thiourea aqueous solution at 8/8/6.5 compositions. Aqueous NaOH/urea/thiourea solution as non-derivatizing solvent broke the intra- and inter-molecular hydrogen bonding of cellulose and prevented the approach toward each other of the cellulose molecules, leading to the salvation of cellulose which the hydrophilic properties imparted to the fabric. The effect of percentage of cellulose solution coating has been studied on some physical properties such as fabric wettability, water wicking, stiffness, and air permeability, as well as the method of application of the cellulose coating. The surface characterization of the coated Polyester fabric is performed using FTIR and SEM. The results relate to coated Polyester fabric demonstrated enhanced and durable hydrophobicity and rewetting properties due to hydrophilic properties imparted to these substrates

Superamphiphobic overhang structured coating on a biobased material

A superamphiphobic coating on a biobased material shows extreme liquid repellency with static contact angles (CA) greater than 150° and roll-off angles less than 10° against water, ethylene glycol, diiodomethane and olive oil, and a CA for hexadecane greater than 130°. The coating consisting of titania nanoparticles deposited by liquid flame spray (LFS) and hydrophobized using plasma-polymerized perfluorohexane was applied to a birch hardwood. Scanning electron microscopy (SEM) imaging after sample preparation by UV laser ablation of coated areas revealed that capped structures were formed and this, together with the geometrically homogeneous wood structure, fulfilled the criteria for overhang structures to occur. The coating showed high hydrophobic durability by still being non-wetted after 500 000 water drop impacts, and this is discussed in relation to geometrical factors and wetting forces. The coating was semi-transparent with no significant coloration. A self-cleaning effect was demonstrated with both water and oil droplets. A self-cleanable, durable and highly transparent superamphiphobic coating based on a capped overhang structure has a great potential for commercial feasibility in a variety of applications, here exemplified for a biobased material.

Tough Polymer Aerogels Incorporating a Conformal Inorganic Coating for Low Flammability and Durable Hydrophobicity.

Both inorganic and polymeric aerogels are well-known in the materials field. Inorganic aerogels are generally susceptible to brittle fracture, while polymeric aerogels tend to exhibit low modului and high flammability. To overcome these disadvantages, we introduce a new approach to the design of aerogels. A microporous poly(vinyl alcohol) (PVA) aerogel/silica nanocomposite was prepared by growing a silica conformal coating onto a PVA aerogel scaffold. Such aerogel/silica nanocomposites show significant improvement in their mechanical properties over either individual component. The nanocomposites show excellent fire resistance since the silica conformal coating serves as a barrier for heat transfer and mass loss of the coated organic materials. After a fluorocarbon silane treatment, the nanocomposites also show durable superhydrophobicity.

Influence of Precursor Functionality on In Situ Reaction Dynamics in Atmospheric Pressure Plasma

In situ reaction of various long chain hydrocarbon precursors with cellulosic substrate inside plasma zone were investigated. Each of the selected precursor compounds had C12 alkyl chain as the hydrophobic moiety to impart hydrophobicity to the substrate and a functional group to aid reaction with the active sites of the substrate. The selected compounds were dodecyl acrylate (DA, with acrylate group), lauryl alcohol (LA, with hydroxyl group), dodecanoic acid (DODAC, with carboxylic acid) and dodecane (DD, without any functional group). Treatment was carried out in-situ with these compounds using helium gas as a carrier. After the treatment, durable hydrophobicity was obtained in all cases with water absorbency time of substrate increasing to >1 h in the case of DA and LA, up to 20 min in the case of DD and only up to 9 min in the case of DODAC. The functional groups were found to have profound effect on the extent of functionality obtained and the plasma parameters required to obtain effective reaction with the substrate. Both plasma zone and the functionalized surfaces were characterized to understand the chemistry involved with the different precursors.

Investigation of Wash Durability of Silica Nanoparticle Coated 100% Cotton Reactive Dyed Fabric Treated by Sol-Gel Technique

In this research a hydrophobic surface of 100% cotton woven fabric was developed by sol-gel technique. Fabric samples were dyed with Drimarene Reactive Red 5B and Drimarene Reactive Blue BR dyes (0.5% and 3% o.w.f) and then treated with a combination of silica nanoparticles, silane hydrophobes (alkyltrialkoxysilanes), and silane cross-linkers i.e, tetraethoxysilane (TEOS) and teramethoxysilane (TMOS) by dip-dry-cure process. After coating, wash durability of dyed samples was investigated for water repellency and water uptake according to AATCC standards. The effect of coating on dyeing behavior was assessed by measuring the (K/S)λmax value, while change in color (ΔE) and fastness properties of coated fabric also investigated. It has been observed that durable hydrophobicity achieved on cotton reactive dyed fabric through non-fluorine sol-gel route with silica nanoparticles with better fastness properties with little effect on shade.

Highly durable hydrophobicity in simulated space environment

Perfluoropolyether-infused porous anodic alumina maintains superhydrophobicity durably under simulated space irradiations at low earth orbit (LEO).

Preparation of durable superhydrophobic surface by sol–gel method with water glass and citric acid

Durable superhydrophobic surface on cotton fabrics has been successfully prepared by sol–gel method. Cellulose fabric was first coated with silica sol prepared with water glass and citric acid as the acidic catalyst. The silica coated fabric was then padded with hydrolyzed hexadecyltrimethoxysilane afterwards obtaining low surface energy. Water contact angle and hydrostatic pressure were used to characterize superhydrophobicity and washing durability. Scanning electron microscopy was used to characterize the surface morphology changes after certain washing times. All results showed good durable hydrophobicity on cellulose fabrics. In addition, the influence of citric acid and sodium hypophosphite (NaH2PO2) on the durability of hydrophobicity was also investigated. The durability of treated cotton improved with the increase of concentration of citric acid in the presence of NaH2PO2. It could be concluded that citric acid acted as multi-functional heterogeneous grafting chemicals to improve washing durability of hydrophobicity by forming the ester bonds between cotton fabric and silica sol and improved the durability of hydrophobicity.

Durable Hydrophobic Textile Fabric Finishing Using Silica Nanoparticles and Mixed Silanes

Cotton fabric surface was treated with combinations of silica nanoparticles, silane hydrophobes, and silane crosslinkers to obtain durable hydrophobicity. Performance analysis was done by measuring the contact angle of water on the treated fabric surface. To evaluate the durability of the surface hydrophobicity, AATCC crocking and laundering tests were performed. Cotton fabrics with good hydrophobicity (contact angle = 139.1°) and excellent durability (e.g. 95% recovery of contact angle after laundering) were obtained when treated with Aerosil® 90 nanoparticles, n-octyltrimethoxysilane, and bis(triethoxysilyl)ethane. This study demonstrated that the surface treatment using silica nanoparticles and mixed silanes is a promising alternative to fluoropolymer chemistry for achieving durable hydrophobic fabrics.