Surface rheology and its relation to foam stability in solutions of sodium decyl sulfate

Hofmann, Matthias J.; Motschmann, H.

doi:10.1016/j.colsurfa.2017.04.028

Cited by 13 publications

(6 citation statements)

References 27 publications

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“…It has been observed in various studies that the viscosity of the foam mixture also plays an important role in the formation of air bubbles when mixing the reactants, and developing of cellular structure with the action of blowing agent. 25,27 The microstructure of the samples was analyzed with a Hitachi S4700 SEM. As shown in the SEM images of the cellular structure of samples A-1, B-1, and C-1 (Figure 4), it was noted that the samples with lower surface tension had smaller cell size.…”

Section: Density and Cell Structurementioning

confidence: 99%

Effects of surfactants on mechanical and thermal properties of soy-based polyurethane foams

Dhaliwal

Anandan

Bose

et al. 2020

Journal of Cellular Plastics

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Polyurethane foams are widely used for insulation applications due to their high insulation properties as compared to conventional materials such as extruded polystyrene foam and mineral wool. In this study, soy-based polyurethane foams were prepared using five different surfactants while keeping other components such as soy-based polyol, diisocyanate, catalyst, and blowing agent (water) constant. Prepared samples were tested for mechanical and thermal properties to evaluate the effect of different surfactants used in varying quantities. The morphology of the foam samples was observed using a scanning electron microscope. Seventeen fold reduction in the cell size was observed with an increase in the amount of surfactant from 0.5 to 5.0 g. Samples with higher amounts of surfactant also exhibited a higher number of closed cells. Better thermal insulation was observed for samples with 2.0 and 5.0 g of surfactant as compared to samples with 0.5 g of surfactant. A similar trend was observed in the mechanical strength, moisture absorbance, and density of the fabricated foam samples.

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Section: Density and Cell Structurementioning

confidence: 99%

Effects of surfactants on mechanical and thermal properties of soy-based polyurethane foams

Dhaliwal

Anandan

Bose

et al. 2020

Journal of Cellular Plastics

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“…Foaming, a typical effect associated with the use of surfactants, has long been the focus of research. , Foam is thermodynamically unstable, and foaming and foam stability are affected by a number of rheological properties, such as dynamic surface tension (DST), the viscosity of the lamellar phase, and viscoelasticity on the adsorption film of a surfactant. − Therefore, a more detailed understanding of these rheological properties will facilitate the control of foam properties. Polymers have been introduced into surfactant aqueous solutions to control foam properties; however, the interactions between polymers and surfactants in bulk solutions have been the main focus of research. − The surface dynamics and foam properties of polymer–surfactant mixtures have been attracting interest. − Petkova et al examined the influence of cationic and nonionic polymers (polyvinylamine and polyvinylformamide) on the foam properties of surfactants with different types of charges and reported the effects of a polymer on the adsorption film of the surfactant surface .…”

Section: Introductionmentioning

confidence: 99%

Effects of Polypropylene Glycol at Very Low Concentrations on Rheological Properties at the Air–Water Interface and Foam Stability of Sodium Bis(2-ethylhexyl)sulfosuccinate Aqueous Solutions

et al. 2020

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The present study investigates the effects of very low concentrations of polypropylene glycol (PPG) on the rheological properties of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) aqueous solutions at the surface for the precise control of foam properties. Langmuir trough experiments and Brewster angle microscopy (BAM) of the AOT monolayer on the surfaces of PPG aqueous solutions indicated that a very low concentration of PPG increased the number of AOT molecules at the surface. Viscoelastic behaviors at the surface and surface tension isotherms in mixed aqueous solutions of AOT and PPG revealed that AOT interacted with PPG in the surface and bulk phase. A modified Ross−Miles method was performed to assess the foam stabilities of AOT aqueous solutions with and without PPG. The stabilization of foam by PPG was attributed to the rheological properties of AOT aqueous solutions at the surface.

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“…Most of the time, these devices are operated at low frequency (ω/2π ≲ 1 Hz), in order to facilitate the accounting of bulk hydrodynamic effects in the determination of interfacial properties. Oscillations of a hemispherical bubble were used to investigate rheological interface properties in the range of 1–500 Hz. − Despite the high-frequency range considered, because of the small size of the bubble ( d ≈ 0.5 mm), the forcing frequency was negligible compared to those of the shape eigenmode (ω 2 /2π ≈ 10 3 Hz). The shape thus remained hemispherical, the interface experienced a uniform dilation, and inertia was considered to be negligible.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Dynamics and Rheology of a Crude-Oil Droplet Oscillating in Water at a High Frequency

et al. 2019

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We report investigations of a pendant diluted crude-oil droplet in water that is forced to oscillate at a frequency ω. The droplet interface contains a significant amount of surface-active agents and displays a marked viscoelastic rheology with elastic moduli larger than viscous ones. At a low frequency, fluid viscosity and inertia are negligible, which allows a direct determination of the dilatational interface rheology. At a large frequency, eigenmodes of inertial shape oscillations are excited. By decomposing the interface shape into spherical harmonics, the resonance curves of the inertial modes of the interface are determined, as well as the frequency and damping rate of each mode. These two parameters are of major importance for the prediction of the deformation and breakup of a droplet in any unsteady flow without any prior knowledge of either the chemical composition or the detailed rheological properties of the interface. Then, interfacial rheology is related to interface dynamics by solving the coupled dynamic equations for the two fluids and the interface. It turns out that the rheology of the interface is well described by an equivalent two-dimensional viscoelastic material, the elasticities and viscosities of which depend upon the frequency. A first significant result is that shear and dilatational elasticities are closely connected, as are shear and dilatational viscosities. This implies that intrinsic rheology plays a major role and that compositional rheology is either negligible or strongly coupled to the intrinsic one. A second major result is that, for moderately aged droplets (≤5000 s), the elasticity and viscosity at a high frequency (10−80 Hz) can be extrapolated from low-frequency measurements (≤1 Hz) by a simple power law of the frequency, ω z. The exponent z is related to the loss angle θ loss by a relation found in many previous low-frequency investigations of crude-oil interfaces: z = θ loss /2π. The present work thus extends classic observations obtained at a low frequency to a higher frequency range corresponding to the natural frequency of the droplets, where the droplet shape results from the balance between dynamic pressure and surface stresses and the interface involves simultaneous shear and dilatation. These results bring about serious constraints regarding the modeling of physicochemical underlying mechanisms and provide some insights for the understanding of the structure of crude-oil interfaces.

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Surface rheology and its relation to foam stability in solutions of sodium decyl sulfate

Cited by 13 publications

References 27 publications

Effects of surfactants on mechanical and thermal properties of soy-based polyurethane foams

Effects of surfactants on mechanical and thermal properties of soy-based polyurethane foams

Effects of Polypropylene Glycol at Very Low Concentrations on Rheological Properties at the Air–Water Interface and Foam Stability of Sodium Bis(2-ethylhexyl)sulfosuccinate Aqueous Solutions

Interfacial Dynamics and Rheology of a Crude-Oil Droplet Oscillating in Water at a High Frequency

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