Liquid Oil That Flows in Spaces of Aqueous Foam without Defoaming

Ultrastable and Responsive Foams Based on 10-Hydroxystearic Acid Soap for Spore Decontamination

Currently, there is renewed interest in using fatty acid soaps as surfactants. Hydroxylated fatty acids are specific fatty acids with a hydroxyl group in the alkyl chain, giving rise to chirality and specific surfactant properties. The most famous hydroxylated fatty acid is 12-hydroxystearic acid (12-HSA), which is widely used in industry and comes from castor oil. A very similar and new hydroxylated fatty acid, 10-hydroxystearic acid (10-HSA), can be easily obtained from oleic acid by using microorganisms. Here, we studied for the first time the self-assembly and foaming properties of R-10-HSA soap in an aqueous solution. A multiscale approach was used by combining microscopy techniques, small-angle neutron scattering, wide-angle X-ray scattering, rheology experiments, and surface tension measurements as a function of temperature. The behavior of R-10-HSA was systematically compared with that of 12-HSA soap. Although multilamellar micron-sized tubes were observed for both R-10-HSA and 12-HSA, the structure of the self-assemblies at the nanoscale was different, which is probably due to the fact that the 12-HSA solutions were racemic mixtures, while the 10-HSA solutions were obtained from a pure R enantiomer. We also demonstrated that stable foams based on R-10-HSA soap can be used for cleaning applications, by studying spore removal on model surfaces in static conditions via foam imbibition.

Dynamics of Liquid Oil that Flows Inside Aqueous Wet Foam

Wet soap foam spontaneously imbibes liquid oil without defoaming when it is brought into contact. The kinetics behind this recently observed phenomenon was studied experimentally, with focus on the origin of the suction force and on the oil front dynamics. Using an aqueous foam with an air volume fraction slightly greater than the critical value ϕ_C, we show that the pumping pressure of oil and/or miscible liquid into the wet foam is attributed to the interfacial distortion of the bubble surfaces. Two distinct regimes along time t were observed in the oil imbibition dynamics. The proceeding oil front evolves with t^1/2 dependency in the early imbibition time in accordance with the classical theory of penetration of a porous medium, whereas it departs into t^1/3 at late imbibition time. The latter process is attributed to the elongation of an oil branch trapped inside the foam when pumping of the exterior oil has ceased.

Efficacy of the combined use of a mild foaming cleanser and moisturizer for the care of infant skin

Objective

Despite the application of skin care treatments, many infants have skin problems such as dryness and erythema. We proposed a new combination skin care for infants which consisted of a foaming cleanser with lower surfactant activity and moisturizers that contained pseudo-ceramide.

Subjects and methods

A total of 50 infants (age: 3–24 months) with insignificant levels of dry skin were enrolled in this usage trial. The parents washed the infants with the test cleanser while bathing and then applied the moisturizer (lotion or cream) containing pseudo-ceramide. Prior to and following the 4-week usage period, visual evaluation of the skin condition was conducted by a dermatologist, in addition to instrumental analysis.

Results

Erythema and papule, accompanied by dryness, were commonly observed at week 0. However, by week 4, these symptoms significantly improved; the condition of none of the subjects deteriorated. The number of infants with lower cutaneous barrier function and higher skin pH decreased. The parents of the infants recognized improvements in the skin symptoms and were appreciative of the test materials.

Conclusion

The combined usage of the foaming cleanser with lower surfactant activity and a moisturizer containing pseudo-ceramide may be effective in maintaining healthy infant skin and ameliorating the skin symptoms.

Stable oil-laden foams: Formation and evolution

The interaction between oil and foam has been the subject of various studies. Indeed, oil can be an efficient defoaming agent, which can be highly valuable in various industrial applications where undesired foaming may occur, as seen in jet-dyeing processes or waste water treatment plant. However, oil and foam can also constructively interact as observed in detergency, fire-fighting, food and petroleum industries, where oil can be in the foam structure or put into contact with the foam without observing a catastrophic break-up of the foam. Under specific physico-chemistry conditions, the oil phase can even be trapped inside the aqueous network of the foam, thus providing interesting complex materials made of three different fluid phases that we name oil-laden foam (OLF). In this review, we focus on such systems, with a special emphasis on dry OLF, i.e. with a total liquid volume fraction, ε smaller than 5%. We first try to clarify the physical and chemical conditions for these systems to appear, we review the different techniques of the literature to obtain them. Then we discuss their structure and identify two different OLF morphologies, named foamed emulsion, in which small oil globules are comprised within the network of the aqueous foam and biliquid foams, where the oil also comprised in the aqueous foam network is continuous at the scale of several bubbles. Last, we review the state of the art of their evolution in particular concerning topological changes, coalescence, coarsening and drainage.

Understanding about How Different Foaming Gases Effect the Interfacial Array Behaviors of Surfactants and the Foam Properties

In this paper, the detailed behaviors of all the molecules, especially the interfacial array behaviors of surfactants and diffusion behaviors of gas molecules, in foam systems with different gases (N2, O2, and CO2) being used as foaming agents were investigated by combining molecular dynamics simulation and experimental approaches for the purpose of interpreting how the molecular behaviors effect the properties of the foam and find out the key factors which fundamentally determine the foam stability. Sodium dodecyl sulfate SDS was used as the foam stabilizer. The foam decay and the drainage process were determined by Foamscan. A texture analyzer (TA) was utilized to measure the stiffness and viscoelasticity of the foam films. The experimental results agreed very well with the simulation results by which how the different gas components affect the interfacial behaviors of surfactant molecules and thereby bring influence on foam properties was described.

Capillary imbibition of aqueous foams by miscible and nonmiscible liquids

When put in contact with a large liquid drop, dry foams wick owing to surface-tension-driven flows until reaching equilibrium. This work is devoted to the dynamics of this imbibition process. We consider imbibition of both wetting or nonwetting liquid, by putting the dry foam into contact either with the foaming solution that constitutes the foam or with organic oils. Indeed, with the appropriate choice of surfactants, oil spontaneously invades the liquid network of the foam without damaging it. Our experiments show an early-time dynamics in t(1/2) followed by a late-time dynamics in t(1/4). These features, which differ from theoretical works predicting a t(1/3) dynamics, are rationalized considering the influence of the initial liquid fraction of the foam in the driving capillary force and the impact of gravity through the capillary-gravity equilibrium.