Foam drainage placed on a thin porous layer

Koursari, Nektaria; Arjmandi-Tash, Omid; Johnson, Phillip; Trybała, Anna; Starov, Victor

doi:10.1039/c8sm02559b

Cited by 13 publications

(12 citation statements)

References 39 publications

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“…For the kinetics of spreading for Newtonian liquids on thin porous substrates, the process is divided into two parts, fast spreading followed by a slow absorption. This is displayed theoretically in [14,35,36] and agrees with results from experimental investigations [14,27] (see Figures 3 and 4). Similar experimental work which agrees with the results shown in Figure 3 can be found in [37], where the contact angle of water droplets against time were tested on a OH-terminated self-assembled monolayer of thiol prepared on a gold-coated silicon wafer.…”

Section: Newtonian Liquids: Complete Wettingsupporting

confidence: 89%

“…As a result, a system of two ordinary differential equations were derived to describe the evolution on time of both radius of the droplet base (L(t)) and wetted area inside the thin porous substrate (l(t)). The system includes two parameters one which accounts for the effective lubrication coefficient of the liquid over the wet porous substrate and the other is a combination of permeability and capillary pressure inside the porous layer [14,35,36]. Both parameters were determined in independent experiments [14], after that the system of equations does not include any fitting parameters.…”

Section: Newtonian Liquids: Complete Wettingmentioning

confidence: 99%

“…In [14,35,36] the kinetics of spreading of a liquid droplet over the porous layer and imbibition into the layer was considered. A thin porous substrate is that has a thickness (∆) much smaller than the drop characteristic height (h * ) i.e., ∆<<h * .…”

Section: Newtonian Liquids: Complete Wettingmentioning

confidence: 99%

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Kinetics of Spreading over Porous Substrates

Johnson

Trybała

Starov

2019

Colloids and Interfaces

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The spreading of small liquid drops over thin and thick porous layers (dry or saturated with the same liquid) is discussed in the case of both complete wetting (silicone oils of different viscosities over nitrocellulose membranes and blood over a filter paper) and partial wetting (aqueous SDS (Sodium dodecyl sulfate) solutions of different concentrations and blood over partially wetted substrates). Filter paper and nitrocellulose membranes of different porosity and different average pore size were used as a model of thin porous layers, sponges, glass and metal filters were used as a model of thick porous substrates. Spreading of both Newtonian and non-Newtonian liquid are considered below. In the case of complete wetting, two spreading regimes were found (i) the fast spreading regime, when imbibition is not important and (ii) the second slow regime when imbibition dominates. As a result of these two competing processes, the radius of the drop goes through a maximum value over time. A system of two differential equations was derived in the case of complete wetting for both Newtonian and non-Newtonian liquids to describe the evolution with time of radii of both the drop base and the wetted region inside the porous layer. The deduced system of differential equations does not include any fitting parameter. Experiments were carried out by the spreading of silicone oil drops over various dry microfiltration membranes (permeable in both normal and tangential directions) and blood over dry filter paper. The time evolution of the radii of both the drop base and the wetted region inside the porous layer were monitored. All experimental data fell on two universal curves if appropriate scales are used with a plot of the dimensionless radii of the drop base and of the wetted region inside the porous layer on dimensionless time. The predicted theoretical relationships are two universal curves accounting quite satisfactorily for the experimental data. According to the theory prediction, (i) the dynamic contact angle dependence on the same dimensionless time as before should be a universal function and (ii) the dynamic contact angle should change rapidly over an initial short stage of spreading and should remain a constant value over the duration of the rest of the spreading process. The constancy of the contact angle on this stage has nothing to do with hysteresis of the contact angle: there is no hysteresis in the system under investigation in the case of complete wetting. These conclusions again are in good agreement with experimental observations in the case of complete wetting for both Newtonian and non-Newtonian liquids. Addition of surfactant to aqueous solutions, as expected, improve spreading over porous substrates and, in some cases, results in switching from partial to complete wetting. It was shown that for the spreading of surfactant solutions on thick porous substrates there is a minimum contact angle after which the droplet rapidly absorbs into the substrate. Unfortunately, a theory of spreading/imbibition over thick porous substrates is still to be developed. However, it was shown that the dimensionless time dependences of both contact angle and spreading radius of the droplet on thick porous material fall on to a universal curve in the case of complete wetting.

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Section: Newtonian Liquids: Complete Wettingsupporting

confidence: 89%

Section: Newtonian Liquids: Complete Wettingmentioning

confidence: 99%

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Kinetics of Spreading over Porous Substrates

Johnson

Trybała

Starov

2019

Colloids and Interfaces

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“…An extension of this theory and experimental verification was undertaken in [24] were foam drainage placed on thin porous substrates was investigated experimentally and theoretically verifying the three regimes discussed in [22]. This work leads to using porous media as a method to force drainage in a micro gravity environment [25] where the gravitational drainage is impossible and the drainage is forced by the capillary suction into the porous media.…”

Section: Introductionmentioning

confidence: 97%

“…In this investigation, the model was verified by experimental investigations. The new method for drying foams in microgravity conditions was suggested [24].…”

Section: Introductionmentioning

confidence: 99%

Foam Formation and Interaction with Porous Media

et al. 2020

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Foams are a common occurrence in many industries and many of these applications require the foam to interact with porous materials. For the first time interaction of foams with porous media has been investigated both experimentally and theoretically by O. Arjmandi-Tash et al. It was found that there are three different regimes of the drainage process for foams in contact with porous media: rapid, intermediate and slow imbibition. Foam formation using soft porous media has only been investigated recently, the foam was made using a compression device with soft porous media containing surfactant solution. During the investigation, it was found that the maximum amount of foam is produced when the concentration of the foaming agent (dishwashing surfactant) is in the range of 60–80% m/m. The amount of foam produced was independent of the pore size of the media in the investigated range of pore sizes. This study is expanded using sodium dodecyl sulphate (SDS), which has the same critical micelle concentration as the commercial dishwashing surfactant, where the foam is formed using the same porous media and compression device. During the investigation, it was found that 10 times the critical micelle concentration (CMC) is the optimum concentration for a pure SDS surfactant solution to create foam. Any further increase in concentration after that point resulted in no further mass of foam being generated.

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Formation of Sodium Dodecyl Sulfate Foams by Compression of Soft Porous Material

Johnson

Vaccaro

Starov

et al. 2021

J Surfact & Detergents

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Interaction of foams with porous materials is frequently observed in industry and nature. An example is the interaction of foam of a cleaning product with a sponge, which has been investigated previously in Johnson et al., Colloids Surfaces A, 2019, 579, June, p. 123569 with commercial dishwashing solution using a compression device with a sponge saturated with a surfactant solution. The purpose of this study is to investigate the same process using sodium dodecyl sulfate (SDS), which has the same critical micelle concentration (CMC) as the commercial surfactant used. It is found that SDS concentration 10 times the CMC is the optimum concentration for foam formation. Any further increase in concentration above 10 CMC does not result in further increase of foam mass. Although the concentration of the surfactant solution was the most important parameter, temperature and pH of the surfactant also influenced the foam generation. Increasing the temperature resulted in decreasing the mass of foam generated and pH 7 was found as the optimal pH for foam generation.

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Foam drainage placed on a thin porous layer

Abstract: A theory of foam drainage placed on thin porous layer is developed. The rate of foam drainage and imbibition inside the porous layer and the possibility of a build-up of a free liquid layer on the foam/porous layer interface are investigated.

Cited by 13 publications

References 39 publications

Kinetics of Spreading over Porous Substrates

Kinetics of Spreading over Porous Substrates

Foam Formation and Interaction with Porous Media

Formation of Sodium Dodecyl Sulfate Foams by Compression of Soft Porous Material

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