Surface Wetting Properties Research Articles

OGF nanocomposite foam for enhanced recyclability and oil-recovery

Continuous oil spills around the world not only affect the air and water quality but also lead to massive destruction of the natural ecosystem of shallow and deep-waters. Existing methods for oil sorption lack ease of reusability, selectivity and mass production. Thus, there is an urgent need to develop economical, scalable, and efficient oil sorbent material. Here, we report a polymer nanocomposite foam of oxidised graphene frameworks (OGFs) derived using agro-waste. The OGFs impart porosity, hydrophobicity, and super-oleophilicity to the foam, resulting in enhanced sorption capacity of different categories of oils such as lubricants, organic solvents, vegetable oils and locomotive oils. Sorption capacity for DCM, diesel and mustard oil was found to be 27.4, 6.18 and 6.4 gg-1 respectively. Surface-wetting properties improved to super-oleophilic and hydrophobic, with an oil contact angle of 0° and water contact angle of 120 ± 3°, respectively. Compared to pristine polymeric foam, the nanocomposite foam shows ∼80% increase in tensile modulus and compressive strength, making it durable during handling and recycling. It is found to be stable in highly acidic, basic and saline conditions and shows excellent sorption performance even after 500 cycles, making it attractive for commercial applications. OGF-incorporated nanocomposite foam has demonstrated superb sorption and mechanical with excellent recycling properties, which makes it suitable for recovering oils and organic solvents from spills and resolving the problem of oil pollution in sea and surface water with recovery of precious resources. Our findings pave the way for the direct implementation of developed nanocomposite foam for commercial application.

Wetting of Cu-SiC Composite Material Modified by Nanosecond Laser Radiation and Liquid Spreading over It

In the framework of this work, the surface properties of Cu-SiC composite material were studied when spreading micro- and nanoliter liquids. The Cu-SiC samples with a SiC content of 5 to 20 wt.% were fabricated by spark plasma sintering at temperatures from 700 to 850 °C. The Cu-SiC surfaces were processed by two different methods: using abrasive materials and nanosecond laser radiation. Surface analysis was performed by scanning electron microscopy, profilometry, energy dispersive spectroscopy and Vickers methods. The surface properties (wetting and dynamic characteristics of spreading) were studied using a shadow optical technique when interacting the Cu-SiC surfaces with water (up to 10 μL). It was proved that the recorded deterioration of the wettability properties of Cu-SiC surfaces processed by abrasive materials with an increase in their sintering temperature and the reason for the spontaneous hydrophobization of the Cu-SiC composite materials modified by nanosecond laser radiation, are due to the adsorption of airborne hydrocarbon contaminants, similar to the known wetting inversion of metal surfaces. It was established that the wetting properties of materials prior to modification by laser radiation do not affect the intensity, duration of stages, and steady-state values of contact angles upon wetting inversion of Cu-SiC composite materials. It was also found that the processing of Cu-SiC surfaces by laser radiation makes it possible to change the dynamic characteristics of the liquid spreading (at a flow rate of 5 μL/min, the liquid front speed is more than three times, and the dynamic contact angles are in the range of 30°).

Upcycling of Polybutadiene Facilitated by Selenium‐Mediated Allylic Amination

AbstractAccumulation of end‐of‐life plastics presents ongoing environmental concerns. One strategy to solve this grand challenge is to invent new techniques that modify post‐consumer waste and impart new functionality. While promising approaches for the chemical upcycling of commodity polyolefins and polyaromatics exist, analogous approaches to repurpose unsaturated polymers (e.g., polybutadiene) are scarce. In this work, we propose a method to upcycle polybutadiene, one of the most widely used commercial rubbers, via a mild, metal‐free allylic amination reaction. The resulting materials have tunable thermal and surface wetting properties as a function of both sulfonamide identity and grafting density. Importantly, this approach maintains the parent alkene microstructure without evidence of olefin reduction, olefin transposition, and/or chain scission. Based on these findings, we anticipate future applications in the remediation of complex elastomers and vulcanized rubbers.

Upcycling of Polybutadiene Facilitated by Selenium-Mediated Allylic Amination.

Accumulation of end-of-life plastics presents ongoing environmental concerns. One strategy to solve this grand challenge is to invent new techniques that modify post-consumer waste and impart new functionality. While promising approaches for the chemical upcycling of commodity polyolefins and polyaromatics exist, analogous approaches to repurpose unsaturated polymers (e.g., polybutadiene) are scarce. In this work, we propose a method to upcycle polybutadiene, one of the most widely used commercial rubbers, via a mild, metal-free allylic amination reaction. The resulting materials have tunable thermal and surface wetting properties as a function of both sulfonamide identity and grafting density. Importantly, this approach maintains the parent alkene microstructure without evidence of olefin reduction, olefin transposition, and/or chain scission. Based on these findings, we anticipate future applications in the remediation of complex elastomers and vulcanized rubbers.

Preparation of Hydrophobic Optically Transparent Wood via An Efficient UV-Assisted Route

In the context of the double carbon goal, the green, low-carbon and environmentally friendly modern wood construction market is promising and is expected to be further promoted and applied in the construction market. Optically transparent wood is a new building light-transmitting material with excellent performance, designed to reduce the energy consumption of buildings. An efficient and green method for the preparation of hydrophobic optically transparent wood is proposed in this study, in which its microstructure, chemical composition, surface wettability and optical properties are investigated. Hydrophobic optically transparent wood (90% light transmission, 80% haze, 130° water contact angle) with identical optical properties on the positive and negative sides was obtained by UV-assisted hydrogen peroxide treatment of natural wood to remove lignin chromogenic groups in situ, followed by dipping the epoxy resin into the wood substrate template and finally combining it with PDMS low surface energy modifications on the surface. The scanning electron microscopy and chemical composition analysis showed that the epoxy resin was successfully immersed in the internal pores of the wood and exhibited a homogeneous interface with the wood cell walls. All results confirm that this optically transparent wood preparation method is effective, and the resulting hydrophobic optically transparent wood is a new wood composite alternative material with excellent optical and hydrophobic properties, which broadens the application area of traditional wood and offers potential applications in energy-efficient buildings, smart windows and solar cells.

Controlling the Self‐Assembly of Hierarchical PS‐b‐P4VP Structures Prepared by Dip‐Coating and Emulsion Breath Figure Techniques

AbstractThe breath figure (BF) method is a common laboratory‐scale pathway for fabricating porous structures. The emulsion BF approach, one of the BF variations, has attracted increasing attention since it bypasses the high humidity requirement, which is characteristic for the conventional BF method. In this paper, we used the emulsion BF technique with PS‐b‐P4VP block copolymer (BCP) and SiO2 nanoparticles (NPs) as the stabilizers for water droplets. We combined this with the dip‐coating technique to obtain a hierarchical structure consisting of BF pores and BCP nanodomains. By altering the dip‐coating speeds and the NPs’ surface wetting properties and size, the average diameters of BF pores could be controlled. Notably, we were able to achieve both nano and microscale BF pores in the network. The effect of NPs for stabilization and dip‐coating parameters on BF pores and BCP nanodomains formation was established, extending the comprehension of this underdeveloped subject.

Development of surface modified titanium alloy as a promising photocatalyst for textile waste water treatment

TiO2 photocatalyst properties can be enhanced by doping with metals and non-metallic elements or coupling with another semiconductor forming a heterostructure photocatalyst, etc. Doped TiO2 can also be achieved by surface modification of commercially available titanium alloys by plasma electrolytic oxidation (PEO). Herein, Ti-6Al-2Sn-4Zr-6Mo, Ti-10V-2Fe-3Al and Ti-6Al-4V are PEO treated, and the photocatalytic ability of the material was studied. Further, the effect of alpha and beta stabilisers on the polymorphs of TiO2 (anatase and rutile) is investigated. Surface morphology, wettability and optical properties are analysed to determine the material’s photocatalytic ability. All titanium alloys possess a typical PEO porous structure, favouring the adsorption of dyes from the textile wastewater. The EDS and XPS analysis found that the alloying elements such as Fe, V and Mo in the titanium have limited participation in the oxidation reaction. In contrast, Al, Zr, and Sn actively participated in the PEO reaction and doped into the TiO2 lattice. The bandgap of the oxide coatings on Ti-6Al-2Sn-4Zr-6Mo, Ti-10V-2Fe-3Al and Ti-6Al-4 V alloys was found to be 2.92, 2.42 and 2.78 eV, respectively. The charge carrier’s recombination rate and separation efficiency of the PEO-treated Ti-6Al-4V and Ti-10V-2Fe-3Al are better than the PEO-treated pure Ti and Ti-6Al-2Sn-4Zr-6Mo. The PEO-treated Ti-6Al-4V alloy showed the highest MB degradation of 98% under visible light irradiation. The article successfully demonstrated PEO surface-modified commercial titanium alloys as a promising new immobilised photocatalyst for efficient textile wastewater degradation under visible light.

Mechanical, chemical and wetting properties of a superhydrophobic surface based on functionalized ZrO2 on stainless steel

A stable superhydrophobic FAS-ZrO2 (FZr-ESS) surface was created by chemically etching and modifying a 304 stainless steel substrate. The effect of etching parameters such as time and temperature on the surface wetting properties was studied and optimized. The etched steel surface exhibited a honeycomb-like microstructure that, coupled with the low surface energy of the fluorinated ZrO2 nanoparticles, produced a FZr-ESS surface with a surface contact angle (CA) of 165.9° and a sliding angle (SA) of 1.7°. The presence of highly stable functionalized ZrO2 conjugated to the steel matrix contributed to the surface's outstanding mechanical stability, as confirmed by tape peeling and sandpaper abrasion tests. Furthermore, the FZr-ESS surface demonstrated exceptional chemical stability under a variety of pH conditions due to its excellent water repellency. An electrochemical test showed that the resulting surface was highly resistant to corrosion, with the corrosion current density reduced by nearly two orders of magnitude compared to bare stainless steel. The superhydrophobic FZr-ESS surface also displayed excellent long-term stability, wetting diversity, and self-cleaning behavior, making it highly versatile for a range of applications.

Studies on Biobased Non-Isocyanate Polyurethane Coatings with Potential Corrosion Resistance

This work deals with the development of non-isocyanate polyurethane (NIPU) composites with an aniline oligomer, viz., tetraniline (TANI) for corrosion-resistant coatings. Firstly, epoxidizedsoyabean oil was converted to carbonated oil by inserting CO2 under high temperature and pressure into the epoxy ring. Then, varying weights of oligoaniline—0.5, 1, 2 and 4 wt % (based on the weight of CSBO)—were added to CSBO and cured with tetraethylenepentamine (TEPA, 25 wt % based on CSBO) at 80 °C for 12–15 h. The effects of oligomer loading on the thermal, mechanical and surface wetting properties of the free standing films were studied. The ATR-FTIR spectra of the films exhibited peaks corresponding to the bis-carbamate linkages, confirming the formation of urethane linkages. TGA analysis showed that the addition of oligoaniline did not alter the initial degradation temperature much; however, the residue increased with increasing loading of tetraniline. Both tensile strength and elongation (at break) increased with increasing oligoaniline content. While the glass transition temperature of the films was observed at approximately room temperature, i.e., 20–30 °C, for all the compositions, the contact angles of the composites were found to be less than that of the bare NIPU films. However, all the compositions were hydrophobic, exhibiting contact angles in the 98–110° range. SEM analysis of the cross-sections of the films confirmed the uniform distribution of tetraniline particles and surface morphology showed that the roughness increased with the loading of tetraniline from 0.5 to 4%. MS panels coated with NIPU exhibited good barrier properties and as loading of TANI increased, the rate of corrosion decreased. Salt spray tests indicated that oligoaniline improved the adhesion of the coating to MS and corrosion resistance compared to the neat NIPU coating.

Energy Loss for Droplets Bouncing Off Superhydrophobic Surfaces.

A water droplet can bounce off superhydrophobic surfaces multiple times before coming to a stop. The energy loss for such droplet rebounds can be quantified by the ratio of the rebound speed UR and the initial impact speed UI; i.e., its restitution coefficient e = UR/UI. Despite much work in this area, a mechanistic explanation for the energy loss for rebounding droplets is still lacking. Here, we measured e for submillimeter- and millimeter-sized droplets impacting two different superhydrophobic surfaces over a wide range of UI (4-700 cm s-1). We proposed simple scaling laws to explain the observed nonmonotonic dependence of e on UI. In the limit of low UI, energy loss is dominated by contact-line pinning and e is sensitive to the surface wetting properties, in particular to contact angle hysteresis Δ cos θ of the surface. In contrast, e is dominated by inertial-capillary effects and does not depend on Δ cos θ in the limit of high UI.

Fabrication and Properties of Hydrophobically Modified ZnO–SiO2 Nanocomposite with Polysiloxane

Studies on the wettability properties of solid surfaces are very important in any of the scientific and industrial fields. The most common principle for a superhydrophobic self-cleaning surface is the lotus effect induced by surface roughness. In this study, silicate compounds have been used to produce hydrophobic surfaces. In this way, firstly, SiO2–ZnO nanocomposite was produced, and then vinyl trimethoxy silane was used to increase the water contact angle (WCA). The structure and morphology of nanocomposites were investigated by infrared spectroscopy (FT-IR), X-ray diffraction pattern (XRD), scanning electron microscopy (SEM) and energy-dispersion spectrometer (EDS) analyses. The thermal stability of nanocomposite coatings was examined by thermogravimetric analysis (TGA). In order to investigate the wetting properties, the surface roughness was measured using an atomic force microscope (AFM), where the subsurface roughness average was obtained at 37.79 nm. The WCA of the coated surfaces with ZnO–SiO2 and ZnO–SiO2 @Polysiloxane nanocomposites were measured at 69 and 160°, respectively, indicating the surface superhydrophobic properties of ZnO–SiO2 @Polysiloxane nanocomposites. Finally, superhydrophobic properties of nanocomposites were investigated by the Cassie-Baxter model. The value of the f2 parameter in the model was estimated at 0.9556. This means that air occupies about 95.56% of the contact area between the water droplet and nano-coating, which is responsible for the superhydrophobic property of the surface.

Patterning Wettability on Solvent-Resistant Elastomers with High Spatial Resolution for Replica Mold Fabrication of Droplet Microfluidics.

Controlling the surface wetting properties of channels is crucial to the robust and reliable performance of microfluidic devices. Spatially patterned hydrophobic/hydrophilic microchannels have found utility across various applications, notably in the generation of higher-order emulsions. Unfortunately, the patterning of surface wettability currently requires multistep processes with limited spatial resolution, making it impractical for many applications. In this work, we take inspiration from soft lithography and have developed a new replica mold fabrication technique wherein both the channel geometry and surface wettability are transferred from the mold to the replica. In this approach, the mold is a silicon wafer with lithographically defined features etched into its surface to define the channel geometry and lithographically defined patterns of hydrophobic silanes to define surface wetting properties. The replica is a co-polymer network of PFPE-PEG, for which PFPE can be locally enriched by the mold's patterned silanes to define the spatially patterned wetting properties. We demonstrated the utility of this approach by fabricating a PFPE-PEG-based microfluidic chip, with hydrophobic/hydrophilic patterned microchannels, to generate double emulsions.

The effect of high temperature annealing on surface wettability, mechanical and chemical properties of laser ablated nitinol surface

Nitinol shape memory alloys are widely used in medical devices due to their special properties. However, the release of nickel ions into human liquid during corrosion process would cause great harm to human body. It has been found that super-hydrophobic surface with superior anti-corrosion performance could greatly solve this issue. Therefore, the preparation of green and healthy super-hydrophobic layer on nickel-titanium alloy surface has significant medical value. In this work, we explored a newly method of fabricating healthy super-hydrophobic surface with contact angle (WCA) of 153.2° ± 1.5°, and roll angle (RA) of 6° ± 0.5°by combination of nitinol alloy laser irradiation. Particularly, high temperature annealing was firstly adopted in the fabrication procession of super-hydrophobic surface, which can bring great reference value to the research in this filed. Besides, the formation mechanism was also revealed via the analysis of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, corrosion behavior was also investigated by electrochemical impedance (EIS) analysis to illustrate preventing nickel ions release performance. Unlike the traditional super-hydrophobic surface preparation methods, this method does not introduce any toxic substances, which has great application prospects in the medical field.

Structural, thermal, and surface wetting properties of epoxy resin/multiwalled carbon nanotubes composites

The structural, thermal and surface-wetting properties of epoxy resin/multiwalled carbon nanotubes (EP/MWCNTs) composites were studied by preparing nanocomposites by the physical mixing assisted by ultrasonication. The materials were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The contact angles of water droplets formed on the sample surfaces were measured to study their surface-wetting properties. FTIR showed the successful cross-linking of the EP matrix and good interaction between MWCNT and epoxy matrix in the nanocomposites. XRD attested that the incorporation of MWCNT in the EP did not influence the nature of the physical and chemical structures of the matrix polymer. Based on TGA results, the composites with chemically modified nanotubes were found to possess slightly higher thermostability than the analogous materials fabricated with the neat MWCNTs. Further, the EP/pristine MWCNT composites exhibited hydrophobic behavior while the EP/chemically modified MWCNT composites were comparatively hydrophilic which is attributed to the introduction of carboxyl groups during the chemical treatment of the nanotubes with strong acid.

Fiber reinforced polypropylene composites interfacial behavior improvement fabricated by cold plasma jet SiOx nanoparticles deposition

In this study, cold atmospheric pressure plasma jet was adopted to glass fibers surface modification with tetraethyl orthosilicate as a precursor. To enhance the interfacial bonding forces of glass fiber reinforced polypropylene (GFRP) composites, SiOx nanoparticles were polymerized on the fiber surfaces. The effect of two factors (the distance between nozzle and fiber (D) and the treatment time (T)) on the interfacial bonding behavior of GFRP composites was studied. The modified fibers and composites properties, including surface topography, chemical composition, wettability and interfacial mechanical properties, were studied comprehensively. The optimal parameters were obtained at D = 17 mm and T = 12 s. Our results indicated that the interlaminar shear strength of GFRP composites was increased by 30.79% compared to control group. Further studies found that plasma treatment introduced larger surface roughness, surface energy and more oxygen-containing functional groups, which was responsible for the interlaminar shear strength improvement.

Fetuin-A adsorption to tunable polydimethylsiloxane and subsequent macrophage response.

Surface modifications can be applied to biomaterials to alter the various surface properties that influence protein-material interactions and the cellular response. The plasma protein fetuin-A has been found to adsorb to many biomaterials but details of its interactions with polydimethylsiloxane (PDMS) and roles in regulating the immune response are not clear. Here, PDMS modifications are achieved by altering the ratio of PDMS formulations to control elastic modulus, and by coating PDMS with polydopamine (PDA) to attach fetuin-A. Surface characterization confirmed that altering the PDMS formulation changed the elastic modulus without affecting surface wetting properties. Surface roughness was measured using atomic force microscopy and surface chemistry was determined using X-ray photoelectron spectroscopy, with only minor changes detected on the softest samples. PDA deposition on PDMS was confirmed and contact angle measurements demonstrated an increase in hydrophilicity. Fetuin-A adsorption was influenced by the PDMS formulations, adsorption changed in a competitive plasma environment, and PDA was able to immobilize the greatest amount of fetuin-A. The inflammatory effects of fetuin-A were investigated, and data suggests that the elastic modulus influences cytokine secretion from macrophages at certain timepoints, a result likely due to varied protein amounts and orientations/conformations in response to material stiffness. The addition of a PDA layer demonstrated the potentially cytokine mitigating effect upon fetuin-A immobilization when compared to unmodified PDMS samples. The results provide new insight into the interactions of fetuin-A with PDMS and PDA, and the potential immune regulatory properties of fetuin-A modified materials.

Sum frequency generation spectroscopy of fluorinated organic material-based interfaces: a tutorial review.

Molecular interactions at interfaces have a significant effect on the wetting properties of surfaces on a macroscale. Sum frequency generation (SFG) spectroscopy, one of a few techniques capable of probing such interactions, generates a surface vibrational spectrum sensitive to molecular structures and has been used to determine the orientation of molecules at interfaces. The purpose of this review is to assess SFG spectroscopy's ability to determine the molecular orientations of interfaces composed of fluorinated organic molecules. We will explore three different types of fluorinated organic material-based interfaces, naming liquid-air, solid-air, and solid-liquid interfaces, to see how SFG spectroscopy can be used to gain valuable and unique information regarding the molecular orientation of each interface. We hope this review will help to broaden the understanding of how to employ SFG spectroscopy to obtain more complex structural information for various fluorinated organic material-based interfaces in the future.

The Study on Bamboo Microfibers Isolated by Steam Explosion and Their Comprehensive Properties

To overcome the shortage of wood resources as well as to develop novel natural fibers materials, the Chimonobambusa quadrangularis (CQ) and Qiongzhuea tumidinoda (QT) planted in Southwest China were effectively isolated by the steam explosion (SE). The fine and uniform bamboo microfibers derived from CQ and QT were obtained, and their smallest average widths were 12.62 μm and 16.05 μm, respectively. The effects of steam explosion on the micro-morphology, chemical composition, thermal stability, crystallinity, surface wettability, and mechanical properties of bamboo microfibers were comprehensively investigated. The results showed that the relative content of cellulose in bamboo microfibers increased but the hemicellulose and lignin contents decreased after SE. The degrees of crystallinity for CQ and QT increased from 40.49% and 39.46% to 68.90% and 55.78%, respectively. The thermal stability and surface hydrophilicity were also improved. The CQ microfibers had a maximum decomposition temperature of 2.79°C, a tensile strength of 58.54 MPa, an elongation at break of 0.6%, and a water contact angle of 2.7° higher than those of the QT microfibers.

Review of phase change heat transfer enhancement by metal foam

• Enhancement characteristics of metal foam on solid-liquid phase change heat transfer and liquid-gas phase change heat transfer are reviewed. • The mechanism of metal foam enhancing phase change heat transfer and the factors affecting the phase change heat transfer process are comprehensively discussed. • Existing methods for optimizing phase change heat transfer performance within metal foam are classified and evaluated. • The practical applications of metal foam enhanced phase change heat transfer in recent years are summarized and compared. • This review will lead to a better understanding on the designing and applying of efficient metal foam-phase change heat transfer systems. Metal foam is a novel multifunctional material with high porosity, high surface density, and excellent heat transfer performance. Embedding metal foams into phase change heat transfer systems can be used to improve the comprehensive heat transfer performance, which is receiving increasing attention in the field of thermal management. This paper focuses on the lasted advances in solid-liquid phase change heat transfer and liquid-gas phase change heat transfer within metal foams, and specifically analyzes the influencing factors on phase change heat transfer performance as well as the mechanism of metal foam effects on phase change heat transfer. Different optimized techniques for improving phase change heat transfer within metal foams and the current state of metal foam engineering applications for improving phase change heat transfer are reviewed and discussed. It is concluded that the addition of metal foam can significantly enhance the heat transfer performance of solid-liquid phase change systems and liquid-gas phase change systems, but it is accompanied by an inhibitory effect on natural convection, an obstructive effect on bubble overflow and an elevated effect on pressure drop. The application of gradient porous structure, metal foam fins, V-groove structure or changing the surface wettability of metal foam is a feasible way to alleviate the above problems. Meanwhile, it is pointed out that the heat transfer performance of phase change within metal foam is influenced by the interaction of various factors, and some key issues regarding the influence mechanism of PCM-device orientation, pore distribution, surface wettability, and structural properties on heat transfer performance still need to be studied to develop more efficient and compact heat sinks.

Preparation of poly (lactic-co-glycolic acid) microfiber membrane

Poly (lactic-co-glycolic acid) (PLGA) is a kind of medical polymer material with good biodegradability and histocompatibility, which is widely used in postoperative anti-adhesion materials. In this paper, PLGA microfiber membrane was successfully prepared with poly(lactic-co-glycolic acid) as the main material by electrospinning technology. The surface morphology, wettability, dimensional stability and mechanical properties of PLGA microfiber films were characterized by scanning electron microscopy (SEM) and tensile testing machine. The results show that the average diameter of the prepared PLGA fiber is 2.218~2.313 μm, the elongation at break of the fiber film is up to 193%, and the dimensional stability and wettability of the fiber film are maintained at 37°C. The degradation cycle is 2~3 months.