Investigation of Binary Liquids in Unstable States—An Experimental Approach

In this article, we present a methodology for conducting measurements based on pulse heating of a wire probe in partially soluble binary liquids. These liquids, which can be rapidly transferred to the region of unstable states above the diffusional spinodal, are novel research objects for the thermophysics of extreme states. Using the example of aqueous solutions of polypropylene glycol and glycol monobutyl ether having a lower critical solution temperature, the key hypothesis of the study on the general measurability of the properties of unstable solutions has been confirmed. The characteristic heating times from 1 to 15 milliseconds corresponded to the thickness of the heated layer comprising a few micrometers. The pressure was varied from units of MPa to 100 MPa. The conditions for the transition from measurements on pure components to those on solutions are formulated. The characteristic thermal patterns of the decay of unstable states depending on pressure and heating rate are revealed. The general possibility of using partially soluble binary liquids as a promising coolant in processes involving powerful local heat release is demonstrated.

Improved As-Synthesized Oleic Amido Propyl Betaine Surfactant Mixture for Stable Ultra-Low Interfacial Tension: Effect of Mixed Co-Solvents

As-synthesized oleic amido propyl betaine surfactant mixture, that was produced through a “direct formulation through synthesis” process, exhibited ultra-low oil/water interfacial tension (IFT) values as low as 3.5 × 10−4 mN/m when dissolved in seawater at a reservoir temperature of 96 °C. The as-synthesized surfactant, which was left untreated, had a slightly cloudy appearance when mixed with seawater. Polar solvents were introduced to this surfactant to improve its aqueous solubility by changing its overall hydrophilicity, particularly on the oil/water interface. In this study, two types of glycol ether co-solvent, i.e., ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, were used at different concentrations in a single application and as a mixture of co-solvents at a certain ratio. The behavior of the as-synthesized surfactant with the presence of these co-solvents was investigated. As a result, it showed that the co-solvent helps in solubility improvement and alters the interfacial tension behavior of the surfactant. Ethylene glycol monobutyl ether was found to be efficient in maintaining an ultra-low IFT value of the surfactant. However, the aqueous solubility of the surfactant was not significantly improved. In contrast, the addition of diethylene glycol monobutyl ether showed improvement of the aqueous solubility of the surfactant, but it tends to increase the IFT above ultra-low value. Based on this understanding, a set of co-solvent mixing ratios were tested, and the results showed further improvement in both the oil/water interfacial tension behavior and surfactant aqueous solubility. The most stable oil/water IFT of 3.36 × 10−3 mN/m and clearer surfactant solutions were obtained for ratio C at 35 wt.% presence of co-solvent.

Gel-based Microemulsion Design and Evaluation for Topical Application of Rivastigmine

Objective: The aim of the present study was to design nanocarriers for the topical application of rivastigmine. Methods: The effect of cosurfactants, hydrophilic gel and loading amount on the permeability of rivastigmine through rat skin was evaluated. Skin irritation tests and stability tests were performed to evaluate the utility of tested formulations. Results: The results showed that the microemulsion formation and characteristics of drug-loaded formulations were related to many parameters of the components. When using microemulsion systems as a vehicle, the permeation rate remarkably increased about 13.2~24.3-fold and the lag time was significantly shortened from 24 h to 4.7 h. Formulations containing a cosurfactant of Diethylene Glycol Monobutyl Ether (DEGBE) showed higher enhancement effect, while increasing the loading dose from 0.5% to 5% further increased the flux about 2.1-fold and shortened the lag time. Conclusion: The drug-loaded experimental formulation did not cause skin irritation and had good stability at 20ºC and 40ºC storage for at least 3 months. The result showed that gel-based microemulsion formulation could be a promising approach for topical administration.

Optimal Design of Alkaline–Surfactant–Polymer Flooding under Low Salinity Environment

This paper presents an optimal design of alkaline–surfactant–polymer (ASP) flooding and an experimental analysis on the effects of ASP components under low formation salinity, where the assignment of salinity gradients and various phase types are limited. The phase behavior and coreflooding tests confirmed the ASP formula is optimal, i.e., 1 wt % sodium carbonate (Na2CO3) as the alkaline, 1:4 weight ratio for linear alkylbenzene sulfonate (LAS) and dioctyl sulfosuccinate (DOSS) as a surfactant, 5 wt % diethylene glycol monobutyl ether (DGBE) as a co-solvent, and hydrolyzed polyacrylamide (HPAM) as a polymer. The salinity scan was used to determine that the optimum salinity was around 1.25 wt % NaCl and its solubilization ratio was favorable, i.e., approximately 21 mL/mL. The filtration ratio determines the polymer concentrations, i.e., 3000 or 3300 mg/L, with a reduced risk of plugging through pore throats. The coreflooding test confirmed the field applicability of the proposed ASP formula with an 86.2% recovery rate of residual oil after extensive waterflooding. The optimal design for ASP flooding successfully generated phase types through the modification of salinity and can be applicable to the low-salinity environment.