Superhydrophobic Polyurethane Research Articles

Fabrication of superhydrophobic filter paper and foam for oil–water separation based on silica nanoparticles from sodium silicate

We demonstrate the synthesis of hydrophobic silica nanoparticles from sodium silicate and their application in separation of the oil–water mixture. For this, hydrophobic silica nanoparticles of size 35 ± 8 nm were initially synthesized by sol–gel method using sodium silicate and trimethylchlorosilane, and further deposited on commercially available filter paper and polyurethane foam by dip coating technique. The coating cycles were optimized for filter paper to ensure that fibers of the filter paper have been completely covered with hydrophobic silica nanoparticles to provide an ideal porous superhydrophobic/superoleophilic framework for gravity based separation of oil–water mixtures. It was confirmed by water contact angle of ~155° and sliding angle <5°. Whereas the superhydrophobic polyurethane foam was utilized for collection of oil from oil–water mixtures via absorption. The capability of these materials to separate oil from water was tested against the mixtures of water with n-hexane, gasoline, diesel, kerosene oil and engine oil. Moreover, the produced particles can also be used for fabrication of semi-transparent superhydrophobic surfaces.

Robust and Durable Superhydrophobic Polyurethane Sponge for Oil/Water Separation

With the purpose of purging and recycling oil and organic solvent from a water surface, a superhydrophobic polyurethane (PU) sponge was fabricated through a combined method of interfacial polymerization (IP) and molecular self-assembly. The as-prepared sponge has a superwetting characteristic of superlipophilicity in atmosphere and superhydrophobicity both in atmosphere and under oil, and it can quickly and selectively absorb various kinds of oils up to 29.9 times its own weight. More importantly, because of a covalent combination of the sponge skeleton and the polyamide thin film from IP, the superhydrophobic sponges could be reused for oil/water separation over 500 cycles without losing its superhydrophobicity, showing the highest reusability among the reported absorptive materials. The superhydrophobic sponge also can be used in the continuous absorption and expulsion of oils and organic solvents from water surfaces with the help of a vacuum pump. All of these features make the sponge a promising candi...

Polyurethane sponge functionalized with superhydrophobic nanodiamond particles for efficient oil/water separation

Nanodiamonds (NDs) are among the most promising new carbon-based materials for various applications. Inspired by the remarkable adhesive ability of dopamine, a feasible approach was developed for the preparation of superhydrophobic NDs particles. The strategy is based on coating hydroxylated NDs with polydopamine (PDA) and subsequent reaction with 1H,1H,2H,2H-perfluorodecanethiol (PFDT). The resulting f-PDA modified NDs (NDs-fPDA) were firmly anchored onto the skeleton of commercial polyurethane (PU) sponge due to the excellent adhesive ability of PDA. Meanwhile, the as-prepared sponge showed superhydrophobic property, oil/water separation behavior and high organic adsorption capacity. Due to its low cost, feasible fabrication technique, stability and excellent performance, this superhydrophobic PU–NDs-fPDA sponge represents a promising alternative for the selective removal of oil from water.

Preparation of breathable and superhydrophobic polyurethane electrospun webs with silica nanoparticles

Polyurethane (PU) is a unique polymeric material with excellent chemical and physical properties and is widely used in textile materials. There has been a need for superhydrophobic PU for wider applications, such as coating materials. In this research, SiO2 nanoparticle (SNP) incorporated PU webs with superhydrophobic and breathable properties were prepared by one-step sol-gel electrospinning and post-treated with a non-fluorinated water repellent chemical, n-dodecyltrimethoxysilane (DTMS). SNPs were observed to be distributed evenly all over the fiber surfaces when 1–6 wt% SNP and tetraethoxysilane (TEOS)/acetic acid solution were added. TEOS was hydrolyzed to form larger nanoparticles while developing cross-linking with aromatic groups of the PU matrix. Interestingly, the addition of 20 nm SNPs was thought to act as nucleating seeds for enhanced hydrolysis of TEOS within the PU matrix. The hierarchical surface roughness consists of different sized SNPs and polymer beads, which resulted in superhydrophobicity with water contact angles as high as 157° and shedding angles as low as 5°. Laminating PU/SNP/DTMS webs onto polyester fabrics maintained the air permeability and water vapor transmission rate, which proves the potential of the developed PU/SNP/DTMS webs for practical applications as textile laminate materials with simple processing.

Enhanced hydrophobicity of polyurethane via non-solvent induced surface aggregation of silica nanoparticles

Fabrication of superhydrophobic surfaces from hydrophilic polymers has always been regarded as a challenge. In this study, to achieve superhydrophobic polyurethane (PU) surfaces, silica nanoparticles and ethanol as non-solvent were simultaneously utilized during a solution casting-based process. Such modified version of phase separation process was found to be highly efficient, and also it required much lower concentration of nanoparticles to achieve superhydrophobicity as compared to the previously reported methods in the literature. According to the proposed mechanism, non-solvent induces a more profound aggregation of silica nanoparticles at the surface’s top layer causing the surface energy to be highly diminished, and thus, the water repellency is improved. Morphology and topography results showed that a unique “triple-sized” structure was formed on the surface of superhydrophobic samples. X-ray photoelectron spectroscopy results proved that both PU macromolecules and silica nanoparticles were concurrently present at the surface layer of the superhydrophobic sample. It was concluded that surface composition and roughness could be regarded as competing factors in achieving superhydrophobicity. Based on the obtained results, the proposed method exhibits a promising potential in large-scale fabrication of surface layers with superhydrophobic property. Moreover, a mechanism was also presented to further explicate the physics behind the suggested method.

Facile preparation of graphene-coated polyurethane sponge with superhydrophobic/superoleophilic properties

Graphene (GN) is a two-dimensional carbon material with highly hydrophobic and oleophilic properties, and it is prepared by a modified Hummers Method. In this study, superhydrophobic and superoleophilic polyurethane (PU) sponge was fabricated by coating graphene onto it. The contact angle of the coated sponge was as large as 156.1° for water, and 0° for pump oil, soybean oil, and diesel oil. The absorption capability of the coated sponges was up to 60 times their own weight. Additionally, the coated PU sponges could be reused for oil–water separation for more than 60 cycles without losing their superhydrophobic-superoleophilic properties. Therefore, the sponges can be used for the cleanup of oil spills from a water surface.

Facile Fabrication of Robust Ice‐Phobic Polyurethane Sponges

Bio‐inspired superhydrophobicity is a promising anti‐icing (or deicing) strategy, but a superhydrophobic surface may lose its anti‐icing capability once the deposited water freezes. Herein, it is shown that ice can be readily and repeatedly removed from the surface of superhydrophobic polyurethane sponges via a simple mechanical squeezing process. The sponges are fabricated through a mussel‐inspired process and subsequent deposition of Ag nanoparticles. The resulting sponges are able to shed off the ice layers formed on their surfaces up to 90 times, exhibiting robust icephobic properties among the reported superhydrophobic surfaces. The mechanism for the excellent icephobicity is investigated by a highly sensitive microelectrobalance and a fluorescent labeling method. It is revealed that the icephobicity is attributed to low ice adhesion of the superhydrophobic sponges, as well as mechanical durability of their surface textures. The present findings provide a facile strategy to fabricate robust icephobic surfaces for various technological applications.

Transforming an intrinsically hydrophilic polymer to a robust self-cleaning superhydrophobic coating via carbon nanotube surface embedding

Abstract A single-step method, including surface embedding of nanoparticles into a polymer matrix, was employed to fabricate superhydrophobic thermoplastic polyurethane (TPU)/carbon nanotube (CNT) nanocomposite coatings. The main aim was to prove that surface roughness plays a more important role in designing superhydrophobic surfaces as compared with the surface energy. Therefore, TPU was used as the model hydrophilic polymer and CNTs were employed as non-hydrophobic nanoparticles. It was found that, at a certain pressing time, CNTs form an efficient hair-like morphology which is able to highly enclose air within its as-formed pores leading to superhydrophobic behavior. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and confocal microscopy were utilized for characterization of samples. SEM and confocal microscopy results proved that surface roughness played the key role in the final wettability behavior. Based on XPS results, it was also found that a very long pressing time led to partial migration of TPU macromolecules into the CNTs' pores, and hence, superhydrophobicity was reduced. The effects of mechanical abrasion and nanoparticle type on wettability behavior of samples were evaluated as well. In conclusion, it is suggested that surface roughness factor should be highly considered in designing superhydrophobic nanocomposite coatings rather than surface energy.

Magnetic, durable, and superhydrophobic polyurethane@Fe3O4@SiO2@fluoropolymer sponges for selective oil absorption and oil/water separation.

Magnetic, durable, and superhydrophobic polyurethane (PU) sponges were fabricated by chemical vapor deposition (CVD) of tetraethoxysilane (TEOS) to bind the Fe3O4 nanoparticles tightly on the sponge and then dip-coating in a fluoropolymer (FP) aqueous solution. The sponges were characterized using scanning electron microscopy and other analytical techniques. The effects of CVD time of TEOS and FP concentration on wettability, mechanical properties, oil absorbency, and oil/water selectivity of the sponges were also investigated. The sponges exhibit fast magnetic responsivity and excellent superhydrophobicity/superoleophilicity (CAwater = 157° and CAoil ≈ 0°). The sponges also show very high efficiency in oil/water separation and could, driven by a magnet, quickly absorb floating oils on the water surface and heavy oils under water. Moreover, the PU@Fe3O4@SiO2@FP sponges could be used as membranes for oil/water separation and for continuous separation of large amounts of oil pollutants from the water surface with the help of a pump. The in turn binding of Fe3O4 nanoparticles, SiO2, and FP can also improve mechanical properties of the PU sponge. The sponges maintain the superhydrophobicity even when they are stretched with 200% strain or compressed with 50% strain. The sponges also show excellent mechanical stability, oil stability, and reusability in terms of superhydrophobicity and oil absorbency. The magnetic, durable, and superhydrophobic PU sponges are very promising materials for practical oil absorption and oil/water separation.

Multifunctional polyurethane sponge for polymerase chain reaction enhancement.

Selective filtering of target biomaterials from impurities is an important task in DNA amplification through polymerase chain reaction (PCR) enhancement and gene identification to save endangered animals and marine species. Conventional gene extraction methods require complicated steps, skilled persons, and expensive chemicals and instruments to improve DNA amplification. Herein, we proposed an alternative method for overcoming such challenges by imparting secondary functionality using commercially available polyurethane (PU) sponges and cost-effective fabrication approaches through polydopamine and polysiloxane coatings. The porous, highly flexible, and chemically modified superhydrophilic and superhydrophobic PU sponges allow large surface areas and mechanically stable frames for effective extraction of genomic DNA through selective filtering of fish tissues and oils. Furthermore, these chemically modified PU sponges allow separation of genes and improvement of PCR for DNA amplification for the identification of fish species. The combination of a simple fabrication method and functionalized PU sponges could be a useful platform for PCR enhancement and gene-based identification of species for practical applications.

Rapid adsorption for oil using superhydrophobic and superoleophilic polyurethane sponge

AbstractBACKGROUNDCleanup of oil spills is a worldwide task needed to avoid serious environmental pollution. Recently, polyurethane (PU) sponge has been used as an oil absorbent, however, its efficacy is limited by its hydrophilic property.RESULTSThis work describes the modification of PU sponge with ZnO microrods and palmitic acid (PA). A coating of ZnO microrods made the surface of PU sponge rough, which improved the hydrophobicity and oil‐adsorption capacity of the sponge. Further immersion in PA solution reduced the surface energy, which enabled the rough surface to be superhydrophobic (water contact angle (CA) &gt; 150°). The contact angles of water and oil on the prepared ZnO and PA modified (ZnO‐PA sponge) sponge were 168.9° and 0°, respectively. Adsorption capacities of ZnO‐PA sponge varied between 33 and 44 g g−1 for different oil samples, which were higher than those of the non‐modified PU sponge (21–23 g g−1). Adsorption equilibrium for the adsorption process of ZnO‐PA sponge was achieved within tens of seconds. Additionally, the ZnO‐PA sponge showed excellent selectivity for oil over water, and high reusability.CONCLUSIONThese findings indicated that the superhydrophobic PU sponge was a promising oil adsorbent for large‐scale oil‐spill collection. © 2015 Society of Chemical Industry

Facile preparation of a mechanically robust superhydrophobic acrylic polyurethane coating

A mechanically robust superhydrophobic coating was facilely prepared based on bi-component acrylic polyurethane and fluoroalkyl silane modified silicas.

Preparation and application of biomimetic superhydrophobic silica and polyurethane composite coating

A nanosilica (SiO2)/polyurethane (PU) micro-nanocomposite coating with similar surface structure as a lotus leaf was prepared using a simple spraying process via a biomimetic method. In this process, SiO2 and organosilicon-modified PU were used as raw materials, and ethyl acetate was used as a dispersing agent. The formation mechanism and structural characteristics of the coating were analysed. The coating surface was also characterised via scanning electron microscopy. The influence of the contents of SiO2, PU, organosilicon on the coating surface structure and contact angle (CA) was studied and the coating was applied to the surface of different materials. The results showed that the coating surface had a similar micro-nanostructure as the lotus leaf surface. The mass ratio of SiO2 and PU was between 4:5 and 3:5. When the content of organosilicon was greater than 15%, the water CA of the coating and sliding angles were 158° and 3°, respectively. The prepared SiO2/PU micro-nanocomposite coating had superhydrophobic properties.

A novel carbon nanotubes reinforced superhydrophobic and superoleophilic polyurethane sponge for selective oil–water separation through a chemical fabrication

A novel carbon nanotubes reinforced polyurethane sponge with superhydrophobic, superoleophilic and high mechanical properties shows potential for applications in oil–water separation.

Mussel-inspired one-step copolymerization to engineer hierarchically structured surface with superhydrophobic properties for removing oil from water.

In the present study, a superhydrophobic polyurethane (PU) sponge with hierarchically structured surface, which exhibits excellent performance in absorbing oils/organic solvents, was fabricated for the first time through mussel-inspired one-step copolymerization approach. Specifically, dopamine (a small molecular bioadhesive) and n-dodecylthiol were copolymerized in an alkaline aqueous solution to generate polydopamine (PDA) nanoaggregates with n-dodecylthiol motifs on the surface of the PU sponge skeletons. Then, the superhydrophobic sponge that comprised a hierarchical structured surface similar to the chemical/topological structures of lotus leaf was fabricated. The topological structures, surface wettability, and mechanical property of the sponge were characterized by scanning electron microscopy, contact angle experiments, and compression test. Just as a result of the highly porous structure, superhydrophobic property and strong mechanical stability, this sponge exhibited desirable absorption capability of oils/organic solvents (weight gains ranging from 2494% to 8670%), suggesting a promising sorbents for the removal of oily pollutants from water. Furthermore, thanks to the nonutilization of the complicated processes or sophisticated equipment, the fabrication of the superhydrophobic sponge seemed to be quite easy to scale up. All these merits make the sponge a competitive candidate when compared to the conventional absorbents, for example, nonwoven polypropylene fabric.

Facile preparation of super durable superhydrophobic materials

The low stability, complicated and expensive fabrication procedures seriously hinder practical applications of superhydrophobic materials. Here we report an extremely simple method for preparing super durable superhydrophobic materials, e.g., textiles and sponges, by dip coating in fluoropolymers (FPs). The morphology, surface chemical composition, mechanical, chemical and environmental stabilities of the superhydrophobic textiles were investigated. The results show how simple the preparation of super durable superhydrophobic textiles can be! The superhydrophobic textiles outperform their natural counterparts and most of the state-of-the-art synthetic superhydrophobic materials in stability. The intensive mechanical abrasion, long time immersion in various liquids and repeated washing have no obvious influence on the superhydrophobicity. Water drops are spherical in shape on the samples and could easily roll off after these harsh stability tests. In addition, this simple dip coating approach is applicable to various synthetic and natural textiles and can be easily scaled up. Furthermore, the results prove that a two-tier roughness is helpful but not essential with regard to the creation of super durable superhydrophobic textiles. The combination of microscale roughness of textiles and materials with very low surface tension is enough to form super durable superhydrophobic textiles. According to the same procedure, superhydrophobic polyurethane sponges can be prepared, which show high oil absorbency, oil/water separation efficiency and stability.

Superhydrophobic polyurethane and silica nanoparticles coating with high transparency and fluorescence

AbstractA superhydrophobic surface was prepared by spin‐coating trimethylsiloxane functionalized SiO2 (TMS‐SiO2) solutions onto a precoated polyurethane (PU) layer. The superhydrophobic coatings showed high stability with time, and the prepared coatings remained superhydrophobicity even after 6 months. Furthermore, the as‐prepared surface showed high transparency with a transmittance above 70% in visible light region (400–800 nm). The transition of the composite surface from superhydrophobicity to hydrophilicity can be achieved by increasing the drying temperature. More interestingly, the surface showed excellent fluorescent property by the incorporation of fluorescent Europium (Eu) complex into the surface and without deteriorating the superhydrophobic and transparent properties. It was believed that the superhydrophobic surface with multifunction would broaden the applications of superhydrophobic materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Robust superhydrophobic polyurethane sponge as a highly reusable oil-absorption material

The fabrication of robust superhydrophobic 3D porous materials is of great importance for both academic research and industrial applications. The main challenge is the poor adhesion between porous substrates and superhydrophobic coatings. In this study, a robust superhydrophobic polysiloxane layer was coated onto the surface of 3D porous polyurethane sponges through a one-step solution immersion method. The durability of the resulting sponges was investigated by repeated mechanical compressions, ultrasonication in polar solvents, and strong acid/alkali attacks. Results revealed that the superhydrophobic sponges showed excellent elasticity, high mechanical durability and good chemical stability. By combining the special wettability and high porosity, the sponges exhibited high oil-absorption capacity and high selectivity when they were employed as absorptive materials for cleaning oils on the water surface. More importantly, the superhydrophobic sponges could be reused for oil–water separation for more than 300 cycles without losing their superhydrophobicity, exhibiting the highest reusability and durability among the reported counterparts. Therefore, the present study offers a simple and low-cost strategy for large-scale fabrication of robust superhydrophobic 3D porous materials that might be applied to the cleanup of oil spills on the water surface.

Superhydrophobic Thermoplastic Polyurethane Films with Transparent/Fluorescent Performance

In this paper, we report a simple and versatile route for the fabrication of superhydrophobic thermoplastic polyurethane (TPU) films. The approach is based on octadecanamide (ODAA)-directed assembly of nanosilica/TPU/ODAA hybrid with a well-defined sheetlike microstructure. The superhydrophobic hybrid film shows a transparent property, and its water contact angle reaches as high as 163.5° without any further low surface energy treatment. In addition, the superhydrophobic TPU hybrid film with fluorescent properties is achieved by smartly introducing CdTe quantum dots, which will extend potential application of the film to optoelectronic areas. The resulting fluorescent surface produced in this system is stable and has a water contact angle of 172.3°. This assembly method to control surface structures represents an intriguing and valuable route to tune the surface properties of organic-inorganic hybrid films.