Determination Of Contact Angle Research Articles

The role of MFC and hydrophobically modified ethyl(hydroxyethyl)cellulose in film formation and the barrier properties of methyl nanocellulose film

Abstract There is currently a great demand for sustainable and bio-derived coatings for fiber-based packaging materials, which are technically implementable with a high performance. The aim of this work was to investigate the grease resistance of coatings prepared from methyl nanocellulose when applied on paperboard. Co-additives selected from native microfibrillated cellulose (MFC) and hydrophobically modified ethyl(hydroxyethyl)cellulose (EHEC) were used in order to determine their impact on film formation and crack resistance for folds. Small and moderate coat weights were applied in order to determine the critical coat weight for the barrier properties. It was found that high grease resistance can be achieved with methyl nanocellulose and a combination of methyl nanocellulose and MFC coatings. Contact angle determinations for water on uncoated and coated materials showed that EHEC-MFC films have a very high contact angle which is due to both the surface chemistry and roughness. This indicates and confirms that EHEC may facilitate the wetting of oil and greases. Methyl nanocellulose mixed with hydrophobically modified EHEC significantly changed the barrier properties indicating a change in the film formation.

Numerical Calculation of Apparent Contact Angles on the Hierarchical Surface with Array Microstructures by Wire Electrical Discharge Machining.

It is necessary to theoretically research wettability in superhydrophobic surface fabrication. Here, a numerical calculation approach is proposed for determining the contact angle of the water droplets on array micropillars by wire electrical discharge machining (WEDM). A hierarchical model is employed for these array microstructures, including mechanical analysis for a water droplet placed on a smooth array and wettability evaluation on the morphology of the WEDM surface. On pillars, equations are listed to solve the apparent contact angle according to force balance of gravity, tension, and pressure. As for the WEDM morphology, temperature simulation and measurement are carried out, and then the effect of roughness on surface wettability is studied. Constructed formulas predict the contact angle, and then the effect of geometric dimensions is obtained. In order to verify the assumption, array micropillars with different cross-profiles are prepared using high-speed WEDM on the Al alloy surface. Through the results of contact angle determination, the numerical calculation is carried out. This theoretical prediction is beneficial for improving the fabrication of the superhydrophobic surface by WEDM.

Selective Anchoring Groups for Molecular Electronic Junctions with ITO Electrodes.

Indium tin oxide (ITO) is an attractive substrate for single-molecule electronics since it is transparent while maintaining electrical conductivity. Although it has been used before as a contacting electrode in single-molecule electrical studies, these studies have been limited to the use of carboxylic acid terminal groups for binding molecular wires to the ITO substrates. There is thus the need to investigate other anchoring groups with potential for binding effectively to ITO. With this aim, we have investigated the single-molecule conductance of a series of eight tolane or "tolane-like" molecular wires with a variety of surface binding groups. We first used gold-molecule-gold junctions to identify promising targets for ITO selectivity. We then assessed the propensity and selectivity of carboxylic acid, cyanoacrylic acid, and pyridinium-squarate to bind to ITO and promote the formation of molecular heterojunctions. We found that pyridinium squarate zwitterions display excellent selectivity for binding to ITO over gold surfaces, with contact resistivity comparable to that of carboxylic acids. These single-molecule experiments are complemented by surface chemical characterization with X-ray photoelectron spectroscopy, quartz crystal microbalance, contact angle determination, and nanolithography using an atomic force miscroscope. Finally, we report the first density-functional theory calculations involving ITO electrodes to model charge transport through ITO-molecule-gold heterojunctions.

Effect of UV irradiation on surface of collagen film

It is well known that ultraviolet (UV) radiation is considered to be one of the most hazardous external factor that induces skin damage, leading in some cases to skin carcinoma. The most abundant protein in human skin tissue is collagen, which is responsible for conferring strength and resiliency. Taking into account these aspects, the present paper study the influence of the UV-irradiation on surface of a collagen film. Thus, the surface modification of the collagen film after irradiation was monitored with the help of the FTIR spectroscopy in close correlation with contact angle determinations and profilometry analysis. The obtained data reveal that after UV-irradiation, the collagen film has shown different structural changes which depend on the irradiation time. At short irradiation time, some cleavage and reorganization of the surface structural groups take place, but in contrast, the highest radiation exposure led to degradation.

Micelle formation, structures, and metrology of functional metal nanoparticle compositions

<abstract> Micelles are self-assembled aggregates that are formed, in many different structures, from surfactants and have a wide range of applications. The critical micelle concentration (CMC) is the concentration of surfactant above which the micelle formation becomes appreciable. This paper reviews techniques that measure the CMC during the formation of micelles involving metal nanoparticles (NPs) with an emphasis on silver NPs. Specifically this review collects and compares such techniques in terms of their advantages and disadvantages. In doing that, this review identifies the useful experimental data on the CMC that each technique yields, but also points out the limitations of each technique. Furthermore, the authors propose an <italic>in situ</italic> method by using contact angle determination on a substrate/system to measure the CMC in real time. Thus, the goal of this review is to provide a comprehensive list of the most commonly used techniques for the CMC measurement so that future researchers may make informed decisions on what method(s) to use to best meet their needs. </abstract>

Study the effect of sputtering power on wettability properties of chromium oxide coated GFRP composite materials

Coatings of Chromium oxide were deposited on the substrate of GFRP (Glass Fibre Reinforced Polymer) composite using RF magnetron sputtering. GFRP composites exposed to different environmental condition raises new challenges toits wetting surface, so the main aim of this research work is to develop a coating on the surface of GFRP composite in super hydrophobic manner. Chromium Oxide Films were characterized by X-Ray Diffraction (XRD) analysis, Roughness tester and Ramehart Goniometer. Wettability of the GFRP composite have been studied and compared the coated and uncoated GFRP composite. In addition, Ramehart goniometer was used for determining contact angle. Contact angle values was observed 84° to 98.4° experimentally with the change in target power. The results shows that Chromium Oxide (Cr2O3) coatings displays hydrophobic nature with the rise of target power and the contact angle of 98.40 is achieved corresponding to 290 W power. The thin film exhibited hydrophobic nature with the increase in target power.

Studies of the Roughness of Films Based on Organosols of Silver Nanoparticles by Determining Contact Angles

In the present work, we have proposed a method for estimating the roughness coefficient of films based on organosols of silver nanoparticles under conditions of homogeneous and heterogeneous wetting using the method for determining contact angles. Concentrated organosols of silver nanoparticles stabilized with a nonionic surfactant sorbitan monooleate have been used as initial systems. Films based on sols of silver nanoparticles were prepared by the Doctor Blade method followed by thermolysis (473–673 K for 2 h). All the samples were hydrophilic and had a complex, rough, and chemically inhomogeneous surface that could not be studied using the traditional wetting theory. Modification of the surface of the samples, as well as the smooth initial substrate, by deposition of gold nanoparticles of a size of 10 nm by ion sputtering have allowed us to prepare chemically homogeneous surfaces from the same material. Studies of the wettability of finite systems have allowed us to calculate their roughness coefficients. The parameter values ranged from 1.08 to 2.83 depending on the thermolysis temperature.

Electrospun SiO&lt;sub&gt;2&lt;/sub&gt; Nanotextiles for Preservation of a Tangible Cultural Heritage

The developing nanotechnology is getting infiltrated into a wide area of industries. A variety of nanotextiles can be produced from different materials (e.g. polymers, SiO2). Their applications are possible in many industrial branches as well as civil engineering. Silica-based nanotextiles can play a fundamental role in civil engineering. The potential utilization of nanotextiles in civil engineering is promising as surface protective layers. Wettability of SiO2 nanotextiles was studied on different thicknesses of samples and were tested under static conditions by determination of the water contact angle. Their water contact angle, which indicates the degree of wetting, was measured using an optical tensiometer.

Surface analysis of polymer films for wettability and ink adhesion

AbstractThe interaction between inks and substrates is critical during printing. Adhesion of the ink film is determined by the reciprocal interactions of polar and nonpolar (dispersive) components between polymer films and inks. The greater the similarity between the polar and dispersive components of inks, coating and substrates, the better the wetting and adhesion on the surface of printing substrate. Various liquid materials in printing such as inks, varnishes, lacquers, and adhesives contain high ratios of water. The highly polar nature of water makes the interaction of these materials unsuitable with predominantly disperse polymer surfaces. Some films with polyolefin structure, especially polypropylene, and polyethylene, are nonpolar and cannot form strong bonds with ink, varnish, or lacquer coatings due to their chemical structure. Increasing surface energy components overcomes the poor wetting and adhesion on polymer surfaces. In this review, the topics of water contact angle measurement and determination of surface energy, surface tension, and using sessile drop method for the wettability and ink adhesion of polymer films are surveyed. Information on structural and chemical processes was given that assists in obtaining wettable film surfaces. Recommendations were made for good adhesion and printability based on surface treatment methods and ink modification.

Polyethylene three-dimensional nano-networks: How lateral chains affect metamaterial formation

Polymers occupy a central role in current society due to their utility and versatile properties. As part of the class of soft materials, polymers have also been employed in research through nanostructuration and functionalization, looking for the development of new metamaterials with wide applicability in science and society. A particular polymer, Polyethylene, has been widely used both in research and commodities, and new ways to nanostructure and improve its functionality should be considered. Here, we report on the nanostructuration of polyethylene for the fabrication of three-dimensional nanonetworks, by resorting to 3 different variants of polyethylene: low density, high density, and ultra-high molecular weight. Through the melt infiltration of these polymers into well-known three-dimensional interconnected anodic aluminum oxide templates (3D-AAO), a study can be performed to understand the effects of the chain length, structure, and chain-branching of the used polymers on the stability and integrity of the resulting polymeric nanonetworks. This was accomplished by performing infiltrations in the presence of excess bulk material and quenching the infiltration process to access transient infiltration stages. The morphology of these networks was analyzed through SEM and STEM-HAADF to understand the differences arising from polymer structure. The observed results are interpreted through the use of the Lucas-Washburn equation for capillary flow and the determination of the critical contact angle for spontaneous capillary infiltration. The resulting metamaterials also exhibit photonic responses, resulting from the replication of the periodic nature of the employed templates.

The Influence of Rock Composition and pH on Reservoir Wettability for Low-Salinity Water-CO2 Enhanced Oil Recovery Applications in Brazilian Reservoirs

SummaryLow-salinity waterflooding and carbon dioxide (CO2) injection are enhanced oil recovery (EOR) methods that are currently increasing in use worldwide. Linking these two EOR methods is a promising approach in the exploration of mature fields and for post- and presalt basins in Brazil. Moreover, the latter reservoirs already exhibit a high CO2 content by nature. Interfacial phenomena between fluids and rock in a low-salinity water-CO2 (LSW-CO2) environment remain unclear, particularly the wettability behavior that is related to the pH of the medium, among others. This study investigates the influence of rock composition and pH of the brine on reservoir wettability through coreflooding and zeta potential experiments in LSW and determination of contact angles and interfacial tension (IFT) in the crude oil-LSW-CO2 system at reservoir conditions. Brazilian light crude oil, pure CO2, and brine solutions of different concentrations and compositions were used to represent the fluids in actual oil reservoirs. The experiments were carried out on Botucatu sandstone, Indiana limestone, and calcite crystal samples, with mineralogy determined by energy dispersive X-ray (EDX) analysis. Coreflooding experiments were conducted by the injection of 10 pore volumes (PVs) of fourfold diluted synthetic reservoir brine (SRB), followed by 10 PVs of 40-fold diluted SRB to evaluate the low-salinity effects. Interfacial properties, such as contact angle and IFT, as well as density and pH, were determined at elevated pressures to evaluate the synergistic effects between CO2 and salt content. In addition, geochemical modeling using PH REdox EQuilibrium (in C language) (PHREEQC) was performed to predict the in-situ pH and match with the experimental data. An increase in oil recovery and pH of the effluent was observed in the coreflooding experiments during diluted SRB injection. The ionic concentrations of the effluent samples also indicated illite dissolution. Furthermore, zeta potential measurements confirmed the expansion of the water film and shift from positive to negative surface charge of Botucatu sandstone for salt concentrations less than 80,000 mg/L at pH &amp;gt; 7, whereas in Indiana limestone, negative surface charge was only observed in deionized water at pH &amp;gt; 9. These observations indicate that during LSW injection alone, an increase in pH will favor a thicker water layer on the Botucatu sandstone surface that in turn increases water wettability and results in increased oil recovery. Conversely, the presence of CO2 in LSW causes a decrease in the pH of the medium, which is related to further enhancing water wettability when linking pH with contact angle measurements. It seems that a change in the pH of the brine induced by CO2 solubility in LSW enhanced interactions between the rock surface and water molecules. The respective interfacial energy then decreased, resulting in a decreasing water contact angle. It was also noticed that seawater-CO2 systems caused salt precipitation and mineralogical changes in carbonate and sandstone rock induced by calcite and kaolinite dissolution, respectively. This study contributes substantially to the understanding of interfacial properties and wettability behavior in LSW-CO2 systems, facilitating the design of LSW-CO2 EOR applications in Brazilian fields or even CO2 storage. Moreover, the study provides useful data for oil companies that have acquired mature wells and exploration blocks in Brazil, supporting them in operational and investment decisions.

A New Type of Composite Membrane PVA-NaY/PA-6 for Separation of Industrially Valuable Mixture Ethanol/Ethyl Tert-Butyl Ether by Pervaporation.

Pervaporation is a membrane technique used to separate azeotropic and close boiling solvents. Heterogenous PVA composite membranes with NaY zeolite supported on polyamide-6 were fabricated and utilized in organic–organic pervaporation. The efficiency of prepared membranes was evaluated in the separation of ethanol/ethyl tert-butyl ether (EtOH/ETBE) using separation factor (β) and the thickness normalized pervaporation separation index (PSIN). Implementation of the fringe projection phase-shifting method allowed to the determined contact angle corrected by roughness. The influence of the presence of water traces in the feed on the overall separation efficiency was also discussed using the enrichment factor for water (EFwater). The incorporation of NaY into PVA matrix increases surface roughness and hydrophilicity of the composite membrane. It was found that membranes selectively transport ethanol from the binary EtOH/ETBE mixture. The values of β (2.3) and PSIN (288 μm g m−2 h−1) for PVA-NaY/PA6 membrane were improved by 143% and 160% in comparison to the values for the pristine PVA/PA6 membrane. It was found that membranes showed EFwater > 1, thus revealing the preferential transport of water molecules across membranes. These results are also significant for the design of membranes for the removal of water excess from the mixtures of organic solvents.

Determination of contact angles for three-phase flow in porous media using an energy balance

HypothesisWe define contact angles, θ, during displacement of three fluid phases in a porous medium using energy balance, extending previous work on two-phase flow. We test if this theory can be applied to quantify the three contact angles and wettability order in pore-scale images of three-phase displacement. TheoryFor three phases labelled 1, 2 and 3, and solid, s, using conservation of energy ignoring viscous dissipation (Δa1scosθ12-Δa12-ϕκ12ΔS1)σ12=(Δa3scosθ23+Δa23-ϕκ23ΔS3)σ23+Δa13σ13, where ϕ is the porosity, σ is the interfacial tension, a is the specific interfacial area, S is the saturation, and κ is the fluid–fluid interfacial curvature. Δ represents the change during a displacement. The third contact angle, θ13 can be found using the Bartell-Osterhof relationship. The energy balance is also extended to an arbitrary number of phases. FindingsX-ray imaging of porous media and the fluids within them, at pore-scale resolution, allows the difference terms in the energy balance equation to be measured. This enables wettability, the contact angles, to be determined for complex displacements, to characterize the behaviour, and for input into pore-scale models. Two synchrotron imaging datasets are used to illustrate the approach, comparing the flow of oil, water and gas in a water-wet and an altered-wettability limestone rock sample. We show that in the water-wet case, as expected, water (phase 1) is the most wetting phase, oil (phase 2) is intermediate wet, while gas (phase 3) is most non-wetting with effective contact angles of θ12≈48° and θ13≈44°, while θ23=0 since oil is always present in spreading layers. In contrast, for the altered-wettability case, oil is most wetting, gas is intermediate-wet, while water is most non-wetting with contact angles of θ12=134°±~10°,θ13=119°±~10°, and θ23=66°±~10°.

Wettability of welded wood-joints investigated by the Wilhelmy method: part 1. Determination of apparent contact angles, swelling, and water sorption

Abstract This study presents a novel application of the Wilhelmy plate method on welded joints of Scots pine sapwood and beech. Welding resulted in an increase in the contact angle (increased hydrophobicity) as well as a decrease in the water uptake and swelling of the welded pine-joint compared to non-welded pine. When the welding time was extended from 4 to 5 s, these properties were further pronounced. Welding of beech, on the other hand, led to an increase in the contact angle and a decrease in the water uptake, but an increase in the swelling. Fourier Transform Infrared spectroscopy showed that welding increased the aliphatic C–H and unsaturated C=C stretching absorption bands in pine and beech. Scanning electron microscopy showed a dense structure at the welded joints of the both species, giving evidence of a lower porosity that leads to a lower permeability as a result of the welding.

S-XCT experimental determination of local contact angle and meniscus shape in liquid moulding of composites

In-situ spontaneous wicking experiments were scanned using Synchrotron X-ray Computed Tomography (S-XCT) to study the meniscus shape at the fibre scale. To this end, a single tow of E-glass fibres was impregnated with a commercial epoxy resin by using a wicking fixture specially designed for such purpose. The high resolution of the S-XCT images recorded (0.325μm/pixel) allowed the direct access to the surface of the individual menisci formed between fibres and permitted a direct quantification of the contact angle as well as the local curvature measurement. The contact angle values measured were in good agreement with values reported in the literature. The experimental methodology employed was also compared with numerical results obtained using a surface minimization approach. The results obtained with the simulation tool, in terms of effective capillary pressure and meniscus shape, were in good agreement with the experimental data reported.

Hydrophilic Dual Layer Hollow Fiber Membranes for Ultrafiltration.

In this study, a triblock copolymer was used as additive to fabricate new dual layer hollow fiber membranes with a hydrophilic active inner surface in order to improve their fouling resistance. The polymeric components of the solutions for membrane fabrication were poly(ether sulfone), poly(N-vinyl pyrrolidone), and the triblock copolymer. The additive consists of three blocks: a middle hydrophobic poly(ether sulfone) block and two outer hydrophilic alkyl poly(ethylene glycol) blocks. By varying the additive concentration in the solutions, it was possible to fabricate dual layer hollow fiber membranes that are characterized by a hydrophilic inner layer, a pure water permeance of over 1800 L/(m2 bar h) and a molecular weight cut-off of 100 kDa similar to commercial membranes. Contact angle and composition determination by XPS measurements revealed the hydrophilic character of the membranes, which improved with increasing additive concentration. Rheological, dynamic light scattering, transmission, and cloud point experiments elucidated the molecular interaction, precipitation, and spinning behavior of the solutions. The low-molecular weight additive reduces the solution viscosity and thus the average relaxation time. On the contrary, slow processes appear with increasing additive concentration in the scattering data. Furthermore, phase separation occurred at a lower non-solvent concentration and the precipitation time increased with increasing additive content. These effects revealed a coupling mechanism of the triblock copolymer with poly(N-vinyl pyrrolidone) in solution. The chosen process parameters as well as the additive solutions provide an easy and inexpensive way to create an antifouling protection layer in situ with established recipes of poly(ether sulfone) hollow fiber membranes. Therefore, the membranes are promising candidates for fast integration in the membrane industry.

Antimicrobial packaging efficiency of ZnO-SiO2 nanocomposites infused into PVA/CS film for enhancing the shelf life of food products

Abstract In the current work, antimicrobial bionanocomposite films were fabricated based on chitosan (CS), poly (vinyl alcohol) (PVA) and nanocomposites comprised of silicon dioxide nanoparticles doped with zinc oxide nanoparticles (ZnO-SiO2). The ZnO-SiO2 nanocomposite was prepared and incorporated into a PVA/CS blend at different ratios (0.50, 1.0, 3.0 and 5.0 %) to generate the PVA/CS/ZnO-SiO2 bionanocomposites. The prepared ZnO-SiO2 nanocomposites as well as the PVA/CS/ZnO-SiO2 bionanocomposite films were evaluated using SEM, FT-IR, XRD and determination of the final contact angle. Furthermore, the mechanical properties, gas permeability (GTR) and water vapor transmission rate (WVTR) of the prepared PVA/CS/ZnO-SiO2 bionanocomposite films were evaluated. The fabricated bionanocomposite films displayed superior antibacterial activity against Gram-positive bacteria (staphylococcus aureus, S33R) as well as Gram-negative bacteria (Escherichia coli, IRAQ 3). Correspondingly, the prepared PVA/CS/ZnO-SiO2 bionanocomposites were used for bread packaging. The obtained result revealed the greatly improved visual appearance of the bread that was packaged in the PVA/CS/ZnO-SiO2 bionanocomposite film. Moreover, the totality of these various observations and testing methods led to an increase in the shelf life and reduced the amounts of food-borne pathogens in the packaged bread. This PVA/CS/ZnO-SiO2 bionanocomposite film is an antimicrobial packaging material that may reduce the current negative environmental footprint of packaging materials.

Simultaneous determination of wettability and shrinkage in an organic residue amended loamy topsoil

Abstract In agricultural land use, organic residues such as compost, digestate, and sewage sludge are discussed as costeffective soil conditioner that may improve the water holding capacity and crop available soil moisture. The objective of this study is to determine the effect of application of digestates with different compositions in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge on shrinkage behaviour and contact angle of till-derived loamy topsoil of a Haplic Luvisol under agricultural use. Novelty is the simultaneous determination of contact angle and shrinkage of soils amended with digestates composed of different composition in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge. The results suggest that the application of organic residues impacts the air capacity, while the contact angles remained in the subcritical range between &gt; 0° and &lt; 90°. The relationship between CA values and moisture ratios, ϑ, during proportional shrinkage was positive and linear (r2 of 0.98) and negative during residual- and zero-shrinkage (r2 of 0.93).

Evaluation of methods using topology and integral geometry to assess wettability

HypothesisThe development of high-resolution in situ imaging has allowed contact angles to be measured directly inside porous materials. We evaluate the use of concepts in integral geometry to determine contact angle. Specifically, we test the hypothesis that it is possible to determine an average contact angle from measurements of the Gaussian curvature of the fluid/fluid meniscus using the Gauss-Bonnet theorem. Theory and simulationWe show that it is not possible to unambiguously determine an average contact angle from the Gauss-Bonnet theorem. We instead present an approximate relationship: 2πn(1-cosθ)=4π-∫κG12dS12, where n is the number of closed loops of the three-phase contact line where phases 1 and 2 contact the surface, θ is the average contact angle, while κG12 is the Gaussian curvature of the fluid meniscus which is integrated over its surface S12. We then use the results of pore-scale lattice Boltzmann simulations to assess the accuracy of this approach to determine a representative contact angle for two-phase flow in porous media. FindingsWe show that in simple cases with a flat solid surface, the approximate expression works well. When applied to simulations on pore space images, the equation provides a robust estimate of contact angle, accurate to within 3°, when averaged over many fluid clusters, although individual values can have significant errors because of the approximations used in the calculation.

Membranes based on polyacrylamide coatings on metallic meshes prepared by a two-steps redox polymerization. Performance for oil-water separation and biofouling effects

Superhydrophilic oil–water separation membranes were prepared based on chemical (non-photo-induced) polymerization of acrylamide on metal meshes. Membranes were characterized by surface morphological analysis (SEM and AFM), determination of contact angles of water and oil drops, measurement of water flow through the membranes, analysis of dissolved organic in filtered water–oil systems, critical intrusion pressure of oil and surface coverage by bacterial biofilms. The main characteristics of the membranes were studied as function of coverage with polyacrylamide (PAM). The membranes presented efficiencies larger than 99% for toluene-water separation and lifetimes of several months. The intrusion pressure (0.25–1.25 kPa) and water flux (10–300 Lm-2s−1) varied depending on PAM coverage. A mathematical model was implemented for predicting the water flow as function of hydrogel coverage.The results indicate there is a degree of compromise between three factors that are related to the amount of PAM coating: avoiding biofouling (which can block the flow, induce corrosion, etc.), maintaining an important flow of water and sustaining a given intrusion pressure of oil on the membranes.