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Air−liquid interfacial surface tension measurements were performed on four 1-alkyl-3-methylimidazolium-based ([Cnmim], n = 3, 4, 6, 8) ionic liquids at 15 temperatures from (287 to 353) K at atmospheric pressure. To validate the accuracy of the results, the Wilhelmy plate method and the du Nouy ring method were employed in parallel using the Krűss K100MK2 tensiometer. At each temperature, from 33 to 55 Wilhelmy plate and from 10 to 30 du Nouy ring individual readings were taken in most cases. The surface tension average values at particular temperatures are presented with estimated overall standard uncertainty of 0.05 mN·m−1. An empirical surface tension−temperature equation has been developed describing the temperature dependence of each ionic liquid surface tension. To the 69 up-to-now published surface tension values of the above-mentioned four ionic liquids, the present study adds an additional 102 data points representing means calculated from about 3000 individual surface tension readings that altog...

Influences of freeze-drying process and of UV-irradiation are studied on morphology, surface composition and wetting properties of polystyrene-b-poly(acrylic acid) (PS41-PAA(271)) diblock copolymers (dip-coated on the substrate made of stainless steel). Observations by scanning electron microscopy (SEM) and measurements of static water contact angles highlight that morphology of non-UV-irradiated PS41-PAA(271) is re-organised after steps of immersion/emersion in water and freeze-drying. These both processes modify PS41-PAA(271) surface in a microstructured layer of polymer that covers a part of the stainless-steel substrate. Moreover, analyses by X-ray photoelectron spectroscopy (XPS) and measurements of dynamic wetting angles with the Wilhelmy plate method demonstrate that stimuli-responsive properties Of PS41-PAA(271), whose wetting properties depend on the environment, are enhanced after using a step of UV-irradiation for 20 min. This process influences the composition of the coating in order to stabilise the smart material. Consequently, repeated cycles of immersion/emersion in water showed that a maximum gap of 20-25 degrees is obtained between the hydrophobic state (after drying at air for 90 min) and the hydrophilic state (after immersion in water). (c) 2008 Elsevier B.V. All rights reserved.

We study numerically the motion of contact lines in the context of the “Wilhelmy plate" experiment: a vertical solid plate is withdrawn at constant velocity from a bath of liquid. We apply the contact line dissipation quasi-static model to the relaxation of an initially periodically deformed contact line. The obtained numerical data are compared to the experimental results [1] showing a good agreement.

A wettability study was performed on samples of alfa fibers with the Wilhelmy plate technique. The set of test liquids employed in the measurement of the contact angles was composed of water, heptane, diiodomethane, α-bromonaphthalene, and formamide. During their first immersion in high-surface-energy test liquids, the alfa fibers showed anisotropic behavior: they had an advancing contact angle of 67 ± 6° in one orientation of immersion and an angle of 112 ± 9.5° in the opposite one. Optical microscopy revealed the existence of fibrils on the alfa-fiber surface. They kept almost the same orientation and were responsible for the interesting hydrophobic/hydrophilic behavior of the fibers. Contact angle measurements and investigations of the hysteresis were also performed. The various results were examined according to the heterogeneities of the fibers. The surface energy of the alfa fibers was determined with three theoretical models: the geometric model, the Good–Van Oss–Chaudhury model, and the Chang model. A comparative study of these models was undertaken. The study of the wetting properties of alfa fibers will provide essential information for optimized composites and so will help us in choosing the right chemical treatment necessary to enhance adhesion in alfa-fiber-based composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Summary Wettability parameters determined for individual soils often show a considerable variation depending on the kind of sample (aggregated or homogeneous material) and the method used. To investigate the causes of this variation, we assessed wettability of both intact and crushed aggregates and bulk soil using different methods. Wettability of intact aggregates was characterized by a modified technique where the specific infiltration rates of water and a completely wetting liquid were used to define a repellency index. Contact angles were determined on crushed aggregates and bulk soil using the Wilhelmy plate and capillary rise methods. The repellency index was found to be sensitive to slight differences in wettability and was in good agreement with Wilhelmy plate contact angles. Contact angles measured with the capillary rise method showed a strong deviation from those determined with the Wilhelmy plate method. This can be ascribed to the underlying assumptions of the capillary rise method (i.e. cylindrical and parallel capillaries) resulting in an over-estimation of contact angle, particularly for the small-sized particle fraction because of the impact of inertia and pore structure. No significant differences were found between intact and crushed aggregates whereas the bulk soil was slightly more water-repellent, probably because of a somewhat larger organic carbon content. We conclude that the contact angle determined by the Wilhelmy plate method and the repellency index are appropriate parameters for characterizing soil water repellency because they detected small changes in wettability over a wide range extending from subcritical water repellency to hydrophobicity.

The influence of the viscoelastic thermal compression (VTC) of wood on its surface chemistry, wettability, and surface free energy was evaluated. The changes in surface chemistry were studied by means of Fourier transform infrared spectroscopy (FTIR). Wettability was determined on the basis of the contact angle of water, using the Wilhelmy plate method. Surface free energy was determined according to the Owens Wendt Rabel and Kaelble (OWRK) theory, using the contact angle data of diiodomethane and formamide. The studied material was wood of the low-density hybrid poplar (Populus deltoides × Populus trichocarpa), which was densified to three different degrees of densification (63%, 98%, and 132%) using the VTC process. The results, based on the FTIR spectra, revealed that the VTC process caused minor chemical changes on the wood surface. However, wettability changed significantly. The VTC wood surface exhibits rather hydrophobic behaviour. Evaluation of the surface energetics using the OWRK approach showed that total surface free energy dropped significantly due to the VTC process.

New experimental data on the surface tension of methanol are reported obtained by the Wilhelmy plate method using the Krűss K100MK2 tensiometer at 13 temperatures from (279 to 333) K. At each temperature, from 11 to 42 individual measurements have been carried out. The surface tension average values at particular temperatures are presented with the estimated overall standard uncertainty of ± 0.1 mN·m−1. An empirical surface tension−temperature equation has been developed describing the temperature dependence of the methanol surface tension from 225 K to the critical point at 512.6 K. The equation is fitted to the data of the present work and to critically assessed data of other authors compiled from the literature. The uncertainties associated with the correlation are estimated to be ± 0.3 mN·m−1.

The objectives of this study were to investigate the effect of heat treatment of fibres on the advancing and receding contact angles and wicking of panels by the Wilhelmy plate method; to verify the possible relationships between wetting properties and water absorption of the panels; and to determine the surface composition of heat-treated fibres by X-ray photoelectron spectroscopy (XPS). Fibres were treated at 150 and 180 °C for 15, 30 and 60 min. Our results showed that the treatment increased contact angles and decreased water absorption. Wicking was reduced by about 70% for the 150 °C group and 80% for the 180 °C group. XPS analysis demonstrated a slight decrease of the O/C ratio and changes of the C1/C2 ratio following treatment.

An attempt to evaluate the kinetically effective critical micelle concentration CMC of sodium dodecyl sulfate (SDS) in micellar solutions and in O/W emulsions at 40°C and pH 9 utilizing the pseudo first order rate constant of benzyl acetate hydrolysis was implemented. The critical micelle concentration of SDS in micellar solutions was determined by both surface tension measurements utilizing Wilhelmy plate technique and by rate constant of hydrolysis. Hydrolysis reaction of benzyl acetate was monitored in surfactant solutions as well as in o/w emulsions as a function of time. Emulsion droplets were controlled using microfluidizer 110 T and oily droplets were separated from the emulsion by ultracentrifugation at (11,500 rpm or 9,800 g) prior to analysis by high performance liquid chromatography. The value of the critical micelle concentration (CMC) in micellar solutions in the presence of benzyl acetate as determined from the Wilhelmy plate technique was 7.8 × 10−4 moles/L (CMC in micellar solution was 10 ...

The relationship between surface tension, free fatty acid concentration and the foaming properties of milk was investigated. The surface tension of milk with varying free fatty acid concentration was determined using the Wilhelmy plate technique and the milks were subsequently foamed by steam injection using a commercial coffee machine and by air injection using a specially designed foaming apparatus. Foaming properties of milk in terms of initial foam volume, foam stability and visual appearance of foam as functions of free fatty acid concentration were determined. Surface tension of milk showed a negative relationship with its free fatty acid concentration and foaming properties. However, natural variations in the surface tension of milk due to other surface active components such as protein, fat and phospholipids made it difficult to determine an absolute surface tension value below which the foaming properties of milk are negatively affected.

To evaluate the effect of polymer architecture on surface tension, glass transition, and other thermodynamic properties, we synthesized a series of 4-arm and 11-arm symmetric star polystyrenes. Surface tension was measured as a function of molecular weight of the stars and temperature in the melt using a modified Wilhelmy plate technique. We find that architectural effects play a significant role in determining the molecular weight dependence of polymer melt surface tension. A variable density lattice model that considers effects of entropic attraction of polymer chain ends to surfaces, compressibility and density gradients in the region near the surface is used to determine the origin of this observation. This analysis is complemented with surface tension calculations using more classical thermodynamic models that consider only bulk property changes with polymer architecture and molecular weight. Bulk thermodynamic properties for selected stars were derived from pressure−volume−temperature (PVT) measurem...

The structure of sulfoalkylated cyclodextrins (CDs) have been varied and optimised to improve their performances as mass-transfer promoters in an aqueous biphasic hydroformylation reaction. Their surface tensions have been measured using the Wilhelmy plate technique and compared. Their behaviour towards two hydrosoluble derivatives of triphenylphosphine has been evaluated by 31P{1H} and 1H NMR measurements and their catalytic activity has been assessed in a rhodium-catalyzed hydroformylation reaction of 1-decene. The best result was obtained using a β-CD sulfobutylated on the primary face and methylated on the secondary face. Indeed, this CD increased the reaction rate by a factor of 250 without inducing selectivity decrease. The accessibility to the secondary face of the CD appears to be determining in the catalytic process as it governs the approach between the CD-included substrate and the water-soluble catalyst. The impact of the nature of the CD substituents on the chemo- and regioselectivity of the reaction is also discussed.

The aim of the present study was to design amphiphilic cellulose that can self-assemble into polymeric vesicle or as nontoxic surfactants. Sulfate was firstly introduced as hydrophilic groups, then the hydrophobic groups for three cellulose derivatives. Effects of the hydrophobic length on the surface tension and critical aggregate concentration (cac) were investigated by the conventional Wilhelmy plate method. Results showed that the cac value decreased from 0.28 to 0.08 wt% and the corresponding surface tension increased from 44 to 55 mN/m when the hydrophobic chain length changed from C8 to C18. The aqueous self-assembly of the modified polymer was investigated using transmission electron microscopy (TEM) and dynamic laser scattering (DLS). Results showed that three cellulose derivatives were capable of forming polymeric micelles in water with an average particle diameter ranging from 20 to 67 nm. And the diameter of the nano-micelles was proportional to the length of hydrophobic chain under the experimental conditions. These amphiphilic polymers showed more remarkable shear shinning rheological behavior as expected since higher shear rates lead to disruptions of hydrophobic associations. These data suggest that the amphiphilic cellulose derivative may form nano-micelles and might find use as surfactant or a potential drug carrier. 2008 Elsevier Ltd. All rights reserved.

The goal of this research was to study the effect of advancing velocity and liquid viscosity on the dynamic contact angle between a solid surface and various hydrocarbons. The Wilhelmy plate technique was used to measure the dynamic contact angle at advancing velocities between 20 and 264 μm/s. In addition to hydrocarbons, two silicon oils were also tested for comparison purposes. The results indicate that advancing velocity and oil viscosity have a significant effect on the dynamic contact angle for both hydrocarbon and silicon oils. For example, the advancing contact angle for viscous (1540 mPa s at 15 °C) oils was up to 2 times higher at 200 μm/s than at 20 μm/s. As a result, it is recommended that when values for dynamic contact angles are reported, the advancing velocity at which they were measured be indicated. This will ensure correct data interpretation, meaningful comparison between various studies, and better prediction of multiphase flow or adhesion processes that depend on the dynamic contact angle.

An experiment was conducted to investigate the effects of drying methods, namely rotary drum, lab oven, microwave and air-drying, on the surface wettability of wood strands by the Wilhelmy plate method. The measurements included the surface contact angle, free energy, and liquid sorption capacity. Thirty industrial strands including southern yellow pine (Pinus spp.) and poplar (Populus spp.) were randomly collected for each drying method. The results from this study showed that the surface contact angle of a strand depends on the liquid used as well as the drying method and wood species. Liquid sorption capacity of the pine strands increased with decreasing surface contact angle, but this trend was not observed with the poplar strands. The total surface energy was almost the same for strands within species, regardless of the drying method, but it was higher on poplar strands than on pines. The polar and disperse components of surface free energy varied with both drying method and wood species. The surface polar energies of oven-dried pine strands and rotating drum-dried poplar strands were higher than on strands dried by other methods. For lower temperature drying methods (air and microwave), the lowest polar component was observed on the radial face of the pine strands. For the higher-temperature drying methods (oven and rotary-drum), the lowest polar component was found to on the tangential face of the pine strands.

A new family of amphoteric surfactant – 2-hydroxy-3-(N,N-dimethyl-N-dodecyl-ammonium)-propyloxy cellulose sulfate (GDCS) was synthesized by etherification of cellulose sulfate with glycidyl dodecyl dimethylammonium chloride (GDDMAC) in this paper. GDCS was characterized by FT-IR spectroscopy, 13C NMR, elemental analysis and TG. The surface-active properties such as surface tension, critical aggregation concentration were determined by the Wilhelmy plate method. The micellar conformation of GDCS in aqueous solution at different concentration was investigated by environmental scanning electro microscopy (ESEM). Rheological measurements of GDCS indicated that the solution first behaved like a pseudoplastic property, the apparent viscosity decreased sharply, and then exhibited a Newtonian property, the apparent viscosity did not change obviously anymore.

The equilibrium, dynamic surface tensions, and surface dilatational elasticity of aqueous solutions of nonionic fluorocarbon surfactant are reported. The critical micellar concentration, CMC (0.023 mM) and equilibrium surface tension (24.6 m N . m−1) at CMC were measured by Wilhelmy plate method for aqueous solution of C8F17SO2N(C3H7)(C2H4O)nH (n=20), abbreviated as EF122A. The surface tension decay is slower for C8F17SO2N(C3H7)(C2H4O)nH (n=10) system, abbreviated as EF122B compared to the EF122A system over short time region, which indicates the slow transport of the surfactant molecules to the surface. The relaxation time for surface tension decay is estimated by fitting a series of exponentials to the dynamic surface tension data and it decreases with temperature for EF122A. Slow exchange of monomers between bulk and interface is reflected in the high elasticity value of the air‐liquid interface for EF122B compared with EF122A within measured frequency window (0.125–1.25 Hz).

A novel cellulose-based hydrophobically associating water-soluble polymer-cellulose octaonate sulfate (COS) was synthesized in this paper. The basic physico-chemical properties such as surface tension and the critical aggregation concentration (cac) were measured by the conventional Wilhelmy plate method. The obtained cac value was compared with environmental scanning electron microscopy (ESEM) and Rheology data. All these results indicated that cac of this amphiphilic polymer was between the range 0.04 and 0.2 wt% and the corresponding surface tension was around 55 mN/m. The conformation of aggregates and size of particles in aqueous solution were carefully investigated by ESEM and dynamic laser scattering (DLS) measurements. When the concentration is around 0.04 wt%, loose aggregates are formed; around 0.5 wt%, network structure formed. DLS results indicated that average size of particle was increased from 54.7 nm to 73 nm and finally to 168.1 nm with the increase of concentration from 0.04% to 0.1% and even to 0.2%. These results suggested that almost all of micelles in aqueous solution aggregated at the experimental concentration range 0.04–0.5 wt%. Rheological properties of this polymer were similar to hydrophobically associating polymers’ (HMP). As the shear rate increased, the solution passed through a shear-thickening region before exhibiting a sharp decrease in viscosity, eventually exhibited Newtonian behavior.

The surface activity of mixed films of phospholipids (dipalmitoyl-phosphatidyl-choline, DPPC, dioleoyl-phosphatidyl-choline, DOPC, and dipalmitoyl-phosphatidyl-ethanolamine, DPPE) and sunflower protein isolate (SPI) and its hydrolysates at different degrees of hydrolysis (DH=5.62%, 23.5%, and 46.3%) was studied. The surface pressure data were determined by the Wilhelmy plate method, over a range of protein concentrations (5-1×10-6 wt%), at pH 7, and at 20 °C. Surface pressure data at low protein concentration indicate low surface activity that rises to a plateau as the monolayer is saturated at higher protein concentrations. The existence of protein-phospholipid interactions depends on the interfacial composition and on the protein/phospholipid ratio. The surface activity of mixed protein-phospholipid films is determined by the protein as the protein saturates the monolayer at higher protein concentrations in the bulk phase. However, the phospholipid increases the surface activity of protein films at low protein concentrations in solution. These results are of practical importance because peptides formed during hydrolysis may be too small to stabilize fluid interfaces, which is essential for the formation and stability of food dispersions (emulsions and foams). © 2006 Elsevier Ltd. All rights reserved.

The amphipathic character of soyasaponins and their consequent biological and technological properties are well-recognised. However, mainly due to the absence of purified compounds, no data are available on the amphiphilic surfactant properties of individual soyasaponins. In this study we developed a preparative method for the purification of the main soyasaponins species from soy germ. Reversed-phase chromatography (Source 15 RPC) gave a good resolution of the various soyasaponins, and was used for the purification of non- and fully-acetylated soyasaponin Ab, DDMP-conjugated and unconjugated soyasaponins Ba and Bb. For these compounds, the critical micelle concentration (CMC), the minimal attainable surface tension (γCMC) and the surface density (Γmax) were determined using the Wilhelmy plate method. The order of CMC values was as follows: soyasaponin Bb < Ba < βg < αg < Ab < non-acetylated Ab, and the CMC was found to range from 0.56 and to 3.2 g/L. It was concluded that the number of sugar side chains, the presence of acetyl groups and the presence of a DDMP-group are the main factors influencing the CMC of soyasaponins.

A semi-rigid, semi-flexible SU-8 polymer microdevice was designed to measure changes in interfacial tension at an air-water interface. The suspended microtensiometer enclosed a clean air-water interface, with an insoluble surfactant on the exterior. The difference in surface tension between the inside and the outside of the device, called the surface pressure, caused the 850 µm by 3 mm device to deflect. Finite element simulations were performed to predict device behavior prior to fabrication. Finished devices were tested in a Langmuir trough during multiple compression and expansion cycles using large area changes and slow compression speeds. Shorter experiments subjecting the interface to rapid local monolayer concentration variations were also performed. A platinum Wilhelmy plate was used as an independent surface pressure measurement. The microtensiometer had a theoretical resolution of 0.02 mN·m-1 publisher: Elsevier articletitle: Langmuir monolayer characterization via polymer microtensiometers journaltitle: Sensors and Actuators A: Physical articlelink: http://dx.doi.org/10.1016/j.sna.2015.03.041 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved. ispartof: Sensors and Actuators A, Physical vol:229 pages:110-117 status: published

The ability to quantify adhesion based on surface energies of the bitumen and aggregate components enables selection of compatible materials and quantitative assessment of moisture susceptibility. Reliable surface energy characterization is required in order to implement this technology successfully. One proven method to estimate bitumen surface energy is to calculate it using contact angles measured with various liquids. However, improper selection of probe liquids or interpretation of resulting data can easily mislead users into drawing inaccurate conclusions. This paper presents a refined test method and analysis procedure customized to estimate bitumen surface energy using contact angles measured by the Wilhelmy plate. Results for five neat and three modified bitumen are presented and results are interpreted to study the relationships between contact-angle based surface energies and damage in hot mix asphalt. In a separate study by Bhasin et al. in 2004, surface energy characteristics of bitumen determined using methods described in this paper were combined with surface energies of aggregates to successfully predict moisture susceptibility of mixes.

Wettability of soil affects a wide variety of processes in soils like infiltration, percolation, preferential flow, and surface run-off. Even though efforts have been made to determine contact angles and surface tension or energy of smooth surfaces, the determination on granular materials like soil particles remains unsolved. One objective of this study was to test the consistency of contact angles (CA) measured with the newly modified and easy-to-apply Wilhelmy plate method by using solid particles and liquids with defined variations of surface tension. A second objective was to derive basic physical surface properties for the irregularly shaped and chemically heterogeneous soil particles. Advancing contact angles were determined by using model soils varying in texture from clay to coarse sand to check the impact of grain size on the CA measurements. Varying the solid-surface tension with dichlorodimethlylsilane treatments provided for pure-water wetting stages ranging from wettable to extremely hydrophobic. The surface tensions of the liquids were varied from 72 mN m -1 to 25 mN m -1 by using water or water-ethanol mixtures. The surface tensions of the model soils were determined with the zero degree-contact angle method following Zisman's critical-surface tension concept. Results show that the measured CA varied continuously with the variations of the surface tension of the liquid and the solid phase, respectively. A general interpretation of the results is possible by using the concept of the Equation of State Approach.

Three methods for the determination of the surface tension of liquids based on force measurements namely, the vertical plate method of Wilhelmy, the frame method of Lenard and the ring method of du Nouy are compared and studied in respect of a common principle of correction. It is shown that these three most important force-based methods allow the determination of the surface tension under static conditions. The force components of the corresponding liquid column below the measuring wire obtained for the straight part of the withdrawal curve up to the transition in its curved part provides exact surface tension values. The experimentally accessible value of the force component describes the physical background of the measured value correction contrary to the approximate equations obtained by mathematical way. Usually the determination of surface tension of liquids is based merely at the vertical plate method on exact equations thermodynamically derived whereas in the case of the frame and ring methods correction factors in approximate equations are used. At usual application of the force-based methods under the non-static condition of the withdrawal of a liquid column, the force maximum measured at withdrawal of the measuring object (plate, frame, or ring) is the basis for the determination of surface tension. In these cases, the measured surface tension values are compensated by correction equations for the frame and ring methods which are based on an correction factor and correction tables empirically obtained. The surface tension values obtained in this usual way agree with those obtained by using the force component of the corresponding liquid column below the measuring wire for the straight part of the withdrawal curve up to the transition in its curved part. Problems arising at the force measurements with increasing thickness of the measuring wires inside and outside the rings are discussed. Drei auf Kraftmessungen basierende Methoden zur Bestimmung der Oberflächenspannung von Flüssigkeiten, nämlich die Vertikalplattenmethode von Wilhelmy, die Bügelmethode von Lenard und die Ringmethode von du Noüy werden miteinander verglichen und auf ein experimentell zugängliches gemeinsames Korrekturprinzip hin untersucht. Auf Basis der Messresultate wird demonstriert, dass diese drei wichtigsten auf Kraftmessungen basierenden Methoden eine exakte Bestimmung der Oberflächenspannung ermöglichen. Dies basiert auf Berücksichtigung der Kraftkomponente der entsprechenden Flüssigkeitssäule unterhalb des Messdrahtes, der für die Austauchgerade bis zum Übergang in den gekrümmten Teil der Austauchkurve erhalten wird. Der experimentell zugängliche Wert der Kraftkomponente beschreibt den physikalischen Hintergrund der Messwertkorrektur im Gegensatz zu den auf mathematischen Weg erhaltenen Näherungsgleichungen. Gebräuchlicher Weise basiert die Bestimmung der Oberflächenspannung von Flüssigkeiten lediglich bei der Vertikalplattenmethode auf thermodynamisch-exakt ableitbaren Gleichungen, während bei Bügel- und Ringmethode Korrekturfaktoren für Näherungsgleichungen bzw. Korrekturtabellen üblich sind. Die so erhaltenen Oberflächenspannungswerte stimmen mit denen überein, die unter Berücksichtigung der Kraftkomponente der entsprechenden Flüssigkeitssäule unterhalb des Messdrahtes erhalten werden. Probleme, die mit zunehmender Dicke des Messdrahtes innerhalb und außerhalb des Rings entstehen, werden diskutiert.

The equilibrium surface tensionsγ eq of aqueous Pentaethylenglycol-monododecylether (C12E5) solutions at temperature 25 °C were measured by means of Wilhelmy plate method and the determined critical micelle concentration (cmc) is 6.8 x 10-2 mol·m-3. To study adsorption kinetics of aqueous submicellar and micellar solutions, the dynamic surface tensionsγ(t) were measured by means of maximal bubble pressure method. Using the derived equations of adsorption kinetics for submicellar and micellar solutions, the experimental data were analyzed and the adsorption kinetics was studied. For micellar solution (c0>cmc) of C12E5, the demicellization constant $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\leftarrow}$}}{k} $$ was calculated.

Most methods used to characterize the magnitude of soil water repellency consist of direct or indirect measurements of the initial advancing contact angle (0) at the solid-liquid-vapor interface. Aqueous ethanol solutions (AETS) are commonly used as testing liquids having different liquid-vapor surface tensions (γ LV ); however, θ measurements using AETS have rarely been performed on water-repellent soils (WRS). Measurements of 0 in this study were conducted using both the Wilhelmy plate method (WPM) and the CRM (weight-gain capillary rise method) for three natural and four hydrophobized WRS (water-repellent soils). The values of the Young equation (solid-vapor and solid-liquid surface tension) were calculated, and correlated with the Goods-Girifako interaction parameter, Φ. The factor Φ was found to be a linear function of the solid-liquid surface tension: Φ = 1 -0.011γ SL , with no significant differences between soils. This relation was then used to formulate an ESIT (empirical equation of state of interfacial tension), suggesting that from one universal constant, 0 can be predicted as function of γ SV . The applicability of the ESIT approach to WRS was found to be inferior, in contrast to its successful use for ideal solid polymers. Nevertheless, it was found that for a water-WRS system, Φ was ∼0.6 rather than 1.0 as previously assumed. Applying Φ = 0.6 was successfully used in predicting γ SV as well as the hydrophilic domain of 0 vs. γ LV for water and AETS.

The effect of electrolytes and nonelectrolytes on the micellar behavior of amitriptyline (AMT), an amphiphilic drug, has been investigated using cloud point (CP) and dye solubilization techniques. The critical micelle concentration (cmc) of AMT determined by the Wilhelmy plate method was about 40 mM in the presence of 10 mM sodium phosphate, and it reduced to about 20 mM in the presence of 500 mM sodium phosphate. Interestingly, the CP phenomenon was observed even below the cmc in cationic AMT solutions. Increasing AMT concentration reduced the CP below the cmc, while it had the opposite effect above the cmc. An increase in the pH of the AMT solutions from 6.2 to 6.8 at a given AMT concentration decreased the CP and increased the AMT micellar size. Addition of an electrolyte such as sodium chloride to 100 mM AMT in water increased both the CP and the AMT micellar size. On the other hand, added nonelectrolytes such as dextrose, sucrose, and urea decreased both the CP and the micellar size. Experimental res...

The stability (area loss as a function of time) of dipalmitoylphosphatidylcholine (DPPC) at the air–water interface is an important property in the context of studying its behaviour as a major component of synthetic lung surfactant. However, some Langmuir troughs cannot support a stable monolayer of lung surfactant for long periods of time owing to adhesion between the surfactant and the materials that compose the trough. In this work, the stability has been measured as a function of surface pressure, Wilhelmy plate length and width, compression barrier material and the height of the water surface relative to the edge of the compression barriers on a Nima 601M Langmuir trough. Octadecanoic acid (stearic acid) and a non-amphiphilic porphyrin, 5,10,15,20-tetrakis(3,4-bis[ethylhexyloxy]phenyl)-porphyrinatozinc (Zn EHO) have also been investigated in order to identify the features of area loss which are surfactant material dependent and those which are affected by the properties of the trough itself. Stability of the highly amphiphilic monolayers was greatly improved when using Delrin barriers instead of PTFE barriers but had little effect on the porphyrin monolayers.

Mixed polyelectrolyte surfactant layers co-adsorbed at the surface of aqueous solutions have an unusual behavior. The adsorption is irreversible and the response to large compressions is highly nonlinear, as evidenced by Brewster angle microscopy. As a consequence, it is very difficult to measure equilibrium surface tension with bubble shape techniques, as soon as bubble volume is varied. These difficulties seem, however, specific to strongly viscoelastic layers. They are never found with surfactant solutions, and perhaps more surprisingly not seen either with more rigid layers such as those obtained with proteins. Long equilibration times are found, much longer than in Wilhelmy plate experiments. Uncontrolled convective motions occurring with the plate technique might explain the observed differences. It is easier to obtain reliable compression viscoelastic moduli with the oscillating bubble technique.

Surface modification of high-density-polyethylene (HDPE) and linear-low-density polyethylene (LLDPE) films is promoted by sodium hypochlorite solutions using two different processes (I and IT). Such an oxidation system introduces limited amounts of carbonyl-carboxyl and hydroxyl groups onto the surface of hydrocarbon polymers. FTIR, XPS, and SEM were used to assess the efficiency of the oxidation. The hydrophilicity of the studied surfaces was investigated by the sessile drop technique and the Wilhelmy plate and a plausible oxidation mechanism is proposed. (c) 2006 Wiley Periodicals, Inc.

A cross-web non-uniformity ('laning') in the flame surface modification of polypropylene (PP) film was investigated using flame temperature measurements and Wilhelmy plate force measurements. To associate the cross-web non-uniformity in the flame treatment with specific features of the flame supported on an industrial 4-port ribbon burner, the temperature and force measurements were registered to a specific burner port. The Wilhelmy force measurements show that the upstream pair of ribbon-burner ports causes a slightly greater treatment of the PP surface than the corresponding downstream pair of ports. The average temperature experienced by the PP as the film traverses through the flame is noticeably higher along the down-web line of the upstream burner ports as compared with a line passing through the downstream pair. This greater average temperature correlates to an exposure to a greater concentration of the active species, such as OH radicals, that cause the surface oxidation of the PP.

The surface tensions and densities of aqueous solutions of oxalic, malonic, succinic, maleic, malic, and cis-pinonic acids were measured as a function of the acid mole fraction at 25 °C. These organic acids are typically found in atmospheric aerosols. The surface tensions were measured using the Wilhelmy plate method and were measured also as a function of temperature. The measurable mole fractions were limited by the solubilities of the acids at room temperature. All the acids lower the surface tension of pure water. cis-Pinonic acid lowers the surface tension most effectively. The measured surface tensions were fitted with equations covering the acid mole fraction range from zero to one and assuming a theoretical surface tension of pure, supercooled acids at room temperature. The measured densities were also fitted in a similar way. These equations can be used in model calculations of formation and growth of atmospheric particles.

Medium density fibreboard (MDF) was produced from fibres treated with maleated polypropylene wax. The objectives of this study were to investigate the effect of fibre treatment with maleated polypropylene wax on the advancing and receding contact angle and wicking of MDF panels by the Wilhelmy plate method; to verify the chemical reactions occurring between fibres and maleated polypropylene wax by infrared spectroscopy, and to verify if there are relationships with the water absorption of panels. Three maleated polypropylene wax contents (0, 3, 5%) and two resin types (urea–formaldehyde, UF and melamine–urea–formaldehyde, MUF) were considered in this study. Our results showed that the treatment increased the advancing contact angle of panels bonded with UF resin. The receding contact angles of MDF panels produced from treated fibres with 5% maleated polypropylene wax content were also increased by the treatment. Also, the wicking was reduced by the treatment independent of the maleated polypropylene wax content. Reductions of the wicking were 59% for panels bonded with UF resin and 73% for panels bonded with MUF. Relationships between the wicking and water absorption were observed. Chemical analysis realized by infrared spectroscopy did not detect the presence of an esterification reaction between wood fibres and anhydride groups of the maleated polypropylene wax. This suggests, therefore, that an esterification reaction did not take place or that chemical modifications were so small that they are not visible by infrared spectroscopy.

The combined approach of the molecular-kinetic and hydrodynamic theories for description of the motion of three-phase gas-liquid-solid contact lines has been examined using the Wilhelmy plate method. The whole dynamic meniscus has been divided into molecular, hydrodynamic, and static-like regions. The Young-Laplace equation and the molecular-kinetic and hydrodynamic dewetting theories have been applied to describe the meniscus profiles and contact angle. The dissipative forces accompanying the dynamic dewetting have also been investigated. The experiments with a Wilhelmy plate made from an acrylic polymer sheet were carried out using a computerized apparatus for contact angle analysis (OCA 20, DataPhysics, Germany). The extrapolated dynamic contact angle versus velocity of the three-phase contact line for Milli-Q water and 5x10(-4) M SDBS solution was experimentally obtained and compared with the combined MHD models with low and moderate Reynolds numbers. The models predict similar results for the extrapolated contact angle. SDBS decreases the equilibrium contact angle and increases the molecular jumping length but does not affect the molecular frequency significantly. The hydrodynamic deformation of the meniscus, viscous dissipation, and friction were also influenced by the SDBS surfactant.

Water-based antifoams are investigated extensively for their effectiveness in reducing the total volume of air in froth and foam by enhancing bubble coalescence. These are suspensions of fatty alcohol particles in an aqueous phase containing essentially a non-ionic surfactant and polysaccharides. The time dependent total volumes of air in froth and foam are recorded in a glass column in which air is continuously bubbled through a pool of surfactant solution. An optimum mean particle diameter is found to exist for maximum antifoaming efficiency. The % reduction in air content due to the antifoam with an optimum particle size increased with temperature until a maximum is reached. Correspondingly, the solid fatty alcohol content in the antifoam suspension has been measured to be about half of the initial value. The % reduction in air subsequently decreased to a negligible value as the fatty alcohols melted completely at a higher temperature. When the low melting fatty alcohol particles are replaced by a high melting fraction, the efficiency at higher temperature is restored. A model is presented, which characterizes the measured kinetics of foaming and bubble coalescence for different antifoams. The observed antifoaming efficiencies are related to the local conditions prevailing at the air–water–solid contact region. Scanning electron microscope images show the fatty alcohol particles to be almost spherical at room temperature. Advancing contact angles measured within the aqueous phase using the Wilhelmy plate tensiometry exceeded 90 ° , which is the critical angle for initiating film drainage for a smooth spherical particle.

The effect of temperature on the surface tension of soluble and insoluble surfactants was investigated at an air−water interface. Equilibrium surface tension measurements were performed using the Wilhelmy plate technique in which both temperature and concentration were varied systematically. Insoluble surfactants (oleyl alcohol and hemicyanine) and soluble surfactants (Triton X-100 and sodium dodecyl sulfate (SDS)) were used since they are commonly used in hydrodynamic experiments in which the effects of surfactants on free surface dynamics are studied. The principal result of this investigation is that the surface tension of the above-mentioned surfactants decreases linearly with temperature, independent of concentration, with the exception of oleyl alcohol whose surface tension becomes relatively independent of temperature above 23 °C. The adequacy of standard models for surfactant behavior in describing these data is considered.

In this work we describe a simple thermodynamic method for determination of the adsorption (amount per unit area) of ionic surfactant. The latter is obtained from the interfacial tension isotherm measured in the presence of arbitrary (and fixed) concentration of inorganic electrolyte. Polynomial fit of the interfacial tension versus the logarithm of the mean ionic activity is combined with the Gibbs adsorption equation written in a form suitable for arbitrary content of salt. This procedure is an extension of the approach of Rehfeld [J. Phys. Chem. 71 (1967) 738]. We have performed measurements with sodium dodecyl sulfate (SDS) on water/air and water/oil (n-hexadecane and Soybean Oil) boundaries, at different salt concentrations (10 and 150 mM NaCl). Wilhelmy plate method was used for the water/air measurements; for water/oil we applied drop shape analysis with pendant drops. The obtained isotherms, together with literature data, are processed and the adsorption is determined. The results are compared and discussed in view of the role of the salt and the type of the hydrophobic phase. On oil/water boundaries the adsorption is always lower than that on air/water surface; addition of inert electrolyte increases the adsorption. We analyze theoretically the asymptotic behavior of the adsorption as a function of the solute concentrations in the limit of high surface coverage. The treatment is based on models existing in the literature (Langmuir isotherm with account for the counterion binding, as formulated by Kalinin and Radke [Colloids Surf. A 114 (1996) 337]; the activity coefficients were taken into consideration in the frames of the DebyeH¨ uckel theory). The obtained asymptotic functional dependence of the adsorption is used for fitting of data. The agreement is always good, in the concentration region below and near the critical micellization concentration (CMC). From the fits we determine the limiting adsorption at maximum coverage (i.e., at saturation); therefrom, the degree of coverage of the interface with surfactant is estimated. It turns out that at the CMC the coverage is lower than about 90%. Thus, we confirm literature results for absence of saturation with ionic surfactants at the CMC. The dependence of the surface coverage upon the mean ionic activity is rather insensitive toward the type of the fluid interface (air/water, oil/water with different hydrocarbons), and the salt concentration. © 2004 Elsevier B.V. All rights reserved.

Summary Water repellency can be a significant factor in soil physical behaviour, but little is known about the depth dependence of the contact angle of field soils. We investigated contact angles and wetting properties as a function of depth for a wide range of agricultural and forest soils in Germany. The agricultural soils ranged from silty to sandy texture (six profiles), and the forest soils ranged from sandy to loamy texture (eight profiles). Contact angles (CA) were measured with the Wilhelmy plate method (WPM). In most of the soils, advancing WPM contact angles were considerably greater than 0° and they varied irregularly with depth. In general, sandy soils had larger WPM contact angles than silty soils. From the relation of the contact angle with texture and pH the quality of soil organic matter (SOM) was considered as more important for the wetting properties than the total amount of soil organic carbon (SOC). Finally, it was found that for soils with intermediate sand contents either under agricultural or forest use, the kind of land use seemed not to influence CA. Coarse-textured sandy soils that were used only as forest sites were more hydrophobic than silty soils which were exclusively used as agricultural soils. We conclude that a coarse texture favours, in combination with other factors (mainly pH), hydrophobic SOM.

A tensiometer operating on the Wilhelmy plate method was employed to measure liquid-vapor interfacial tensions of three binary mixtures and one ternary mixture of decane with eicosane, docosane, and tetracosane. Tensions of binary mixtures n-C10H22 + n-C20H42, n-C10H22 + n-C22H46, and n-C10H22 + n-C24H50 and the ternary n-C10H22 + n-C20H42 + n-C24H50 were measured from 293.15 K (or above the solution melting temperature) up to 343.15 K. An average absolute deviation of 1.3% was obtained in comparison with pure component literature data. No mixture information for the reported systems was found in the literature. Results were modeled with a recently proposed corresponding states model. The average absolute deviation was found to be 1.2%.

Physicochemical properties of PBLG (poly(gamma-benzyl-l-glutamate))-PEO (poly(ethylene oxide)) diblock copolymers composed of PBLG as the hydrophobic rod component and PEO as the hydrophilic component were investigated at the air-water interface. Surface pressure-area isotherms obtained by the Wilhelmy plate method provide several variables such as molecular size, compressibility of PEO, and the free energy change of the PBLG-PEO block copolymer. GE-1 (M(w) of PBLG:PEO=103,700:12,000), with a relatively longer rod, has negative temperature effects and GE-3 (M(w) of PBLG:PEO=8400:12,000), with a relatively shorter rod, shows a positive temperature effect because of the large entropy loss. These competitions were based on the block size of PBLG and PEO and were affected by various microstructures of the PBLG-PEO diblock copolymer. Monolayer aggregations transferred onto mica from the air-water interface were analyzed with AFM. AFM images of GE-1 monolayers show cylindrical micelles, but the self-assembled structure has many large domains. The monolayer of GE-2 (M(w) of PBLG:PEO=39,800:12,000), which has a medium size rod, forms a spherical structure at the air-water interface. Monolayers of GE-3, with a short rod length, form bilayer structures. These results demonstrate that the microstructures of PBLG-PEO diblock copolymers are related to free energy changes between rod and coil blocks.

X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic wetting measurements with the Wilhelmy plate method were used to characterize layers of three polystyrene-b-poly(acrylic acid) (PS-PAA) diblock copolymers (differing by their block lengths) created by dip coating or spin coating on glass and gold substrata. The copolymer layers were thick and continuous, whatever the substratum, with a preferred exposure of PS chains at the extreme surface for the copolymers with a small PS block. The surface roughness decreased as the PAA/PS block length ratio increased and was larger for dip-coated than for spin-coated layers. The dip-coated layers obtained with the copolymer with the large PAA block presented self-assembled nanostructures of worm-like type. Dynamic wetting measurements showed that the coated layers were able to reorganize, upon immersion-emersion in solution at different pH, due to the deprotonation and swelling of the PAA chains. This phenomenon was dependent on the block length and on the pH. A water contact angle typical of pure PS was obtained with the large PS block. A hydrophilic surface was obtained for the large PAA block after immersion at pH 11. In intermediate situations (large PAA block in water, large PS block at pH 11), the advancing contact angle was dependent on the time of contact with air subsequent to the preceding immersion. This demonstrates the possibility to modulate hydrophobicity-hydrophilicity switching and pH sensitivity of the coatings by the copolymer composition. (C) 2004 Elsevier B.V. All rights reserved.

A novel homologous series of 1-N-l-phenylalanine-glycerol ether surfactants was synthesized in satisfactory yields via reaction of epichlorohydrin with aliphatic alcohols with alkyl chains of 10–15 carbon atoms. Structural assignment of the new compounds was made on the basis of elemental analysis and spectroscopic data. Critical micelle concentration (CMC), surface tension at the CMC (γCMC), surfactant concentration required to reduce the surface tension of the solvent by 20 mN/m (pC20), and the interfacial area occupied by the surfactant molecules (Amin) were determined from aqueous surface tension measurements using the Wilhelmy plate technique.

The interfacial phenomena of spreading and adhesion of fluids on rock surfaces have serious implications because of their impact on production strategy and oil recovery. The present study reports new experimental data on the effect of brine dilution and surfactant addition on spreading and adhesion behavior of Yates crude oil on dolomite surfaces. Spreading and adhesion have been characterized through measurements of oil–water interfacial tension (IFT) and dynamic (water-advancing and receding) contact angles. The interfacial tension was measured using computerized axisymmetric drop shape analysis (CADSA) technique, which was calibrated against the well-known du Nuoy Ring technique. The dual-drop dual-crystal (DDDC) technique and the Wilhelmy plate technique have been used to measure dynamic contact angles. In order to study the effect of brine dilution, Yates reservoir brine was mixed with deionized water (DIW) in various proportions. The oil–water IFT initially decreased as the volume percent of brine in the mixture decreased but IFT increased with further dilution of reservoir brine with DIW. A decreasing trend was observed in the behavior of water-advancing contact angle with brine dilution. However, a strange behavior of spreading of crude oil drop against brine on the dolomite surface (with large water-receding contact angles) was observed at certain brine dilutions. This spreading of crude oil appears to be related to interfacial tension in a manner similar to Zisman’s observations in solid–liquid–vapor systems. The use of surfactants to enhance oil recovery through reduction in IFT is well known in the industry. However, this study examines the capability of certain surfactants to alter wettability in addition to reducing IFT. For the Yates reservoir rock-fluids system, an ethoxy alcohol surfactant altered the strongly oil-wet nature (advancing angle of 158°) to water-wet (advancing angle of 39°) at a concentration of 3500 ppm. While the DDDC technique yielded significant changes in wettability due to surfactant addition, the Wilhelmy Plate technique remained insensitive throughout the range of surfactant concentrations. The practical significance of this study is that it identifies two simple modes through surfactant addition and brine dilution to alter wettability to minimize capillary trapping of oil.

A general dynamic surface adsorption equation Γ(t) for maximum bubble pressure method was derived by solving Fick’s diffusion equation for the bubbles under different initial and boundary conditions. Different from the planar surface adsorption(Ward-Tordai equation), the derived dynamic surface adsorption Γ(t) for the short time consists of two terms, one of them reflects the geometric effect caused by the spherical bubble surface. This kind of effect was discussed. The equilibrium surface tension γeq and the dynamic surface tension γ(t) of aqueous C10E8 (CH3(CH2)9(OCH2CH2)8OH) solution at temperature 25 °C were measured by means of Wilhelmy plate method and maximal bubble pressure method respectively. In the region of t→0 (short time limits) a good agreement of experimental results with the theory was reached and the adsorption was controlled by diffusion. However, for the long time limits, a mixed diffusion-kinetics controlled process was proved.

We have investigated Langmuir films at the water surface using grazing-incidence diffuse X-ray scattering. We show that beyond structural parameters like the film thickness and density, diffuse scattering also gives access to phase transitions and elastic properties (surface tension and bending rigidity). We find that the surface tension measured with X-rays is consistent with the Wilhelmy plate measurements, at least for tilted phases. The bending rigidity is found to be on the order of 20–30kBT whatever the phase. The underlying molecular mechanisms are discussed using different models.

Here, we present experimental surface-tension isotherms of mixed solutions of two surfactants, sodium dodecyl sulfate (SDS) and cocoamidopropyl betaine (Betaine), measured by means of the Wilhelmy plate method. The kinetics of surface-tension relaxation exhibits two characteristic time scales, which have been distinguished to determine correctly the equilibrium surface tension. The transition from the zwitterionic to the cationic form of Betaine is detected by surface-tension measurements. Synergistic dependence of the critical micellization concentration on the composition of the surfactant blend is established. The experimental surface-tension isotherms are fitted by means of the two-component van der Waals model, and an excellent agreement between theory and experiment was achieved. Having determined the parameters of the model, we calculated different properties of the mixed surfactant adsorption layer at various concentrations ofSDS, Betaine, and salt. Such properties are the adsorptions ofthe two surfactants, the surface dilatational elasticity, the occupancy of the Stern layer by bound counterions, the surface electric potential, and so forth. In particular, the addition of a small amount of Betaine to SDS significantly increases the surface elasticity. The results could be further applied to predict the thickness and stability of foam films or the size of the rodlike micelles in the mixed solutions of SDS and Betaine.

The effect of surface topography of a rolled sheet on the contact angle of test liquids of various surface tension was studied using the Wilhelmy plate technique. The contact angle is lower when the liquid front moves along the rolling lines than transverse to the rolling lines due to the capillary rise along the grooves formed by the rolling lines. The contact angle is proportional to the surface topography parameter A2, with a slope related to the surface tension of the test liquid. The observed phenomenon can be rationalized in terms of Cassie's theory, where the liquid spreading over the surface does not fill the entire topographic valleys, and this results in the formation of air cushions between the liquid and metal surfaces described by A2. The effect of surface topography on the contact angle was only slightly influenced by the velocity of liquid front motion.

Surfactant replacement therapy has a vital role in the management of respiratory distress syndrome (RDS). Several techniques and models have been largely used to investigate interfacial physico-chemical properties in vitro and to assist clinical efficiency of exogenous surfactant preparations (ESPs) in vivo. Among them are interfacial tensiometry (Langmuir balance coupled with Wilhelmy plate method for surface tension measurement) and black foam film (BFF) method for measuring the capability of ESPs for bilayer foam film formation. Here, we report some freshly established data from a comparative study of Exosurf, Survanta, Curosurf, Alveofact and clinical samples of tracheal aspirate (TA) of newborns with RDS treated with Curosurf. New observations concerning the properties of foam films of ESPs are also reported and discussed. Measured interfacial physico-chemical parameters prove “better” properties in vitro of the SP-B and -C containing preparations Curosurf and Alveofact. Their properties are similar, Alveofact showing a higher surface tension lowering capacity under dynamic conditions. A comparison with measured interfacial parameters of clinical samples shows that after treatment with Curosurf the phospholipid concentration in tracheal aspirates (367 μg/ml) is higher than the minimum phospholipid concentration for stable black film formation ( C t ) of all four ESPs studied, while before treatment this concentration (63 μg/ml) is lower than C t . Values of measured “dynamic” parameters of clinical samples after treatment with Curosurf approach those of the exogenous surfactant preparation itself.

In this study, the plasma polymerization of ethylene has been used to deposit a polyethylene (PE)-like thin layer on the surface of the selected expanded poly(tetrafluoroethylene) (ePTFE) films. To evaluate the activity of the PE-like surface, acrylic acid (AAc) graft polymerization was carried out for the pretreated films. The modified ePTFE films were characterized by X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopies. The surface morphologies of the films were investigated by scanning electron microscopy and atomic force microscopy, and the wettability was evaluated with the sessile drop method and Wilhelmy plate method. It was found that the PE-like surface of the plasma treated specimen can be further grafted by AAc implying that the deposited surface remained active sites. After grafting by AAc, the advancing contact angle (θ a ) and the receding contact angle (θ r ) decreased approximately 40° and 50°, respectively, exhibiting an improvement of the surface hydrophilicity for the modified ePTFE specimens. It was also found that the lap shear strength of the polyAAc–grafted ePTFE specimen, adhered between two stainless steel surfaces by a selected epoxy resin, was enhanced by approximately three times.

A principal conclusion drawn from observations of time- and concentration-dependent liquid–vapor (LV) interfacial tension γlv of a diverse selection of proteins ranging from albumin to ubiquitin spanning nearly three decades in molecular weight (MW) is that concentration scaling substantially alters perception of protein interfacial activity as measured by reduction in γlv. Proteins appear more similar than dissimilar on a weight/volume basis, whereas molarity scaling reveals a “Traube-rule” ordering by MW, suggesting that adsorption is substantially driven by solution concentration rather than diversity in protein amphilicity. Scaling as a ratio-to-physiological-concentration demonstrates that certain proteins exhibit the full possible range of interfacial activity at and well-below physiological concentration, whereas others are only weakly surface active within this range, requiring substantially higher solution concentration to achieve reduction in γlv. Important among this latter category of proteins are the blood factors XII and XIIa, assumed by the classical biochemical mechanism of plasma coagulation to adsorb to procoagulant surfaces, even in the presence of overwhelming concentrations of other blood constituents such as albumin and immunoglobulin that are shown by this work to be among the class of highly surface-active proteins at physiologic concentration. A comparison of pendant drop and Wilhelmy balance tensiometry as tools for assessing protein interfacial activity shows that measurement conditions employed in the typical Wilhelmy plate approach fails to achieve the steady-state adsorption condition that is accessible to pendant drop tensiometry. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 544–557, 2004