Pendant drop method, surface tension

Recently, Samec et al. [38] have investigated the same system by the video-image pendant drop method. Surface tension data from the two studies are compared in Fig. 2, where the potential scale from the study [36] was shifted so that the positions of the electrocapillary maxima coincide. The systematic difference in the surface tension data of ca. 3%, cf. the dotted line in Fig. 2, was ascribed to the inaccurate determination of the drop volume, which was calculated from the shape of the drop image and used further in the evaluation of the surface tension [38]. A point of interest is the inner-layer potential difference A (pj, which can be evaluated relative to the zero-charge potential difference A cpp c by using Eq. 

In order to calculate polymer/filler interaction, or more exactly the reversible work of adhesion characterizing it, the surface tension of the polymer must also be known. This quantity is usually determined by contact angle measurements or occasionally the pendant drop method is used. The former method is based on the Young, Dupre and Eowkes equations (Eqs. 21,8, and 10), but the result is influenced by the surface quality of the substrate. Moreover, the surface (structure, orientation, density) of polymers usually differs from the bulk, which might bias the results. Accuracy of the technique maybe increased by using two or more liquids for the measurements. The use of the pendant drop method is limited due to technical problems (long time to reach equilibrium, stability of the polymer, evaluation problems etc.). Occasionally IGC is also used for the characterization of polymers [30]. 

The pendant drop method has been used to measure the interfacial tension at the surface between mercury and cyclohexane solutions of stearic acid at 30 and 50°C. 

To apply the sitting or pendant drop method to measure the surface tension of a liquid the drop must be large enough so that gravitation plays a significant role. Why ... 

The pendant drop method and the sessile drop methods for surface tension appear quite different, but are similar in principle. In each case a drop is formed which either sits on a plane surface (sessile, see Figure 3.10) or hangs as a pendant drop... 

Surface Tension Measurement. The surface tension of the surfactant solution was determined by means of the Dynamic Contact Angle Tester FIBRO DAT 1100 (FIBRO Systems, Sweden) using the pendant drop method. It was also an output of the ADSA captive bubble contact angle measurements with surfactant solutions. 

Pendant drop method of measuring surface tension Drop of liquid hangs from pipette the z axis is vertical, the x axis is horizontal, and R is the (maximum) radius of the drop. To obtain / , many values of the radii S S— 0 to R) are measured at heights z (z = 0 to R) above the apex of the drop 4> is the tangent angle at the radius S. 

The pendant drop method (Fig. 4.16) measures the contact angle 6 and drop radius R to determine the surface tension for any liquid surrounded by gas, or the interfacial tension between any two liquids A drop is hung from a syringe tip in air, and the interfacial surface tension J gl is... 

Methods used to measure interfacial tension are reviewed by Drelich, Fang, and White [ Measurement of Interfacial Tension in Fluid-Fluid Systems, in Encyclopedia of Surface and Colloid Science (Dekker, 2003), pp. 3152-3156]. Also see Megias-Alguacil, Fischer, and Windhab, Chem. Eng. Sci., 61, pp. 1386-1394 (2006). One class of methods derives intertacial tension values from measurement of the shape, contact angle, or volume of a drop suspended in a second liquid. These metho(Js include the pendant drop method (a drop of heavy liquid hangs from a vertically mounted capillary tube immersed... 

Variations in chemical composition and molecular structure can also have important repercussions on the surface energy of the material. Several techniques have been proposed for the experimental determination of surface tension, the sessile and pendant drop methods being the most promising and commonly used... 

In theory, every surface tension measurement method can be used to determine the interfacial tension between two liquids. However, the accuracy of these methods is reduced when applied to liquid-liquid interfaces, or when one or both of the liquids is viscous. In practice, the maximum bubble pressure and pendant drop methods are the most suitable, giving consistent and reliable values for interfacial tensions, although there is sometimes the... 

FIGURE 16,3-14 Surface tension of 4 x ICn4 kmol/m3 dodecylamine hydrochloride solution as a function of pH determined by pendant drop method, measured 15 s after Forming drop.9 (After R. W, Smith, personal communication, 1967.)... 

Pendant Drop Method A method for determining surface or interfacial tension based on measuring the shape of a droplet hanging from the tip of a capillary (in interfacial tension the droplet may alternatively hang upward from the tip of an inverted capillary). Also termed the hanging drop (or bubble) method. 

Surface tensions of both the ST copolymers in homopolymers and the PS-PTHF homopolymer blend were measured in argon by the pendant drop method described by Roe (5). 

DSS lowers the surface tension of liquids e.g. water and various electrolyte solutions. The effect of DSS on surface tension may be measured by a variety of methods however, the Pendant Drop Method (12) seems to be most satisfactory for measuring changes in surface tension. The effect of concentration of DSS on surface tension as determined by Pendant Drop Method is shown in Table VII. 

SURFACE TENSION OF DIOCTYL SODIUM SULFOSUCCINATE EY PENDANT DROP METHOD TEMPERATURE, 25°C. SURFACE AGE, 5 SECONDS ... 

Morita, A. T., Carastan, D. J., and Demarquette, N. R., Influence of drop volume on surface tension evaluated using the pendant drop method, Colloid Polym. Sci., 280,857-864 (2002). 

Surface and interfacial tensions of the two liquids were measured with a Kruss DSA 100 drop analyser system by the pendant drop method. The liquid was injected... 

Langmuir adsorption isotherm Pendant drop method Sanchez approximation Surface tension of polymer blends Surface tension of random copolymers... 

Surface tension was determined via the pendant drop method using a Kruss EasyDrop. The liquid was suspended from an 1832 pm needle with equatorial and neck diameters measured for the largest stable drop. The surface tension was calculated using the relationship ... 

Drops of liquids have held researchers interest for many years. As mathematical curiosities for famous early fluid dynamicists, the pendant drop from a capillary provided an interesting and practical challenge. Young (1805) and Laplace (1806) independently developed the theory of surface tension and drop formation while the first analytical solutions to their theory were completed by Gauss in 1830. Much of the early woik on pendant drops involved numerous methods involving the determination of drop volume or shape with experimental techniques and using the available theory to determine surface tension of the liquid-gas interface. These methods are well detailed in the works by Adamson, Padday, and Reed Hah. ITie studies of the early researches developed into the rich and diversified field of interfacial fluid dynamics. The advancement of theory and numerical techniques has steadily increased the ability of researchers to better understand and control interfacial behaviors. 

Abstract The interfacial properties of tracheal aspirate from infants with untreated neonatal respiratory distress syndrome (NRDS), and NRDS infants after therapy with the exogenous surfactant Curosurf were assessed. The interfacial characteristics of the aspirate (equilibrium surface tension, maximal and minimal surface tension during lateral compression-decompression cycles) were determined with the pendant drop method. Our results show that the tracheal aspirate of infants with untreated NRDS had high equilibrium, maximal and minimal surface tension values. In contrast, the samples from infants, treated with Curosurf , showed lower surface tension values, suggesting that the application of Curosurf improves the composition and the properties of the pulmonary surfactant in the infant lung. 

Keywords Alveolar surfactant Curosurf Pendant drop method Surface tension... 

In order to determine the infants lung maturity and the necessity of surfactant therapy it is of great importance to substantiate the functionality of the alveolar surfactant, derived via invasive techniques [13], Several techniques and models have been largely used to investigate inteifacial physicochemical properties in vitro and to assess clinical efficiency of ES in vivo the Langmuir monolayer technique in combination with Wilhelmy plate method for surface tension measurements and black foam film method for determination of the ability of ES for stable film formation [14]. The pendant drop method combined with the Axisym-metric Drop Shape Analysis (ADSA) has been also used for similar purposes [4,15-18]. 

Modern methods of measuring the surface tension include the pendant drop method, the sessile drop method, and others (7,8,15). These methods depend on the shape of a drop of the polymer or a bubble in it, and on the balance of surface tension and gravitational forces see Figure 12.3 (8). 

The shape adopted by a drop stems from a compromise between the effect of surface tension, which favors a sphere, and gravity (or any other force field), which will cause distortions. For any given situation, analyzing the shape of the drop ought to make it possible to extract the surface tension. Several methods currently used to measure surface (or interfacial) tensions are based on this principle, such as the sessile drop method or the pendant drop method. The latter is the most commonly used. ... 

Surface activity at the air-water interface of solutions of the oligomer salt is inferred from measurements of surface tension lowering. Typical data obtained from two refined molecular weight fractions are presented graphically in Figure 1. Surface tension is estimated by the pendant drop method with the aid of tables supplied by Adamson (4). 

Only methods based on drop profiles are suitable for both surface and interfacial tension measurements. These include the pendant drop method [125-127], the sessile bubble or drop method [128, 129], and the rotating drop or bubble method [130, 131]. These methods are independent of the solid-Uquid contact angle but require accurate knowledge of the density difference across the interface. The demand of accurate density data becomes even greater when the two phases have similar densities. The rotating drop or bubble method is particularly suited for the determination of very low surface and interfacial tensions. 

The most versatile, convenient, and reliable technique for determining the surface and interfacial tension of polymer melts is the pendant drop method [19, 20, 45, 54, 56, 122, 126, 127, 152-155]. The results obtained by the pendant drop method constitute the bulk of the available data [10, 120]. The method is... 

Determinations by Roe [154] and Wu [127, 152, 153] using the pendant drop method and by Hata and coworkers [128, 175] using the sessile bubble technique have yielded values for a number of polymer pairs as a function of temperature. Gaines [ 174] and Wu [ 10,120,176] provided extensive reviews of the early work in the area of surface and interfacial tension of polymer liquids and melts. 

Other techniques are of interest but will not be covered here. For example, emphasis is put on the pros and cons of the pendant drop technique by Ambwani and Fort [63]. The pendant drop method has been very laborious traditionally. A fas standard instrumentation using computer image analysis has been described by Hansen and Rodsrud [64]. The characterization of monolayers can be carried out by this technique. For example, Li et al. described the required equipment and the application of the pendant drop technique to measure the surface tension of a insoluble monolayer covered onto a water drop surface [65]. 

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