Link between surface elasticity and foam stability

Georgieva, Daniela; Cagna, Alain; Langévin, D.

doi:10.1039/b822568k

Cited by 242 publications

(165 citation statements)

References 38 publications

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“…Moreover, Marangoni stresses arise when compressional or dilatational deformations drive gradients in surfactant concentration (and thus surface tension). The resulting dilatational surface elasticity resists surface area changes, slowing drainage and rupture of the thin fluid films between adjacent bubbles (4,5,(10)(11)(12)(13).…”

mentioning

confidence: 99%

Surface shear inviscidity of soluble surfactants

Zell

Nowbahar

Mansard

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

116

123

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Foam and emulsion stability has long been believed to correlate with the surface shear viscosity of the surfactant used to stabilize them. Many subtleties arise in interpreting surface shear viscosity measurements, however, and correlations do not necessarily indicate causation. Using a sensitive technique designed to excite purely surface shear deformations, we make the most sensitive and precise measurements to date of the surface shear viscosity of a variety of soluble surfactants, focusing on SDS in particular. Our measurements reveal the surface shear viscosity of SDS to be below the sensitivity limit of our technique, giving an upper bound of order 0.01 μN·s/m. This conflicts directly with almost all previous studies, which reported values up to 10 3 -10 4 times higher. Multiple control and complementary measurements confirm this result, including direct visualization of monolayer deformation, for SDS and a wide variety of soluble polymeric, ionic, and nonionic surfactants of high-and low-foaming character. No soluble, small-molecule surfactant was found to have a measurable surface shear viscosity, which seriously undermines most support for any correlation between foam stability and surface shear rheology of soluble surfactants.S urfactants facilitate the formation of foams and emulsions by reducing surface tension, thereby lowering the energy required to create excess surface area (1-3). These multiphase materials, however, are thermodynamically unstable, and coarsen through bubble or drop coalescence, as well as diffusive exchange between bubbles or drops (1, 4-6). Surfactants can additionally be used to control this coarsening rate, with effective foaming surfactants retarding coalescence, and defoamers speeding it. For example, coalescence may be slowed by repulsive forces between the surfactant monolayers adsorbed to either side of the (continuous) phase separating bubbles or drops. Ionic surfactants, for example, introduce electrostatic repulsions (1, 2, 5), whereas nonionic surfactants (e.g., polymers, proteins, or particles) provide steric barriers against coalescence (7-9). Moreover, Marangoni stresses arise when compressional or dilatational deformations drive gradients in surfactant concentration (and thus surface tension). The resulting dilatational surface elasticity resists surface area changes, slowing drainage and rupture of the thin fluid films between adjacent bubbles (4, 5, 10-13).Additionally, surfactant monolayers may exhibit nontrivial rheological responses. For example, the surface shear viscosity η S gives the excess viscosity associated with shearing deformations within the 2D surfactant monolayer. Because surfactant interfaces are inherently compressible, they may exhibit a surface dilatational viscoelasticity η D *, in addition to η S *, even under small-amplitude deformations. This contrasts with incompressible Newtonian liquids, which are well-described by a single scalar viscosity. Moreover, surface shear and dilatational viscosities need not have equal (14), or even compara...

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mentioning

confidence: 99%

Surface shear inviscidity of soluble surfactants

Zell

Nowbahar

Mansard

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

116

123

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“…High values of surface viscoelasticity can potentially lead to the suppression of marginal regeneration and a reduced rate of foam film drainage [24][25][26] and coalescence [3,12] therefore, a good correlation between the liquid film or foam stability and the surface viscoelasticity has been found [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. If the enhanced viscoelasticity is developed on airwater interface during foam generation (at surface ages < 1s), foamability can also be enhanced.…”

Section: Surface Viscoelasticitymentioning

confidence: 99%

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Wang

Nguyen

Farrokhpay

2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. • Antifoam efficacy of DOH and decreased bubble surface potential explain the decreased foamability of pre-CMC SDS-DOH solutions.• Complex effect of surfactant mixtures on foamability is demonstrated.4 AbstractConventional theories indicate that surfactant solutions with low surface tension, fast adsorption kinetics, and high interfacial viscoelasticity increase foamability. These theories are applicable to single surfactants of pre-CMC. Here, we examine whether these theories are applicable for surfactant mixtures. Specifically, we investigated the foamability of sodium dodecyl sulfate (SDS)-dodecanol (DOH) solutions. We found that the foamability of SDS-DOH solutions exhibited 'anomalies' that were unexplained by conventional theories. The remarkable decrease in the foamability of SDS solutions caused by the addition of DOH could not be easily explained by the theories of surface tension and surface viscoelasticity.Instead, we proposed alternative mechanisms to resolve these unexpected results. Below the DOH solubility limit, the replacement of SDS molecules by DOH molecules at the air-water interface results in a reduced surface potential, leading to a lower foamability. The antifoam effects of DOH droplets can account for the reduced foamability above this limit. This paper highlights the complex effect of surfactant mixtures on foamability.

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“…By far the most studied and well-understood foaming systems are those based on aqueous-based continuous media [1][2][3][7][8][9][10][11][12][13]. Generally two types of foam can be identified: short-lived foam whose stability is determined by the drainage rate between adjacent bubbles (e.g.…”

Section: Introductionmentioning

confidence: 99%

Non-Aqueous and Crude Oil Foams

Blázquez

Emond

Schneider

et al. 2013

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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D o s s i e rRe´sume´-Mousses non aqueuses et mousses pe´trolie`res -Les mousses produites a`partir de syste`mes non aqueux sont moins fre´quentes que les mousses a`base d'eau, mais elles jouent un roˆle important dans de nombreuses applications et proce´de´s industriels. La faible tension de surface des liquides a`base d'hydrocarbures limite l'adsorption des agents de surface classiques et par conse´quent diffe´rents compose´s et me´thodes doivent eˆtre conside´re´s afin de ge´ne´rer et de stabiliser les mousses a`base d'huile. De meˆme, le cassage des mousses non aqueuses inde´sirables ne´cessite des conside´rations spe´cifiques a`ces syste`mes. Les mousses de pe´trole pre´sentent un inte´reˆt particulier de par leur complexite´en raison de la grande varie´te´des compose´s et des gaz qui peuvent les constituer. Nous pre´sentons dans cet article un aperc¸u des principaux me´canismes reconnus comme importants pour la stabilite´des mousses non aqueuses avec une conside´ration toute particulie`re pour les mousses de pe´trole brut.Abstract -Non-Aqueous and Crude Oil Foams -Foams produced from non-aqueous media are less common than water-based foams but they play an important role in many industries and engineering processes. The low surface tension of hydrocarbon fluids limits the adsorption of common surface activity substances and different compounds and methods must be considered to generate and stabilize oil-based foam. Likewise, the destruction of unwanted non-aqueous based foam requires specific considerations not found with aqueous systems. Of particular interest are petroleum-based foams, which are highly complex due to the wide variety of compounds and gases that can be found. We provide an overview of the major mechanisms known to be important for non-aqueous foam stability with a spotlight on crude-oil foams.

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Link between surface elasticity and foam stability

Cited by 242 publications

References 38 publications

Surface shear inviscidity of soluble surfactants

Surface shear inviscidity of soluble surfactants

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Non-Aqueous and Crude Oil Foams

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