Emulsion Inversion Point Research Articles

Simple preparation of silicone rubber Pickering emulsions using silica nanoparticles for water-borne thermal protection coating

Abstract In this study, we aimed to develop stable silicone rubber Pickering emulsions by employing silica nanoparticles as stabilizers in order to produce a water-borne thermal protection coating. Initially, silica nanoparticles were synthesized using the Stöber method and subsequently functionalized with γ-glycidoxypropyltrimethoxysilane (GTMS). The size and grafting efficiency of the GTMS-modified silica nanoparticles were characterized using transmission electron microscopy and thermogravimetric analysis, respectively. Furthermore, the functionalization mechanism was elucidated by monitoring the pH and Zeta potential of the silica sols. Subsequently, the silicone rubber Pickering emulsion was prepared via the emulsion inversion point method and characterized using transmission electron microscopy. The emulsification process was analyzed by measuring the conductivity of the emulsion during the phase transition. Finally, the water-borne coating was formulated by blending the emulsions with Kaolin, glass fiber, and glass microspheres. The thermal protection performance of the resulting coating was evaluated under typical test conditions, with the highest heat flow reaching 242 kW m−2 for 40 s.

A Comprehensive Review on Chalcone Analogues-Versatile Scaffold with Medicinal and Biological Potential

Nanoemulsions are well-liked drug delivery system in the pharmaceutical world. These are clear, thermodynamically stable and isotropic liquid-in-liquid dispersion with an average size range of 20 to 200 nm. They are having elevated surface area, strong stability, optically clear appearance, acceptable rheology and good drug loading capacity because of their characteristic droplet size. The methods used for the preparation of nanoemulsions include bubble bursting method, micro-fluidization, phase inversion temperature, emulsion inversion point, ultrasonication and spontaneous emulsification high-pressure homogenization etc. In the present paper, the advantages, methods of preparation and applications of nanoemulsions are critically reviewed.

Combined Approach to Evaluate Hydrate Slurry Transport Properties through Wetting and Flow Experiments.

A condensate oil system was evaluated with respect to its hydrate properties by two experimental methods, namely, the wetting index (WI) procedure and a flow loop called the wheel flow loop. The WI was used to initially indicate the efficiency of a gas hydrate antiagglomerant (AA), while the wheel flow loop was used for evaluating the transport properties of systems without and with AA. The results provide new insight into the effect of water cut and flow properties on the risk of hydrate plugging. The test case used in the study was a relevant field from the Vega gas condensate asset on the Norwegian continental shelf. This asset is currently producing using continuous monoethylene glycol (MEG) injection as a hydrate prevention philosophy. The wettability of the hydrate particles was determined for uninhibited, underinhibited (10% MEG), and AA-inhibited systems, and the results indicated favorable wettability of the AA-protected system by changing the emulsion inversion point to higher water cuts. Furthermore, the wettability data were then confirmed by flow tests utilizing SINTEF's wheel flow loop. Moreover, both uninhibited and underinhibited systems led to plugging upon hydrate formation, indicating the need for optimized AA concentrations for a given fluid system and water cut. The overall results show that the WI combined with the wheel flow loop or similar equipment is an effective method for better selection and description of the plugging potential and transport properties for gas hydrate systems.

Nanoencapsulation of Vitamin D3 by the Emulsion Inversion Point Method for Enrichment of Coconut Yogurts

Nanoencapsulation of Vitamin D₃ by the Emulsion Inversion Point Method for Enrichment of Coconut Yogurts

Preparation and characterization of patauá and pracaxi Brazilian vegetable oil emulsions

In this work, the stability of oil-in-water emulsions (O/W) of patauá (Oenocarpus bataua) and pracaxi (Pentaclethra macroloba) oils, both from Amazon rainforest, was investigated. Low-energy emulsification methods were used, such as Emulsion Inversion Point (EIP) and Phase Inversion Temperature (PIT), both based on the minimal interfacial surface, combined with optimized Hydrophilic-Lipophilic Balance (HLB). Phase inversion was determined by electrical conductivity measurements. The surfactants used were Span® 80, Tween® 20, Tween® 60, and Tween® 80. Surfactant mixtures of Span® 80 + Tween® 80 were the best samples prepared. The composition of the most stable samples was 80.00 wt% aqueous phase, 15.00 wt% nonionic surfactants, and 5.00 wt% oil phase (patauá or pracaxi oil). The samples with the best kinetic results were those prepared with the required HLB and PIT values of 12.86 and 84.05 °C, for patauá oil, and of 9.61 and 79.50 °C for pracaxi oil. The kinetic stability of the oil emulsions was characterized by creaming index (CI), by evolution over time of the droplet size, viscosity, and electric conductivity. The results showed that: (1) the droplet size distribution influenced electric conductivity; (2) the relative amount of surfactants Tween® and Span® used is more important to determine the physicochemical and interfacial properties of the emulsion than the oil identity itself; (3) it is crucial to pay attention to the influence of air bubbles—involuntarily inserted into the mixture during the emulsification process—in the physicochemical properties of the system. These conclusions can be extended to other oil-in-water emulsions.

Evaluation and manipulation of the key emulsification factors toward highly stable PCM-water nano-emulsions for thermal energy storage

PCM emulsions represent a common type of fluid media for thermal energy storage (TES) systems. However, a major challenge for their application is to maintain a stable homogeneous fluid. Reduction of the droplet size is one of the most effective approaches for improving stability, such as the preparation of nano-emulsions. This work aims to develop stable PCM-water nano-emulsions prepared with n-hexadecane by manipulating the key emulsification factors, particularly the emulsifier combinations and process conditions. Two low-energy emulsification methods, phase inversion temperature (PIT) and emulsion inversion point (EIP), were applied to prepare the nano-emulsions, using Brij L4 as the emulsifier. Several important properties of the emulsions were evaluated including droplet size distribution, conductivity, and rheological characteristics and the stability of emulsions over extended periods and multiple freeze-thaw cycles. Moreover, the thermal performance for their potential application in TES systems were examined. Eventually, nano-emulsions with small and uniform droplets were obtained by both PIT and EIP methods with suitable emulsifier concentrations. The smallest droplet size (~60 nm) was attained with 11% emulsifier and 30% PCM by the PIT method, and the most stable emulsion attained with 15% of emulsifier and 30% of PCM. The PCM nano-emulsions behaved as a Newtonian liquid with a good fluidity and a superior stability over long-time storage and freezing-cycles. The degree of supercooling was reduced with the addtion of nano SiO2 as a nucleating agent. The findings from the study are useful for better understanding of the controlling factors and further development of stable and effective nano-emulsions.

Study on optimum parameters of high content paraffin wax microemulsion

As a by-product of crude oil processing, paraffin wax has high economic potential to be converted into microemulsion for various applications. Herein, paraffin wax microemulsion was prepared by emulsion inversion point (EIP) method in the presence of non-ionic surfactants. The focus of the study is to determine optimum preparation parameters for obtaining stable microemulsion. The initial results showed that paraffin wax microemulsion can be prepared when hydrophilic-lipophilic balance (HLB) value was 10 with a wax composition of 40 wt%. This HLB value is used as a reference for obtaining stable microemulsion by varying emulsification temperature and time. Emulsion stability was determined by observing phase change for 60 days, which then was quantized using particle size analyzer. The morphology of the microemulsion droplets was observed using optical microscope. The droplets showed a bright spot under polarized light owing to its solid phase in room temperature. Stable microemulsion with particle size average diameter of about 290.6 nm could be formed at emulsification temperature of 80 °C and emulsification time of 40 minutes.

Synthesis and Characterization of Ozonated Oil Nanoemulsions

AbstractIn recent years, the use of ozonated oil (ozone enriched oil form) is being increasingly preferred for biomedical applications because of its antibacterial activity. Among most important reasons of this choice is the high molecular affinity of the ozone molecule and intracellular effects of the products of ozone and the unsaturated fatty‐acid chemical reactions in cellular signaling systems. The aim of the present study was to synthesize and optimize the ozonated oil nanoemulsion system that would be transferred into the living systems easily, suggesting a promising carrier system for various biomedical applications. By varying formulation parameters (surfactant‐to‐oil ratio, surfactant concentration, mixing rate, and surfactant type), nanoemulsions were investigated in terms of mean particle diameters, distributions, and stabilities. Nanoemulsions with high stability and small droplet diameters (212.7 nm) could be produced under optimized conditions with Tween 40 as the surfactant at a 750 rpm mixing rate using the emulsion inversion point (EIP) low‐energy method. Spherical and uniformly distributed nanoemulsions were observed by SEM, which also supports mean particle diameter measurements. Fourier‐transform infrared spectroscopy (FTIR) and 13C NMR (nuclear magnetic resonance) studies indicated an ozonide structure within the nanoemulsion system, which remained even after 30 days of storage. The antibacterial activity of ozonated oil emulsions against Staphylococcus aureus and Escherichia coli suggests promising applications in the biomedical field.

Production, physicochemical stability of quercetin-loaded nanoemulsions and evaluation of antioxidant activity in spreadable chicken pâtés

Quercetin is recognized by its high antioxidant activity, but its incorporation in food products can be challenging due to its hydrophobicity. This disadvantage can be overcome by encapsulation in lipid-based matrices like nanoemulsions. In the present study nanoemulsions encapsulating quercetin were produced, using a low-energy method - emulsion inversion point - and using two surfactants (Tween 80 and Brij 30). The average droplet diameters of the nanoemulsions were in the range 180–200 nm, and the nanoemulsions containing 0.30 g quercetin/100 g were capable of preserving around 70% of the flavonoid after 90 d of storage. Conductivity curves indicated the stabilization of nanoemulsions by Brij 30 required a longer time to occur. Both quercetin-loaded nanoemulsions incorporated in chicken paté were capable of protecting it against lipid oxidation, but not against protein oxidation The inhibition of secondary lipid oxidation by the quercetin-loaded nanoemulsions was highly expressive (about 60% after 24 wk of storage, against 8.4% of inhibition in pâtés added with butylated hydroxytoluene – BHT - and sodium nitrite). Sensory data indicated the panelists approved the chicken pâtés incorporated with quercetin-loaded nanoemulsions in terms of odor, taste and color, and that encapsulation of the flavonoid was required to avoid undesirable sensory effects due to its addition.

Formulation and characterization of a paediatric nanoemulsion dosage form with modified oral drug delivery system for improved dissolution rate of nevirapine

ABSTRACTBackground: The development of appropriate dosage forms for paediatric antiretroviral therapy is key for improved therapeutic outcomes in children. The focus of this study was to improve solubility, dissolution rate, drug release and maintain high drug permeability.Methodology: A nanoemulsion was prepared using emulsion inversion point and evaluated. The nanoemulsion had nevirapine (3% w/w). In vitro drug release studies were performed using dialysis membrane. Permeability studies using the Caco-2 cell model were performed for the formulation.Results: The optimized nevirapine nanoemulsion had a mean droplet size of 36.09±12.27nm, low pdI of 0.598 and zeta potential of -7.87±4.35mV. At pH 2, the nanoemulsion released 76 ± 2 % of nevirapine within 2 h, while at pH 6.4 value representing the small intestine, amount of nevirapine released was 41.6± 4 %. The permeability rate of the nevirapine nanoemulsion was 30.02 x 10-6cm/s and higher than that of propranolol. Efflux ratio was 0.02 indicating low chance of drug efflux occurring.Conclusion: The results showed that a modified liquid drug release formulations of nevirapine could improve rate of dissolution and maintain high permeability and low drug efflux improving bioavailability of nevirapine in vivo.

Catastrophic Emulsion Inversion Process of Highly Viscous Isosorbide Biobased Polyester Monitoredin situ by Torque and Light Backscattering.

Highly viscous hydrophobic isosorbide biobased polyester O/W emulsions are prepared through catastrophic phase inversion. The process is followed in situ with two different methods: torque and light backscattering (LBS). Considering high viscosity of the system, only discontinuous conductivity monitoring is performed for comparison. Torque and LBS allow to highlight the emulsion inversion point (EIP) with relatively close water weight fraction values (fw≈0.20). The torque and LBS signals are rather noisy before inversion (evolution of different structures) and more smooth after phase inversion (continuous aqueous phase). Torque gives a more macroscopic information, representative of the global state of the dispersion. Consistent conductivity and torque measurements suggest indeed an inversion pathway through multiple o/W/O emulsions leading to multiple complex structures before getting continuous aqueous final emulsion. This hypothesis is confirmed with continuous LBS monitoring and microscopic observations. LBS signal seems more complete because it combines the information of conductivity and torque and allows to clearly follow in situ the inversion from the beginning to the end of the process.

Technological and sensory evaluation of pineapple ice creams incorporating curcumin‐loaded nanoemulsions obtained by the emulsion inversion point method

This study evaluated the feasibility of incorporating curcumin‐loaded nanoemulsions (CLNE) produced by the emulsion inversion point method in pineapple ice creams to replace artificial yellow dyes. For this purpose, ice creams with formulations: A (pineapple flavour commercial mix), B (partial replacement of commercial mix by CLNE), C (complete replacement of commercial mix by CLNE) and D (complete replacement of commercial mix by nonencapsulated curcumin) were characterized. Results showed that CLNE incorporation was a feasible alternative for reducing the use of artificial dyes, as the ice creams showed similar physicochemical and rheological properties, and formulations A and B had similar sensory acceptance.

Nanoemulsion - An ideal drug delivery for nose-to-brain targeting

Nanoemulsions are well-liked drug delivery system in the pharmaceutical world. These are clear, thermodynamically stable and isotropic liquid-in-liquid dispersion with an average size range of 20 to 200 nm. They are having elevated surface area, strong stability, optically clear appearance, acceptable rheology and good drug loading capacity because of their characteristic droplet size. The methods used for the preparation of nanoemulsions include bubble bursting method, micro-fluidization, phase inversion temperature, emulsion inversion point, ultrasonication and spontaneous emulsification high-pressure homogenization etc. In the present paper, the advantages, methods of preparation and applications of nanoemulsions are critically reviewed.

A General Route for Nanoemulsion Synthesis Using Low-Energy Methods at Constant Temperature

The central dogma of nanoemulsion formation using low-energy methods at constant temperature-popularly known as the emulsion inversion point (EIP) method-is that to create O/W nanoemulsions, water should be added to a mixture of an oil and surfactant. Here, we demonstrate that the above order of mixing is not universal and a reverse order of mixing could be superior, depending on the choice of surfactant and liquid phases. We propose a more general methodology to make O/W as well as W/O nanoemulsions by studying the variation of droplet size with the surfactant hydrophilic-lypophilic balance for several model systems. Our analysis shows that surfactant migration from the initial phase to the interface is the critical step for successful nanoemulsion synthesis of both O/W and W/O nanoemulsions. On the basis of our understanding and experimental results, we utilize the reverse order of mixing for two applications: (1) crystallization and formulation of pharmaceutical drugs with faster dissolution rates and (2) synthesis of alginate-based nanogels. The general route provides insights into nanoemulsion formation through low-energy methods and also opens up possibilities that were previously overlooked in the field.

Facile Formation of Medium‐Chain‐Length Poly‐3‐Hydroxyalkanoates (mcl‐PHA)‐Incorporated Nanoparticle Using Combination of Non‐Ionic Surfactants

AbstractThe assembly of nanoparticles incorporating bacterial medium‐chain‐length poly‐3‐hydroxyalkanoates (mcl‐PHA) via phase inversion emulsification (PIE) was investigated. Sequential addition of water into an agitated mixture of carrier oil (jojoba oil), nonionic surfactants (Cremophor EL and Span 80) and melted mcl‐PHA triggered phase inversion of water‐in‐oil (W/O) to oil‐in‐water (O/W) emulsion. The emulsion inversion point (EIP) at 30% w/w of water content was determined by abrupt changes in viscosity and conductivity of the suspension. Concurrently, infrared transmittance of the O–H group of water, the C–O–C group of surfactants and the C–H group of alkane chain were practically identical while Small Angle X‐ray Scattering indicated the presence of a bi‐continuous/lamellar structure. The morphology of the emulsion changed, with increasing water content, from W/O to bi‐continuous/lamellar structure and finally to O/W. mcl‐PHA appears to form a bridging polymeric network, covering the nanoparticle with a protective layer for enhanced protection of the encapsulated compound. A hypothetical mechanism for the mcl‐PHA‐based nanoparticle assembly is also proposed.

Curcumin-loaded nanoemulsions produced by the emulsion inversion point (EIP) method: An evaluation of process parameters and physico-chemical stability

Curcumin is a natural antioxidant dye that has a wide spectrum of biological activities (e.g., anti-cancer, anti-hypertensive, anti-inflammatory and neuroprotective activities), and there is a high interest within the food industry to increase its use as a natural additive. However, due to its high hydrophobicity, it is difficult to incorporate into aqueous formulations and its bioavailability can be severely decreased. Lipid-based encapsulation systems such as nanoemulsions can help to overcome both of these drawbacks. In this study, curcumin-loaded nanoemulsions were produced by the emulsification inversion point method, for which some of the operational parameters were optimized. The most stable formulations were composed of 20% soybean oil, 10% Tween 80 and 20% glycerol and were produced with an anchor blade impeller operating at 300 rpm; this combination of parameters resulted in 0.07% encapsulation of the curcumin. After 60 days, 70% of the initial amount of curcumin remained in the nanoemulsions, which is a promising result when compared with those of other lipid-based encapsulation systems. The data also indicated that the catastrophic phase inversion occurred due to the formation of multiple o/w/o emulsions.

Ultrasound assisted manufacturing of paraffin wax nanoemulsions: Process optimization

This work reports on the process optimization of ultrasound-assisted, paraffin wax in water nanoemulsions, stabilized by modified sodium dodecyl sulfate (SDS). This work focuses on the optimization of major emulsification process variables including sonication time, applied power and surfactant concentration. The effects of these variables were investigated on the basis of mean droplet diameter and stability of the prepared emulsion. It was found that the stable emulsion with droplet diameters about 160.9nm could be formed with the surfactant concentration of 10mg/ml and treated at 40% of applied power (power density: 0.61W/ml) for 15min. Scanning electron microscopy (SEM) was used to study the morphology of the emulsion droplets. The droplets were solid at room temperature, showing bright spots under polarized light and a spherical shape under SEM. The electrophoretic properties of emulsion droplets showed a negative zeta potential due to the adsorption of head sulfate groups of the SDS surfactant. For the sake of comparison, paraffin wax emulsion was prepared via emulsion inversion point method and was checked its intrinsic stability. Visually, it was found that the emulsion get separated/creamed within 30min. while the emulsion prepared via ultrasonically is stable for more than 3 months. From this study, it was found that the ultrasound-assisted emulsification process could be successfully used for the preparation of stable paraffin wax nanoemulsions.

Enhancement of aqueous stability of allyl isothiocyanate using nanoemulsions prepared by an emulsion inversion point method

Allyl isothiocyanate (AITC), an organosulfur compound in cruciferous vegetables, is a natural antimicrobial and potential chemopreventive agent. However, the instability of AITC in aqueous systems restrains its applications. In this study, oil-in-water AITC nanoemulsion was prepared by the emulsion inversion point (EIP) method, aiming at improving the aqueous stability of AITC. The optimal hydrophilic–lipophilic balance (HLBop) value of surfactants containing Tween 80 and Span 80 was established at 11.0–13.0, yielding nanodroplets with diameters of 137–215nm. The mechanism of droplet formation within the HLPop region was discussed in terms of the possible structure of adsorbed surfactant layers at the oil–water interface in multiple emulsion droplets. In a 6.5-month storage test, the droplet sizes and the count rates (intensity of scattered light) of nanoemulsions decreased only slightly by 4–13% (depending on surfactant-to-oil ratio), even in highly diluted status, indicating the desirable stability of the nanoemulsions. Moreover, the nanoemulsion demonstrated superior protection against AITC degradation (78% remaining after 60d at 30°C), compared with protein nanoparticles as well as non-encapsulated aqueous dispersion. This work shows for the first time that AITC can be formulated into nanoemulsions and thus obtains satisfactory aqueous solubility and chemical stability.

Evaporation of aqueous dispersed systems and concentrated emulsions formulated with non-ionic surfactants

Vacuum evaporation of aqueous surfactant systems and concentrated oil-in-water (O/W) and water-in-oil (W/O) emulsions was studied as a function of the base oil (castor oil, heavy mineral oil and light mineral oil), and the kind of non-ionic surfactant (Tween and Span series) used in their formulation. Water evaporation rates were measured from aqueous surfactant solutions/dispersions (5% w/w surfactant), and O/W emulsions (5% w/w surfactant) in 1:1 water/oil weight ratio. Vacuum evaporation of W/O emulsions was also investigated, since a W/O emulsion is formed when the emulsion inversion point is surpassed during the evaporation of O/W emulsions. Surface tension, conductivity and particle/droplet size distribution were measured to characterize the formulated systems. Three simple models were tested to fit the evaporation rate data and their consistency depends on the system under consideration.

Miniemulsion Polymerization Based on Low Energy Emulsification with Preservation of Initial Droplet Identity

A study was conducted to demonstrate the first synthesis of polymeric nanoparticles employing a low energy miniemulsification procedure. Styrene was polymerized at 70 °C in aqueous miniemulsion initiated by azobis(isobutyronitrile) (AIBN) employing the anionic surfactant disulfonated alkyl diphenyloxide sodium salt (Dowfax 8390). The system offered excellent control over monomer droplet and particle size, with a unique degree of preservation of initial droplet identity in addition to the benefits of a low energy process. Miniemulsions stabilized by ionic surfactants were obtained by dilution of a bicontinuous or an oil-in-water (O/W) microemulsion with excess water in the low energy emulsion inversion point (EIP) method. Three different miniemulsions were also prepared by dilution of the O/W microemulsion precursor at the arrow corresponding to 57.8 wt % water.