Stability Of Aqueous Foams Research Articles

Characterization of aqueous foams of alkyl polyglycoside, GreenZyme, alpha-olefin sulfonate, and cetyltrimethylammonium bromide in the presence of divalent ions

In this study, the impacts of divalent ions (calcium and magnesium) on aqueous foam stability and its rheological properties are investigated. A biodegradable surfactant of alkyl polyglycoside, (APG) and a commercial enzyme (GreenZyme, GZ) are used and their performance were compared with synthetic surfactants of alpha-olefin sulfonate (AOS) and cetyltrimethylammonium bromide (CTAB). The findings of the study revealed that the stability of all foams decreased with increasing concentrations of divalent ions, GZ recorded the lowest foam stability in the presence of the two ions and precipitation occurred in the AOS solution. On the other hand, foams generated by APG achieved the highest stability and the foams generated by CTAB showed the second highest stability among the foaming agents. Through rheological analyses, APG and CTAB exhibited shear thinning behaviour and their behaviour were modelled using a power law model in which the model can incorporate the effects of temperature and salinity.

Effects of Clay Contamination on the Stability of Aqueous Foams at High Pressure

Summary Because of its low density, high viscosity, and good hole-cleaning performance, foam is used in the industry as a drilling and completion fluid. Due to these unique properties, foam can be applied in underbalanced drilling. After an extended period, however, the degradation of its thermodynamically unstable structure leads to the gradual loss of these valuable properties. While a number of research studies have been performed to investigate foam flow behavior, more is needed to know about their drainage characteristics and stability at high pressure. The primary goal of this investigation is to examine the effects of clay contaminants on the drainage of foam at high pressure. Moreover, the results and findings of this study not only show the effect of clay contaminants on foam stability but also help develop clay-based stable foam formulations without using chemicals that have the potential to contaminate groundwater or seawater. This paper shows the findings of an investigation on the aqueous foam stability in the presence of clay (bentonite and kaolinite) contaminants. Experiments were conducted at ambient temperature while varying foam quality and clay concentration at a constant pressure of 6.8 MPa. During the study, the foam was created in a flow loop. After generation, its rheology and stability were measured using a pipe viscometer and a vertical test tube (column). The hydrostatic pressure profile in the column was measured with time to assess foam drainage. The results show that clay type and concentration affect aqueous foam drainage and flow behavior. The impact of clay on these foam properties is controlled by foam quality. Adding more than 2.5% bentonite considerably enhanced foam stability and viscosity. In contrast, the impacts of kaolinite on these foam properties were minimal at the same concentration. The drainage became negligible when 5% bentonite was added to the foam. However, at a reduced concentration (2.5%), bentonite addition was only an effective stabilizer for low-quality foam (40%). Microscopic examination of the foams prepared under ambient conditions demonstrated the accumulation of colloidal particles at the plateau borders and nodes that block the drained liquid flow and reduce drainage.

Size-structure-property relationship of wood particles in aqueous and dry insulative foams

Three size-fractionated samples of pine beetle-killed wood particles were used to prepare lightweight insulative foams. The foams were produced by foam-forming an aqueous slurry containing wood particles (125–1000 μm), a polymer binder, and surfactant, followed by oven drying. The effect of wood particle size on the aqueous foam stability, structure, and performance of insulative foams was investigated. While all aqueous foams were highly stable, aqueous foam stability increased with decreasing particle size. For dry foams, the cell size distribution was similar for all particle sizes as it was primarily controlled by the surfactant; differences occurred within the cell wall structure. A size-structure-property relationship was identified using x-ray micro-computed tomography where smaller particles produced lighter cell wall frameworks, leading to lower densities and decreased thermal conductivity and compressive strength. Larger particles produced denser cell wall frameworks that were more resistant to deformation, although all dry foams had sufficient mechanical properties for use as insulation panels. Thermal conductivity for all wood particle size-fractionated samples was <0.047 W m−1 K−1 making the foams similar to expanded polystyrene/polyurethane and supporting their use as thermal insulation in buildings.

The influence of bilayer fluidity on the stability of aqueous foams made from surfactant vesicle dispersions

The structures formed by surfactant self-assembly in bulk can affect the surface properties of the resulting solutions, thus impacting foam formation and stability. Bilayer fluidity in surfactant vesicle dispersions is expected to influence molecular packing at the surface and the viscosity of the continuous phase, thereby affecting the quality of the aerated dispersions. Hence, it should be possible to control foam characteristics by tuning the surfactant organization within bilayers. In this work, surfactant vesicle dispersions were prepared in the presence of an unsaturated fatty alcohol, at different concentrations, used to induce variations in bilayer fluidity at room temperature. A variety of experimental techniques was employed to characterize both bulk and surface properties of the vesicle dispersions and the resulting foams prepared by the hand-shaking method. It was seen that added fatty alcohol reduced the packing of surfactant in the bilayers. All tested dispersions presented similar foaming ability, although foams produced from vesicles with highly ordered surfactant chains were remarkably more stable, making this the first direct evidence of bilayer fluidity impact on foam stability. Such an enhanced stability was attributed to the formation of a dense surfactant film at the surface of the bubbles and to the low rate of liquid drainage in the foams, thus opening new possibilities of accurately controlling foam stability in products in which surfactant vesicles can be found.

Enhanced foamability and stability of aqueous foams through novel pickering fat globules formulated with solid lipid particles

Pickering fat globules (PFGs), known for their remarkable stability via the Pickering effect, eco-friendliness, and ability to carry hydrophobic flavors and nutrients, play a pivotal role in the advancement of food foam systems. This study investigates highly unsaturated and exceptionally stable aqueous foams stabilized by PFGs with interfacial activity. These PFGs are derived from two types of solid lipid particles (SLPs): fully hydrogenated soybean oil with sodium caseinate (FHSO-SC-SLPs-PFGs) and glyceryl stearate citrate (GSC-SLPs-PFGs), which were formulated with varying SLPs concentrations (0.5 wt%, 2.5 wt% and 5 wt%) while coating 10 wt% and 20 wt% oil droplets. Remarkably, 0.5 wt% SLPs could accommodate up to 20 wt% of low-melting-point liquid oil, enhancing the unsaturation of PFGs. GSC-SLPs-PFGs generated foams with overrun values reaching up to 235%, exhibiting stability for at least 40 days. In contrast, foams derived from FHSO-SC-SLPs-PFGs, with the highest overrun value of 145%, remained stable for only 2 h. Compared with FHSO-SC-SLPs-PFGs, GSC-SLPs-PFGs exhibited superior foaming performance and stability attributed to their properties such as smaller particle size, enhanced hydrophilicity, higher apparent viscosity, increased surface potential, and superior surface tension reduction. Furthermore, increasing the concentration of SLPs and/or reducing the oil phase can also improve the properties of SLPs-PFGs, resulting in greater foamability and foam stability. Surface dynamic adsorption, interfacial shear rheology, and microstructural observations revealed robust adsorption of all SLPs-PFGs at the air-liquid interface, indicative of pronounced Pickering stabilization, with GSC-SLPs-PFGs also exhibited three-dimensional network structure. These SLPs-PFGs stabilized foams presented heightened stability and reduced saturated fat content, paving the way for novel and healthier foam-based food products.

Stability of CO2/N2 foam generated in CaCO3 nanoparticle/CTAB aqueous dispersion

In an attempt to design a thermally stable foam with carbon sink attributes, the foamability and stability of aqueous foams generated from dispersions of CaCO3 nanoparticles (NPs) and hexadecyltrimethylammonium bromide (CTAB) are investigated. Much higher foam stability is reported here relative to literature. When compared to CTAB alone, the addition of CaCO3 NPs increases foam half-life from 5–7 min to 5–6 h in the presence of pure N2 and a gas mixture of CO2 and N2, respectively. Although there is no evidence of CTAB adsorption onto the NPs, the presence of CTAB is crucial to create the initial foam structure that is later stabilized by a network of NPs. Relative to CTAB alone, CaCO3 NPs/CTAB foam displays a higher bubble density and an average bubble size reduction of 67 %. In addition, CaCO3 NPs/CTAB foam is 20-fold more stable at 80 °C.

Synergistic effects between anionic surfactant SDS and hydrophilic silica nanoparticles in improving foam performance for foam flooding

In foam flooding, foams stabilized by conventional anionic surfactants are usually raptured in contacting with crude oil, which behaves as a strong defoamer. In this article the synergistic effects between anionic surfactant SDS and negatively charged hydrophilic silica nanoparticles in stabilization of aqueous foams were examined. The results show that in either deionized (DI) water at 25 °C or Daqing simulated connate (SC) water with a total salinity of 6,778 mg/L at 45 °C, in absence of oil adding low concentration of silica nanoparticles into the SDS aqueous solutions can improve the foam performance of SDS mainly by increasing foam stability, as indicated by a synergistic effect index Se(d/s) (ratio of the composite foaming index of dispersion to that of solution) of 2.7 to 2.8. In presence of oil the foam performance of SDS in SC water at 45 °C can still be improved as indicated by an increased Se(d/s) of 3.7, but the maximum composite forming index is catastrophically reduced from 3222 Ls in absence of oil to 470 Ls in presence of oil. As similarly charged nanoparticles the silica nanoparticles do not adsorb at gas/liquid or oil/water interface to stabilize Pickering foams or Pickering emulsions but can improve emulsification of the oil, and the emulsified oil droplets together with the silica nanoparticles distribute in aqueous lamellae enhancing liquid viscosity and slowing down the liquid drainage in the foams. However, this effect weakens at high surfactant concentration, and addition of silica nanoparticles does not significantly reduce the interfacial tensions involved. The Enter (E), Spreading (S) and Bridging (B) coefficients of the oil in the foam systems are therefore still positive. The defoaming action of the oil in this system is not eliminated by only partially inhibited by addition of silica nanoparticles.

Tailoring Amphiphilic Copolymers for Improved Aqueous Foam Stability.

Amphiphilic copolymers of various-molecular-weight (MW) poly(ethylene glycol) (PEG) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The first PEG series, poly(ethylene glycol)monomethacrylate (PEGMA, average Mn 200 and 400 MW), contained an -OH terminal group, and the second series, poly(ethylene glycol) monomethyl ether monomethacrylate (PEGMMA, average Mn 200, 400, and 1000 MW), possessed an -OCH3 terminal group. A total of five PEG-functionalized copolymers contained the same hydrophobic monomer, butyl acrylate (BA), and were successfully reproduced via a one-pot synthesis. The resulting PEG-functionalized copolymers provide a systematic trend of properties including surface tension, critical micelle concentration (CMC), cloud point (CP), and foam lifetime based on the average MW of the PEG monomer and final polymer properties. In general, the PEGMA series produced more stable foams with PEGMA200 demonstrating the least change in foam height with time over a 10 min period. The important exception is that at elevated temperatures, the PEGMMA1000 copolymer had longer foam lifetimes. The self-assembling copolymers were characterized by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (NMR), attenuated total reflection Fourier transform infrared (FTIR-ATR), CMC, surface tension, dynamic light scattering (DLS), as a foam using a dynamic foam analyzer (DFA), and foam lifetime at ambient and elevated temperatures. The copolymers described highlight the importance of the PEG monomer MW and terminal end group for surface interaction and final polymer properties for foam stabilization.

Enhancing the Aqueous foam Stability Using Nanoparticles: A Review

Today, there is much demand for stabilised foam globally. The primary concern for surfactant foam in enhanced oil recovery (EOR) is its foam stability. The applications of surfactant-nanoparticles mixture for foam stabilisation have been increased significantly because of the combined role of nanoparticles (NPs) and surfactant in the mechanism of foam stabilisation. This paper focuses on enhancing the aqueous foam stability by NPs and respective mechanisms of the aqueous foam stability. Nanoparticles have unique physical and chemical properties, so they alter the surface and rheological properties of the fluid system. It is the outcome of various research that nanoparticles adhere to the gas-liquid interface of the foam to improve foam stability. Therefore, NPs can enhance the stability of surfactant-stabilised foams. The use of nanoparticles increases foam stability, but its drawbacks cannot be ignored. Probable, the synthesis and production technique of nanoparticles is steeply-priced, which have to be made cheap using cutting-edge technology.

"Foam Marble" Stabilized with One Type of Polymer Particle.

There has been increasing interest in colloidal particles adsorbed at the air-water interface, which lead to stabilization of aqueous foams and liquid marbles. The wettability of the particles at the interface is known to play an important role in determining the type of air/water dispersed system. Foams are preferably formed using relatively hydrophilic particles, and liquid marbles tend to be formed using relatively hydrophobic particles. In this study, submicrometer-sized polystyrene particles carrying poly(N,N-diethylaminoethyl methacrylate) hairs (PDEA-PS particles), which are synthesized by dispersion polymerization, are demonstrated to work as a particulate stabilizer for both aqueous foams and liquid marbles. A key point for the hydrophilic PDEA-PS particles to stabilize both aqueous foams and liquid marbles, which have been generally stabilized with hydrophilic and hydrophobic particles, respectively, is the wetting mode of the particles with respect to water. The flocculates of PDEA-PS particles adsorb to the air-water interface from the aqueous phase to stabilize foam in a Wenzel mode, and the dried PDEA-PS particles adsorb to the interface as aggregates from the air phase to stabilize liquid marbles in a metastable Cassie-Baxter mode. On the basis of the difference in the wetting mode, stabilization of an air-in-water-in-air multiple gas-liquid dispersed system, named "foam marble", is realized. After the evaporation of water from the foam marble, a porous sphere is successfully obtained with pore sizes of a few tens of micrometers (reflecting the bubble sizes) and a few tens of nanometers (reflecting the gap sizes among the PDEA-PS particles).

Responsive Material and Interfacial Properties through Remote Control of Polyelectrolyte-Surfactant Mixtures.

Polyelectrolyte/surfactant (P/S) mixtures find many applications but are static in nature and cannot be reversibly reconfigured through the application of external stimuli. Using a new type of photoswitchable surfactants, we use light to trigger property changes in mixtures of an anionic polyelectrolyte with a cationic photoswitch such as electrophoretic mobilities, particle size, as well as their interfacial structure and their ability to stabilize aqueous foam. For that, we show that prevailing hydrophobic intermolecular interactions can be remotely controlled between poly(sodium styrene sulfonate) (PSS) and arylazopyrazole tetraethylammonium bromide (AAP-TB). Shifting the chemical potential for P/S binding with E/Z photoisomerization of the surfactants can reversibly disintegrate even large aggregates (>4 μm) and is accompanied by a substantial change in the net charging state of PSS/AAP-TB complexes, e.g., from negative to positive excess charges upon light irradiation. In addition to the drastic changes in the bulk solution, also at air-water interfaces, the interfacial stoichiometry and structure change drastically on the molecular level with E/Z photoisomerization, which can also drive the stability of aqueous foam on a macroscopic level.

Effects of Fe (II) on stability of aqueous foam prepared by hydrolyzed rice protein in the presence of oil

Fluorinated foams have outstanding stability in contact with oil, but the use of fluorocarbon surfactants has been restricted due to toxicity and environmental persistence. The hydrolyzed protein may be a potential non-fluoro replacement for fluorocarbon surfactants to stabilize aqueous foams. In this work, the effects of Fe (II) on the stability of aqueous foam prepared by hydrolyzed rice protein (HRP) in the presence of oil were systematically studied. Three model foams made from surfactants were used for comparison in terms of their stability. Multiscale approaches including small-angle X-ray scattering (SAXS) technique, surface tension measurements and microscopic technique were employed to investigate the interaction between Fe2+ and HRP as well as the foam stabilization mechanism. The results show that the foam stabilized by HRP solely is unstable in contact with oil compared to the fluorinated foams but the stability of HRP foam can be remarkably enhanced after adding FeSO4. The addition of FeSO4 allows the formation of HRP-Fe2+ complexes in solution to stabilize foam and SAXS results reveal the interaction between Fe2+ and HRP is well described by the Beaucage model. The improved foam stability is related to the adsorption of HRP-Fe2+ complexes at the air-liquid interface, which protects the bubbles against coalescence and rupture, rather than lowering the surface tension. The proposed formulation can be a potential fluoro-replacement, which provides better foam stability than silicone and glucoside surfactants.

Effects of surfactants on aqueous foams properties: a step towards mineral foams

This study focus on foaming properties of three surfactants: α-olefin sulphonate sodium salt (Hostapur OSB), Trimethyl tetradecyl ammonium bromide (Cetrimide) and Hexadecyl trimethyl ammonium bromide (CTAB) usable for mineral foaming. The ability of these surfactants to reduce surface tension is evaluated. Foamability and foam stability of aqueous foams made up with these surfactants are assessed at different concentrations, using the Dynamic Foam Analyzer providing parameters which describe the foaming and decay phases. They considerably depend on the type of surfactant and its concentration. By analysing the bubble size distribution, the relationship between the stability and the foam structure can be observed. The Hostapur OSB appears to be the most efficient surfactant in terms of stability and foamability, representing the thinnest foam structure and the highest characteristic times (deviation, transition and half-life) at CMC (critical micelle concentration).

Effects of anti-clay agents on bubble size distribution and stability of aqueous foam under pressure for earth pressure balance shield tunneling

The earth pressure balance (EPB) shield inevitably encounters heavy clay soils during tunneling, which form mud cakes on the cutter head. To prevent this, it is necessary to add anti-clay agents to foam agents. However, the effect of anti-clay agents on foam properties and its optimal concentration under different conditions remain unknown. In this study, the bubble size distribution and half-life of foam produced by foam agents and anti-clay agents under pressure were measured and analyzed. The results show that the mean bubble radius decreases with the addition of anti-clay agents at 0 bar but increases at a pressure of 1 bar or 2 bar. The anti-clay agents weaken the stability of foam, and optimal concentrations of anti-clay agents for different test pressures are proposed. The test results obtained provided guidance for selection of the optimal concentration of anti-clay agents to be used in EPB shield tunneling.

The Effect of Salt on Stability of Aqueous Foams

The properties of foams are often affected by environmental variables such as salt contamination. The objective of this study is to investigate the impact of salt on the drainage behavior of aqueous foams. To accomplish this objective, drainage experiments were conducted on aqueous foams. Test variables were foam quality (40–65%), and salt content (0% to 18%), and type. To investigate drainage, the foam was generated in a flow loop and trapped in a vertical test section. Then, the pressure profile in the foam column was measured using ten pressure sensors. Foam drainage is determined as a function of time using measured pressure profiles. The results show that the drainage of NaCl-containing foams decreased with foam quality, whereas the CaCl2-containing foams did not exhibit a clear trend with foam quality. The effect of salt content on foam rheology was minimal.

Egg white protein microgels as aqueous Pickering foam stabilizers: Bubble stability and interfacial properties

The aim of this study was to design and characterize aqueous foams stabilized by egg white protein microgels (EWPM) and compare their stability with conventional foams stabilized by egg white protein (EWP). Sub-micron sized EWPM (hydrodynamic diameter = 359 ± 21 nm) were designed using a top-down approach involving the formation of a thermally-crosslinked egg white protein hydrogel (90 °C/30 min, pH 7.0) followed by controlled shearing using jet homogenization (300 bar, two passes). Microstructural evaluation at multiple length scales (confocal laser scanning microscopy and cryogenic scanning electron microscopy) indicated that the EWPM stabilized the aqueous foams via a Pickering-type mechanism. Foamability was higher in EWP-stabilized foams compared to EWPM-stabilized foams, irrespective of the protein concentrations tested (0.5–3.0 wt%). However, EWPM-stabilized foams exhibited higher stability to disproportionation over long periods (p < 0.05), even though the initial air bubble size was smaller than with EWP. Bubble coalescence experiments also confirmed that the fraction of the coalescence was much lower in EWPM systems as compared to the EWP counterparts. Changes of surface shear viscosities of EWP at the air-water interface indicated that EWP films were more brittle, exhibiting shear thinning during the measurements, whereas the viscosities of the EWPM films were independent of shear after 24 h of ageing. In summary, our study demonstrates for the first time that microgels of EWP have distinct advantages over EWP itself in terms of generating edible foams with ultra-high stability against disproportionation.

The effect of silica nanoparticles on the stability of aqueous foams

An experimental study was performed on aqueous foams stabilized by a mixture of hexadecyltrimethylammonium bromide (HTAB) and negatively-charged silica nanoparticles. The effects of the nanoparticles on the stability of foams at different HTAB concentrations were investigated. The foams were characterized by measuring their foamability and stability. Rheological behavior of the foams was also studied. Furthermore, rheology of the air–water interfaces was studied in the linear and nonlinear deformation ranges. The thickness of the monolayer at the interface was measured. The actual size of the silica nanoparticles at the air–water interface was measured by transmission electron microscopy. Based on these measurements, the interaction between the monolayers across the foam film containing HTAB and nanoparticles was investigated. Smaller silica nanoparticles (i.e. diameter less than 10 nm) adsorbed at the air–water interface whereas the larger particles remained in the sub-phase or in the bulk liquid phase. It was found that these nanoparticles strongly influenced the foaming behavior at the low HTAB concentrations (i.e. below the CMC). A Langmuir-type monolayer was formed. The presence of the nanoparticles at the air–water interface provided mechanical strength to the foam films and prevented their rupture. This hindered coalescence of the bubbles, which resulted in a stable foam.

PROPIEDADES MECÁNICAS INTERFACIALES EN EQUILIBRIO DE MONOCAPAS DE PUNTOS CUÁNTICOS DE ZnO EN LA INTERFASE AIRE/AGUA

In this work, the mechanical properties at equilibrium of two dimensional layers made by ZnO Quantum dots deposited at the air/water interface were studied. ZnO nanoparticles were synthesized by the sol-gel method and their functionalization was made by the hydrolytic silanization method. Their mechanical properties were evaluated using a Langmuir trough equipped with a Du Nouy-Padday rod. With this technique, isotherms, compression modules and hysteresis cycles of the system were obtained. Our results showed that partially hydrophobic particles form two dimensional soft solids at the air/water interface, reaching values of their adiabatic compression modulus corresponding to a liquid condensed phase when they are compressed above surface concentrations of the order of 1x101 mg/m2. Nanoparticle layers presented dependence with the rate of compression and significant hysteresis, showing their complex behavior. Layers did not present collapse, but a semi constant value of the pressure upon high surface concentrations was observed, an indicative of the high adsorption energy of the nanoparticles. The mechanical properties reported, make these particles suitable for further applications on the stabilization of aqueous foams.

Effect of colloidal particleson the foamability and stabilization of aqueous foams by cationic surfactant CTAB

Colloidal particles can influence the foamability and stabilization of aqueous foam by addition of surfactant at the air-water interface. This occurs because particles are activated via the interaction with surfactant and are adsorbed onto the surfaces of foams. This phenomenon has been applied extensively to the development of new materials and techniques. Whether particle surface can be activated or not is decided by the interaction between the surfactant and the particle. In this work, we studied the effects of cationic surfactant CTAB (cetyltrimethylammonium bromide) on PS (polystyrene), SiO2, and TiO2 particles in aqueous solution, and compared the difference in their surface activation according to foam volume of the particles/CTAB/water system, and the degrees of foamability and foam stabilization. In addition, the influence of anionic surfactant SDS (sodium dodecyl sulfate) on the surface activation of PS in aqueous solution was also analyzed and compared with that of CTAB.

Effects of silica nanoparticles and polymers on foam stability with sodium dodecylbenzene sulfonate in water–liquid paraffin oil emulsions at high temperatures

The foam stability of oil–water emulsions stabilised by various surface-active components at high temperature is one of the major problems facing foam-flooding petroleum recovery because of foam instability at the high temperature underground. In this paper, foams stabilised by sodium dodecylbenzene sulfonate (SDBS), polyethylene glycol (PEG) and silica (SiO2) nanoparticles in water–liquid paraffin (50%/50%) emulsions at temperature from 20 to 80°C were studied. Foam properties such as foam stability over time at different temperatures, equilibrium surface tension, and bubble morphology (bubble size) were determined by surface tension measurements and inverted fluorescence microscopy. High foam stability was demonstrated by emulsions of SDBS, PEG, SiO2 nanoparticles, and liquid paraffin from 40 to 80°C. The properties of the PEG–SDBS foams improved when SiO2 nanoparticles were added. Foam stability increased when SDBS was adsorbed on the bubble surface as the bubbles did not rupture easily in the liquid phase in the presence of SDBS because of the formation of closely packed small bubble droplets bridging between neighbouring large bubbles, which were separated by long chain polymers. This phenomenon may arise because the SiO2 nanoparticles formed networks and were adsorbed with surfactant molecules on the bubble surface of the oil–water emulsion, causing the foam inflexibility to increase and thus improving aqueous foam stability at high temperature.