Emulsification of Chemically Modified Vegetable Oils for Lubricant Use

Oil in water emulsions of several vegetable oils were studied in order to prepare a useful lubrication fluid. Several previously uncharacterized systems were studied in this paper, including those made from epoxidized vegetable oils. A series of different surfactants were studied in order to obtain emulsions suitable for lubrication applications. The epoxidized oils were found to form stable oil in water emulsions using several different surfactant systems. Only the (4) lauryl ether dodecyl polyethoxylated nonionic surfactant and a modified palm stearin methoxy ester ethoxylate were able to stabilize ordinary soybean oil for 1 week under our test conditions. Overall, the best surfactants were those with an HLB value slightly above 9. The droplet size of emulsions made with surfactants formed submicron droplets, whereas only droplets of larger diameter were obtained when surfactants were not added. Most importantly, a lubrication study was performed showing that even a 1% emulsion of the vegetable oils used in this study can reduce friction nearly as well as using the base oil alone.     

The effect of shear and oil/water ratio on the required hydrophile-lipophile balance for emulsification

Required hydrophile-lipophile balance (HLB) values were examined in terms of the nature of kerosene-water, both oil-in-water (O/W) and water-in-oil (W/O), emulsions formed using Span 80/Tween 80 surfactant blends. Both the nature of the emulsification method and the oil/water ratio were critical in determining the resulting emulsion type. Both high- and low-shear conditions were investigated. Under high shear, low internal phase emulsions formed using the surfactant mixtures that corresponded to the required HLB values for emulsification involving kerosene (6 for W/O and 14 for O/W). However, at low shear, high internal phase (concentrated) emulsions resulted. Furthermore, depending on the oil/water ratio, some of the high internal phase emulsions were opposite to the type expected, given the HLB of the surfactant blend used. From these results, it appears that the emulsification technique (applied shear and oil/water ratio) used can be of greater importance in determining the final emulsion type than the HLB values of the surfactants themselves.     

Edible oil-in-water emulsions stabilized by hydrophile–lipophile balanced sucrose ester

Conventional emulsions are mostly stabilized by surfactants and for stabilization of oil-in-water emulsions the surfactants should be hydrophilic or with HLB numbers larger than seven. In this work, we report that edible oil-in-water emulsions can also be stabilized by surfactants with an HLB value close to seven. With edible sucrose ester C-1807 (HLB no. = 7) as emulsifier and three edible oils (canola oil, olive oil, soybean oil), edible oil-in-water emulsions can be stabilized by C-1807 at concentrations beyond its critical aggregation concentration (CAC). Although monomeric C-1807 behaves as an inferior emulsifier, they assemble to form multilamellar vesicles in water at concentrations higher than the CAC giving a viscoelastic/gel-like aqueous phase which is partly responsible for emulsion stabilization. Specifically, at 2 wt%, high internal phase emulsions (HIPEs) with ϕ_o = 0.75 can be obtained, which are stable against cooling–heating cycles between 5 and 30°C during storage. The vesicles disperse in the aqueous lamellae surrounding the oil droplets, which together with the viscoelastic/gel-like continuous phase prevents them from flocculation and coalescence.     

玉米油W1/O/W2型多重乳状液稳定性的研究

高脂食品严重危害着人类健康,这引起人们对低脂食品的的不断追求,因此脂肪替代品的开发越来越受到人们重视。本试验以玉米油和生物高聚物为主要原料通过两步乳化法制备W1/O/W2多重乳状液作为脂肪替代品(FS),以离心稳定性为衡量标准,用显微镜直接观察,探讨了初复乳乳化工艺、各相相对体积比对玉米油W1/O/W2型多重乳状液体系稳定性的影响。结果表明:1.影响玉米油多重乳状液稳定性的主要因素有:复乳的乳化工艺,内水相与油相体积之比等。2.两步乳化工艺中第二步乳化工艺对复乳稳定性影响较大,其规律是随着乳化强度的提高,粒径减小,稳定性呈上升趋势,适宜的乳化条件为7200 r.min.1,13 min,而第一步乳化工艺对复乳稳定性几乎没有影响。3.内水相与油相、初乳与外水相均是影响复乳稳定性的主要因素,前者主要是依靠改变初乳黏度来影响复乳稳定性,后者主要是乳滴间范德华力与电排斥力共同作用的结果,适宜的体积比分别为1:4和1:1。     

Effects of Surfactant Headgroups on Oil-in-Water Emulsion Droplet Formation: An Experimental and Simulation Study

Nonpolar oils such as kerosene and diesel oil are common collectors in coal flotation. Surfactants are usually added to the pulp to emulsify the oil collectors. The present study used dodecane as the oil collector and anionic sodium dodecyl sulfonate (SDS) and nonionic tetraethylene glycol monododecyl ether (C₁₂EO) with different headgroups and identical chain alkyls to investigate the effect of the surfactant headgroups on oil-in-water emulsion droplet formation. The morphology and stability of dodecane emulsions were determined experimentally. Density functional theory (DFT) and molecular dynamics (MD) simulations were used to explain the microscopic mechanism. The results of DFT indicated a larger interaction between SDS and the water molecules than that between C₁₂EO and water molecules. The results obtained by MD suggested that the SDS headgroup exhibited a loose arrangement and a relatively large gap size, thereby weakening the interaction between SDS and water molecules at the dodecane/water interface. In contrast, the headgroups of C₁₂EO were bent and interwoven with others to form a tight reticulation at the interface. According to the simulation results, the ability of the surfactant to form dodecane-in-water emulsion droplets depends on the arrangement of the surfactants at the oil–water interface rather than on the interaction strength between the headgroups of the surfactants and water molecules. The presented microscopic mechanism of the surfactant headgroup formation of oil-in-water emulsion droplets offers surfactant selection and design references.     

乳化方式及助乳化剂对蓖麻油乳化液性能的影响

分别采用恒速搅拌乳化、高剪切乳化及超声波乳化3种方式,以非离子型表面活性剂失水山梨醇单脂肪酸酯(Span)与聚氧乙烯失水山梨醇单脂肪酸酯(Tween)为复合乳化剂对蓖麻油进行乳化,考察了助乳化剂正辛醇、异辛醇、十二醇对乳化体系稳定性的影响。结果表明,随助乳化剂脂肪醇碳链长度的增加,蓖麻油的乳化稳定性提高;采用超声波乳化方式可制得稳定的蓖麻油乳化液,且稀释稳定性良好。     

Novel evaluation method for the water- in- oil (W/O) emulsion stability by Turbidity Ratio Measurements

The turbidity ratio method of evaluating the stabilities of water-in-oil emulsions has been established with two wavelengths (450 and 850 nm) by taking the intensity ratio of two beams. The slopes of turbidity ratio of several water-in-oil emulsions with time were calculated to evaluate the emulsion stabilities at different HLB (Hydrophilie-Lipophile Balance), the amounts of emulsifiers, and water contents. The results of the turbidity ratio technique were consistent with the amount of phase separation of emulsions incubated for 30 days at room temperature. From the turbidity ratio measurements, we determined that the required HLB of diesel oil was about 6.0, and that the stability of emulsion increased with the amount of emulsifier. The increasing amount of the water showed a negative effect on emulsion stability. Finally, this method provides a useful tool for the quick evaluation of the required HLB and the condition of emulsification throughout this study.     

Parameter Selection of Emulsification Processes: Conditions for Nano‐ and Macroemulsions

Beside factors like nature of the emulsifier as well as rheology of the interface and continuous phase, the droplet size distribution of an emulsion governs emulsion properties such as long‐term stability over months or years, texture, and optical appearance. Consequently, emulsions with droplets in nano‐scale are of interest when well‐defined emulsion properties are needed. The formation of emulsions consisting of water, corn oil, and nonionic surfactants using disc systems and high‐pressure homogenizers was studied. The emulsion droplet size distributions were obtained by means of a laser diffraction method. The influence of parameters affecting the emulsion formation, such as emulsification time, viscosity for the disc system, pressure, and homogenizing steps for high‐pressure homogenization, was investigated. Data to determine the effect of the surfactant type and concentration were collected for both systems. The emulsification process using a disc system was evaluated in order to highlight its advantages and limits in comparison to high‐pressure homogenization.     

Water-in-Diesel Fuel Nanoemulsions Prepared by High Energy: Emulsion Drop Size and Stability, and Emission Characteristics

Water-in-diesel fuel nanoemulsions were prepared with mixed nonionic surfactants. The high energy emulsification method was used to form three emulsions containing different water contents: 5, 10 and 14% (v/v). These nanoemulsions were stabilized with a mixture of 20% sorbitan monooleate, and 80% polyethoxylated (20 EO) sorbitan trioleate, resulting in an HLB of 10 (HLB—hydrophilic-lipophilic balance). The effect of water on the droplet size, emulsion calorific value, and emission gases such as nitrogen oxides, carbon dioxide emissions and exhaust gas temperatures in diesel engines has been studied. It was found that the mean sizes of the droplets formed (between 19.3 and 39 nm) depend on the water content and the concentration of the blend emulsifiers.     

Oil splitting in industrial cleaning systems as studied by conductivity and interfacial tension

Characteristics of emulsion formation and splitting into aqueous and oily phases in simple and formulated surfactant systems were studied via conductivity. In systems composed of mixed nonionic ethoxylated alcohol surfactants, K₂CO₃, and emulsified n-hexadecane, conductivity decreased linearly with increasing oil volume fraction at HLB (hydrophile-lipophile balance) values of 12.9 and 13.9. The slope of the plot was ca. −3/2, in agreement with the Maxwell expression. At values less than or equal to an HLB of 11.3, conductivity first increased with a small addition of oil and then decreased nearly linearly with subsequent amounts. This was probably due to low HLB surfactants partitioning into the oily phase. When the type of oil was varied, the reduced conductivity also decreased linearly with volume fraction of emulsified oil. The slope was ca. −3/2 for oil weights ranging from very light (n-hexadecane) to very heavy (80W–90 gear oil), also in agreement with the Maxwell expression. Oil separation rates were measured by monitoring the change in conductivity in the lower region of the emulsion (where the aqueous layer formed) during splitting of the oily phase. Heavier oils were found to separate faster than light oils. Oils containing lubricity agents split at the slowest rate. Systems with lower HLB surfactants also displayed slower splitting rates. Splitting rates for a variety of systems, from simple oil and saline systems to more complex formulated systems, over temperatures from 23 to 75°C, were related to oil-aqueous interfacial tension values through a power law expression composed of the maximum splitting rate and the interfacial tension between saline and oil at 23°C.     

Alkyd emulsions

Various aspects of alkyd emulsion technology have been investigated. The influence of alkyd oil length, acid value and hydroxyl number and type of surfactant used as emulsifier, on shear stability of alkyds emulsions have been studied. It was found that the acid value was the most important alkyd parameter, the stability increasing with increasing oil length. It is also shown that anionic surfactants give emulsions with small droplet sizes at lower concentrations than do nonionics. Polymerizable nonionic surfactants have been tested as emulsifiers and compared with conventional surfactants of the same hydrophilic lipophilic balance (HLB). It was found that surfactants capable of participating in the autoridative curing process give faster drying and improved film hardness compared with nonreactive surfactants. The distribution of driers between the alkyd phase and the water phase has been investigated. It was found that low pH and the use of hydrophilic anionic surfactants, such as sodium dodecyl sulphate, favour partitioning of cobalt into the aqueous phase which is unfavourable with respect to drying properties.     

Preparation of epoxy acrylate emulsion using mixed surfactants and its polymerization

Summary A series of epoxy acrylate emulsions were prepared with several surfactants ranging from HLB 12 to 14 at 40°C. For epoxy acrylate emulsion, additives and conditions were established among factors: HLB value of emulsion, agitation speed, water dropping speed, and dropping amount of the deionized water. For emulsion polymereization with water soluble initiator KPS, emulsion was broken during polymerization, because interfacial complex formed by association of surfactant with co-surfactants stabilizing emulsion was weakened by interpenetration of radicals formed at aqueous. Accordingly, the polymerization of epoxy acrylate emulsion was carried out by using oil soluble initiator, AIBN, and the conversion changes with initiator concentration and HLB values were investigated.     

Effect of mixing protocol on formation of fine emulsions

Emulsions are usually stabilised with a mixture of surfactants with different hydrophilicity. The initial partitioning of surfactants between the dispersed phase and continuous phase, and how these phases are brought into contact, can significantly affect the emulsification processes. Dynamic-phase behaviour maps were prepared to allow for a systematic investigation of the effects of emulsification routes on emulsion properties. Six semibatch modes of additions with constant surfactant concentration across the routes were selected. For a target cyclohexane-in-water emulsion using a pair of polyoxyethylene nonylphenyl ether surfactants with a specified HLB and water volume fraction, fine droplets could form only if water dissolving the water-soluble surfactant was added to the oil dissolving the oil-soluble surfactant. This route allowed the transitional inversion to occur and as a result fine droplets were formed due to an ultra-low interfacial tension. The addition of water dissolving the water-soluble surfactant to oil dissolving the oil-soluble surfactant, direct emulsification method, produced by far large droplets because of a rather high interfacial tension. In a series of experiment, the semibatch direct and phase-inversion emulsification method, were assimilated in situ. The impeller location was used as a variable that controls which phase is added as the dispersed phase. The location of impeller in relation to the interface did not affect the emulsion drop size at a high agitation rate, but it did at a low agitation rate. Under low agitation speed and when the impeller was placed in the oil phase, the oil layer progressively, but slowly, dragged the water phase and eventually inverted to an oil-in-water emulsion, indicating that transitional-phase inversion has locally occurred in the oil layer. At a high agitation speed the mechanical energy provided by the impeller homogenised the emulsion instantaneously and did not allow the optimum formulation and the associated ultra-low interfacial tension to be reached regardless of location of the impeller. A high impeller speed increased drop size by transforming the transition inversion mechanism to a catastrophic mechanism under which the size of drops is mainly determined by the mechanical energy provided. This paper aims to show how some of the complexities involved in emulsification processes can be explained by consulting with dynamic-phase maps.     

Use of pulsed nuclear magnetic resonance to predict emulsion stability

Pulsed nuclear magnetic resonance (NMR) was used to measure extent of oil solidification during cooling of oil-in-water emulsions. “Percent interaction,” derived from these measurements, was found to correlate well with actual resistance of the emulsion to creaming and phase separation during storage. Average oil droplet size gave a fair correlation with stability, but the correlation of required Hydrophile-Lipophile Balance (HLB) with stability was poor. Pulsed NMR cooling curve measurements on emulsions offer an improved method for prediction of emulsion stability. Presented at the AOCS Meeting in Chicago, September 1976.     

非离子表面活性剂HLB乳化规则的研究(Ⅱ)HLB界面模型验证与影响乳液稳定的各种实验因素

以白油为乳化对象 ,AEO3 、AEO9、TX4 、TX12 为乳化剂 ,在不同的乳化剂配比 (HLB值 )、用量的实验条件下 ,通过观察乳液破乳 ,分层的程度和测定乳液显微镜粒径分布 ,发现乳液稳定性随HLB值的变化规律与文Ⅰ相同 ,可用同样的界面模型稳定机理解释。本文还考察了乳化剂用量、超声乳化、乳化剂种类对乳液稳定性的影响。实验中发现乳化体系的最佳HLB值随活性剂用量的增加而上升 ,此现象被解释为粒子粒径小的乳化体系的最佳HLB值更大。     

Effect of emulsifiers on the preparation of food‐grade oil‐in‐water emulsions using a straight‐through extrusion filter

This paper describes the preparation characteristics of food‐grade soybean oil‐in‐water (O/W) emulsions using a novel straight‐through extrusion filter, named a silicon straight‐through microchannel (MC). Polyglycerol fatty acid ester (PGFE), polyoxyethelene sorbitan monolaurate (Tween 20), and sucrose fatty acid ester were tested as emulsifiers. Optical observations of the emulsification process exhibited that monodisperse oil droplets were stably formed from an oblong straight‐through MC for PGFE and Tween 20. The effect of the emulsifier on the straight‐through MC emulsification behavior is discussed. The selected PGFE‐ and Tween 20‐containing systems enabled us to prepare monodisperse O/W emulsions with droplet diameters of 38—39 μm and coefficients of variation below 3% using an oblong straight‐through MC with a 16 μm‐equivalent channel diameter.     

Influence of surfactants on the parameters of polylactide nanocapsules containing insulin

The aim of this work was to investigate the influence of nonionic emulsifiers on the characteristics of poly(d,l-lactide) (PLA) nanocapsules, which were formulated using an ultrasound probe by a modified water-in-oil-in-water (W/O/W) emulsification and solvent evaporation method. The different types of surfactants were used in both steps as hydrophobic and hydrophilic emulsifiers, respectively. The effects of emulsifiers in modifying the size of the nanocapsules were compared with respect to their weighted hydrophilic-lipophilic balance (HLB) value, and the size was also affected by the content of the emulsifying agent. The mean diameters of insulin-loaded nanocapsules ranged from 150 to 320 nm and were dependent on the types and content of the surfactants. The variations are due to the aggregation of the surfactants on the inner interface between the inner water and oil of the double emulsion. The encapsulation efficiencies and drug release rates were also affected by the addition of emulsifiers in the preparation process.     

Application of magnetic nanoparticles as demulsifiers for surfactant-enhanced oil recovery

Nonionic surfactants are increasingly being applied in oil recovery processes due to their stability and low adsorption onto mineral surfaces. However, these surfactants lead to the production of emulsified oil that is extremely stable and difficult to separate by conventional methods. This research characterizes the stability of crude oil mixed with a nonionic surfactant, L24–22, in a brine solution. When subjected to gravity separation, a middle oil-rich and bottom water-rich emulsion are generated for various water–oil ratios. Thermal treatments can effectively break oil-rich emulsions, but the bottom water layer remains contaminated with micron-sized crude oil droplets. A magnetic nanoparticle treatment is shown to demulsify the crude oil emulsions, dropping the total organic carbon (TOC) in the water layer from 1470 to 30 ppm.     

Influence of Processing on the Physical Stability of Multiple Emulsions Containing a Green Solvent

The influence of the emulsification process on the microstructure and physical stability of model water‐in‐oil‐in‐water (W/O/W) emulsions formulated with a green solvent and a mixture of amphiphilic copolymers as emulsifiers was investigated. Emulsions were prepared by applying a homogenization step with a rotor‐stator device followed by high‐pressure homogenization. Viscous flow tests, transmitted light optical microscopy, globule size distribution (GSD), and multiple light scattering (MLS) measurements were carried out. The GSDs obtained were the result of a recoalescence due to overprocessing and the coalescence of inner droplets with the outer water phase. MLS detected a main destabilization mechanism by creaming. The passing of the emulsion through a high‐pressure homogenizer (HPH) significantly delayed the creaming process.     

Smectites as colloidal stabilizers of emulsions: I. Preparation and properties of emulsions with smectites and nonionic surfactants

Bentonites, montmorillonites, and hectorites were used as colloidal stabilizers of oil-in-water (O/W) emulsions. The enrichment of the solid particles on the oil–water interface was attained by the addition of nonionic coemulsifiers (glycerol monostearate (GMS), deca(ethylene glycol) hexadecyl ether, alkyl polyglucoside, and lecithin). The clay mineral content of the aqueous dispersion was 2% (w/w). Stable emulsions required amounts of 0.5–1.5 g coemulsifier per 100 ml aqueous dispersion. Oil volume fraction was varied between φ=0.17 and φ=0.50. At φ>0.50 the O/W emulsions changed into water-in-oil (W/O) emulsions. The number average diameter of the droplets was about 25 nm. The volume average diameter (50–100 nm) more strongly depended on the clay mineral/coemulsifier combinations. Wyoming bentonite and the corresponding delaminated sodium montmorillonite were useful stabilizers; technical, soda-activated bentonites yielded unstable emulsions, or emulsification was not successful. A synthetic hectorite which caused pronounced thickening of the coherent phase was an effective stabilizer. Creaming was often observed because of the buoyancy of the large droplets. Most of the creamed emulsions were stable over long periods and did not separate an oil phase. The resistance against creaming increased with the oil volume fraction. An increase of the solid content had to be accompanied by an increase of the coemulsifier concentration to reduce the rate of creaming.