Factors Affecting the Phase Inversion Process of Alkyl polyglycol ether C16-18/Fatty Alcohol/Oil/Water System

Nano-emulsions: Formation by low-energy methods

PIT tuning effects of hydrophobic co-surfactants and drugs

In this study, black pepper essential oil nanoemulsions formulated using low-energy methods (emulsion phase inversion and phase inversion temperature) were compared. In both the methods, optimum components' concentration was 10% of essential oil, 20% of Tween 80, and 70% of distilled water. All nanoemulsions were unchanged after centrifuging at 825 or 1,467 g for 10 min and were more stable when kept at 30°C. Phase inversion temperature nanoemulsions quickly increased droplet size and polydispersity index after 2 weeks, then separated, and created creaming layer on the top after 4 weeks while emulsion phase inversion nanoemulsions were still homogeneous for 4 weeks. However, phase inversion temperature nanoemulsions were more stable than emulsion phase inversion nanoemulsions during heating–cooling cycles. In addition, the loading efficiency of emulsion phase inversion samples was also higher than phase inversion temperature samples, 92.13% and 81.52%, respectively. Practical applications Black pepper essential oil such as other plant essential oils has proved their bioactivity of antimicrobial, antioxidant. Therefore, utilization of essential oil in food industry has set a new trend as a natural food additive. However, essential oils are not easy to add into food products due to the presence of hydrophobic and volatile components. Nanoemulsion is expected to be one of suitable systems for dispersing essential oil in food environment. Essential oil nanoemulsion made from black pepper, very popular spice all over the world, has potential for using as a food preservative for not only many food techniques, but also many kinds of food: dripping fresh food material, spraying on food material, using as seasoning for canning food, or other processing food. Novelty impact statement In this study, Vietnamese black pepper (Piper nigrum) essential oil nanoemulsions were successfully formulated using the phase inversion temperature (PIT) method. Both the emulsion phase inversion (EPI) and PIT methods formed small droplet of 32.4 and 82.4 nm, respectively. However, EPI nanoemulsions were not only more homogeneous, but also more steady than PIT nanoemulsions in our experiment condition.

In this study, the emulsification performance of functionalized colloidal silica is explored with the aim to achieve phase inversion of particle-stabilized (Pickering) emulsion systems. An increased understanding of inversion conditions can facilitate surfactant-free emulsion fabrication and expand its use in industrial applications. Phase inversion was achieved by adjusting the temperature but without changing the composition of the emulsion formulation. Silica nanoparticles modified with hydrophobic propyl groups and hydrophilic methyl poly(ethylene)glycol (mPEG) groups are used as emulsifiers, enabling control of the wettability of the particles and exploration of phase inversion phenomena, the latter due to the thermoresponsiveness of the attached PEG chains. The phase inversion conditions as well as the reversibility of the emulsion systems were examined at varying electrolyte concentrations and pH values of the suspensions. Transitional phase inversions, from oil-in-water and water-in-oil and back, were observed in functionalized silica particle-stabilized butanol emulsions at distinct temperatures. The phase inversion temperature was affected by electrolyte concentration and pH conditions due to salting-out effects, PEG-silica interactions, and the effects of the particle surface charge. Investigations of phase inversion conditions, temperature, and hysteresis effects in Pickering emulsions can improve the theoretical understanding of these phenomena and facilitate the implementation of low-energy emulsion preparation.

The role of critical points and binodal surfaces in emulsion type, HLB, and the phase inversion temperature: Evidence from the cyclohexane/Water/ i-C 9H 19C 6H 4(OC 2H 4) 9.2OH/Temperature diagram

Phase inversion emulsification: Current understanding and applications

Factors that affect the phase-inversion temperature (PIT) based on nonionic surfactant fatty alcohol ethoxylates were investigated. Phase-inversion process was continuously monitored by determining changes in conductivity with temperature. The influences of oil-to-water ratio, emulsifier concentration, emulsifier mixing ratio, sodium chloride, and oil types on the PIT of emulsions were investigated. Results showed that the PIT of the emulsions declined with increased oil-to-water ratio. Emulsifier concentration significantly affected the PIT temperature. High sodium chloride content suppressed phase inversion. A lower Brij72-to-Brij721 ratio corresponded to higher PIT. Different oils required different HLB numbers in the phase-inversion process.

This paper provides a fundamental study of the effect of sodium chloride on the formation and stability of n‐dodecane/nonionic surfactant (Brij30)/NaCl nanoemulsions produced by the phase inversion temperature (PIT) method. Nanoemulsions are an emulsion system containing droplets from 20 to 200 nm and widely used in cosmetics and pharmaceutical industries. The PIT method was chosen due to its low energy and surfactant usage to produce the nanoemulsions by heating and quenching an emulsion system. The changes of conductivity with temperatures were continuously monitored to determine phase inversion, and are found to be the same in low surfactant concentrations. PIT point was found to decrease with NaCl concentration especially from 5 to 7 wt% Brij30. At the storage temperature (20 °C), the initial droplet size decreases with NaCl concentration; however, the decrement only occurs from 4 to 7 wt% Brij30 while no nanoemulsions can be produced at 8 wt%. By adding salt, the surfactant concentration needed for the most stable nanoemulsions is reduced to 6 wt% from 7 wt%. Therefore, similar stable nanoemulsions can be produced with less surfactant in a brine system. Furthermore, most of the ageing brine‐continuous nanoemulsions could be reproduced to their freshly prepared state by heating process but not for the most stable nanoemulsions. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.

Nanoemulsification in the vicinity of phase inversion: Disruption of bicontinuous structures in oil/surfactant/water systems

Synopsis Oil-in-water emulsions stabilized with nonionic emulsifiers change to water-in-oil emulsions as the temperature rises when the hydrophilic and lipophilic properties of the mixed emulsifier are just balanced. Preparation above the phase inversion temperature followed by rapid cooling yields emulsions that exhibit very fine droplet size and extreme long-term stability. Cosmetic emulsions were prepared by this phase inversion temperature (PIT) method using typical raw materials such as polar oils, e.g. decyl oleate, 2-octyl dodecanol or isopropyl myristate, and nonionic emulsifiers, e.g. ceteareth-12 or polyoxyethylene eicosyl/docosyl ether combined with cetostearyl alcohol as a co-emulsifier. The phase inversion temperature was measured as a function of the oil polarity and the concentration of mixed emulsifier. The relationship between phase inversion temperature, droplet size and emulsion stability was investigated. In addition, self-bodying agents such as cetostearyl alcohol or monoglycerides were added to these thin, fine disperse emulsions to adjust the consistency. The influence of these ingredients on phase inversion temperature, droplet size, yield value and emulsion stability was studied.

Droplet sizes of oil/water (O/W) nanoemulsions prepared by the phase inversion temperature (PIT) method, in the water/C16E6/mineral oil system, have been compared with those given by a theoretical droplet model, which predicts a minimum droplet size. The results show that, when the phase inversion was started from either a single-phase microemulsion (D) or a two-phase W+D equilibrium, the resulting droplet sizes were close to those predicted by the model, whereas, when emulsification was started from W+D+O or from W+D+Lalpha (Lalpha = lamellar liquid crystal) equilibria, the difference between the measured and predicted values was much higher. The structural changes produced during the phase inversion process have been investigated by the 1H-PFGSE-NMR technique, monitoring the self-diffusion coefficients for each component as a function of temperature. The results have confirmed the transition from a bicontinuous D microemulsion at the hydrophile-lipophile balance (HLB) temperature to oil nanodroplet dispersion in water when it is cooled to lower temperatures.

Synopsis The phase inversion emulsification is a convenient method of preparing fine-disperse and long-term stable oil-in-water emulsions, which are stabilized with nonionic emulsifiers. On the basis of EACN-values (equivalent alkane carbon numbers) the calculation of phase inversion in concentrates (CAPICO) is possible, which yields emulsifier and oil mixing ratios corresponding to a given phase inversion temperature (PIT). The CAPICO-method is illustrated for the example of a cosmetic oil-in-water lotion containing an oil mixture, glyceryl monostearate and a fatty alcohol ethoxylate. Of special interest is the influence of silicone oils on the PIT. At a constant emulsifier oil ratio the complete phase behaviour of this emulsion system is represented in a temperature/water content graph. Optimum emulsification results are obtained if during PIT emulsification a microemulsion or a lamellar phase is passed. The emulsions were characterized by particle sizing, and emulsion stability against sedimentation was evaluated by ultrasonic velocity changes. A fine-disperse and long-term stable oil-in-water emulsion was prepared by a time and energy-saving two-step hot-cold process.

In low-energy emulsification processes, phase inversion occurs when the phases of a dispersion exchange, because of changes in the medium's properties. This paper reports experiments to determine the phase inversion temperature (PIT) of orange oil/water emulsions stabilized by nonionic surfactants. Two techniques were employed: rheology, which is already commonly used to obtain the PIT, and microcalorimetry, which has been proposed as a new technique. Continuous monitoring of the emulsions' viscosity permitted identifying different phenomena that occur while the temperature varies. For all the dispersions prepared, the rheological curves obtained showed two peaks, one attributed to the phase separation process and the other to the phase inversion phenomenon. The microcalorimetry technique showed two endothermic transitions as the dispersion's temperature increased. The initial temperatures were comparable to those obtained by rheology. The influence of the surfactant concentration and the hydrophilic-lipophilic balance (HLB) of the mixture of surfactants and the reduction in volume of the phases at the phase inversion temperature were also evaluated. In general, both methods used to evaluate the phase inversion of the orange oil/water systems (rheology and microcalorimetry) presented concordant results, both for the phase separation process and the phase inversion temperature.

Fabrication of protein nanoparticles and microparticles within water domains formed in surfactant–oil–water mixtures: Phase inversion temperature method

Phase property, composition and temperature-induced phase inversion of ATPS-C formed by aqueous cationic–anionic surfactant mixtures