Encapsulation and Prolonged Release Behaviour of W/O/W Type Multiple Emulsions

W/O/W type multiple emulsions were prepared by two step emulsification procedures using an oily lymphographic agent, lipiodol, as an inner oil phase and Pluronic F-68 as a hydrophilic emulsifier contained in the outer aqueous phase. Span 80, Pluronic L-64 and HCO-60 were used as emulsifiers incorporating them into the inner oil phase. The phase volume of the inner and outer aqueous phases and the yield of the w/o/w type multiple emulsions were studied. The dissolution behaviour of the w/o/w type multiple emulsions were determined by a dialysis method employing cellulose tubing. The effect of emulsifier type and the amount of HCO-60 on the stability and prolonged release behavior of the w/o/w type multiple emulsions with or without lecithin, was also examined. The results indicate the HCO-60 is a better emulsifier than Span 80 or Pluronic L-64. Its use improves the stability and the prolonged release behavior of w/o/w type multiple emulsions.     

Influence of the HLB parameter of surfactants on the dispersion properties of brine in residue

In order to study the relationship between the hydrophilic–lipophilic balance of surfactants and the dispersion properties of brine in residue, using droplet size and droplet distribution analytical method were determined on emulsions prepared with emulsifier blends of varying hydrophilic–lipophilic balance (HLB) values the required HLB values of emulsion. The objective of this study was to investigate the effect of HLB on the dispersion properties of brine in residue. The type of emulsion was prepared using emulsifiers with various hydrophilic–lipophilic balance values. The droplet size and droplet distribution varied widely among emulsions containing emulsifiers with different HLB values. The results obtained in this study indicate that the different systems of residue/brine need different HLB values. The HLB value of the emulsion with the least dispersion ratio or the least average droplet diameter was taken as the system of residue/brine required HLB the required HLB values of (NH₄)₆Mo₇O₂₄·4H₂O, Co(NO₃)₂, NiSO₄, Ni(NO₃)₂ and FeSO₄. The results showed that the values of HLB were determined as different system of emulsion.     

Effect of emulsifier HLB and stabilizer addition on the physical stability of thyme essential oil emulsions

The objective of this work was to formulate and to further improve the stability of emulsions based on thyme essential oil. Several nonionic surfactants of different nature and with different hydrophilic?lipophilic balance (HLB) values were investigated. The surfactant with optimal HLB found for the thyme essential oil was Appyclean 6548 (HLB: 9-9.5). Afterwards, stabilizing biopolymers were added in order to improve emulsion stability. Properties of emulsions were evaluated in terms of droplet size and physical stability. Thyme essential oil/W emulsions formulated with a new biodegradable emulsifier (alkyl polypentoside) and welan gum as stabilizer were obtained with high shelf-life.     

Oil Base Mud. Part I: Synthesis of Some Local Surfactants Used as Primary Emulsifiers for Oil Base Mud and Evaluation of Their Rheology Properties

Six oil soluble nonionic surfactants with different HLBs have been prepared. Their HLBs situate between 3.9 and 6.7. Transesterification was carried out for glycerol and triethanol amine with oleic acid at different moles to obtain six emusilifiers. They named glycerol momooleate (I), glycerol diooleate (II), glycerol trioleate (III), triethanol amine mono-, di- and tri-oleate (IV), (V,) and (VI). The chemical structure was confirmed using; the elemental analysis, FTIR and ¹HNMR. They were evaluated as a primary emulsifiers (PE) for thdrilling fluids (oil base mud) comparing with a currently used primary emulsifier (Fc). The water in oil base mud (w/o emulsions) was prepared. The concentration of emulsifiers and their HLB exhibited interesting rheology properties including shear-thinning behavior, yield value, viscoelastic effects, thixtropy, gel strength, and filtration loss. The rheology properties of such emulsions strongly depended on the average size distribution of the dispersed droplets that could be varied both with the bulk concentration and HLB value of the emulsifiers. The interfacial and surface properties of these emulsifiers suggest that the droplet size of the dispersed phase and bulk concentration are strongly related to the HLB value of emulsifiers. The w/o emulsion (mud formulation) stability is sensitive to the droplet size of the dispersed phase and HLB value of the used emulsifier. The results were discussed on the light the chemical structure of the primary emulsifiers and the emulsion ingredients.     

Thermoanalytical and microscopical investigation of the microstructure of emulsions containing polymeric emulsifier

Polymeric emulsifiers provide exceptional stability to oil-in-water, water-in-oil or multiple emulsions by their steric stabilization. Pemulens as polymeric emulsifiers are able to stabilize o/w type emulsions because their short lipophilic part integrates into the oil droplets while their long hydrophilic part forms a micro gel around the droplet. In our present study the microstructure and integration of the polymeric emulsifier at the water-oil interface was investigated with thermogravimetric and microscopical methods. It was established that depending on the amount of both of the polymeric emulsifier and added coemulsifier the microstructure of the system changes.     

Properties of various phospholipid mixtures as emulsifiers or dispersing agents in nanoparticle drug carrier preparations

The characteristics of mixed phospholipids were examined when used as dispersing agents and emulsifiers. Synthesized phospholipids were mixed to investigate the potential effects of different hydrophilic or lipophilic groups on emulsification and dispersion. To examine the effects of the hydrophilic polar head group on the dispersing or emulsifying potency of phospholipids, l--phosphatidylcholine dimyristoyl (DMPC) and l--phosphatidylethanolamine dimyristoyl (DMPE) were mixed in various ratios. Moreover, all combinations of two kinds of phosphatidylcholines (PCs) out of l--phosphatidylcholine dilauroyl (DLPC), DMPC, l--phosphatidylcholine dipalmitoyl (DPPC) and l--phosphatidylcholine distearoyl (DSPC) were tested (50:50, w/w) to examine the effects of the hydrophobic carbon chains on the dispersing or emulsifying potency of phospholipids. Mean diameters of vesicles and O/W emulsions prepared by sonication were measured. Vesicles prepared with DMPC–DMPE mixtures gave larger particle sizes than those of DMPC alone. Particle sizes of vesicles prepared with a mixture of two kinds of PCs increased when adding a PC with a longer carbon chain, while particle sizes in a mixture with a PC having a shorter carbon chain was comparable to those in pure PC. In vesicles that were generated by hydration of phospholipids and had a bilayer form, the physical form of the phospholipids consisting of bilayers was thought to be an important factor influencing particle sizes. Among the emulsions, DMPC–DMPE mixtures gave a similar droplet size to DMPC alone. Droplet size in emulsions prepared with a mixture of two kinds of PCs had a strong positive correlation with the total number of carbons, which corresponds to hydrophilic–lipophilic balance (HLB). In O/W emulsions, in which phospholipids were absorbed at water–oil interfaces and which have a single layer form, HLB was thought to be a major factor in the determination of particle size; likewise with non-ionic emulsifiers.     

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.     

Some aspects of stability of multiple emulsions in personal cleansing systems

The two dominant factors that were found to affect the stability of multiple emulsions in high HLB surfactant systems are the osmotic pressure imbalance between the internal aqueous phase and the external aqueous phase, and the adsorption/desorption characteristics of the emulsifier/surfactant film at the oil/water interface. Synergistic interaction between the low HLB emulsifier and the high HLB surfactant that produces very low interfacial tension of the order of 10(-2) mN/m at the oil/water interface was found to occur in some of the systems investigated. Long term stability was observed in multiple emulsion containing these systems. However, no synergy was observed in systems in which either the oil or the emulsifier, or both, contained unsaturated chains. In fact, desorption of the adsorbed surfactant film was observed in systems containing unsaturated chains. The observed desorption from the interface of the emulsifier in these systems was attributed mainly to the inability of the unsaturated chains to form a close packed, condensed interfacial film. Presence of closely packed, condensed interfacial film is necessary to prevent solubilization of the adsorbed low HLB emulsifier by the high HLB surfactant. Multiple emulsions prepared using systems containing unsaturated hydrocarbons were highly unstable.     

Influence of composition on the encapsulation properties of P/O/W multiple emulsions for Vitamin C

Abstract

The aim of this work was to study the encapsulation properties of polyols-in-oil-in-water (P/O/W) multiple emulsions for Vitamin C (Vc). The influence of formulation factors, including the concentration of lipophilic emulsifier, hydrophilic emulsifier, salt and glycerol had been investigated. The results indicated that the encapsulation stability could be improved by increasing the lipophilic emulsifier concentration which could strengthen the interfacial film. In contrast, the excess of hydrophilic emulsifier destabilized the emulsion. The presence of glycerol in the outer aqueous phase accelerated the phase transfer, thus reduced the encapsulation rate. The addition of salt in inner polyols phase had little effect on encapsulation rate while markedly affected the morphology and stability of this system. P/O/W multiple emulsions showed better encapsulation stability than the W/O/W multiple emulsions as the former’s encapsulation rate could remain more than 75% after 2?weeks while the latter only remained less than 60%. Meanwhile, the P/O/W emulsions exhibited higher storage modulus (G’), bigger loss modulus (G’’) and broaden linear viscoelastic regions than W/O/W emulsions.     

Emulsifying potency of new amino acid-type surfactant (II): stable water-in-oil (W/O) emulsions containing 85 wt% inner water phase

The ternary phase diagram for N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L-glutamate (C12HEA-Glu), a new amino acid-type surfactant, /oleic acid (OA)/water system was established. The liquid crystal and gel complex formations between C12HEA-Glu and OA were applied to a preparation of water-in-oil (W/O) emulsions. Stable W/O emulsions containing liquid paraffin (LP) as the oil and a mixture of C12HEA-Glu and OA as the emulsifier were formed. The preparation of stable W/O emulsions containing 85 wt% water phase was also possible, in which water droplets would be polygonally transformed and closely packed, since the maximum percentage of inner phase is 74% assuming uniformly spherical droplets. Water droplets would be taken into the liquid crystalline phase (or the gel complex) and the immovable water droplets would stabilize the W/O emulsion system. The viscosity of emulsions abruptly increased above the 75 wt% water phase (dispersed phase). The stability of W/O emulsions with a lower weight ratio of OA to C12HEA-Glu and a higher ratio of water phase was greater. This unusual phenomenon may be related to the formation of a liquid crystalline phase between C12HEA-Glu and OA, and the stability of the liquid crystal at a lower ratio of oil (continuous phase). W/O and oil-in-water (O/W) emulsions containing LP were selectively prepared using a mixture of C12HEA-Glu and OA since the desirable hydrophile-lipophile balance (HLB) number for the emulsification was obtainable by mixing the two emulsifiers.     

Preparation of Water-in-Diesel Fuel Nanoemulsions Using High-Energy Emulsification Method and a Study of Some of Their Surface Active Properties

In this work, formations of water-in-diesel fuel nanoemulsions using water/mixed nonionic surfactant/diesel fuel system has been studied. The high-energy emulsification method was used to form three emulsions using different water contents: 5, 10, and 14% (v/v) namely; E1, E2, and E3, respectively. These nanoemulsions were stabilized with emulsifiers having different hydrophilic lipophilic balance (HLB), namely, Span 80 (HLB = 4.3), Emarol 85 (HLB = 11), and their mixture (SE) with HLB = 10. The effect of water on the droplet size formation has been investigated. The interfacial tension and thermodynamic properties of the individual and emulsifiers blends have been studied. The interfacial tension (γ) measurements at 30°C were used to determine the critical micelle concentration (CMC) and surface active properties of these emulsifiers. The water droplet sizes were measured by dynamic light scattering (DLS). From the obtained data, it was found that mean sizes between 19.3 and 39 nm were obtained depending on the water content and concentration of blend emulsifiers (SE). Also, the results show that the interfacial tension (γ) gives minimum value (10.85 mN/m) for SE comparing with individual emulsifier (17.13 and 12.77 mN/m) for Span 80 and Emarol 85, respectively. The visual inspection by transmission electron microscopy showed that the obtained results support the data obtained by dynamic light scattering.     

Optimization of Oil-in-Water Emulsion Stability: Experimental Design,Multiple Light Scattering,and Acoustic Attenuation Spectroscopy

To find an optimal formulation of oil-in-water (O/W) emulsions (φ_o = 0.05), the effect of emulsifier nature and concentration, agitation speed, emulsifying time, storage temperature and their mutual interactions on the properties and behavior of these dispersions is evaluated by means of an experimental design (Nemrodw software). Long-term emulsion stability is monitored by multiple light scattering (Turbiscan ags) and acoustic attenuation spectroscopy (Ultrasizer). After matching surfactant HLB and oil required HLB, a model giving the Sauter diameter as a function of emulsifier concentration, agitation speed and emulsification time is proposed. The highest stability of C₁₂E₄-stabilized O/W emulsions is observed with 1% emulsifier.     

Effects of compositions on the stability of polyols-in-oil-in-water (P/O/W) multiple emulsions

Polyols-in-oil-in-water (P/O/W) multiple emulsions were successfully prepared by using polyols as inner aqueous phase to avoid instabilities caused by water. The influence of polyols, oils and emulsifiers on the morphology and stability of P/O/W multiple emulsions were studied and the stability mechanisms of this new kind of multiple emulsions were also explored. Glycerol that has the worst solubility in oil phase contributed to the formation of stable inner droplets which agree with the Ostwald Ripening theory. Mineral oil worked well with the system proving that oils possessing similar solubility parameters with the hydrophobic group of emulsifiers benefited for system stability. Several typical surfactants had been investigated in this article, and it turned out that emulsifiers Cetyl PEG/PPG-10/1 Dimethicone and the block copolymer Poloxamer 407 were suitable for the P/O/W system. The stability of the system affected by different compositions was evaluated based on microscopic observation and rheological measurements. The novel multiple emulsions will provide enlightening recommendations for future investigations and applications in cosmetic, food and pharmaceuticals, including drug delivery and the encapsulation of hydrophilic actives and actives that are soluble in polyols.     

淀粉/丙烯酸反相乳液体系的稳定性研究

以丙烯酸(AA)单体的水溶液为水相,液体石蜡为油相,失水山梨醇三油酸酯(Span 85)和辛基苯基聚氧乙烯醚(Opan 10)为复合乳化剂,合成了淀粉/丙烯酸反相乳液;考察了乳化剂亲水亲油平衡值(HLB值)、油水比、乳化剂用量、单体浓度、温度对乳液稳定性和类型的影响.结果表明,合成淀粉/丙烯酸稳定反相乳液体系的适宜条件...     

A Three-Step Model for Submicron W/O Emulsion Formation in a Transitional-Phase Inversion Process

A three-step model of the transitional phase inversion (TPI) process for the formation of water-in-oil (W/O) emulsions is presented. Three types of emulsions exist in an emulsification process at different oil–water ratios and hydrophilic–lipophilic balance (HLB). A stable W/O emulsion was obtained using Sorbitan oleate (Span 80) and polyoxyethylenesorbitan monooleate (Tween 80) with a specified HLB and oil volume fraction. Oil was added into water, which contained the water-soluble surfactant, to dissolve the oil-soluble surfactant. This route allowed TPI to occur, and an interesting emulsification process was observed by varying the HLB, which corresponded to the change in the oil–water ratio. Two types of emulsions in the emulsification process were found: transition emulsion 1 (W/O/W high internal phase emulsion) and target emulsion 2 (W/O emulsion with low viscosity). This study describes the changes that occurred in the emulsification process.     

表面活性剂HLB值与渣油乳化体系分散性及电学性质的关系研究

为了研究表面活性剂亲水亲油平衡值（HLB值）与渣油乳化体系分散性和电学性质的关系,采用粒径和粒径分布相结合的方法来评价乳化体系的分散性,利用电导率值的变化来反应体系电学性质的差异,以表面活性剂B和A复合成实验用渣油乳化分散剂来分散渣油加氢裂化水溶性盐,考察了表面活性剂HLB值对渣油包盐水体系的分散性和电学性质的影响。结果表明,随表面活性剂HLB值从小到大的变化,不同水溶性盐在同种油中的分散性和电学性质不同,同种盐在不同油中的变化也存在着差异。乳化体系的分散性及电学性质随着HLB值的增加呈非线性变化。     

Stability and phase behavior of acrylamide-based emulsions before and after polymerization

The stability and phase behavior of acrylamide-based emulsions, prepared with surfactants consisting of lipophilic Span80 and hydrophilic OP10, before or after polymerization were investigated. The research results indicated that the phase separation behavior of the W/O-type emulsions is related to the toluene/water ratio. When the water volume fraction was larger, the phase separation mechanism was mainly a penetration of aqueous molecules from the dispersed-phase droplets. When the water volume fraction was smaller, the phase separation mechanism was mainly a sedimentation of the separated aqueous droplets. At a fixed toluene/water ratio, the emulsion stability and the emulsion type are related not only to the ratio of the two surfactants but also to the acrylamide concentration, and the effect of increasing acrylamide concentration on the character of the emulsions is similar to that of increasing OP10 mass fraction (increasing HLB value), which determines the corresponding relationship between acrylamide concentration and HLB value in the most stable emulsion system. To obtain the most stable emulsion at a fixed acrylamide concentration, the emulsion with higher acrylamide concentration needs a lower HLB value for the emulsion systems.     

Rapid Evaluation of Water-in-Oil (w/o) Emulsion Stability by Turbidity Ratio Measurements

In this Note, we investigated the turbidity ratio method for the evaluation of water-in-oil emulsion stability. The slope of turbidity ratio of water-in-oil emulsions with time was taken as an index of stability; the higher the slope, the less stable the system. Various factors affecting the stability of emulsion such as HLB of emulsifier, amount of emulsifiers, and water were tested using this technique. The results of the turbidity ratio technique for the evaluation of emulsion stability were well consistent with those obtained by the measurement of phase separation when incubated for 30 days at room temperature. Copyright 2000 Academic Press.     

柴油-生物质油乳化燃料最佳HLB值及理化性质研究

采用超声波乳化法制备柴油-生物质油乳化燃料,并研究了乳化燃料所需乳化剂的最佳亲水亲油平衡（HLB）值以及乳化条件对乳化燃料稳定性的影响,测定了乳化燃料的密度、黏度、闭口闪点、烟点、凝点和总热值等理化性质。结果表明,柴油-生物质油乳化燃料乳化剂的最佳HLB值为5.5~6.2;当乳化温度为50℃~60℃、单位容积输入功为180J/mL~300J/mL时,乳化燃料的稳定性最好;乳化燃料的密度、黏度、闪点和烟点随生物质油比例的增加而增大,而凝点和总热值则随生物质油比例的增加而降低。     

Influence of hydrophilic–lipophilic balance of nonionic emulsifiers on emulsion copolymerization of styrene and methacrylic acid

Emulsion copolymerizations of styrene and methacrylic acid (MAA) with various nonionic emulsifiers having a hydrophilic–lipophilic balance (HLB) range of 13.7–17.2 were performed to clarify the influence of emulsification state on polymerization. The emulsification state with a lower-HLB value emulsifier was worse than that with a higher one. In the lowest HLB value, MAA was predominantly polymerized over styrene in the early stage of the copolymerization, resulting in predominant (heterogeneous) distribution of MAA units in the inside of the final polymer particles. In the higher-HLB emulsifiers, styrene and MAA were simultaneously copolymerized, resulting in a homogeneous MAA distribution. The percentage of incorporation of the nonionic emulsifier inside the particles was the highest (49% based on the total amount of the emulsifier) in the lowest HLB, whereas it was 1% in the highest HLB. Part CCLXXXIV of the series “Studies on suspension and emulsion”.