Foam System Research Articles

Keys to improve the efficiency of nanoparticle‐stabilized foam injection based on influential mechanisms

AbstractThe effect of the existence of nanoparticles on foam stability, foamability, and the oil recovery factor (RF) has been studied experimentally, and influential phenomena and mechanisms have been examined. A sequence of experiments, including, ‘foam bulk‐static experiments’, ‘surface tension (ST) measurements,’ and ‘micromodel foam flood,’ were designed and then implemented to study the foam behaviour in two foam systems: (1) anionic‐nanoparticles + cationic‐surfactant and (2) anionic‐nanoparticles + anionic‐surfactant. This study provides a comprehensive insight into the mechanisms affecting the stability of nanoparticle‐stabilized foam. Also, despite previous studies, the effect of Marangoni flow on nanoparticle‐stabilized foam has been discussed briefly. Results show that the interactions of effective mechanisms work differently in the two series. In the like‐charge system, surfactant molecules accumulate in the interface of lamellas due to repulsive forces; therefore, stability and foamability improve as surface tension and molecular diffusion reduce. Additionally, Marangoni flow restitutes the negative impact of gravity drainage. In the unlike‐charge system, observations illustrate that nanoparticles reach the interface. The presence of nanoparticles at the interface increases detachment energy significantly, and as a result, the stability is boosted. The accumulation of nanoparticles in the interface changes it to a solid‐like surface with limited diffusibility and viscosity. Although Marangoni flow is lost, reducing molecular diffusion improves foam stability. Flooding tests show that foam stability increment improves sweep efficiency at near‐wellbore areas even when foamability is weak. Finally, it can be claimed that in the unlike‐charge system, the sweep efficiency and foam stability increase to a greater extent.

Effects of the surfactant, polymer, and crude oil properties on the formation and stabilization of oil-based foam liquid films: Insights from the microscale

Stable foams frequently hinder the efficient treatment of liquids produced by chemical flooding. Studies into the formation and stabilization mechanisms of these foams, are therefore essential to overcoming this problem in oilfield surface systems. However, previous investigations have mainly focused on water-based foams. Although a small number of studies have examined oil-based foams, only a few well-known properties similar to those of water-based foams have been reported. Therefore, in this study, different oil-based foam systems were prepared to investigate the impact of the surfactant (sodium dodecyl benzene sulfonate, SDBS), the polymer (partially hydrolyzed polyacrylamide, HPAM), and physical properties of the crude oil, on the foaming characteristics and the foam liquid film drainage behavior of liquids produced by chemical flooding. For this purpose, molecular dynamics (MD) simulation were employed, and the simulation results were verified experimentally. It was found that the SDBS molecules aggregated to form micelles on the liquid film of the oil-based foam; this contrasts to the directional adsorption observed at the gas − liquid interfaces of water-based foams. In addition, upon increasing the SDBS adsorption concentration at the gas − liquid interface, the formation ability and stability of the liquid film of the oil-based foam system were enhanced. Furthermore, an increase in the HPAM concentration increased the coverage area of the co-adsorption layer of the liquid film, thereby strengthening the stability of the foam system. However, upon increasing the HPAM concentration from 150 to 450 mg/L, the absolute value of the interfacial formation energy decreased from 511.16 to 495.70. This indicates that the liquid film formation ability of the foam system decreased with an increasing HPAM concentration. This was attributed to the fact that an increase in the carbon number of the straight-chain alkanes present in the foam system decreased the liquid film drainage rate and the possibility of Ostwald ripening. These new insights provide support for the design and development of new defoaming processes.

Experimental study on the in-situ foam performance stabilized by microbial polysaccharide and its diverting characteristics at high temperature

Foam fluid shows good performance as diverting agent for reservoir stimulation, but complex generation procedure and high flow friction restrict its further application especially in offshore fields. To overcome these limitations, the objective of this study is to create stable in-situ foam system and investigate its potential in diverting fluid in heterogeneous reservoirs at high temperature. To prepare in-situ foam system, self-generated gas system was analyzed in terms of gas production volume and production efficiency. Foaming agents and foam stabilizers were optimized at the temperatures ranging from 70 ℃ to 90 ℃. Then in-situ foaming performance of the system combining self-generated gas reactants (sodium nitrite and ammonium chloride), the foaming agent (alpha olefin sulfonate), and the foam stabilizer (diutan gum) without blender was investigated based on foaming volume and bulk stability. Single core and parallel core flooding experiments were applied to investigate the plugging ability and diverting characteristics of in-situ foam. The results showed that the large pore volume was blocked by in-situ foam even at 150 ℃ as shown by the increase of residual resistance factor during subsequent water flooding. Parallel core flooding experiments also proved the diverting ability of in-situ foams as the diversion ratio of low-permeability core was higher than that of high-permeability core during subsequent water flooding. Moreover, the diversion performance of in-situ foam strongly depended on the permeability contrast, environment temperature, permeability of low-permeability core, and injection rate. Although diversion failed when permeability contrast was more than 10, in-situ foam also had good thermal stability and diverting ability at 150 ℃ in the permeability contrast range of 3 to 8. Such stable in-situ foam shows promising potential as diverting agent in heterogeneous formation for reservoir stimulation at high temperature.

The Phase Behavior Study of Air-foam Flooding in Changqing Ultra-Low Permeability Reservoirs

For phase change characteristics of air foam flooding in Changqing ultra-low permeability reservoirs,  experiments were performed with the air and the gas-phase oxidation of P-X diagram under reservoir conditions using the PVT high pressure physical device and gas chromatograph. The phase behavior of crude oil and air bubbles after multiple contacts was determined by PVT simulation and the phase equilibrium model. The critical temperature and critical pressure of crude oil were determined to be 424.4? and 9.85MPa. Results show gas dissolved in crude oil after oxidation was strong in the air under the same pressure. Because the foam system and crude oil emulsification during contact have produced multiple contact oxidation, the effect was less than that in air and oil, resulting in a relatively small oxidation of C2-C6, while the oxidation of C7-C16 was relatively more. Furthermore, the trend of gas phase composition approaching C2-C6 was relatively slow, while oil phase composition was closer to C7+, due to the increase in the C7-C16 component. The study provides important insight for miscible flooding and non-miscible flooding applications, as well as for gas injection project design.

Effect of airflow rate and drainage on the properties of 2D smectic liquid crystal foams.

As a two-phase system, foams are widely applied in the industry and exist ubiquitously in our daily lives. For this reason, studying them and investigating the parameters that affect their properties is crucial for the development of new and improved foam-based products. In this paper, we create 2D foam using an ordered fluid, the smectic liquid crystal (LC), and discuss the experimental parameters that affect their fabrication, including temperature and confining conditions. Then, we examine the influence of the injected airflow rate and drainage on their structure, size, liquid fraction, and stability. Finally, we compare their behavior to that of low-viscosity liquid foams and discuss the difference between them. Our findings indicate that surface tension is the dominant parameter in LC foam systems. Despite the strong elasticity of LCs, surface tension plays a crucial role in determining the properties of elastic foams. These results provide valuable insights that can be applied to different industrial applications. For instance, they may find relevance in the fields of cosmetics, thermal insulation, oil recovery, and sensing, where the fabrication of foams with high-viscosity fluids is required.

Experimental investigation on the influencing factors of preparing three-phase foam

A three-phase foam is considered one of the promising advanced materials for fighting fires. However, the preparation conditions, cost and effect are key factors for industrial applications. In this study, new three-phase foam systems with fly ash and a complex surfactant are proposed. Five types of surfactants alcohol polyoxyethylene ether sodium sulfate, coconut oil diethanolamine, sodium lauryl sulfate, polyacrylamide and polyether-modified silicone resin emulsion were selected as foaming agents. Through laboratory experiments, the effect on the expansion ratio and foam stability of the surfactant type/concentration, fly ash particle concentration/size and pH were investigated. The foaming condition was determined by numerical optimization. The results of this study may serve as a reference for understanding the preparation of a novel threephase foam. It is hoped that this work could provide useful guidance for the preparation of efficient three-phase fire-extinguishing foam for the safe guarding of process safety in the field of chemical production, transportation, and storage suitable for drug delivery than Al12P12 and Al12N12 based on their recovery times.

Study on the Adaptability of Jurassic Nitrogen Foam Cone Pressing

Aiming at the problems of bottom water coning and oil well flooding caused by the large impact of the early production strength of the Jurassic bottom water direct contact well in the Seventh Oil Production Plant. Carry out research on nitrogen foam control bottom water coning technology, mainly including: ①laboratory test to optimize foam system suitable for Jurassic system of No. 7 Oil Production Plant, determine injection concentration and optimal gas-liquid ratio; ②The nitrogen foam injection timing and shut in time were optimized by numerical simulation method; ③Summarize the field tests that have been carried out, and determine the optimal combination of parameters suitable for the Jurassic nitrogen foam pressure cone of No. 7 Oil Production Plant.

PROSPECTS OF SEARCHES AND PROBLEMS OF GAS DEVELOPMENT OF SEALED COLLECTORS OF THE DNIPRO-DONETSK DEPRESSION

The article considers the current problem of the hydrocarbon base of Ukraine. Materials that can serve as prerequisites for exploration and further development of gas from compacted reservoirs on the territory of the Dnieper-Donetsk graben are analyzed. In this article, the main parameters, that indicate the presence of gas in compacted reservoirs, are briefly considered. The data contain information about the features of the sedimentary section of the Paleozoic complex, namely, the geological structure of promising areas, the degree of catagenesis of gas-bearing rocks, the content of organic carbon in parent rocks, reservoir properties, and depths of gas-promising intervals. These data, taken from the results of drilling numerous wells, indicate a high probability of successful exploration for central basin gas within the axial zone of the Dnieper-Donetsk basin. As such deposits are difficult to extract, due to the complex geological structure of promising areas, a wide range of depths and, above all, poor reservoir properties of rocks containing gas, its development is impossible without the use of intensification methods. There are many chemical, thermal, mechanical technologies to cause the inflow of fluid from the reservoir, among which the hydraulic fracturing of the reservoir has become widespread. Modern methods of intensification are quite effective, but still remain imperfect, and therefore, there are some defects that cause certain complications in the development of the deposit. Тo cause the inflow of hydrocarbons from the compacted reservoirs, a foam gap of the formation is indicated, the use of which, in the opinion of the authors, is appropriate for deposits of this type. The article also points out the advantages of using a foam system compared to conventional fracturing and the need to improve some indicators of the foam system to its further use for compacted terrigenous reservoirs of the Dnieper-Donetsk avlakogen.

Preparation for the introduction of SWAG at the fields of PJSC «Tatneft»

The results of laboratory studies of filtration processes on models of a terrigenous reservoir are presented in order to develop optimal compositions for simultaneous water and gas injection and foam assisted water alternating gas injection on the reservoir. The experiments were carried out on rock samples drilled from the core of terrigenous deposits of the Kynovsko-Pashiy horizon. The use of water-gas mixtures with foam-forming surfactants taking into account the field conditions of the fields of PJSC TATNEFT has been established will make it possible to obtain the greatest increase in oil recovery. Studies of the multiplicity and stability of foam systems have shown that non-ionic foaming surfactants TN-PO-1, TN-PO-2 and AF9-12 are best suited for use in FAWAG of the reservoir. The results of studies of the properties of foams depending on the concentration of surfactants are presented, recommendations are given on the use of specific reagents for the implementation of FAWAG, taking into account the conditions of specific fields. The use of SWAG and FAWAG technologies is not only increase oil recovery, but also significantly reduce the volume of irrationally used associated petroleum gas, which is one of the most important tasks for sustainable development goals. Keywords: enhanced oil recovery; filtration studies; simultaneous water and gas injection; foam assisted water alternating gas injection; foaming surfactants.

Study on the Performance of a Novel Highly Stable Nano-Hydroxyapatite Gel Foam to Inhibit Coal Spontaneous Combustion

ABSTRACT The preparation of gel foams with high stability for inhibiting coal spontaneous combustion remains a huge challenge. In this paper, a highly stable gel foam (SCTH) was developed by introducing nano-hydroxyapatite (HAP) into gel foam system (sodium alginate/calcium L-lactate/tannic acid/composite forming agent). The effects of HAP on the foam performances of SCTH were analyzed. The results showed that HAP could improve the stability of SCTH by forming hydrogen bonds, metal ion bonds with the system and interfacial barriers. After 100 days, SCTH without HAP had only 44.8% of the foam volume remaining. The SCTH with 1.2 wt% HAP had 80% of the volume remaining. In addition, the SCTH had better safety. Thermogravimetric analysis showed that the SCTH could improve the maximum weight loss rate temperature, and increase the residual weight of the coal after thermal decomposition. The coal temperature-programmed oxidation experiment showed that the SCTH could increase the temperature of coal entering the rapid oxidation stage from 120 to 190°C, and the CO inhibition rate was 85.3% at 200°C. Fire suppression experiment showed that the SCTH could reduce the temperature of burning coal by 81.9% within 10 min, thus achieving rapid fire suppression. X-ray photoelectron spectroscopy analysis showed that the SCTH could more effectively reduce the total content of C=O and -COO in coal and block the chain cycle reaction of coal. This work presents a new design idea for using multifunctional nanoparticles to prepare highly stable gel foams with excellent inhibition performance of coal spontaneous combustion.

Discussion on the sweep efficiency of hybrid steam−chemical process in heavy oil reservoirs: An experimental study

Non-condensable gas (NCG), foam and surfactant are the three commonly-used additives in hybrid steam−chemical processes for heavy oil reservoirs. Their application can effectively control the steam injection profile and increase the sweep efficiency. In this paper, the methods of microscale visualized experiment and macroscale 3D experiment are applied to systematically evaluate the areal and vertical sweep efficiencies of different hybrid steam−chemical processes. First, a series of static tests are performed to evaluate the effect of different additives on heavy oil properties. Then, by a series of tests on the microscale visualized model, the areal sweep efficiencies of a baseline steam flooding process and different follow-up hybrid EOR processes are obtained from the collected 2D images. Specifically, they include the hybrid steam–N2 process, hybrid steam–N2/foam process, hybrid steam−surfactant process and hybrid steam–N2/foam/surfactant process (N2/foam slug first and steam−surfactant co-injection then). From the results of static tests and visualized micromodels, the pore scale EOR mechanisms and the difference between them can be discussed. For the vertical sweep efficiencies, a macroscale 3D experiment of steam flooding process and a follow-up hybrid EOR process is conducted. Thereafter, combing the macroscale 3D experiment and laboratory-scaled numerical simulation, the vertical and overall sweep efficiencies of different hybrid steam−chemical processes are evaluated. Results indicate that compared with a steam flooding process, the areal sweep efficiency of a hybrid steam–N2 process is lower. It is caused by the high mobility ratio in a steam–N2–heavy oil system. By contrast, the enhancement of sweep efficiency by a hybrid steam–N2/foam/surfactant process is the highest. It is because of the high resistance capacity of NCG foam system and the performance of surfactant. Specifically, a surfactant can interact with the oil film in chief zone and reduce the interfacial energy, and thus the oil droplets/films formed during steam injection stage are unlocked. For NCG foam, it can plug the chief steam flow zone and thus the subsequent injected steam is re-directed. Simultaneously, from the collected 2D images, it is also observed that the reservoir microscopic heterogeneity can have an important effect on their sweep efficiencies. From the 3D experiment and laboratory-scaled numerical simulation, it is found that a N2/foam slug can increase the thermal front angle by about 15° and increase the vertical sweep efficiency by about 26%. Among the four processes, a multiple hybrid EOR process (steam–N2/foam/surfactant process) is recommended than the other ones. This paper provides a novel method to systematically evaluate the sweep efficiency of hybrid steam–chemical process and some new insights on the mechanisms of sweep efficiency enhancement are also addressed. It can benefit the expansion of hybrid steam−chemical processes in the post steamed heavy oil reservoirs.

Stability mechanisms of viscoelastic zwitterionic-anionic surfactants enhanced foam system for low-permeability reservoirs

Polymers are generally applied to enhance foam stability and boost the efficiency of foam flooding for enhanced oil recovery (EOR). In low-permeability reservoirs, the polymers can unavoidably damage the formation. In this study, a novel viscoelastic surfactant system was developed by combining zwitterionic surfactant erucic acid amide propyl hydroxysulfonyl betaine (EHSB) and anionic surfactant sodium dodecyl sulfate (SDS) to enhance air foam stability without damaging the formation in low-permeability reservoirs. The Waring Blender method was used to comprehensively investigate the foam parameters, including foaming volume, drainage half-life, and foam half-life under practical formation conditions. After that, an optical microscope and Turbiscan stability analyzer were used to study the stability of the foam. The interfacial viscoelasticity, electric double layer, and continuous phase viscoelasticity were investigated to clarify the stability mechanisms. The results indicate that the foam composite index of the optimum formulation 0.3 % EHSB-SDS (mass ratio = 1.1:1) system was 175500 min·mL, which is 6 times higher than that of EAB-SDS system with a same viscosity. The EHSB-SDS system also provides a certain degree of strong resistances on temperature and crude oil, which has fair stability below 55 °C and 10 % oil content. EHSB-SDS has stronger interfacial strength and foam stability than EAB-SDS system due to its higher interfacial elastic modulus and surface activity. Meanwhile, the EHSB-SDS has a higher absolute value of Zeta potential (34.91 mV) than EAB-SDS (20.66 mV), indicating a stronger electrostatic repulsion. Hence, the newly viscoelastic surfactant-enhanced foam possesses sufficient stability and exhibits great EOR potential in low-permeability reservoirs.

Influence of external conditions on the stability of inorganic gel foam and exploration of the mechanism of action

Foams are widely used in tertiary oil recovery because of their dual function (profile control and oil displacement), and foam stability is still the focus of research when implementing foam plugging technologies. In addition to the chemical ingredients of the foam system, external conditions are vital factors affecting foam performance. The main purpose of this study is to explore the effects of the different reservoir conditions on the stability of the gel foam system. The stability of a gel foam was investigated by changing temperature, pressure, salinity and oil saturation, and its foam properties, coarsening properties, defoaming behavior and rheological properties were investigated. The Ostwald ripening rate and the gas molecular diffusion coefficient ratio of the gel foam decay process were obtained by statistical methods, and the foam effect was analyzed by the rheological properties of the gel foam. Finally, the influence of the oil–water interface properties on the stability of the oil-bearing gel foam was explored. Experimentally, our results show that heating aggravates the decay behavior of gel foam, and pressurization increases the strength and delays the liquid drainage speed of the foam lamella. When the salinity is less than 5 × 104 mg/L, the gel foam has higher stability and shows obvious salinity synergy. When the oil saturation is less than 10 %, the gel foam can change the defoaming behavior of crude oil behavior to a stable foam behavior. This study shed light on the stability law of gel foams under different external conditions and clarified the decay mechanism of gel foam.

Study on hydrate formation and absorption effect in LNG-High expansion foam system

In the context of energy transformation, the demand for liquefied natural gas is only increasing, and the risk of leakage during storage and transportation needs to be further researched. High expansion foam technology is considered to be an effective way to mitigate LNG vapor hazard. In the experimental process of inhibiting LNG leakage evaporation by high expansion foam, it was found that LNG and water in foam would generate hydrates under atmospheric pressure. In order to study the absorption effect of hydrate on LNG vapor, a set of experimental equipment for hydrate formation in LNG-foam system was designed, and the gas content test of hydrate was carried out. The formation temperature of LNG hydrate under atmospheric pressure was theoretically analyzed, and the heat transfer model of high expansion foam covered LNG was established. The spatial and temporal regions of hydrate formation and the variation of gas holdup with temperature were obtained.This work shows that the foam hydrate solid can absorb up to 37.5 times of alkanes per cubic meter, and the gas absorbed by the whole foam hydrate layer accounts for 13.4 % of LNG evaporation gas. The hydrate layer in LNG-high expansion foam is crucial to improve the effectiveness of high-expansion foam technology application.

Systematic study of the condensed phase of phosphorus-based flame retarded foams

This study investigates different types of model phosphorous compounds for flame retardancy purposes to find new FR structures to flame retard rigid polyisocyanurate (PIR) and/or polyurethane (PUR) foams. Triethylphosphate (TEPate) has been taken as a reference since it is already known to enter into the composition of some FR systems for PIR or PUR foams. Commercially available phosphate, phosphonate, phosphite and phosphine oxide were chosen. All the foam systems were characterized using TGA analysis, rheology tests, and mass loss cone tests, and analyzed using solid state NMR and chemical analysis. DEPonate shows the best efficiency for improving the FR properties of PIR and PUR foam. For the other FRs, the effect on the fire behavior is less relevant especially for PUR foams. This behavior was explained by the fact that even if the FRs slightly decrease the pHRR, the THR or the flaming time, smoke production is usually strongly increased. The systematic study of the condensed phase demonstrates that even if a charring effect is induced by the FR, the effect is not strong enough to improve the FR properties of the material. DEPonate have the least developed char but the best FR properties in PIR and PUR foam, demonstrating that the gas phase effect is more predominant than the condense phase effect.

Atorvastatin-loaded emulsomes foam as a topical antifungal formulation

Dermal fungal infection faces many challenges, especially for immunocompromised patients. Recently, the repositioning of atorvastatin (ATO) as a promising anti-mycoses therapy is used to overcome some issues of conventional therapeutic agents such as microbial resistance. The goal of this study was to develop a suitable formula for dermal fungal infection. Wherefore, ATO was entrapped into emulsomes and then incorporated in a foam system for topical convenient application. The D-optimal design was used for the optimization of ATO-emulsome and foam to achieve suitable responses. Regarding emulsomes, cholesterol weight and sonication time were independent variables that impact emulsome size, polydispersity index, surface charge, and entrapment efficiency. The optimum formula showed a size of 359.4 ± 8.97 nm, PDI of 0.4752 ± 0.012, a zeta potential of −21.27 ± 0.53 mV, and a drug entrapment of 95 ± 2.38%. Transmission electron microscope and Fourier-transform infrared spectroscopy (FT-IR) proved the assembly of ATO-emulsome. Foam composition was optimized to achieve good expansion, stability, and viscosity using a surfactant triple mixture and hydroxypropyl methylcellulose. The selected ATO-emulsome foam which consisted of 1% HPMC, 1.249% SDS, and 4% pluronic showed prolonged drug release. Efficient permeation through skin layers was asserted by using a confocal laser scanning microscope. Moreover, the homogenous distribution of the foam bubbles upholds stability and conserves the system from rapid collapse. The antifungal activity was confirmed by an in-vitro and in-vivo microbiology study beside in-vivo biocompatibility. In conclusion, ATO-emulsome and incorporation in foam have demonstrated good antifungal activity which presented a unique aspect for potential clinical applications.

Experimental Study of the Influence of Inorganic Salts on Foam Stability

The aqueous film-forming foam (AFFF) extinguishing agent is suitable for fighting various hydrocarbon fuel fires due to its dual fire-fighting effect of foam and liquid film. Because the action law and microscopic mechanism of inorganic salts on the stabilization process of surfactant-generated AFFF are not perfect, this paper employs an experimental approach to investigate the effects of inorganic salt types and concentrations on sodium dodecyl sulfate-containing foam systems (SDS). Prior to critical micelle concentration (CMC), increasing inorganic salt concentration decreased solution surface tension, but the opposite was true after CMC. The CMC value of an SDS solution decreases as inorganic salt concentration increases, and the "salting effect" of inorganic salt cations also has an effect on the CMC value. Based on the resistance of the liquid film at the gas-liquid interface affecting gas transport, the foam evolution was divided into three stages: foam generation, liquid drainage, and gas transfer. The effect of inorganic salts on these three stages was studied at the molecular level, and it was discovered that the addition of NH4Cl and MgCl2 could improve the saturation adsorption at the gas-liquid interface, reduce the surface tension of the surfactant solution, and improve foam stability. Meanwhile, inorganic salts can change the force of gas molecules, so the equilibrium force of gas across the liquid membrane increases as inorganic salt concentration increases. Additionally, the addition of inorganic salts raises the diffusive drainage coefficient, but the gravity drainage coefficient still reigns supreme in the predecay period.

Study of foam drainage agent based on g-C3N4 nanosheets reinforced stabilization

In order to solve the problem of foam instability in foam drainage gas recovery technology, a nanosheets-stabilized foam drainage agent was constructed. The synergistic effect of anionic foaming agent AOS and amphoteric betaine foaming agent CHSB were studied by measuring the foam properties and surface tension of the two foaming agents. The results showed that the foaming agent system with enhanced foam performance was obtained when the mass ratio of CHSB to AOS was 3:1, with a minimum surface tension γ of 24.3 mN/m, a foaming volume V0 of 510 mL and a half-life t1/2 of 12.03 min. To further improve the foam stability, nanosheet foam stabilizers were obtained by hydrophobic modification of g-C3N4 nanosheets, and their structures were characterized by XRD, XPS, FT-IR and contact angle. The nanofoam drainage agent was constructed by adding g-C3N4 nanosheets to the foaming system, and the half-life t1/2 reached 27.66 min. The microstructure of the foam was observed by optical microscopy to reveal the foam stabilization mechanism. The system evaluation results show that the foam drainage agent has good resistance to salt, temperature, condensate oil, and liquid carrying properties.

Oleofoams and emulsion foams stabilized by sodium stearoyl lactylate: Insight into their relations based on microstructure, rheology and tribology

Herein, three types of oil-containing foams, including oleofoams (OF), W/O and O/W emulsion gel foams (EGFs), with high overrun and desirable shaping properties were designed and prepared with sodium stearoyl lactylate (SSL). SSL-based OF and W/O EGFs were stabilized depending on the combination of the crystal adsorption at the O-A interface and viscosity enhancement in the continuous oil phase though the introduction of water droplets influenced the crystal size and distribution, while the dense assembly of oil droplets stabilized by SSL crystals jammed in the channels between bubbles was responsible for the stability and the enhancement in the strength of O/W EGFs. Of particular interest was that the introduction of concentrated air bubbles in oil-continuous foams greatly increased the strength of gel systems. Moreover, the type and water content of foams impacted both the texture and the rheology properties. The presence of three phases gave more length scales to the foaming systems and allowed finer property control through modifying various structural units. Tribological evaluation indicated that all foams had better lubrication properties with lower COF values, and there were obvious differences in the lubrication performance between gels and foams, especially for oil-continuous foams in which dense bubbles exerted influence significantly on the tribological behaviors. Particularly, the property of water-continuous foams was closely linked to emulsions, and the water phase dominated the lubrication ability which could be enhanced by forming patcher of oil films. This work would benefit further to design desired application properties and facilitate innovative development of aerated-foods products.

Cruciferin versus napin – Air-water interface and foam stabilizing properties of rapeseed storage proteins

Rapeseed protein extract has high nutritional value and good techno-functionalities, e.g. in foam systems. Yet, its exact interface and foam stabilizing mechanisms are not well understood. Rapeseed proteins comprise mainly of cruciferin and napin. Our aim was to systematically investigate the interface stabilization behaviors of cruciferin, napin and combinations of both at air-water interfaces. We used surface (dilatational and shear) rheology and microstructure imaging (AFM) and linked their behavior to their foaming properties. We observed that napin adsorbed faster at the air-water interface than cruciferin due to its smaller size, leading to 90% higher foam overrun than cruciferin (320%). The interfaces showed distinct differences in structure and mechanical properties, as cruciferin formed stiff solid-like interfaces with Ed’ = 72.5 mN/m and Gi’ = 9.0·10−3 Pa m, leading to high foam stability (half-life time 220 min). Napin formed weaker less stretchable interfaces (Ed’ = 61.8 mN/m; Gi’ = 6.7·10−3 Pa m), leading to substantially lower foam stability (half-life time 23 min). Cruciferin and napin were also mixed at 3:1, 1:1 and 1:3 (w/w) ratios. Napin increased the foamability of all mixtures with foam overrun between 400 and 420%. The mixture at 3:1 cruciferin-to-napin ratio had comparable foam stability with pure cruciferin since cruciferin dominated the mechanical properties of the air-water interface. Higher napin contents largely decreased foam stability with half-life time decreasing to 80 min. These findings provide a comprehensive understanding of the behaviors of rapeseed proteins at air-water interfaces and their link to foaming properties, which can be used to tailor the properties of aerated products stabilized by rapeseed proteins.