Emulsification Process Research Articles

Macroporous Polyimide Aerogels: A Comparison between Powder Microparticles Synthesized via Wet Gel Grinding and Emulsion Processes

It is noteworthy to mention that synthesizing the polyimide aerogel powder, which is carried out in this study, benefits from two advantages: (i) the powder particles can be used for some specific applications where the monolith is not suitable and (ii) there is a possibility to investigate how a polyimide aerogel monolith can be made through the polyimide powder to reduce its cost and cycle time. In this study, two straightforward methods, wet gel grinding and emulsion, are introduced to prepare polyimide aerogel powders using ambient pressure drying. The microscopic properties of interest, including skeletal and porous structures, microparticle size and assembly, combined with macroscopic properties such as thermal stabilities and conductivities (0.039 W/m·K), confirm that the fabricated microparticles with a size in the range of 7-20 μm and porosity in the range of 65-85% are thermally stable up to 500 °C.

Chitosan-based nanocapsules by emulsification containing PUFA concentrates from tuna oil.

Chitosan nanocapsules containing polyunsaturated fatty acid (PUFA) concentrates from tuna oil, with EPA + DHA contents around 57% (w/w), were developed by emulsification process, using different chitosan concentration (1.0%, 1.5%, 2.0%, w/v) and stirring speed (10,000, 15,000, 20,000 rpm). The effects of these parameters on particle size and zeta potential were evaluated. The physical and oxidative stabilities were used to measure the product quality during storage. Chitosan concentration, stirring speed and its interaction significantly affected (p < 0.05) the particle size. In addition, chitosan concentration significantly affected (p < 0.05) the zeta potential of nanocapsules emulsion. Based on the results of physical and oxidative stabilities, the nanocapsules were stable for 30 days under refrigeration temperature (7 °C), and with 1.5-2% chitosan resulted in improved protection against oil oxidation. The nanocapsules produced with 2% chitosan and 10,000 rpm showed the lowest variations of polydispersity index and nanocapsules size after 30 days of storage (221.8 ± 3.0 nm). These conditions can be considered the most suitable to produce nanocapsules of PUFA concentrates from tuna oil using chitosan as wall material. These nanocapsules showed physical characteristics and oxidative stability, which could enable their application in the food industry, representing an important source of EPA and DHA fatty acids.

Comparative Study and Performance Evaluation of Chemical and Biosurfactants in Water-in-Oil Emulsification Process

Surfactants are used to lower the interfacial tension by adsorption process at the interface between oil and water. Chemical surfactants pose detrimental effects to equipment used and the environment as it consists of toxic compound. Environmentally friendly surfactant such as biosurfactant nowadays is the most sought after as perceived to be biodegradable, less toxic, high selectivity and biocompatible over chemical surfactant. In this study, stability of water-in-oil emulsion was observed using A-MeG (chemical surfactant) and Hylocereusundatus foliage (biosurfactant) at varying concentrations (samples A, B, C) via several measurement methods namely; droplet size, surface tension, rheology and creaming index. Results revealed that sample A with A-MeG and sample C with Hylocereusundatus foliage had smaller droplet sizes at 7.844 μm and 8.032 μm, respectively; lower average interfacial tension at 29.0 mN/m and 29.2 mN/m, respectively; higher average viscosity at 0.004061 mPa.s and 0.004171 mPa.s, respectively; which indicated that both were the most stable emulsion samples. Sample A with A-MeG had high creaming index, however, no water separation was recorded. While, sample C with Hylocereusundatus foliage recorded lower creaming index which indicated high stability. In conclusion, it is proven that there is a possibility of using Hylocereusundatus foliage in stabilising the water-in-oil emulsion.

The effect of disperse phase viscosity in the emulsification of a semi-dairy beverage–combining emulsification experiments and numerical single drop breakup simulations

Due to the rise in the demand for semi-dairy beverages (vegetable fat in a de-fatted dairy matrix) as well as for fully plant-based formulations, there is a growing interest in better understanding how emulsification processes are influenced by raw material choices. Semi-dairy beverages, for example, utilize a wide variety of vegetable oils in their formulation. This contribution combines traditional emulsification experiments with high-resolution numerical drop breakup simulations to improve the understanding of how oil viscosity influences the emulsification process. It is concluded that the experimentally observed increase in drop diameter with oil viscosity is well predicted by the viscosity-corrected Kolmogorov Hinze theory. The numerical simulations are able to reproduce this trend and allow further insight into breakup mechanism; suggesting that it is the prolonging of the deformation phase that make more viscous oils more challenging to homogenize. From a beverage processing perspective, the homogenizing pressure (and energy cost) necessary to achieve the same physical stability needs to be 73% higher if using a typical high-viscosity vegetable oil than if using a typical low viscosity vegetable oil.

Comparative Study on the Oxidative Stability of Encapsulated Fish Oil by Monoaxial or Coaxial Electrospraying and Spray-Drying

The impact of the encapsulation technology on the oxidative stability of fish-oil-loaded capsules was investigated. The capsules (ca. 13 wt% oil load) were produced via monoaxial or coaxial electrospraying and spray-drying using low molecular weight carbohydrates as encapsulating agents (e.g., glucose syrup or maltodextrin). The use of spray-drying technology resulted in larger capsules with higher encapsulation efficiency (EE > 84%), whilst the use of electrospraying produced encapsulates in the sub-micron scale with poorer retention properties (EE < 72%). The coaxially electrosprayed capsules had the lowest EE values (EE = 53-59%), resulting in the lowest oxidative stability, although the lipid oxidation was significantly reduced by increasing the content of pullulan in the shell solution. The emulsion-based encapsulates (spray-dried and monoaxially electrosprayed capsules) presented high oxidative stability during storage, as confirmed by the low concentration of selected volatiles (e.g., (E,E)-2,4-heptadienal). Nonetheless, the monoaxially electrosprayed capsules were the most oxidized after production due to the emulsification process and the longer processing time.

Construction of Janus silicon carbide membranes with asymmetric wettability for enhanced antifouling in water-in-oil emulsification process

Given that the membrane emulsification process involves the interaction between the membrane surfaces and two different phases (i.e., oil and water), separately manipulating the wettability of each surface would be crucial to achieve the high emulsification efficiency. Herein, the Janus silicon carbide (SiC) membranes were designed and prepared by using an emerging reactive sintering method and the subsequent chemical grafting modification on one of the hydrophilic surfaces. The surface wettability was selectively controlled by using hexadecyltrimethoxysilane (HDTMS) and 1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane (FOTS) as the hydrophobic or amphiphobic modifiers, respectively. Meanwhile, the modified side of Janus SiC membranes showed super-hydrophobicity under oil. It was found that the hydrophobic surface can inhibit the spread of water on membrane surface and the oleophobic surface can reduce the pollution of the membrane, which both affected the membrane emulsification performance. The water-in-oil (W/O) emulsions with mean water droplet size of 1.26–1.57 μm can be prepared using amphiphobic-hydrophilic Janus membranes at a high emulsification flux (1910 L·m−2·h−1). Importantly, the pure water permeance only declined 15.6% of the original value after three times of membrane emulsification. Moreover, the polluted membranes can be easily and effectively regenerated by ultrasonic cleaning in ethanol with a flux recovery ratio of 95.8%. Therefore, the amphiphobic Janus SiC membranes showing improved anti-fouling ability can be effectively utilized in the emulsification of high-viscosity oil.

Pickering emulsion stabilized by temperature-sensitive PS@PNIPA nanoparticles as microcontainers

Pickering emulsion has attracted the attention of many researchers because of its good stability. In some cases, such as catalyst separation and drug release, control of emulsion stability and demulsification under mild temperature is required. In this work, temperature-sensitive PS@PNIPA (polystyrene@polyisopropylacrylamide) with controlled PNIPA thickness was applied as the Pickering solid emulsifier. The effect of PNIPA thickness on the Pickering emulsion formation was studied by Polarizing optical microscope (POM). PS@PNIPA concentration was also found to be related to the size of the emulsion and the droplet size could be controlled from 17 μm to 39 μm. By changing the temperature, the emulsification/demulsification process of Pickering emulsion is reversible and repeatable for several cycles. Using ibuprofen as a chemical model, the maximum ibuprofen release rate reaches 93% and can be tuned by the temperature. Therefore, this opens up more potential applications for temperature-induced controlled demulsification for chemicals release and related fields.

Design, Preparation and Properties of Polyurethane Dispersions via Prepolymer Method.

A waterborne polyurethane dispersion for foamed synthetic leather base was designed and prepared using prepolymer method. There are many variables in the emulsification and chain-extension process of waterborne polyurethane (WPUR) dispersions prepared by prepolymer method. This work thoroughly evaluated the impacts of the steps of adding emulsified water, the temperature of the prepolymer and emulsified water, and concentration of ammonia water on WPUR dispersions by investigating the particle sizes/distributions and the mechanical stability. Changes in the temperature of the prepolymer and emulsified water, the concentration of ammonia water, and the step of adding emulsified water showed great impacts on the appearance and particle size of dispersions. Decreasing the temperature of the prepolymer and emulsified water and increasing the dilution ration of H2O to ethylenediamine (EDA) led to safe emulsification and dispersions with good appearance and narrow particle size distributions can be prepared. Surprising results were obtained by adding emulsified water in two steps, WPUR dispersions with a small particle size, narrow particle distribution and excellent tensile properties can be obtained. The optimized WPUR1 was applied to prepare water-based synthetic leather base after mechanical foaming, and the base presented the desired high performance, such as high folding resistance and peel strength.

Fabrication of stable Pickering double emulsion with edible chitosan/soy β-conglycinin complex particles via one-step emulsification strategy

Double emulsion is the most common multiple emulsion with compartmentalized internal structure. It can be used for delivery of both hydrophilic and hydrophobic bioactives and fat reduction in foods. However, conventional approach for stable double emulsion preparation often requires high dosage of synthetic surfactants (e.g., polyglycerol polyricinoleate, PGPR) and complicated two-step emulsification process. Herein, we report a facile approach to create stable double emulsion using particular emulsifier of edible chitosan/soy β-conglycinin (7S) complex nanoparticles via one-step emulsification. By modulating chitosan/7S complex ratio of particles and algal oil content in oil phase, water-in-oil-in-water (W/O/W) Pickering double emulsion was generated in most cases. The dominant mechanism for one-step generation of Pickering double emulsion can be attributed to the polyunsaturated fatty acids (PUFA) in algal oil. The binding of PUFA on particle surface contributes to hydrophobization of the chitosan/7S complex nanoparticles, leading to stabilization of W/O interface. Moreover, stability of the resultant Pickering double emulsions is correlated to particle contact angle. When using nanoparticles with chitosan/7S complex ratio of 1:2 and oil phase containing 40 wt% algal oil, particle contact angle at O/W interface is near 90°, which is the optimum condition to produce highly stable Pickering double emulsion. This facile approach for the fabrication of stable double emulsion is promising for a wide range of applications, particularly in food field.

Injectable cell-laden hybrid bioactive scaffold containing bioactive glass microspheres.

The rising incidence of bone disorders has resulted in the need for minimally invasive therapies to meet this demand. Injectable bioactive filler, alone or with cells, could be applied in a minimally invasive manner to fulfill irregular cavities in non-load bearing sites, which do not require high mechanical properties. Thermosensitive chitosan hydrogels that transition from a liquid to a mechanically stable solid at body temperature provide interesting features as in-situ injectable cytocompatible biomaterials, but they are not osteoconductive. Osteoconductivity can be applied in combination with bioactive ceramics e.g., 45S5-Bioglass® (BG). However, BG addition in chitosan hydrogels results in pH elevation, due to rapid ions release, which adversely affects gel formation, mechanical properties, and cytocompatibility. To address this, we created hybrid hydrogels, where BG is concentrated in chitosan-based microbeads, incorporated in in-situ gelling chitosan hydrogels. We then compared the hybrid hydrogels' properties to chitosan hydrogels with homogenously distributed BG. By varying the stirred emulsification process, BG percentage, and CH formulation, we could tune the microbeads' properties. Incorporation of BG microbeads drastically improved the hydrogel's compressive modulus in comparison to homogeneously distributed BG. It also strongly increased the survival and metabolic activities of encapsulated cells. Calcium/phosphate increase on BG microbeads suggests hydroxyapatite formation. The small diameter of microbeads allows minimally invasive injection through small needles. The feasibility of freezing and thawing microbeads provides the possibility of long-term storage for potential clinical applications. These data indicate that this hybrid hydrogel forms a promising injectable cell-laden bioactive biomaterial for the treatment of unloaded bone defects.

Injectable sustained-release poly(lactic-co-glycolic acid) (PLGA) microspheres of exenatide prepared by supercritical fluid extraction of emulsion process based on a design of experiment approach.

This study aimed to develop an improved sustained-release (SR) PLGA microsphere of exenatide using supercritical fluid extraction of emulsions (SFEE). As a translational research, we investigated the effect of various process parameters on the fabrication of exenatide-loaded PLGA microspheres by SFEE (ELPM_SFEE) using the Box-Behnken design (BBD), a design of experiment approach. Further, ELPM obtained under optimized conditions and satisfying all the response criteria were compared with PLGA microspheres prepared using the conventional solvent evaporation (ELPM_SE) method through various solid-state characterizations and in vitro and in vivo evaluations. The four process parameters selected as independent variables were pressure (X 1), temperature (X 2), stirring rate (X 3), and flow ratio (X 4). The effects of these independent variables on five responses, namely the particle size, its distribution (SPAN value), encapsulation efficiency (EE), initial drug burst release (IBR), and residual organic solvent, were evaluated using BBD. Based on the experimental results, a desirable range of combinations of various variables in the SFEE process was determined by graphical optimization. Solid-state characterization and in vitro evaluation revealed that ELPM_SFEE improved properties, including a smaller particle size and SPAN value, higher EE, lower IBR, and lower residual solvent. Furthermore, the pharmacokinetic and pharmacodynamic study results indicated better in vivo efficacy with desirable SR properties, including a reduction in blood glucose levels, weight gain, and food intake, for ELPM_SFEE than those generated using SE. Therefore, the potential drawback of conventional technologies such as the SE for the preparation of injectable SR PLGA microspheres could be improved by optimizing the SFEE process.

Establishing the regularity of the emulsification process

The study is aimed at assessing the influence of the degree of quantitative content of vegetable oil in an aqueous-oily medium on the emulsification process. Safflower oil was chosen as the main ingredient of the oil phase. The degree of quantitative content of safflower oil varied from 20 to 80% in relation to water. The stability of emulsions depends on many factors, including the degree of ultrasonic action, the stability of water-oil emulsions is ensured only if a film forms on the interfacial surface that mechanically prevents the aggregation of particles of the dispersed phase. It is the stabilizing adsorption film, and not the low interfacial tension, that exclude the possibility of fusion of particles of dispersed phases. The production of water-oil emulsions based on various oils, including emulsions used in perfumery, food, petrochemical and other industries. The disadvantage of the above analogues is that the influence of quantitative parameters on the emulsification process has been established and they do not have a set of functional and technological properties necessary for the production of new types of food products. This paper presents the results of the influence of the quantitative parameters of the components on the formation of a water-oil emulsion based on safflower oil under ultrasound exposure. The process of formation of a water-oil emulsion largely depends on the quantitative parameters of the components and the parameters of ultrasonic exposure - the frequency and amplitude of ultrasound, as well as its power. Therefore, establishing the regularity of the emulsification process of a water-oil mixture based on safflower oil using ultrasonic exposure is an urgent task. In connection with the expansion of the scope of ultrasound in the production of various types of emulsions, studies are being conducted on the influence of quantitative parameters of components in the process of ultrasonic treatment on the physico-chemical and rheological parameters of the final product.

Towards Solar-Driven Formation of Robust and Self-Healable Waterborne Polyurethane Containing Disulfide Bonds via in-situ Incorporation of 2D Titanium Carbide MXene

Waterborne polymers are vital for coating industry to reduce carbon emissions. However, formation of robust and self-healable films at ambient temperature remains a challenge owing to high energy cost of film formation process. This work reports a solar-driven film formation of waterborne polyurethanes (WPUs) containing disulfide bonds via in-situ incorporation of 2D titanium carbide (MXene) with ability to convert light to heat. Instead of directly mixed with WPUs, MXene is added to join the reaction with isocyanate-terminated pre-polymer before emulsification process. This approach not only prevents aggregation of MXene in water but stabilizes MXene against thermal degradation which is the key hurdle for mass production of MXene/WPU composites. More importantly, our results show that mechanical performance of WPU films under visible light (100 mW/cm2) is overwhelmingly competitive with that processed in oven. Furthermore, the existence of disulfide bonds in PU chains enables fast self-healing of micro-cracks under natural visible light which could vanish completely within 40 min. The fractured specimens were repaired under natural visible light for 2 h, and the self-healing efficiency of tensile strength and elongation at break reached over 94.00%.

Novel O/W Emulsions by Utilizing a Vesicle/Disc Transformation of Polyether Modified Silicone.

Emulsification is an important technology in the field of cosmetics and household products. Emulsions are in non-equilibrium state; therefore, the products vary depending on the preparation process, and their state changes with time. Furthermore, it is known empirically that different types of oils have different emulsification properties (preparation and stability). For these reasons, the variables in emulsification research are numerous and complicated to analyze. As a result, many industrial applications have had to rely on empirical rules. In this study, emulsions with a lamellar liquid crystalline phase as an adsorption layer at the emulsion interface were investigated. The characteristics of O/W emulsions formed with the excess solvent phases (aqueous and oil phases) separated from the lamellar liquid crystalline phase were investigated based on the phase equilibrium of the ternary system.As a result, it was found that by agitating the aqueous phase containing dispersed vesicles of emulsifier (polyether modified silicone) together with the oil phase, an emulsion with a uniform interfacial membrane of lamellar liquid crystalline phase could be obtained. The emulsions prepared by this method were found to have good stability against coalescence. The process of transformation from vesicles to the uniform liquid crystal interfacial membrane during the emulsification process was clarified by a freeze-fracture transmission electron micrograph and the calculation of interfacial membrane thickness based on precise particle size analysis. Furthermore, the emulsification properties of polyether-modified silicones were clarified using polar oils and silicone oils, which are a combination of high/low and low/high compatibility with hydrophilic (polyethylene glycol) and lipophilic (polydimethylsiloxane) groups of polyether modified silicone, respectively. It is expected that this research will lead to the evolution of various functionalities in products in the fields of cosmetics, household products, food, pharmaceuticals, paint and others.

Dual-responsive colloidosome-like microgels as the building blocks for phase inversion of Pickering emulsions.

The intelligent regulation of microgel-stabilized Pickering emulsions with multi-responsiveness is presently constrained to the processes of emulsification and destabilization. However, the expansion of multi-control over Pickering emulsions to involve phase inversion and the investigation of the accompanying processes and mechanisms present a great challenge. In this study, a microgel with dual responsiveness to both pH and temperature was synthesized using an emulsion template. The resulting microgel exhibited a robust colloidosome-like structure, distinguished by the presence of monolayer-adsorbed silica nanoparticles. The regulation of the packing of surface-covered silica nanoparticles was easily achieved through the swelling of the microgel matrix. Furthermore, the wettability of the microgel can be adjusted between hydrophilic and hydrophobic intervals, allowing for the effective and dual-responsive phase inversion of Pickering emulsions. Moreover, it has been observed that colloidosome-like microgels can lead to unique interfacial structures during the emulsification process, thereby elucidating the fundamental mechanism governing emulsion phase inversion.

Emulsion‐Induced Polymersomes Taming Tetrodotoxin for Prolonged Duration Local Anesthesia (Adv. Therap. 1/2023)

In article number 2200199, Chao Zhao and co-workers report emulsion-induced polymersomes. Through a simple emulsification process, the polymer forms polymersomes within seconds, and the formed polymersomes effectively encapsulate water-soluble drugs in them.

Exploring effects of polymeric stabiliser molecular weight and concentration on emulsion production via stirred cell membrane emulsification

Polymer stabiliser adsorption kinetics influence a stirred-cell membrane emulsification process output. An optimized combination of low/higher MW PVA at very low concentration (0.1 wt%) produces narrow size distribution and size-controlled droplets.

SolidWorks flow simulation software potential in hydrodynamic processes analysis for cone vortex emulsion

The purpose of this work is to compare the hydrodynamic data of the real flow simulated by SolidWorks Flow Simulation in an emulsor of vortex type. The object of the study is an emulsion, in the central part of the energy separation chamber of which a zone of low pressure, the cavitation zone, is created. In this zone the dispersion phase collapses. Computer simulation of fluid dynamics of the emulsification process has been suggested to optimise the design of this type of emulsor. To check adequacy of results of modelling and real process, visualization and comparative evaluation of shape of flows at pressure of liquid at the inlet 0.4 MPa and its kinematic viscosity 10−6 m2/s. The use of SolidWorks Flow Simulation software has been found to give a fairly close-to-reality overall flow pattern. When considering the calculated flow from the position of fluid displacement and comparing it with experimental data, a good match is seen in the shape of near-axis flows. Three vortex zones are clearly visible in the model. In the real flow there are similar vortex zones which, although not clearly visible, are visualised by photography. With the software, the overall flow pattern is fairly close to reality. However, it is not possible to conclude that the velocities of the calculated and real flows coincide. By considering the various design changes in the simulation and evaluating their effect on the hydro and thermodynamics of the process, some regularities can be identified and used in the design of new designs, i.e., the results of computer simulation can be a good guide in the design of new devices.

Understanding droplet breakup in a post-array device with sheath-flow configuration.

Microfluidic post-array devices have the potential to generate quasi-monodisperse emulsion droplets with high throughput and dispersed phase fractions by splitting droplets with regularly arranged posts. However, the lack of understanding of post-array devices makes it challenging to predict droplet size and quantitatively evaluate the influence of post geometry, hindering their widespread application. Therefore, we investigated the characteristics of droplet breakup through a post array using a series of devices with sheath-flow configurations, in which the dispersed and continuous flow rates could be flexibly tuned. Using a poly(dimethylsiloxane)-glass device fabricated via soft lithography, we found that the volume ratio of the dispersed phase to the continuous phase significantly affects the droplet size, even when the viscosity ratio is close to one. For the first time, we demonstrated that the effective capillary number calculated from the emulsion viscosity and effect of the dispersed phase fraction consistently describes various experimental results. Furthermore, our flow observations and droplet diameter measurement showed two breakup modes: the size-constant obstruction and shear-induced modes with a power-law correlation similar to droplet splitting in a T-junction. Thus, the power-law correlation in microfluidic droplet splitting successfully expresses the droplet generation characteristics in post-array devices. A combination of effective viscosity correction and curve fitting allowed us to evaluate the influence of the material and post-geometry on droplet generation characteristics. This study contributes to the understanding of droplet breakup in post-array devices and extends their unique droplet generation properties to include high-throughput, high-fraction, robust, and continuous emulsification processes.

Pickering emulsions stabilized by reassembled oleosome protein nanoparticles for co-encapsulating hydrophobic nutrients

In this study, oleosome proteins were disassembled using guanidine hydrochloride to form shell-core colloidal particles (reassembled oleosome proteins, ROPs). These particles were then used to prepare a dual-compartment-structured Pickering emulsion to co-deliver curcumin (Cur) and vitamin D. The results showed that ROP can effectively encapsulate Cur inside the hollow structure. Moreover, at a Cur concentration of 100 μM, the ROP-Cur contact angle was 71.5°, which aids the preparation of stable Pickering emulsions. The most stable Pickering emulsion was then prepared by adjusting the ROP-Cur emulsifier and oil phase concentrations. The Pickering emulsion prepared with 2.0 mg/mL emulsifier and the addition of 10% oil phase displayed the best stability, with an average particle size, ζ-potential, and Turbiscan Stability Index of 2.2 μm, −31.5 mV, and 3.63, respectively. Notably, the emulsification process doesn't destroy the shell-like structure of ROP-Cur. Instead, it triggers the aggregation of ROP-Cur, which is finally adsorbed at the oil–water interface. Our designed strategy successfully affords double-compartment microdroplets and improves the storage stability of biologically active compounds.