A review of: “Nineteenth Century Attitudes: Men of Science (Chemists and Chemistry Series,Vol. 13)”. Sydney Ross. Kluwer Academic Publishers; Dordrecht, 1991. pp. xi+235. $69.00.

Abstract

The potential of polytetrafluoroethylene (PTFE) membranes as water‐in‐oil (W/O) emulsification devices was investigated to obtain uniformly sized droplets and to convert them into microcapsules and polymer particles via subsequent treatments. Uniform W/O emulsion droplets have not been achieved using glass membranes unless the membrane was rendered hydrophobic by treatment with silanes. If a PTFE membrane is capable of providing uniform droplets for a W/O emulsion, a coordinated membrane emulsification system can be established since glass membranes have been so successful for O/W (oil‐in‐water) emulsification. In order to examine the feasibility of PTFE membrane emulsification, O/W and W/O emulsion characteristics prepared using PTFE membranes were compared with those prepared by the conventional SPG (Shirasu porous glass) membrane emulsification method. A 3 wt.% sodium chloride solution was dispersed in kerosene using a low HLB surfactant. Effects of the membrane pore size, permeation pressure, and the type of emulsifiers and concentration on the droplet size and on the size distribution (CV, coefficient of variation) were investigated. The CV of the droplets was fairly low, and the average droplet size was correlated with the critical permeation pressure of the dispersed phase, revealing that the PTFE membrane could be used as a one‐pass membrane emulsification device. Low CV values were maintained with a Span 85 (HLB = 1.8) concentration, 0.2–5.0 wt.% and a range of HLB from 1.8–5.0. For a brief demonstration of practical applications, nylon‐6,10 microcapsules prepared by interfacial polycondensation and poly(acrylamide) hydrogels from inverse suspension polymerization are illustrated.     

Effects of sorbitan monooleate on the interactions between cyclopentane hydrate particles and water droplets

The effects of a typical anti-agglomerant, sorbitan monooleate (Span80), on the interactions between cyclopentane (CyC5) hydrate particles and water droplets were investigated using a micromechanical force (MMF) apparatus. The concentration of Span80 in CyC5 was ranged from 0.01?wt% to 1?wt%, and the experimental temperature was set at 1.5°C and 7°C, respectively. The results indicate that the absorption of Span80 on the droplet surface can render the interfaces more stable, preventing hydrate agglomeration. When the preload/contact force exceeds the strength of the interface (相似文献   

A new modified low-energy emulsification method for preparation of water-in-diesel fuel nanoemulsion as alternative fuel

In this research, 24 of water-in-diesel fuel nanoemulsions were prepared using mixed nonionic surfactants of sorbitan monooleate and polyoxyethylene sorbitan trioleate (MTS). The emulsions were formed using a new modified low-energy method at hydrophilic-lipophilic balance (HLB) value of 10 and a working temperature of 20°C. Five HLB values of 9.6, 9.8, 10, 10.2, and 10.4 were prepared to identify the optimum value that gives low water droplet size at working conditions as: 5 wt% of water contents, 10 wt% of mixed surfactant concentration, and a temperature of 20°C. The effect of mixed surfactant concentration and water content on the droplet size for 0, 15, 30, 60, and 90 days has been studied. Droplet size of the prepared nanoemulsions was determined by dynamic light scattering and the nanoemulsion stability was assessed by measuring the variation of the droplet size as a function of time. Results show that the mean droplet sizes were formed between 26.23 and 277.1 nm depending on the surfactant concentrations, water contents, and storage time.     

Using the Ethoxylated Polyalkylphenol Formaldehyde Additives to Enhance the Physical Properties of Egyptian Jet Fuel A1

Nine ethoxylated polyalkyl phenol formaldehydes were prepared. From our results, it was found that the maximum (Ec) enhancement was obtained by DDP3 (20 pS/m) while it was (9 pS/m) for the blank jet fuel A1. On the other hand, the decreasing of freezing point was achieved by DDP3 (?70°C), while it was (?57°C) for the blank jet fuel. The gross and net calorific values (Cv) were ameliorated enhancement, compared with blank Cv of the jet fuel A1. The maximum net Cv was obtained by DDP3 (45.3 Mj/kg), while it was 43.7 Mj/kg for the blank sample. Also, the density increased for both molecular weight and the alkyl chain length of the prepared polymers. The minimum emulsion stability was marked for DDP3 (10 minutes), which exhibited the minimum droplet size (10 mm) at the same time the maximum reduction of surface tension (γ) for DDP3 was obtained in both jet and water (34 and 29 mNm^?1). This results means that the maximum atomization of fuel during injection should be obtained by the DDP3, which leads to complete ignition in the combustion chamber. These general enhancements of the physical properties gives the used fuel a marvelous industrial reflection and enables us to use it for military purposes.     

A novel cationic emulsifier used for preparing slow-cracking and rapid-setting asphalt: Synthesis,surface activity,and emulsification ability

A novel cationic emulsifier including nonionic fatty alcohol polyoxyethylene ether was synthesized in two steps from epichlorohydrin, octadecyl dimethyl amine, and fatty alcohol polyoxyethylene ether, and the intermediate product could also be used as an emulsifier. Their structures were characterized by FTIR, and the surface activities were investigated by surface tension, electrical conductivity, and HLB. The obtained results indicated that the critical micelle concentration (CMC) of the final product was low, 0.442 mmol/L, and the surface tension at the CMC was 41.02 mN/m. The hydrophile-lipophile balance (HLB) value was 12, which meet the requirements of asphalt emulsifiers. A series of experiments of the emulsified asphalt prepared by the emulsifiers were performed. The results showed that the emulsified asphalt could be stably stored for more than 5 days when the emulsifier was 2 wt% and the pH value was between 3 and 4. The result of demulsification experiments showed that the emulsifier is a slow-cracking and rapid-setting asphalt emulsifier.     

脂肪醇聚氧乙烯醚磺酸钠的性能研究

对合成的不同碳链脂肪醇聚氧乙烯醚磺酸钠(AnESO,EO=3,n=14,16,18)的应用性能及与重烷基苯磺酸钠(HABS)的复配进行了研究.结果表明:(1)AnESO的γcmc分别为36.16 mN·m-1,35.47 mN·m-1和34.85 mN·m-1,A14ESO发泡性较好,A18ESO稳泡性较强,耐钙稳定性分别达到了8700mg/L,9500mg/L和10000mg/L,耐盐性为A18ESO ＞ A16ESO ＞A14ESO;(2)AnESO与HABS复配可以改善HABS的耐盐性,AnESO/HABS体系与大庆原油间的界面张力在ω(AnESO):ω(HABS)约为3:7时最低,达到了3.9×10-2mN·m-1,1.4×10-2mN·m-1和4.3×10-3mN·m-1,A18ESO/HABS体系油水界面张力在NaCl含量为0～15000mg·L-1下均达到10-3mN·m-1数量级.     

Studies of Interfacial Activities of Four Kinds of Surfactants at Oil/Water Interface

This article aims to compare the interfacial activities of different kinds of surfactants in the same oil/water system. The anionic surfactants of alkylbenzene sulfonates, the polyoxyethylenated nonionic surfactants, the cationic surfactants of alkyl trimethyl ammonium chlorides, and the zwitterionic surfactants of alkyl hydroxyl sulfobetaines were used, and the interfacial tensions of the surfactant solutions against kerosene at different NaCl concentrations were measured. It is found that the interfacial activities of the alkylbenzene sulfonates are high and ultralow interfacial tensions (<0.01 mN/m) can be obtained at proper salinities. While, the nonionic surfactants have relatively low interfacial activities and the minimum tensions are around 0.01 mN/ms. The salinity scanning curves of the alkylbenzene sulfonates and nonionic surfactants decrease first, then increase, showing their interfacial activities can be changed by the salinity effectively. The cationic and zwitterionic surfactants have very low interfacial activities, of which all the tensions are higher than 0.1 mN/ms and are hard to be changed by the salinity. The experimental results may have important reference values for enhanced oil recovery.     

Water-in-Oil-in-Water Nanoemulsions Containing Temulawak (Curcuma xanthorriza Roxb) and Red Dragon Fruit (Hylocereus polyrhizus) Extracts

Hydrophobic curcumin in temulawak extract and hydrophilic betacyanin in red dragon fruit extract are high-value bioactive compounds with extensive applications in functional food. In this study, these extracts were encapsulated in water-in-oil-in-water (w/o/w) nanoemulsions as a delivery system using a two-step high-energy emulsification method. PGPR and Span 20 were used as lipophilic emulsifiers for the primary w/o emulsion. The most stable w/o/w formulation with the least oil phase separation of 5% v/v consisted of w/o emulsion (15% w/w) and Tween 80 (1.5% w/w) as hydrophilic emulsifier. The formulation was characterized by a 189-nm mean droplet diameter, 0.16 polydispersity index, and –32 mV zeta potential. The freeze–thaw stability may be attributed to the combination of low w/o emulsion content and high Tween 80 concentration in the outer water phase of the w/o/w nanoemulsions used in this study. The IC₅₀ values of the nanoemulsion and the red dragon fruit extract were similar. It means that the higher concentration of curcumin in the nanoemulsions and the lower IC₅₀ value of temulawak extract ensured sufficient antioxidant activities of the w/o/w nanoemulsions.     

Viscoelastic properties and interfacial tension of polystyrene–polyethylene blends

The linear viscoelastic properties of polystyrene polyethylene (PS/PE) blends have been investigated in the molten state. For concentrations of the dispersed phase equal to 30 vol %, the blends exhibited a droplet‐matrix morphology with a volume‐average diameter of 5.5 μm for a 70/30 PS/PE blend at 200 °C and 14.7 μm for a 30/70 PS/PE blend at 230 °C. Enhanced elasticity (G′) for both blends, in the terminal zone, compared to the modulus of the matrix (PS and PE, respectively) was observed. This is related to the deformation of the droplets in the matrix phase and hence to the interfacial forces between the blend components. The results for these uncompatibilized blends are shown to be in agreement with the predictions of the emulsion model of Palierne. These predictions were used to obtain the interfacial tension between PS and PE, which was found to be between 2 and 5 mN/m at 200 °C and 4 ± 1 mN/m at 230 °C. Independent interfacial tension measurements using the breaking‐thread method resulted in a value of 4.7 mN/m and 4.1 mN/m at 200 °C and 230 °C for the respective blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1359–1368, 2000     

Synthesis of Copolymer of Acrylamide and a Cationic-Nonionic Bifunctional Polymerizable Surfactant and Its Micellar Behavior in Water

A novel cationic-nonionic bifunctional polymerizable surfactant (PEP) was prepared by the quaternarization of poly (ethylene oxide-propylene oxide) block polymers (PEO-PPO) having terminal tertiary amine group with chloropropene. Polymeric surfactant (PAM-g-PEP) was prepared by the copolymerization of acrylamide and PEP in water and the product was confirmed by FTIR. PAM-g-PEP has exhibit excellent surface and interfacial activity and its surface tension and interfacial tension at cmc are 40.13 mN/m and 11.69 mN/m, respectively. The influence of temperature on the micellar behavior of the PAM-g-PEP in water was studied by the dynamic laser scatting (DLS) and ultraviolet spectroscope. The results showed that PAM-g-PEP in water is thermo-associative. In diluted PAM-g-PEP solution, the R_h of the polymeric surfactant increases with the temperature due to the interpolymeric aggregations are formed. In the case of concentrated PAM-g-PEP solution, the light transmittance of PAM-g-PEP aqueous solution decreases with the increasing temperature, which is may be caused by the increase of the number of the interpolymeric PEP chain aggregates.      

Effects of Homogenization Models and Emulsifiers on the Physicochemical Properties of β-Carotene Nanoemulsions

Microfluidization and high pressure valve homogenization were applied to prepare β-carotene nanoemulsions, and the mathematical relationship between homogenization pressures and emulsion temperatures, homogenization pressures/cycles, and droplet sizes, were established. Emulsions through Microfluidizer had lower temperature and much smaller droplet sizes, compared with those through high pressure valve homogenizer. Four emulsifiers were compared for their capacities to stabilize nanoemulsions. The two large molecule emulsifiers, octenyl succinate starch (OSA) and whey protein isolate (WPI), were less effective for the formation of nanoemulsions with smaller droplets than the two small molecule emulsifiers, polyoxyethylene sorbitan monolaurate (Tween 20, TW) and decaglycerol monolaurate (DML). The nanoemulsion containing WPI was the most stable, while the one containing DML was the least stable. During storage, significant degradation of β-carotene occurred in all nanoemulsions, especially in the DML stabilized one, while WPI showed the greatest capacity to protect β-carotene from degradation.     

Modeling phase separation and droplet size of W/O emulsions with oregano essential oil as a function of its formulation and homogenization conditions

Oregano essential oil emulsions (W/O) were prepared using different emulsifiers’ blend concentrations of Tween 80/Span 20, to study their phase separation during storage and to optimize the homogenization processing parameters by minimizing the droplet size of emulsions. Phase separation followed a second-order kinetic model, and relationships between the kinetic parameters and the blend concentrations of emulsifiers were established for determining the best emulsion formulations. The instability mechanism of emulsions demonstrated to be Ostwald ripening; therefore, by means of surface response methodology, mechanical homogenization parameters (11,700?rpm for 12 minutes at 1°C) were specified in order to minimize the droplet size of emulsions (1.02?±?0.12?µm).     

Dynamic and Rheological Properties of Span 80 at Liquid–Liquid Interfaces

The adsorption characteristics of Span 80 at liquid/liquid interfaces were investigated. The equilibrium interfacial tension values were successfully fitted with a Langmuir isotherm resulting in the determination of a mean molecular area from 25 to 35 Å²/mol. The measured interfacial tension values and deduced adsorption parameters depend on the experimental technique used to obtain them, either Du Noüy ring or profile analysis tensiometry. Two possible explanations to such phenomenon are provided. Adsorption kinetics of Span 80 at liquid/liquid interfaces were studied, and it was concluded that the diffusion of Span 80 molecules from the bulk is the rate determining step of the adsorption. Finally the interfacial rheology properties were investigated and compared to the Lucassen–van den Tempel model. A good match was obtained when the isotherm parameters determined by profile analysis tensiometry were used.      

CMC系列高分子表面活性剂与原油超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达2835mN/m,界面张力达到10^-110mN/m.碱的加入可显著降低高分子表面活性剂与原油的界面张力,在适当条件下界面张力达到超低值(10^-3mN/m),可望作为三次采油的驱油剂.等效烷烃模型研究表明,用碱与原油酸性组分的作用来解释碱能使界面张力下降至超低值的传统观点是不完善的,加入碱能使高分子表面活性剂胶束解缔,胶束数量增多,胶束粒径减小,单分子自由链增加,有利于高分子表面活性剂向界面迁移和排布,这是高分子表面活性剂和碱复配体系与原油界面张力下降至超低值的主要原因.     

The life of an anise-flavored alcoholic beverage: does its stability cloud or confirm theory?

The well-known alcoholic beverage Pastis becomes turbid when mixed with water due to the poor solubility of trans-anethol, the anise-flavored component of Pastis in the water solution formed. This destabilization appears as the formation of micrometer-sized droplets that only very slowly grow in size, thus expanding the life of the anise-flavored beverage. The slow growth has been attributed to an extremely low interfacial tension of the droplets. Fitting experimental droplet growth rates to an Ostwald ripening model, interfacial tensions were deduced in the past. Direct determination of the interfacial tensions was not yet reported on these systems. We have measured the interfacial tensions and used these data to predict droplet growth rates using an Ostwald ripening model and a model for creaming of the droplets. The interfacial tension was measured to be about 11 mN/m for a 30/70 w/w % ethanol/water mixture, and it decreases slightly to a value of 1.4 mN/m in the case of a 70/30 w/w % ethanol/water mixture. These values are not as low as those deduced in the past. The theoretical predictions for both the Ostwald ripening rates and the creaming rates, using the directly measured interfacial tensions, are found to contradict with the experimental results on Ostwald ripening and creaming. While the experiments on Ostwald ripening show an increase in stability with increasing ethanol concentration, the results based on our interfacial tension measurements in combination with the same Ostwald ripening model show a decrease in stability with an increase in ethanol concentration. Further research is needed to understand fully which parameters play a role in both droplet growth and the stability of these three-component emulsions to elucidate the current discrepancy between model and experiment. This could be useful for a better control of "spontaneous emulsification" processes.     

Incomplete phase inversion W/O/W emulsion and formation mechanism from an interfacial perspective

Water-in-oil-in-water (W/O/W) double emulsion can be prepared by incomplete phase inversion method using both medium chain triglycerides (MCT) and isopropyl myristate (IPM) as oil phase, Span 85-Tween 80 (HLB values of 2.5-3.0) as mixed emulsifiers. The preparation method was simple, and the final double emulsions were proved of good microstructure and particle size distribution. Owning to the addition of Tween 80 to Span 85, interfacial tension, interfacial viscosity and modulus decreased, which contributed to the phase inversion. Furthermore, formation of reverse micelles under high-speed dispersion may be a hypothesis to explain the incomplete phase inversion phenomenon.     

Model Compounds for Asphaltenes and C80 Isoprenoid Tetraacids. Part I: Synthesis and Interfacial Activities

Three model compounds for asphaltenes and two model compounds for the C₈₀ isoprenoid tetraacids (ARN) have been synthesized and their interfacial and solubility properties were investigated. All compounds exhibit high interfacial activities. The asphaltene models lowered the interfacial tension between toluene and pH 9 to around 5 mN/m at 12.5–35 μM and the tetraacid models gave a drop in the interfacial tension between chloroform and pH 9 to 13 mN/m at only 5 μM, which is consistent with previous findings for the natural occurring C₈₀ tetraacids. A sudden drop in the IFT over a very narrow concentration range was observed for two of three asphaltene models. NIR spectroscopy studies indicated an aggregation most likely a result of polar and hydrogen bond interactions. The IFT results also showed different behavior with only small changes in chemical structure. The tetraacid models have similar interfacial behavior as the C₈₀ tetraacids and will thus be suitable model compounds with their highly UV active and fluorescent properties.     

Synthesis of Surfactants from Alkali Lignin for Enhanced Oil Recovery

With the cheap and abundant resource of alkali lignin as feedstock, surfactants for enhanced oil recovery were synthesized by amination and alkylation reaction of lignosulfonate. The effects of amination conditions, including the ratio of raw materials, amination reagent, temperature, and reaction time, on nitrogen contents and surface tension of the surfactants were investigated. The results showed that ethylenediamine was more suitable for amination, and the molar ratio of alkali lignin, ethylenediamine, and formaldehyde was 1:2:1.5 at 80°C for 5 hours. The structure of synthesized products was characterized by Fourier transform infrared spectrometry. The HLB value of synthesized product was 10. The interfacial tension between Daqing crude oil and synthetic water could be decreased to 10^?2 mN/m with synthesized surfactant and NaOH at 45°C. Moreover, the effects of molecular weight of surfactants on interfacial tension were also studied. The synthesized surfactant (M_w > 10,000) showed a better interfacial activity on Daqing crude oil.     

Double inversion of emulsions induced by salt concentration

The effects of salt on emulsions containing sorbitan oleate (Span 80) and Laponite particles were investigated. Surprisingly, a novel double phase inversion was induced by simply changing the salt concentration. At fixed concentration of Laponite particles in the aqueous phase and surfactant in paraffin oil, emulsions are oil in water (o/w) when the concentration of NaCl is lower than 5 mM. Emulsions of water in oil (w/o) are obtained when the NaCl concentration is between 5 and 20 mM. Then the emulsions invert to o/w when the salt concentration is higher than 50 mM. In this process, different emulsifiers dominate the composition of the interfacial layer, and the emulsion type is correspondingly controlled. When the salt concentration is low in the aqueous dispersion of Laponite, the particles are discrete and can move to the interface freely. Therefore, the emulsions are stabilized by particles and surfactant, and the type is o/w as particles are in domination. At intermediate salt concentrations, the aqueous dispersions of Laponite are gel-like, the viscosity is high, and the transition of the particles from the aqueous phase to the interface is inhibited. The emulsions are stabilized mainly by lipophilic surfactant, and w/o emulsions are obtained. For high salt concentration, flocculation occurs and the viscosity of the dispersion is reduced; thus, the adsorption of particles is promoted and the type of emulsions inverts to o/w. Laser-induced fluorescent confocal micrographs and cryo transmission electron microscopy clearly confirm the adsorption of Laponite particles on the surface of o/w emulsion droplets, whereas the accumulation of particles at the w/o emulsion droplet surfaces was not observed. This mechanism is also supported by the results of rheology and interfacial tension measurements.     

Evaluation of adsorption of nonionic surfactants blend at water/oil interfaces

The inherent biocompatibility of Span and Tween surfactants makes them an important class of nonionic emulsifiers that are employed extensively in emulsion and foam stabilization. The adsorption of Span-Tween blend at water/oil surface of emulsion has been investigated using a population balance model for the first time. Destability of emulsion was modeled by considering sedimentation, coalescence and interfacial coalescence terms in population balance equation (PBE). The terms of coalescence efficiency and interfacial coalescence time were considered as a function of surface coverage of droplets by surfactant molecules. The surface coverage at different surfactant concentrations was determined by minimization of difference between the model predictions and experimental average droplet sizes. After optimization, the surface coverage outputs were fitted with different adsorption isotherms to evaluate the adsorption behavior of Span-Tween surfactants blend at water/oil surface. The results show that Freundlich isotherm can predict the adsorption behavior of closer to the experimental observation. Moreover, fitted parameters imply the favorable adsorption of Span-Tween blend at water/oil interface.