Foam Films Research Articles

Properties of the micelles of sulfonated methyl esters determined from the stepwise thinning of foam films and by rheological measurements

HypothesesThe micellar solutions of sulfonated methyl esters (SME) are expected to form stratifying foam films that exhibit stepwise thinning. From the height of the steps, which are engendered by micellar layers confined in the films, we could determine the micelle aggregation number, surface electric potential, and ionization degree. Moreover, addition of the zwitterionic surfactant cocamidopropyl betaine (CAPB) is expected to transform the small spherical micelles of SME into giant wormlike aggregates. ExperimentsStratifying films from SME solutions are formed and the heights of the steps are recorded. The viscosity of mixed SME + CAPB solutions is measured at various concentrations and weight ratios of the two surfactants. FindingsBy theoretical analysis of the foam film data, we established that at 30–100 mM SME spherical micelles are formed and their aggregation number was determined. The addition of calcium ions, as in hard water, does not produce significant effect. However, SME and CAPB exhibit a strong synergism with respect to micelle growth as indicated by the high solution’s viscosity. For this reason, the SME + CAPB mixtures represent a promising system for formulations in personal-care and house-hold detergency, having in mind also other useful properties of SME, such as high hard water tolerance, biodegradability and skin compatibility.

Sensory Polymeric Foams as a Tool for Improving Sensing Performance of Sensory Polymers.

Microcellular sensory polymers prepared from solid sensory polymeric films were tested in an aqueous Hg(II) detection process to analyze their sensory behavior. First, solid acrylic-based polymeric films of 100 µm thickness were obtained via radical copolymerization process. Secondly, dithizone sensoring motifs were anchored in a simple five-step route, obtaining handleable colorimetric sensory films. To create the microporous structure, films were foamed in a ScCO2 batch process, carried out at 350 bar and 60 °C, resulting in homogeneous morphologies with cell sizes around 5 µm. The comparative behavior of the solid and foamed sensory films was tested in the detection of mercury in pure water media at 2.2 pH, resulting in a reduction of the response time (RT) around 25% and limits of detection and quantification (LOD and LOQ) four times lower when using foamed films, due to the increase of the specific surface associated to the microcellular structure.

Glucose sensing characterization of non-enzymatic nickel film and nickel foam electrodes in sodium hydroxide solution

Recently, a non-enzymatic glucose sensor has gained a lot attention, because it is re-useable, fast and simple, as opposed to traditional enzymatic glucose sensor. In this work, two types of electrodes, including electroplated Ni film and Ni foam, were used as sensing electrodes for a non-enzymatic glucose sensor. The studied sensing properties of the Ni film and Ni foam included glucose-detecting sensitivity, selectivity, and detection limit. For the sensitivity and selectivity analysis, the sensing electrodes, with geometrical working area of 1 and 2 cm2 for Ni foam and Ni film respectively, were submerged in a 1M NaOH solution, connected as a working electrode with Ag/AgCl and Pt as a reference and counter electrodes, respectively. Amperometric scanning measurement was used for the sensitivity and selectivity analysis. Sensitivity measurement was tested by dropping glucose solutions into 1M NaOH solution and recording the amperometric response of these sensor under varying sugar contents. The glucose-detection sensitivities are 1.1048 and 6.4228 mA mM-1 cm-2 for Ni plate and Ni foam, respectively. Limit of detection (LOD) of Ni film and Ni foam are 0.0072 and 0.0144 mM, respectively. The selectivity of electrodes were tested by dropping 3 types of disturbing agents: Quinine, Acetic acid and NaCl. The disturbing agents showed no effect on the current density signal during the amperometric measurement for both of the Ni plate and Ni foam electrodes.

Coreflood Study of Effect of Surfactant Concentration on Foam Generation in Porous Media.

The propagation of foam in an oil reservoir depends on the creation and stability of the foam in the reservoir, specifically the creation and stability of foam films, or lamellae. As the foam propagates far from the injection well, superficial velocity and pressure gradient decrease with distance from the well. Experimental (Friedmann et al. Steam-foam mechanistic field trial in the midway-sunset field. SPERE. 1994, 9 (4), 297–304) and theoretical (Ashoori, et al. Roles of Transient and Local Equilibrium Foam Behaviour in Porous Media: Traveling Wave. Colloids Surf. A2011, 337 (1–3), 228–242). studies relate concerns about foam propagation at low superficial velocity to the minimum velocity or pressure gradient for foam generation near the well (Gauglitz et al. Foam Generation in Homogeneous Porous Media. Chem. Eng. Sci.2002, 57, 4037–4052; Rossen et al. Percolation Theory of Creation and Mobilization of Foams in Porous Media. AI Chem Eng. J.1990, 36, (8)). The objective of this work is to measure the impact of surfactant concentration and gas fractional flow on foam generation. Theory (Kam et al. Model for Foam Generation in Homogeneous Media. SPE J.2003, 8 (4): 417–42, SPE-87334-PA; Rossen 1990) relates foam generation to gas fractional flow and, indirectly, to the stability of foam films, or lamellae, which in turn depends on surfactant concentration (Apaydin et al. Surfactant Concentration and End Effects on Foam Flow in Porous Media. (Apaydin et al.Transp Porous Media. 2001, 43, 511–536). However, the link between foam generation and surfactant concentration has not been established experimentally. In our experiments, nitrogen foam is generated in a core of Bentheimer sandstone. The foam-generation experiments consist of measuring the minimum velocity for foam generation as a function of gas fractional flow at three surfactant concentrations well above the critical micelle concentration. Experimental results show that the minimum velocity for foam generation decreases with increasing liquid fraction, as shown by previous foam generation studies (Friedmann et al., 1994; Rossen and Gauglitz, 1990). Additionally, our results show that this velocity decreases with increasing surfactant concentration, far above the CMC. We also propose a workflow for screening out the experimental artifacts that can distort the trigger velocity.

Influence of interfacial elasticity on liquid entrainment in thin foam films

Thin-film experiments with an interferometric apparatus show an absence of a strong relationship between interfacial elasticity and liquid entrainment in thin foam films, which can affect rational design of aesthetic and tactile properties in foaming consumer products.

Mechanism of Foam Film Destruction Induced by Emulsified Oil: A Coarse-Grained Simulation Study

Hydrophobic oil additives have been shown to be a unique class of chemicals in solution, which affect the stability of foam films. While the oil-induced destruction of a foam film has been largely ...

Measurement of Instability of Thin Liquid Films by Synchronized Tri-wavelength Reflection Interferometry Microscope.

Film thickness measurement of unstable thin liquid films (TLFs) remains a challenge due to the difficulty in determining the order of fringes prior to the film rupture. In the present work, a synchronized tri-wavelength reflection interferometry microscope (STRIM) was developed and employed to determine the spatiotemporal thickness profiles of the TLFs between air bubbles and various hydrophobic surfaces in 10-2 M NaCl solutions. Both accuracy and precision of film thickness measurements were found to be better than 3 nm over the range of 0-1 μm. It was found that when the radii of air bubbles were in the range 0.71-0.88 mm, the critical rupture thicknesses of the wetting films formed on hydrophobic quartz surfaces having water contact angles of 95° scattered over a range of 57-335 nm with a medium rupture thickness of 122 nm. For smaller air bubbles with radii of 0.13-0.26 mm, the critical rupture thicknesses were much more narrowly distributed with a medium rupture thickness of 27 nm. The result obtained with the TLFs between two air bubbles, i.e., foam film, showed that the critical rupture thickness was increased from 25 to 40 nm, when the sizes of air bubbles were increased from 220 to 960 μm. Compared to rupture thickness of the foam film, the critical rupture thickness of the TLF between an air bubble and a dodecane droplet was smaller, indicating that the film rupture might be related to the hydrophobicity of interacting surfaces. In addition to attractive surface forces, both wave motions and gas molecules in TLF might be associated with the film rupture.

Relaxation Dynamics of Surface Fluctuations of Foam Films Decorated by Gel-Like Polymer-Surfactant Complexes

In many applications, the stability of foams is controlled by adding soluble polymers, together with low-molecular-weight surfactants. Recent experiments hint that the polymers form gel-like comple...

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.

Dynamic Measurement of Foam-Sized Yarn Properties from Yarn Sequence Images

Abstract Unlike the normal sizing method, the foam sizing had been proven to be a low-add-on technology. To investigate the effect of foam sizing, film thickness, sized-yarn evenness, and size penetration rate were necessary to evaluate the performances of foam-sized yarns. However, the conventional image analysis of sized-yarn cross sections primarily relied on artificial testing with a low efficiency. This paper proposed a novel dynamic method to measure the sized-yarn properties including film thickness, sized-yarn evenness, and size penetration rate based on yarn sequence images captured from a moving yarn. A method of dynamic threshold module was adopted to obtain threshold for segmenting yarns in the sequence images. K-means clustering algorithm was applied to segment pixels of the images into yarn and background. To further remove burrs and noise in the images, two judgment templates were carried out to extract the information of yarn core. The film thickness, sized-yarn evenness, and size penetration rate were measured based on the yarn core of each frame in sequence images. In order to compare with the experimental results of the dynamic method, the yarn properties of the same samples were tested by static and artificial testing. Results revealed that the proposed method could efficiently and accurately detect the film thickness, sized-yarn evenness, and size penetration rate.

The Effect of the Ratio between Water and Foam Concentrate at the Desired Density in the Foam Concrete Mixes

The scientifically grounded and experimentally confirmed features of formation of stable foam concrete mixes in time are considered. It is shown that the formation of such gas-filled structures is possible only with water content, the value of which is sufficient for wetting the surface of all solid dispersed particles of raw materials, the formation of foam films and the processes of adsorption and chemical hydration of binder particles. It is proved that taking into account the value of the aeration potential of the foaming agent, it is possible to obtain stable foam concrete mixtures of a given density

Investigating Supercritical CO2 Foam Propagation Distance: Conversion from Strong Foam to Weak Foam vs. Gravity Segregation

This study investigates how to determine the optimal supercritical CO2 foam injection strategies, in terms of total injection rate (or injection pressure, equivalently) and injection foam quality, to place injected foams deep and far into the reservoir. Two different mechanisms that limit field foam propagation, such as “conversion from strong foam to weak foam” and “gravity segregation,” are examined separately, and the results are combined together. The first is performed by using a mechanistic foam model based on bubble population balance, while the second is conducted by an analytical model (called Stone and Jenkins model) and reservoir simulations with a commercial software (CMG-STARS). Note that the gas-phase mobility, required as a key input parameter for gravity segregation simulations, is calibrated by the mechanistic model, which is a significant advance in this study. The results from both mechanisms show in general that foam propagation distance increases with increasing injection pressure or rate (which is often limited by the formation fracturing pressure) and increases with decreasing foam quality down to a certain threshold foam quality below which the distance is not sensitive to foam quality any longer. It is found that the mobilization pressure gradient (i.e., the pressure gradient above which foam films are mobilized to create a population of bubbles) plays a key role to determine the distance. Therefore, the injection of supercritical CO2 foams with lower mobilization pressure gradient should be more favored in field applications. As a step prior to real-world reservoir applications, this study deals with a relatively ideal reservoir (i.e., large homogeneous cylindrical reservoir) focusing on the steady state after foam treatment in the absence of oil.

Foaming Behavior of CO2-Soluble, Viscoelastic Surfactant

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 190302, “Foaming Behavior of CO2-Soluble Viscoelastic Surfactant in Homogeneous Porous Media,” by Galang Ramadhan, The University of Texas at Austin; George Hirasaki, SPE, Rice University; and Quoc P. Nguyen, SPE, The University of Texas, prepared for the 2018 SPE Improved Oil Recovery Conference, Tulsa, 14–18 April. The paper has not been peer reviewed. Aqueous foam has been demonstrated to have promise in conformance-control applications. This paper explores the foaming behavior of a CO2-soluble, cationic, amine-based surfactant. A distinguishing feature of this surfactant is its ability to dissolve in supercritical CO2 and to form wormlike micelles (WLMs) at elevated salinity. The presence of WLMs leads to an increase in viscosity of the aqueous surfactant solution. This paper investigates how the presence of WLM structures affects transient foam behavior in a homogeneous porous media (sandpack). Introduction Aqueous foam is a dispersion of a gas in an aqueous phase with a surface-active agent (surfactant) to lower the interfacial tension between the two phases. Foam functions as an effective mobility-control agent because of its high apparent viscosity in porous media. Foam’s mobility in porous media is also influenced by the media’s relative permeability. In porous media, foam’s ability to flow from one pore to another is heavily dependent upon overcoming the capillary forces imposed by the pore-throat constrictions. Because of this yield-stress requirement, a large portion of a foam system in a porous media is not mobile. This fraction of trapped foam could occupy up to 65% of total pore volume, depending on foam-injection quality, injection velocity, and porous-media morphology. Trapped foam severely reduces the effective permeability of gas moving through a porous media by reducing the number of conduits through which the foam can flow. Addition of Polymer and Polymer-Like Structures The addition of polymer to a surfactant solution typically increases a foam’s apparent viscosity. From the perspective of foam generation, the addition of polymer to a surfactant solution seems to decrease the rate of foam-generation events. With the addition of liquid-phase-viscosifying polymer, a greater pressure gradient needs to be applied to reach the onset of strong foam generation. The higher pressure-gradient requirement could translate to fewer foam-generation events and potentially limit the foam generation to the near-injection-well region. From the perspective of foam stability, addition of polymer seems to reduce the occurrence of lamellae destruction. Immediately after the formation of fresh foam bubbles, the lamellae are subjected to disturbance forces that reduce the thickness of the lamellae’s liquid phase (film). The thinning process continues until the film reaches a critical thickness at which the lamella is not stable and tends to coalesce. Polymer improves the stability of thick foam film by increasing its viscosity and reducing the rate of film drainage.

Progressive contact-separate triboelectric nanogenerator based on conductive polyurethane foam regulated with a Bennet doubler conditioning circuit

Scavenging the energy of human motions has attracted widespread attentions with the development of wearable electronics. This paper for the first time proposed a progressive triboelectric nanogenerator based on macro-triangle-prism-shaped conductive polyurethane (PU) foam and polytetrafluoroethylene (PTFE) film, which occupy the top and bottom spots of the triboelectric table respectively. The proposed macro-structured conductive PU foam also integrates the functions of spring, spacer and electrode. Thanks to the innovative structures and chosen of the materials, an extended current pulse width is obtained. A maximum RMS power density of 100 nJ/cm2/tap was obtained with a 60 MΩ resistive load and press force of 10 N@5 Hz. By regulating the TENG with a Bennet doubler conditioning circuit, the ubiquitous voltage saturation phenomenon when charging a storage capacitor using full-wave rectifiers is avoided. Moreover, the energy per cycle, charging efficiency and totally stored energy can be exponentially pumped up. With a Bennet circuit charging a 5 nF capacitor, a harvested energy density of ~ 710 nJ/cm2/tap was obtained when voltage across the capacitor was 400 V. Putting the device under sole within 25 human steps, the totally stored energy was 0.43 mJ with a Bennet circuit, 3.6 times higher than that using a full-wave rectifier (0.12 mJ). The Bennet was proven better for regulating the triboelectric nanogenerators with long operation-time compared to the classical full-wave rectifier.

STABILITY OF FOAMS CONTAINING DIESIL FUEL

The comparative characteristic of the stability of foams formed by sodium dodecylsulfate and gelatin at their various concentrations at the presence of the diesel fuel under the action of an applied pressure drop was carried out in this work. It was shown that the change in the gelatin/ surfactant ratio in the initial solution changed the stability of such foams at the presence of an organic liquid. The surfactant and protein concentrations when these dispersions are more stable at the presence of the organic phase were determined. The isolated foam films obtained from a solution of sodium dodecyl sulfate + gelatin / diesel fuel were studied. It was shown that there was no correlation between the stability of the isolated film and the foam under the action of applied pressure drops: the films in contact with diesel fuel retained considerable stability, unlike the foams obtained from this aqueous solution of gelatin and surfactant in the presence of said organic substance. The coefficients of initial spreading of diesel fuel on the surface of an aqueous solution containing gelatin and surfactant were calculated. The change in the interfacial energy at the interface of the aqueous solution of sodium dodecylsulfate + gelatin/ diesel fuel with time when changing of the surfactant: protein ratio in the initial solution and different concentrations of the organic liquid was investigated. The change in the interfacial tension at the interface of the aqueous solution of sodium dodecylsulfate + gelatin/ diesel fuel over time was accompanied by a significant decrease in the stability of foams obtained from aqueous solutions containing gelatin and an ionic surfactant. If the interfacial tension did not change or slightly decreased, the foams containing diesel fuel remained stable.Forcitation:Vilkova N.G., Mishina S.I., Dorchina O.V. Stability of foams containing diesil fuel. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 6. P. 48-53

Thickness-Dependent Phase Transition Drives Nanoridge-to-Mesa Instability in Micellar Freestanding Films.

Understanding fluxes and instabilities within freestanding ultrathin films is necessary for a better understanding of, and control over, the stability and lifetime of foams and emulsions. In micellar foam films, confinement-induced layering of micelles leads to stepwise thinning or stratification that occurs by the expansion of thinner, darker domains. Often, because of a nanoridge-to-mesa instability, one or more brighter white spots or "mesas" appear at the circular moving front between thinner domains and the thicker (less dark) surrounding film. Previous studies assume that the instability and the appearance of white spots are similar to the capillarity-driven Rayleigh instability that leads to the breakup of a coherent liquid jet. Using the IDIOM (interferometry digital imaging optical microscopy) protocols we recently developed, we characterize the nanoridge-to-mesa instability with exquisite spatiotemporal resolution (thickness <1 nm, time <1 ms). The instability could be classified as a Rayleigh instability if a similar sequence of thick and thin undulations is visualized around the expanding domains. However, quantitative analysis reveals that only mesas grow in size after the instability, whereas the rest of the nanoridge preserves its shape. By analogy to the phase separation into compositionally distinct regions, we show that the spontaneous nucleation of thicker mesas in stratifying films is a phase transition driven by the oscillatory nature of the free-energy functional.

Cellular polypropylene foam films as DC voltage insulation and as piezoelectrets — A comparison

Polymer foams are in industrial use for several decades. More recently, non-polar polymer foams were found to be piezoelectric (so-called piezoelectrets) after internal electrical charging of the cavities. So far, few studies have been carried out on the electrical-insulation properties of polymer foams. Here, we compare the piezoelectric and the DC-voltage electrical-insulation properties of cellular polypropylene (PP) foams. Their cavity microstructure can be adjusted via inflation in high-pressure nitrogen gas in combination with a subsequent thermal treatment. While inflation is effective for improving the piezoelectricity, it is detrimental for the electrical-insulation properties. The original cellular PP foam shows a breakdown strength of approximately 230 MV/m, within the same range as that of solid PP. The breakdown strength decreases with increasing degree of inflation, and the dependence on the foam thickness follows an inverse power law with an exponent of 1.2. Nevertheless, up to a thickness of 140 μm (3.5 times the original thickness), the breakdown strength of cellular-foam PP films is at least 7 times that of an air gap with the same thickness. In addition, the influence of high temperatures and high humidities on the piezoelectricity and the breakdown strength of cellular PP was studied. It was found that the piezoelectric d33 coefficient decays rapidly already at 70 °C, while the breakdown strength slightly increases during storage at 70 or 90 °C. Under a relative humidity of 95%, the breakdown strength increases with storage time, while the piezoelectric d33 coefficient slightly decreases.

Study on a Novel Gelled Foam for Conformance Control in High Temperature and High Salinity Reservoirs

A novel gelled foam for conformance control was investigated for its ability to enhance oil recovery (EOR) in high temperature and high salinity reservoirs. The formulation optimization, foaming performance, and core flooding performance of the gelled foam were systematically evaluated under harsh reservoir conditions. The gelled foam formulation was optimized with 0.4% polymer (hydrolyzed polyacrylamide; HPAM), 0.06% cross-linker (phenolic) and 0.2% foaming agent (sulphobetaine; SB). The addition of the gel improved the stability of the foam system by 3.8 times that of traditional foam. A stabilization mechanism in the gelled foam was proposed to describe the stabilization process of the foam film. The uniformly distributed three-dimensional network structure of the gel provided a thick protective layer for the foam system that maintained the stability of the foam and improved the strength and thickness of the liquid film. The gelled foam exhibited good formation adaptability, profile control, and EOR performance. The foam flowed into the high permeability layer, plugged the dominant channel, and increased the swept volume. Oil recovery was enhanced by 29.4% under harsh high -temperature and high salinity conditions.

Pulsed electrodeposition of reduced graphene oxide on Ni[sbnd]NiO foam electrode for high-performance supercapacitor

Through electrodeposition, controlling hydrogen evolution reaction and selective electrochemical dealloying of copper from NiCu porous foam, highly nanoporous nickel and nickel oxide is fabricated on the copper surface. Electrochemically reduced graphene oxide (ERGO) is loaded on the NiNiO foam as high-performance electrodes for supercapacitors through pulsed galvanostatic reduction of drop casted graphene oxide nanosheets at different duty cycles and frequencies. Surface morphology and composition of fabricated ERGO/NiNiO foam composite electrodes are characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Raman Spectroscopy. Electrochemical impedance spectroscopy (EIS) measurements, galvanostatic charge/discharge (GCD) and cyclic voltammetry (CV) are carried out to study the electrochemical behavior of ERGO/NiNiO foam electrodes. From structural and electrochemical characterizations, optimized parameters for pulse duty cycle and frequency were found to be 10% and 1000 Hz, respectively. As a result, the ERGO/NiNiO foam film (ic = −10 mA/cm2, f = 1000 Hz and DC = 10%) provides a specific capacitance of 2298 F/g in 1 M KOH at a current density of 1 A/g. Stability study of fabricated film represents a long cycling life up to 4000 cycles with 0.7% decay in specific capacitance at the high current density of 20 A/g in the potential range of 0–0.6 V vs. saturated calomel electrode (SCE).

From Pickering foams to porous carbonate materials: crack-free structuring in drying ceramics

Particle-stabilized foams have attracted considerable research interest, due to their long term stability (months to years) and the possibility to use them as precursors for production of porous materials with hierarchical porosity. In our previous study [Lesov et al., J. Colloid Interface Sci. 504 (2017) 48–57] we clarified the role of the rheological properties of the foamed suspensions and the type of foam film stabilization in the production of porous silica materials with low mass density and excellent insulating properties. In the current study we extend our approach to prepare lightweight carbonate ceramics with controlled density, shrinkage and good mechanical properties. To prepare the wet foam precursors, we tested a series of eight anionic surfactants which were previously reported to provide sufficient hydrophobization of CaCO3 particles and long-term stability of the liquid foams. From those surfactants, the medium-chain fatty acids led to crack-free porous materials with superior mechanical strength, compared to the conventional surfactants. We study the reasons for the formation of cracks in drying Pickering foams and, on this basis, propose optimal conditions for obtaining dry porous carbonate materials with required porosity. Mechanistic explanations are proposed for the main observed effects.