Wilhelmy Plate Technique Research Articles

Thermodynamic and surface active investigations of aqueous solution of sodium dodecylbenzene sulfonate in presence of builders: sequestration of Ca2+ ions and interaction with H2O2

Abstract The current investigation examines the micellization process of sodium dodecylbenzene sulfonate in aqueous media with builders at temperatures ranging from 298.15 K to 313.15 K. Using conductometry and tensiometry analyses, the study examines changes in micellar properties in different surfactant solutions, focusing primarily on CMC. Additionally, the variation of CMC with temperature was used to determine the thermodynamic parameters of micellization such as ∆ G m ° , Δ H m ° , ${{\increment}G}_{\mathrm{m}}^{{}^{\circ}},{\Delta }{H}_{\mathrm{m}}^{{}^{\circ}}\text{,}$ and ∆ S m ° ${{\increment}S}_{\mathrm{m}}^{{}^{\circ}}$ . This approach provides valuable insights into the behavior of the surfactant and the different intermolecular interactions involved in the system. The different surface active parameters π CMC, A min, and Γ max were elucidated using tensiometry via the Wilhelmy plate technique. Moreover, the capacity of the builder to sequester calcium ions was studied using a well-established titration method, offering valuable insights into their effectiveness. Their efficiency under oxidative conditions, particularly in preventing the interaction between copper ions and hydrogen peroxide, was evaluated. This article provides a comprehensive analysis of different builders when used with the anionic surfactant, sodium dodecylbenzene sulfonate. Their combination provides improved efficiency in protecting metals from corrosion, extracting heavy metals from polluted soils, and in personal care products such as shampoos and soaps.

Experimental study on contact angle of water based Si–C nanofluid

The effects of solid surface, concentration and temperature on dynamic angles of water and water based Si–C nanofluid were experimentally investigated. Dynamic advancing and receding contact angles measurements by the Wilhelmy plate technique were performed for three types of solid surfaces (aluminum, copper and stainless steel), five temperatures values of nanofluid (20–50 °C) and two nanoparticles concentrations (0.5% and 1.0%). The contact angle of nanofluids decreases with both the increasing temperature and nanoparticles concentration. The values of average contact angles of nanofluids are smaller compared to the base fluid, meaning that the wettability of the nanofluid on all studied solid surfaces is better compared to water. Results revealed that the values of average contact angle of stainless steel/Si-C nanofluid are greater than for Al/Si-C nanofluid and Cu/Si-C nanofluid, which means that Cu/Si-C nanofluid exhibits better wettability than Al/Si-C and SS/Si-C nanofluids. The results of the current study may be contributing to a better understanding of parameters that influence contact angle values.

Assessing the surface free energy of modified asphalt binder with image processing technique

When the asphalt binder does not comply with the required specification for pavement, the suggested remedy is the implication of modifiers to enhance the quality. In the present investigation, asphalt cement binder was modified with varying percentages of two types of modifiers, Sulfur (3, 5, 7, and 10) % and Carbon Black (5, 10, and 15) % by weight of asphalt cement. The image processing technique was implemented to evaluate the surface free energy components (dynamic and static contact angles) of the treated asphalt cement by implementing the sessile drop and Wilhelmy plate techniques. The aim of this investigation is to assess how the image processing can detect the variation in the adhesive properties through the assessment of surface free energy of the asphalt cement due to the addition of the modifiers. For the comparison process, the surface free energy components of the control asphalt are also determined. Considering the test result obtained, it was concluded that Carbon black is more appropriate additive, it gives an ultimate total surface free energy increment of (7.7 and 6) % as compared with (2.8 and 3.1) % for sulfur when Sessile drop and Wilhelmy plate methods are implemented respectively when compared with the control binder.

Life-Inspired Endogenous Dynamic Behavior of Lipid Droplet-like Microcompartments in Artificial Adipocyte-like Structures

Chemical systems that can replicate cellular behaviors are gaining increasing attention and are being used to study various biological processes. Here, a protein- or amylose-based assembly at an oi...

Dynamic contact angle measurements on lubricant infused surfaces

HypothesisEven though lubricant-infused surfaces (LISs) are known to affect the mobility of working fluid depending on the infused lubricant, previous studies have not yet quantified their slippery property. This study proposes the slippery nature of the LIS can be assessed by dynamic contact angles of the working fluid on the LIS and its scaling model. ExperimentsWe measured the apparent dynamic advancing and receding contact angles on a LIS using a modified Wilhelmy plate technique for the first time. Lubricant having different viscosities was infused into the sanded polytetrafluoroethylene surface to fabricate the LIS. The surface was immersed into or withdrawn from an aqueous glycerol-water solution by varying the capillary number and the lubricant viscosity. FindingsThe dynamic contact angles on LIS was found to be sensitive to changes in both the lubricant viscosity and the capillary number. The cube of the dynamic contact angles on the LIS was proportional to θD3~Ca1, which follows a conventional hydrodynamic theory. In addition, the decreasing lubricant viscosity shifted the cube of the dynamic contact angles to high capillary numbers. Our dynamic contact angle data coincided with the prediction from a scaling law derived in this study.

Adsorption Kinetics of a Cationic Surfactant Bearing a Two-Charged Head at the Air-Water Interface

We studied the dynamics of adsorption at the air-water interface of a cationic surfactant bearing two charges, Gemini 12-2-12, at concentrations below and above the critical micelle concentration (cmc). We used maximum bubble pressure and Wilhelmy plate techniques in order to access all time scales in the adsorption process. We found that the adsorption dynamics are controlled by diffusion at the initial stage of the adsorption process (milliseconds) and it is kinetically controlled by an electrostatic barrier (minute) approaching the equilibrium surfactant surface concentration. Between these two extremes, we found several relaxation phenomena, all following exponential decays with characteristic times spanning from one to hundreds of seconds. By means of time-resolved surface potential measurements, we show that these processes involve charge redistribution within the interfacial region. The surface tension data are analyzed and interpreted in the framework of the free energy approach.

Contact Angle Determination on Hydrophilic and Superhydrophilic Surfaces by Using r-θ-Type Capillary Bridges.

To avoid the restrictions of the captive bubble and the Wilhelmy plate techniques, a method was introduced for contact angle measurements under equilibrium conditions. It enables to determine even ultralow contact angles with high precision without prewetting the investigated surface because in this case, the capillary bridge of the test liquid is formed from a pendant drop and used as a probe. The contact angle is determined from the measured capillary force and liquid bridge geometry by using Delaunay's analytical solution. The method was experimentally proved to be valid. As a demonstration, contact angles less than 1° were measured with the uncertainty down to 0.1° on lightly corroded glass surfaces. Moreover, a new observation was obtained in complete wetting situations: the receding contact line starts to advance again during the increase of the bridge length. The contact angle is much lower in this readvancing phase compared to the advancing and receding values because the contact line finds prewetted surface in front of itself. Further advantage of the method is that the existing contact angle goniometers can be developed further into the presented measurement setup.

Robust Oil-Fouling Resistance of Amorphous Cellulose Surface Underwater: A Wetting Study and Application.

The antioil-fouling characteristic of an amorphous cellulose (a-cellulose) surface was elucidated using the sessile droplet method (static) and a modified Wilhelmy plate technique (dynamic). As compared to other hydrophilic surfaces (cellulose acetate, poly(vinyl alcohol), and glass), the oil (poly(dimethylsiloxane)) contact angle on the a-cellulose surface underwater shows the largest value (170.5 ± 5.0°), having the smallest deviation from its theoretical value (180.0°) as estimated by Young's equation. Also, the a-cellulose surface demonstrates the strongest affinity with water in an oil medium (stable hydrophilicity). Moreover, the work of adhesion between the receding oil phase and a-cellulose underwater is quantified to be 10.3 mN/m, approximately one-fourth of that in air (42.0 mN/m). The overall wetting study suggests a rather low oil/solid/water three-phase contact line (TPL) friction in the direction that water displaces oil. A proposed mechanism attributes these phenomena to the water-accessible rigid cellulose chains and supramolecular structure of a-cellulose. The former hinders molecular rearrangement during processing or upon exposure to oil, such that its polar hydroxyl groups are readily accessible to water, thereby retaining its hydrophilicity. The latter allows water to diffuse across the TPL, forming the hydration shells that weaken the van der Waals interactions between oil and cellulose chains. Such findings of the a-cellulose surface can be exploited to fabricate mesh membranes with high water permeation flux (375.4 ± 13.5 L m-2 h-1 Pa-1), high oil/water separation efficiency (93-98%), and long-lasting stability, which is suitable for offshore oil spill remediation.

Capillary wave method: An alternative approach to wave excitation and to wave profile reconstruction

The capillary wave method is a well-known classical technique to measure surface tension and surface rheological properties. Despite the large number of theoretical works devoted to capillary waves, this technique has serious difficulties associated with its implementation, and therefore, it is not widely used by researchers. In this paper, we introduce our modifications of the existing method to overcome its drawbacks. First, a capillary wave is excited by pressure fluctuations generated locally at the interface. Being contactless, the proposed method is suitable for any liquid irrespective of its electrical properties. Second, the application of optical interferometry together with the spatial phase shifting method allows to quantify the surface profile with high accuracy. A new data processing algorithm makes it possible to subtract the parasitic deformation of the surface caused by external perturbations avoiding, thereby the thorough vibroisolation procedure. The relative error for surface measurements and surface tension calculations is 0.3%. The results of surface tension measurements of several liquids obtained by the modified method are in good agreement with the data determined by the Wilhelmy plate technique. The main advantage of our method is that is well suited for measurements of low liquid volumes, which makes it of particular interest in biological and chemistry applications. Additionally, our version of the examined method allows one to extend the frequency range to 103–104 Hz, where only the quasi-elastic light scattering technique is currently applicable.

Evaporation of aqueous solutions of organic acids through spread films of poly(diallyldimethylammonium chloride)/sodium dodecylsulfate complex

ABSTRACTThe films with the extreme concentration of poly (diallyldimethylammonium chloride)/sodium dodecylsulfate complex spread to the surface of aqueous solutions of formic and acetic acids reduce the evaporation rate of liquids by 3–6% and demonstrate selective properties increasing water content in the vapor by 1–3 abs.%. The concentrations of solutions were up to 30 vol.%. The formation conditions of such films were determined by means of the Wilhelmy plate technique. Surface tension isotherms of aqueous solutions of acids were also obtained.

Tensiometric Characterization of Superhydrophobic Surfaces As Compared to the Sessile and Bouncing Drop Methods.

We have considered in this work the Wilhelmy plate tensiometer to characterize the wetting properties of two model surface textures: (i) a series of three superhydrophobic micropillared surfaces and (ii) a series of two highly water-repellent surfaces microtextured with a femtosecond laser. The wetting forces obtained on these surfaces with the Wilhelmy plate technique were compared to the contact angles of water droplets measured with the sessile drop technique and to the bouncing behavior of water droplets recorded at a high frame rate. We showed that it is possible with this technique to directly measure triple-line anchoring forces that are not accessible with the commonly used sessile drop technique. In addition, we have demonstrated on the basis of the bouncing drop experiments wetting transitions induced by the specific test conditions associated with the Wilhelmy plate tensiometer for the two series of textured surfaces. Finally, the tensiometer technique is proposed as an alternative test for characterizing the wetting properties of highly liquid-repellent surface, especially under immersion conditions.

Comparison of Wilhelmy plate and Sessile drop methods to rank moisture damage susceptibility of asphalt – Aggregates combinations

The present study compares two techniques namely Wilhelmy plate (WP) and Sessile drop (SD) methods to rank moisture damage susceptibility of twelve different asphalt-aggregate combinations. Three asphalt binders: unmodified (VG30), polymer modified (PMB40), and crumb rubber modified (CRMB60) binders, and four aggregates (basalt, limestone, granite, and sandstone) were selected in this study. The contact angle of selected asphalt binders was measured using both WP and SD techniques. Thereafter, surface free energy (SFE) components of asphalt binders, bonding energy and compatibility ratio (CR) of selected asphalt-aggregate combinations were estimated. The results showed that the SD method showed a high variability in measurement of contact angle of asphalt binders compared to the WP method. The SD method found to be less sensitive to capture acid component of SFE of asphalt binders. Both the methods showed that PMB40-basalt, VG30-basalt, PMB40-limestone combination can have least susceptible to moisture damage. However, in majority of the cases (9 out of 12 asphalt-aggregates combinations, excluding PMB40-basalt, VG30-basalt, PMB40-limestone), both the methods resulted in different moisture damage ranking of asphalt-aggregates combinations. Currently set a minimum threshold value of CR as 0.5 based on the WP method for screening moisture damage susceptibility of asphalt-aggregate combination may not be applicable to the SD method. The present study develops a correlation between the CR of asphalt-aggregate combination estimated from the WP and SD methods.

Evaporation of aqueous solutions of organic acids through spread films of sodium polystyrene sulfonate/dodecyl trimethyl ammonium bromide complex

The Wilhelmy plate technique was used to determine surface tension isotherms of aqueous solutions of formic and acetic acids with concentration up to 30 vol% and with a film of solution of sodium polystyrene sulfonate/dodecyl trimethyl ammonium bromide complex spread to the surface. The formation conditions of films with the extreme concentration of the complex were determined. Such films reduce the evaporation rate of binary liquids by 3-6% and demonstrate selective properties increasing the water content in the vapor by 2-5 abs%.

Dynamic contact angle measurements of viscoelastic fluids

In this study, the dynamic contact angles of a series of viscoelastic fluids were measured through a modified Wilhelmy plate technique. The advancing and receding contact angles were measured by immersing and withdrawing a PTFE (Teflon) Wilhelmy plate from a reservoir containing a series of different Newtonian and viscoelastic test fluids. The viscoelastic fluids that were tested consisted of either solutions of polyethylene oxide or polyacrylamide in water where the concentration of the polymer was varied to produce solutions with different amounts of fluid elasticity with and without shear thinning. The advancing contact angles of all the viscoelastic fluids tested were found to increase with increasing plate velocity. Conversely, the receding contact angles in each case were found to decrease with increasing contact line velocity. A number of previous measurements have been performed for shear thinning fluids. The measurements presented here are the first to probe the response of the dynamic contact angle at large Weissenberg numbers where the elasticity of the liquid becomes important. For fluids with increased fluid elasticity, the onset of the variation of receding contact angles was found to be delayed to higher contact line velocities and capillary numbers. It was also found that, unlike the case of Newtonian fluids, the cube of advancing and the cube of the receding contact angles were both found to be proportional to the square of the capillary number for highly elastic fluids. Finally, a simple model was proposed to account for the role of elasticity and shear thinning of the viscosity on the dynamic contact angle.

Contact angle measurements on oxidized polymer surfaces containing water-soluble species

Advancing and receding contact angle measurements on polymer surfaces can be performed using a number of different methods. Ballistic deposition is a new method for both rapidly and accurately measuring the receding contact angle of water. In the ballistic deposition method, a pulsed stream of 0.15-μL water droplets is impinged upon a surface. The water spreads across the surface and then coalesces into a single 1.8-μL drop. High-speed video imaging shows that, on most surfaces, the water retracts from previously wetted material, thereby forming receding contact angles that agree with the receding angles measured by the Wilhelmy plate technique. The ballistic deposition method measures the receding angle within one second after the water first contacts the surface. This rapid measurement enables the investigation of polymer surface properties that are not easily probed by other wettability measurement methods. For example, meaningful contact angles of water can be obtained on the water-soluble low-molecular-weight oxidized materials (LMWOM) formed by the corona and flame treatment of polypropylene (PP) films. Use of the ballistic deposition method allows for a characterization of the wetting properties and an estimation of the surface energy components of LMWOM itself. Both corona- and flame-generated LMWOM have significant contact angle hysteresis, almost all of which is accounted for by the non-dispersive (polar) component of the surface rather than by the dispersive component. Surface heterogeneity is thus associated primarily with the oxidized functionalities added to the PP by the corona and flame treatments.

Dynamic contact angle measurements on superhydrophobic surfaces

In this paper, the dynamic advancing and receding contact angles of a series of aqueous solutions were measured on a number of hydrophobic and superhydrophobic surfaces using a modified Wilhelmy plate technique. Superhydrophobic surfaces are hydrophobic surfaces with micron or nanometer sized surface roughness. These surfaces have very large static advancing contact angles and little static contact angle hysteresis. In this study, the dynamic advancing and dynamic receding contact angles on superhydrophobic surfaces were measured as a function of plate velocity and capillary number. The dynamic contact angles measured on a smooth hydrophobic Teflon surface were found to obey the scaling with capillary number predicted by the Cox-Voinov-Tanner law, θD3 ∝ Ca. The response of the dynamic contact angle on the superhydrophobic surfaces, however, did not follow the same scaling law. The advancing contact angle was found to remain constant at θA = 160∘, independent of capillary number. The dynamic receding contact angle measurements on superhydrophobic surfaces were found to decrease with increasing capillary number; however, the presence of slip on the superhydrophobic surface was found to result in a shift in the onset of dynamic contact angle variation to larger capillary numbers. In addition, a much weaker dependence of the dynamic contact angle on capillary number was observed for some of the superhydrophobic surfaces tested.

Thermodynamic work of adhesion measurements of polymer bonded explosive constituents via the Wilhelmy plate technique and their application to AFM pull-off experiments

A major strength limiting factor for polymer bonded explosives above their glass-transition conditions is the magnitude of adhesion that exists between the polymeric matrix binder-system and the filler particles. Experimental measurements of the components of the free surface energy of the binder KEL-F8OO have been made using the Wilhelmy Plate technique. These data can be combined with equivalent data on the filler particles to calculate the so-called Thermodynamic Work of Adhesion. This under-pinning quantity can be used to predict the levels of load (stress) required to cause debonding in different geometries. A simple geometry of interest is a spherical-cap of polymer debonding from a flat substrate. Experiments using this geometry have been performed with an Atomic Force Microscope pulloff technique to measure the critical loads (stresses) required for debonding. There is excellent agreement between the predicted values based on the Wilhelmy Plate data and the measured values from the Atomic Force Microscope. Experimental data and understanding are required for the development and validation of microstructural models of mechanical behaviour.

Novel Wilhelmy plate analysis to determine contact lens dehydration rates

Purpose: Dynamic contact angle (DCA) methodology is currently used in the contact lens literature simply to report contact angle values. We have developed alternative data analyses to model the dynamic surface (de)hydration of lens materials, based on the Wilhelmy plate technique. The aim is to differentiate effectively between new and existing lenses in the rapidly expanding contact lens market. This has potential clinically significant in the search for dehydration resistant materials capable of maintaining a more stable in vivo tear film.

Dynamic contact angle analysis of silicone hydrogel contact lenses using the Wilhelmy plate technique

Purpose: The literature on the use of the Wilhelmy plate technique for the analysis of contact lenses is somewhat limited; there is perhaps only one paper which compared a range of contact lens materials using the technique. This is possibly due to complications associated with its use in the analysis of such materials. The aim of this work is to analyse a range of silicone-based hydrogel contact lens materials using the technique.

Applicability of Contact Angle Techniques Used in the Analysis of Contact Lenses, Part 1

Contact angle, as a representative measure of surface wettability, is often employed to interpret contact lens surface properties. The literature is often contradictory and can lead to confusion. This literature review is part of a series regarding the analysis of hydrogel contact lenses using contact angle techniques. Here we present an overview of contact angle terminology, methodology, and analysis. Having discussed this background material, subsequent parts of the series will discuss the analysis of contact lens contact angles and evaluate differences in published laboratory results. The concepts of contact angle, wettability and wetting are presented as an introduction. Contact angle hysteresis is outlined and highlights the advantages in using dynamic analytical techniques over static methods. The surface free energy of a material illustrates how contact angle analysis is capable of providing supplementary surface characterization. Although single values are able to distinguish individual material differences, surface free energy and dynamic methods provide an improved understanding of material behavior. The frequently used sessile drop, captive bubble, and Wilhelmy plate techniques are discussed. Their use as both dynamic and static methods, along with the advantages and disadvantages of each technique, is explained. No single contact angle technique fully characterizes the wettability of a material surface, and the application of complimenting methods allows increased characterization. At present, there is not an ISO standard method designed for soft materials. It is important that each contact angle technique has a standard protocol, as small protocol differences between laboratories often contribute to a variety of published data that are not easily comparable.