Simultaneous study of interfacial tension,surface tension,and viscosity of few surfactant solutions with survismeter

Surfaces and interfaces are receptive valuable significant property of chemical molecules due to their potential to develop several phenomena in a self‐controlled mechanism. Science of surfaces is vast and is being used industrially since time immemorial. Their accurate and simultaneous estimation is necessary; therefore, the survismeter was used for measuring them along with viscosity. Individually tensiometers, X‐ray reflective microscope, and viscometers are used for surface tension, interfacial tension, and viscosity, respectively. These devices are sophisticated, expensive, and individually consume much time and resources with poor reproducibility in measurements. Survismeter is an alternative device for similar measurements together with higher accuracies and reproducibility. It works on a principle of capillary flow and pressure gradient (PG) inside liquid‐holding and air‐filled bulbs. Several liquids have been used for study with ± 0.01 mN/m, ± 0.01 mN/m and ± 1 × 10^?5 N s/m² accuracies in respective data. Copyright © 2008 John Wiley & Sons, Ltd.     

Comparison of the capillary wave method and pressure tensor route for calculation of interfacial tension in molecular dynamics simulations

We have studied the calculation of surface and interfacial tension for a variety of liquid–vapor and liquid–liquid interfaces using molecular dynamics (MD) simulations. Because of the inherently small scale of MD systems, large pressure fluctuations can cause imprecise calculations of surface tension using the pressure tensor route. The capillary wave method exhibited improved precision and stability throughout all of the simulated systems in this study. In order to implement this method, the interface was defined by fitting an error function to the density profile. However, full mapping of the interface from coordinate files produced enhanced accuracy. Upon increasing the system size, both methods exhibited higher precision, although the capillary wave method was still more reliable. © 2013 Wiley Periodicals, Inc.     

An absolute droplet pressure interfacial tensiometer and its application to bituminous systems of vanishing density contrast

Experimental problems preclude or limit measurements of interfacial tension in bitumen or extra-heavy crude oil-containing systems when there exists a vanishing density difference between the phases. We describe a novel droplet pressure method that allows such measurements to be made. This method is based on a liquid/liquid adaptation of the capillary displacement differential maximum bubble pressure surface tension method of Schramm and Green [29]. In this method, interfacial tension is calculated from the difference between maximum droplet pressures reached at capillaries of differing internal radii, immersed to slightly different depths. The elimination of the influence of liquid densities allows the measurement of interfacial tensions without independently determining the liquid densities, and in particular, permits measurements in systems for which the density difference is vanishingly small. The absolute measuring technique is illustrated for several systems of pure and practical liquids. Received: 8 March 2000/Accepted: 30 May 2000     

Rheo-optical determination of the interfacial tension in a dispersed blend

In this work, we present two novel methods to determine the interfacial tension of a disperse polymer blend through rheo-optical measurements of flow-induced single drop distortions. A counter-rotating shearing device with transparent plates is used to measure drop distortions. The cell geometry allows for a top view of the deforming drop, i.e., along the velocity gradient direction. Such a view is the only possible option for all currently available commercial rheo-optical instruments. Two different quantities are monitored, namely, the drop axis along the vorticity direction, and the rotation period of the drop surface. We use drops of a polyacrilamide aqueous solution (a shear thinning liquid) immersed in a polyisobutene matrix. Experimental results are interpreted in terms of theories for Newtonian liquids, where the relevant parameter is the Capillary number. If an appropriate viscosity ratio is chosen, that accounts for the shear thinning behaviour of the drop phase, good agreement is found between measurements and theoretical predictions. As a result, a robust estimate of the blend interfacial tension, that makes use only of the information acquired from top view experiments, is obtained.     

Research for reducing minimum miscible pressure of crude oil and carbon dioxide and miscible flooding experiment by injecting citric acid isopentyl ester

The minimum miscible pressure is one of the key factors to realize miscible flooding. As the minimum miscible pressure in the research area is higher than the formation fracture pressure, miscible flooding cannot be formed. To address this problem, it is necessary to find a way to reduce the minimum miscible pressure. Citric acid isopentyl ester can not only be dissolved in crude oil, but also be dissolved in carbon dioxide. Therefore, citric acid isopentyl ester was chosen to reduce the minimum miscible pressure in this research. The effect of citric acid isopentyl ester on reducing the minimum miscible pressure was measured by the method of long slim tube displacement experiment. The minimum miscible pressure in the research area was 29.6 MPa. The experimental results show that the minimum miscible pressure could decrease significantly with increasing the injected slug size of citric acid isopentyl ester, but the decrease became smaller and smaller. The optimum injected slug size of the chemical reagent is 0.003 PV. Under the condition of the slug size, the minimum miscible pressure was 24.1 MPa. The reduction was 5.5 MPa. The reduction rate was 18.58%. The research results have important guiding significance for enhancing oil recovery in the research area.     

The effect of interfacial miscibility on the cell morphology of polyethylene terephthalate/bisphenol a polycarbonate blend foams

Annealing polyethylene terephthalate (PET)/polycarbonate (PC) blends enhance the transesterification reaction and increase the amount of copolymer at the interface of both polymers. The copolymer enhances the compatibility of PET with PC, because it contains both PET and PC blocks, which causes the interface between PET and PC to become fuzzy. When the PET/PC undergoes batch physical foaming with CO₂, the copolymer significantly changes the resulting cell morphology, that is, the annealing time. Before annealing or in the absence of the copolymer, bubble nucleation occurs and dominates growth at the interface. When the PET/PC blends are annealed, the interface impedes bubble nucleation and growth. The polymer is stretched at the interface by bubble growth, forming fibril‐like structures connecting two polymer domains at the interface. Increased annealing time causes the interface to become more homogeneous and makes heterogeneous bubble nucleation difficult. At higher copolymer concentrations, the interface of PET and PC becomes fuzzy and the cell morphology becomes like those of foamed homogeneous polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Measurement of the interfacial tension between polyethersulfone and a thermotropic liquid-crystalline copolyester

Due to the increasing interest in forming blends of liquid-crystalline polymers with conventional thermoplastics, it becomes important to determine the interfacial tension between two such polymers. A method for evaluating the interfacial tension between a thermotropic copolyester based on hydroxybenzoic and hydroxynaphthoic acid residues, and polyethersulfone is presented, based on the Fort and Patterson method. It is found that the value of the interfacial tension in the melt is much higher than is the case between conventional polymer pairs. It is suggested that this high value reflects an entropic effect due to the strong exclusion of the flexible coil polymer from the nematic melt. © 1993 John Wiley & Sons, Inc.     

Measuring the interfacial tension of polymers in the presence of an interfacial modifier: Migrating the modifier to the interface

Compared to the dynamic mixing process used in melt blending operations, most techniques for measuring the interfacial tension can be considered as virtually static. For this reason, in order to measure the interfacial tension of an A-B immiscible system in the presence of an interfacial modifier, the problem of migrating the modifier to the interface is a central issue. In this study, the influence of the addition of an interfacial modifier, a polyethylene copolymer ionomer, on the interfacial tension between two high-density polyethylenes and a polyamide is investigated. The breaking thread method is used and the interfacial tension is measured as a function of ionomer content. In order to enhance the likelihood of placing the modifier in closer proximity to the interface, various sample preparations are compared. In all cases, the interfacial tension significantly drops with increasing ionomer content and tends to a limiting value. It is shown, however, that the preparation of the system for the breaking thread experiment via coextrusion using a conical die brings the modifier in closest proximity to the interface. With this approach an additional 1.45 times reduction of the interfacial tension at 10% compatibilizer concentration (based on the mass of HDPE) is observed compared to the classical technique of preparation. Confirmation of this effect is demonstrated using X-ray photoelectron spectroscopy where analysis of the thread surface of the system prepared by coextrusion indicates a more than fourfold enrichment of interfacial modifier. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1947–1958, 1998     

Influence of hyperbranched polymers on the interfacial tension of polypropylene/polyamide‐6 blends

The compatibilizing effect of polypropylene (PP) grafted with hyperbranched polymers (PP–HBP) has been investigated in PP/polyamide‐6 (PA‐6) blends. Because of its high reactivity and diffusitivity, PP–HBP has been shown to be a more effective compatibilizer in decreasing the interfacial tension than the commonly used maleic anhydride–grafted polypropylene (PP–MAH). This article describes the influence of PP–HBP and PP–MAH on the interfacial tension between PP and PA‐6, as measured by the deformed drop‐retraction method (DDRM). Overall, PP–HBP yielded lower interfacial tension values between PP and PA‐6, which resulted in a finer particle size of the secondary phase. The time dependence of the interfacial tension can be monitored by DDRM, enabling evaluation of the diffusitivity and reactivity of the compatibilizer. A model based on particle coarsening has been developed to describe the time dependence of the interfacial tension. This model showed that the diffusitivity and reactivity for PP–HBP was higher than that of PP–MAH. Therefore, PP–HBP has strong potential as a compatibilizer in diffusitivity‐dependant processes such as film coextrusion and fusion bonding. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2069–2077, 1999     

pH dependence of the kinetics of interfacial tension changes during protein adsorption from sessile droplets on FEP-Teflon

Interfacial tension changes during protein adsorption at both the solid-liquid and the liquid-vapor interface were measured simultaneously by ADSA-P from sessile droplets of protein solutions on fluoroethylenepropylene-Teflon. Four globular proteins of similar size, viz. lysozyme, ribonuclease, -lactalbumin and Ca²⁺-free -lactalbumin, and one larger protein, serum albumin, were adsorbed from phosphate solutions at varying pH values (pH 3-12). The kinetics of the interfacial tension changes were described using a model accounting for diffusion-controlled adsorption of protein molecules and conformational changes of already adsorbed molecules. The contribution of conformational changes to the equilibrium interfacial pressure was shown to be relatively small and constant with respect to pH when compared to the contribution of adsorption of the protein molecules. The model also yields the diffusion relaxation time and the rate constant for the conformational changes at the interface. Around the isoelectric point of a protein the calculated diffusion relaxation time was minimal, which is ascribed to the absence of an energy barrier to adsorption. Energy barriers to adsorption become larger at pH values away from the isoelectric point and can therefore become rate-limiting for the adsorption process. The rate constants for conformational changes at the liquid-vapor interface were maximal around the isoelectric point of a protein, suggesting a smaller structural stability of the adsorbed protein. At the solid-liquid interface the rate constants were smaller and independent of pH. indicating that conformational changes more readily occur at the liquid-vapor than at the solid-liquid interface.     

Studies of synergism/antagonism for lowering dynamic interfacial tension in surfactant/alkali/acidic oil systems. 3. Synergism/antagonism in surfactant/alkali/acidic model oil systems

Experimental studies have been conducted to elucidate the mechanisms responsible for synergism/antagonism for lowering dynamic interfacial tension (IFT) in surfactant/alkali/hydrocarbon and surfactant/alkali/acidic model oil systems. Dynamic IFTs between hydrocarbon/acidic model oil and alkali/surfactant solutions were measured. We learned from our experimental results that alkali has the function of decreasing n(min) values of surfactant solutions. The synergism/antagonism for lowering the stable values of dynamic IFTs in surfactant/alkali/hydrocarbon and surfactant/alkali/acidic model oil systems depends on factors that can change the EACN/n(min) value, such as the oleic acid in the oil phase and the n(min) values of surfactant and alkali. A new explanation with respect to EACN/n(min) values is provided.     

Synergistic effect of mixed anionic and cationic surfactant systems on the interfacial tension of crude oil-water and enhanced oil recovery

Surfactant based enhanced oil recovery (EOR) is an interesting area of research for several petroleum researchers. In the present work, individual and mixed systems of anionic and cationic surfactants consisting of sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB) in different molar ratios were tested for their synergistic effect on the crude oil-water interfacial tension (IFT) and enhanced oil recovery performance. The combination of these two surfactant systems showed a higher surface activity as compared to individual surfactants. The effect of mixed surfactant systems on the IFT and critical micellar concentration (CMC) is strongly depends on molar ratios of the two surfactant. Much lower CMC values were observed in case of mixed surfactant systems prepared at different molar ratios as compared to individual surfactant systems. The lowest CMC value was found when the molar concentration of SDS was higher than the CTAB. When the individual and mixed surfacant systems were tested for EOR performance through flooding experiments, higher ultimate oil recovery was obtained from mixed surfactant flooding compared to individual surfactants. Combination of SDS and CTAB or probably other anionic-cationic surfactants show synergism with substantial ability to reduce crude oil water IFT and can be a promising EOR method.     

A simple derivation of Vonnegut's equation for the determination of interfacial tension by the spinning drop technique

A simple derivation of Vonnegut's equation for use in the determination of interfacial tension by the spinning drop technique is described. The derivation involves a cylindrical approximation and calculates the kinetic energy of rotation of the system from a consideration of its moment of inertia.     

The relative role of coalescence and interfacial tension in controlling dispersed phase size reduction during the compatibilization of polyethylene terephthalate/polypropylene blends

The breaking thread and the sessile drop methods have been used to evaluate the interfacial tension between a polypropylene (PP) and a polyethylene-terephthalate (PET). An excellent correlation was found between the two. The breaking thread technique was then used to evaluate the interfacial tension of these blends at various levels of a styrene-ethylene butylene-styrene grafted with maleic anhydride (SEBS-g-MA) compatibilizer. In order to evaluate the relative roles of coalescence and interfacial tension in controlling dispersed phase size reduction during compatibilization, the morphology of PP/PET 1/99 and 10/90 blends compatibilized by a SEBS-g-MA were studied and compared. The samples were prepared in a Brabender mixer. For the 10/90 blend, the addition of the compatibilizer leads to a typical emulsification curve, and a decrease in dispersed phase size of 3.4 times is observed. For the 1/99 blend, a 1.7 times reduction in particle size is observed. In the latter case, this decrease can only be attributed to the decrease of the interfacial tension. It is evident from these results that the drop in particle size for the 10/90 PP/PET blend after compatibilization is almost equally due to diminished coalescence and interfacial tension reduction. These results were corroborated with the interfacial tension data in the presence of the copolymer. A direct relationship between the drop in dispersed phase size for the 1/99 PP/PET blend and the interfacial tension reduction was found for this predominantly shear mixing device. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2271–2280, 1997     

Sequential injection analysis with dynamic surface tension detection High throughput analysis of the interfacial properties of surface-active samples

A sequential injection analysis (SIA) system is coupled with dynamic surface tension detection (DSTD) for the purpose of studying the interfacial properties of surface-active samples. DSTD is a novel analyzer based upon a growing drop method, utilizing a pressure sensor measurement of drop pressure. The pressure signal depends on the surface tension properties of sample solution drops that grow and detach at the end of a capillary tip. In this work, SIA was used for creating a reagent concentration gradient, and for blending the reagent gradient with a steady-state sample. The sample, consisting of either sodium dodecyl sulfate (SDS) or poly(ethylene glycol) at 1470 g mol⁻¹ (PEG 1470), elutes with a steady-state concentration at the center of the sample plug. Reagents such as Brij®35, tetrabutylammonium (TBA) hydroxide and β-cyclodextrin were introduced as a concentration gradient that begins after the sample plug has reached the steady-state concentration. By blending the reagent concentration gradient with the sample plug using SIA/DSTD, the kinetic surface pressure signal of samples mixed with various reagent concentrations is observed and evaluated in a high throughput fashion. It was found that the SIA/DSTD method consumes lesser reagent and required significantly less analysis time than traditional FIA/DSTD. Four unique chemical systems were studied with regard to how surface activity is influenced, as observed through the surface tension signal: surface activity addition, surface activity reduction due to competition, surface activity enhancement due to ion-pair formation, and surface activity reduction due to bulk phase binding chemistry.     

Dynamic surface tension of micellar solutions studied by the maximum bubble pressure method

A theoretical model for the dynamic surface tension of an air bubble expanding in surfactant solution is proposed. The model accounts for the effect of convection on the surfactant diffusion and the effect of expansion of the bubble surface during the adsorption of surfactant molecules. Assuming small deviation from equilibrium and constant rate of expansion, an analytical solution for the surface tension and the subsurface concentration as a function of time is derived. The parameters of the model are computed from experimental data for sodium dodecyl sulfate obtained by the maximum bubble pressure method.     

Dynamic surface tension of micellar solutions studied by the maximum bubble pressure method

A theoretical model for the dynamic surface tension of an air bubble expanding in micellar surfactant solution is proposed. The model accounts for the effect of expansion of the bubble surface during the adsorption of surfactant molecules (monomers) and the effect of disintegration of polydisperse micelles on the surfactant diffusion. Assuming small deviations from equilibrium and constant rate of expansion analytical expression for the surface tension and the subsurface concentration of monomers as a function of time is derived. The characteristic time of micellization is computed from the experimental data for two surfactants (sodium dodecyl sulfate and nonylphenol polyglycol ether) obtained by the maximum bubble pressure method.     

The measurement of dynamic surface tension by the maximum bubble pressure method

The principle of maximum pressure in a bubble for measurements of dynamic surface tension is realized in a fully automatically operating apparatus. The set-up yields data in the time interval from 1 ms up to several seconds and can be temperature controlled from 5° to 80°C. Experimental data obtained for different surfactants and gelatine in water and/or water/glycerine mixtures at different temperatures are discussed. A direct comparison with results from oscillating jet and inclined plate experiments shows excellent agreement.     

Dynamic surface tension of micellar solutions studied by the maximum bubble pressure method. 1. Experiment

The effect of the micelles on the dynamic surface tension of micellar surfactant solutions is studied experimentally by means of the maximum bubble pressure method. Different frequencies of bubbling ranging approximately between 1 and 30 s^–1 are applied. The time dependence of the surface tension is calculated using a dead time correction. Water solutions of two types of surfactants with different concentrations are investigated: sodium dodecyl sulfate and nonylphenol polyglycol ether. The surface tension relaxes more quickly in the presence of micelles. The characteristic times of relaxation of the surface tension seem to be in the millisecond range. The time constants observed experimentally are explained in terms of the theory of surfactant diffusion affected by micellization kinetics.     

Study of the dynamic interfacial tension at the oil/water interface

A review is given on three recently developed methods to measure the dynamic interfacial tension at the oil/water interface. These are respectively the dynamic drop volume method, the dynamic capillary method, and the (reversed) funnel method. For each method presented the basic principles are described and a few experimental results are given.Paper presented at the 7th International Conference on Surface Active Substances (Bad-Stuer, DDR, 25–30. April 1988).