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Journal ArticleDOI

Effect of cosurfactant on the free-drainage regime of aqueous foams.

15 Dec 2005-Vol. 292, Iss: 2, pp 544-547

TL;DR: The results confirm that a drainage regime corresponding to a high surface mobility can indeed be found for such small bubbles, and show that an increase in the cosurfactant content can induce a transition to a low surface mobility drainage regime, evidencing that the relevant control parameter for drainage regimes includes both bubble size and interfacial contributions.

AbstractWe report results of drainage in aqueous foams of small bubble size D (D = 180 µm) prepared with SDS-dodecanol solutions. We have performed free-drainage experiments in which local drainage rates are measured by electrical conductivity and by light scattering techniques. We have investigated the role of the surfactant–cosurfactant mass ratio on the drainage regime. The results confirm that a drainage regime corresponding to a high surface mobility can indeed be found for such small bubbles, and show that an increase in the cosurfactant content can induce a transition to a low surface mobility drainage regime. We show that the transition is not linked to variations of the bulk properties, but rather to variations of the interfacial properties. However, the results show that the added amount of dodecanol to trigger the transition is quite high, evidencing that the relevant control parameter for drainage regimes includes both bubble size and interfacial contributions.

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Citations
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Journal ArticleDOI
Abstract: Even though foams have been the subject of intensive investigations over the last decades, many important questions related to their properties remain open. This concerns in particular foams which are stabilized by mixtures of surfactants. The present study deals with the fundamental question: which are the important parameters one needs to consider if one wants to characterize foams properly? We give an answer to this question by providing a measuring protocol which we apply to well-known surfactant systems. The surfactants of choice are the two non-ionic surfactants n-dodecyl-β-d-maltoside (β-C12G2) and hexaethyleneglycol monododecyl ether (C12E6) as well as their 1:1 mixture. Following the suggested protocol, we generated data which allow discussion of the influence of the surfactant structure and of the composition on the time evolution of the foam volume, the liquid fraction, the bubble size and the bubble size distribution. This paper shows that different foam properties can be assigned to different surfactant structures, which is the crucial point if one wants to tailor-make surfactants for specific applications.

50 citations


Cites background from "Effect of cosurfactant on the free-..."

  • ...In previous work, two different drainage regimes were identified which can be characterized with the same power law, namely e * t [27, 28]....

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  • ...For g[ 1 one deals with a mobile surface which corresponds to a plug like flow through the plateau borders, whereas g\ 1 indicates a rigid surface with a Poiseuille flow through the plateau borders [27]....

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Journal ArticleDOI
01 Mar 2010
TL;DR: A correlation of the structural properties of foam film and stability of real foams has been found and the formation of a gel-like network within the foam film coincides with the stability of the corresponding 3-D foams.
Abstract: Single foam films made from mixtures of nonaggregated proteins and protein aggregates have been studied using a thin film balance apparatus. Their features (heterogeneity, stability and resistance to pressure change) are dependent on the aggregate size and on the ratio between nonaggregated proteins and protein aggregates. A phase diagram of these foam films has been drawn and a correlation of the structural properties of foam film and stability of real foams has been found. In particular, the formation of a gel-like network within the foam film coincides with the stability of the corresponding 3-D foams.

45 citations


Journal ArticleDOI
Abstract: Foams produced with surfactant concentration below the Critical Micelle Concentration (CMC) are usually moderately stable due to high drainage rates and intense bubbles coarsening/coalescence. Aim of this work is to examine how such low surfactant concentration affects foam destabilization and elucidate the interplay between free drainage and bubble size variation. Foam destabilization experiments are conducted at varying SDS concentrations (below the CMC) where the evolution of liquid fraction and bubbles size is registered simultaneously. Instantaneous volume measurements of the drained liquid and the remaining foam yield the evolution of the global liquid fraction and drainage rate in the foam. Continuous electrical conductance measurements give the local liquid fraction and drainage rate in the foam. Microphotographs allow estimation of bubble size distribution and bubble population at regular time intervals. The present data show that the lifetime of moderately stable foams depend largely on surfactant concentration below the CMC but this effect does not scale linearly with surfactant concentration. Furthermore, measurements are fitted to semi-empirical expressions and are compared to a modified Leonard and Lemlich (L–L) drainage model that has been expanded to incorporate bubble size evolution. The latter is a rough approximation based on certain assumptions but it is a fair approach given the excessive difficulty of detailed numerical calculations. The comparison reveals the significant role of bubble size on the free drainage of moderately stable foams. Interestingly, incorporation of global liquid fraction data into the modified L–L model yields surface shear viscosity values in agreement with literature.

34 citations


Journal ArticleDOI
Abstract: Dispersions of air in gelatine solutions were experimentally investigated in a 2.75 mm circular vertical tube coupled to a microfluidic device. Air and gelatine solutions (1%, 3% and 5% w/w) were mixed in the microfluidic device to produce steady flows of microbubbles by controlling liquid and gas volumetric flow rates. A two-phase flow map and transition lines between flow regimes were examined. In the bubbling regime (e.g., low air fraction) it was possible to produce mono and polydispersed micron-size air bubbles of controllable sizes. In the foam regime (e.g., high air fraction) the foam structure mainly depended on the liquid flow rate. Moreover, uniform foams moved as rigid bodies along the capillary tube, lubricated at the wall by the gelatine solution.

26 citations


Journal ArticleDOI
Abstract: The study at hand investigates the influence of the composition of a surfactant mixture on the free drainage of the respective foams. The Foam Conductivity Apparatus (FCA) was used to study free drainage of foams of homogeneous initial liquid fraction einit. The foams were stabilized with mixtures of the non-ionic surfactant dodecyldimethyl phosphineoxide (C12DMPO) and the cationic surfactant dodecyl trimethylammonium bromide (C12TAB) at mixing ratios of C12DMPO:C12TAB = 1:0, 50:1, 1:1, 1:50 and 0:1. In all cases the liquid fraction e follows a power law with respect to time t, i.e. e ∼ tη with −1.0

24 citations


References
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Abstract: The Forces between Atoms and Molecules. Principles and Concepts. Historical Perspective. Some Thermodynamic Aspects of Intermolecular Forces. Strong Intermolecular Forces: Covalent and Coulomb Interactions. Interactions Involving Polar Molecules. Interactions Involving the Polarization of Molecules. van der Waals Forces. Repulsive Forces, Total Intermolecular Pair Potentials, and Liquid Structure. Special Interactions. Hydrogen-Bonding, Hydrophobic, and Hydrophilic Interactions. The Forces between Particles and Surfaces. Some Unifying Concepts in Intermolecular and Interparticle Forces. Contrasts between Intermolecular, Interparticle, and Intersurface Forces. van der Waals Forces between Surfaces. Electrostatic Forces between Surfaces in Liquids. Solvation, Structural and Hydration Forces. Steric and Fluctuation Forces. Adhesion. Fluid-Like Structures and Self-Assembling Systems. Micelles, Bilayers, and Biological Membranes. Thermodynamic Principles of Self-Assembly. Aggregation of Amphiphilic Molecules into Micelles, Bilayers, Vesicles, and Biological Membranes. The Interactions between Lipid Bilayers and Biological Membranes. References. Index.

18,041 citations


"Effect of cosurfactant on the free-..." refers background in this paper

  • ...In fact, the effect of cosurfactant is to change the shape and size of the micelles [12]....

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Book
01 Jan 1999
Abstract: PREFACE APPENDICES A. THE SHAPE OF SINGLE SOAP FILMS AND BUBBLES B. THE THEOREM OF LAMARLE C. BUBBLE CLUSTERS D. THE DECORATION THEORUM E. THE CONDUCTIVITY FORMULA OF LEMLICH F. THE DRAINAGE EQUATION G. PHYLLOTAXIS H. SIMULATION OF LIQUID FOAMS I. BIBLIOGRAPHY APPENDICES

1,250 citations


"Effect of cosurfactant on the free-..." refers background or methods in this paper

  • ...Firs we use electrical conductometry [1], via a set of electrode installed along the foam container....

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  • ...Foams are dispersions of gas bubbles in a liquid or s phase[1]....

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  • ...They evolve in time three mechanisms: coarsening, drainage, and film rup During coarsening, smaller bubbles dissolve, while big ones grow in size due to gas diffusion across the liq films [1]....

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Journal ArticleDOI
30 Jun 2000-Langmuir
Abstract: A new experimental method is presented using fluorescein dye to determine the spatial and temporal variations of the liquid volume fraction in aqueous foams This method is used for quantitative studies of liquid redistribution (drainage) in three types of experiments: forced, free, and pulsed drainage Characteristic quantities, such as the drainage velocity, show power-law dependences on experimental parameters that are inconsistent with traditional foam drainage models based on Poiseuille-type flow in the liquid-carrying channels (Plateau borders) of the foam To obtain a theoretical description, the foam drainage equation is generalized using an energy argument which accounts for viscous dissipation in both the channels and the nodes (or vertices, which are the junctions of four channels) of the liquid network Good agreement with results for all three types of drainage experiments is found when using this new model in the limit where the dissipation is dominated by the nodes

324 citations


Journal ArticleDOI

225 citations


"Effect of cosurfactant on the free-..." refers background in this paper

  • ...In fact, the effect of cosurfactant is to cha the shape and size of the micelles [12]....

    [...]


Journal ArticleDOI
Abstract: A theoretical model for interstitial liquid flow in a stationary or moving foam was devised by relating the physical structure of the foam to the physical properties of the surfactant and the foam movement. This was accomplished through a differential momentum balance within a typical capillary (Plateau border) of noncircular cross section with finite surface viscosity at its boundaries. Velocity profiles were then calculated and integrated numerically for the randomly oriented capillaries so as to obtain the overall liquid flow through the foam in terms of the pertinent variables. Results are presented in a form suitable for estimating concentrations and flow rates of product and waste streams in foam fractionation.

213 citations