Transient stability of surfactant and solid stabilized water-in-oil emulsions

Abstract

Water-in-oil emulsions with a dispersed phase fraction equal to 15 wt.% were prepared using either a non-ionic surfactant or solid particles under identical conditions of high energy mixing. Acoustic spectroscopy measurements were carried out on these emulsions to determine the initial droplet size distributions and their evolution over a period of one week. A transient stability test was conducted to compare the behavior of surfactant and solid particles at the oilwater interface. The objective of this paper was to elucidate the use of acoustic spectroscopy for characterizing emulsion stabilization/destabilization mechanisms in these emulsions. Experimental results indicate that a destabilization mechanism, such as coalescence, can be characterized using acoustic spectroscopy. Characteristics prevalent in the coalescing system, such as broad droplet size distribution and polydispersity, were captured by acoustic spectroscopy in terms of change in the raw experimental attenuation. Complimentary bottle test and optical microscopy experiments were conducted on these emulsions to validate the droplet size distribution and transient behavior of emulsions measured using acoustic spectroscopy.

Ultrasound control of oil-in-oil Pickering emulsions preparation

“…Emulsions with droplet sizes we formed in our experiment are also often used in industrial applications [75][76][77][78]. Previously reported results concerned characterisation of already prepared emulsions by using acoustic spectroscopy and corresponding scattering theory ECAH for droplet sizes of tens of micrometres [44,45]. It is worth mentioning that the sensitivity of monitoring the droplet sizes by the ultrasonic attenuation is not limited to region of kR 10 −1 .…”

“…Typically, acoustic spectroscopy is employed for in-situ emulsion characterisation [41][42][43]. Venkataramani et al [44] and Tran et al [45] elucidated the use of acoustic spectroscopy to characterise emulsion stabilisation and destabilisation mechanisms in particle-stabilised water-in-oil emulsions. In general, acoustic spectroscopy is a powerful technique, as it provides very accurate information when experimental data are properly fitted to theoretical models.…”

Effect of interfacial rheology on drop coalescence in water–oil emulsion

“…For complex interfaces, s may be subject to both isotropic and deviatoric stress of intrinsic rheological origin. 27 Drop coalescence can be studied through two different points of view: a macroscopic analysis of the stability of the emulsions by evaluating the phase separation over a period of time 19,28 or a microscale study of a single coalescence event between two dispersed droplets. Different approaches have been used in the literature to study the coalescence between two drops; using a droplet formed at a needle tip and forced against a planar interface of a bulk liquid phase [29][30][31][32] or against another droplet, [33][34][35] or by using microfluidic devices.…”

Effect of Interfacial Rheology on the Stability of Water-Oil Emulsion

“…Coalescence can be studied through two different points of view: a macroscopic analysis of the stability of the emulsions by evaluating the phase separation over a period of time [23,38] or a microscale study of a single coalescence event between two dispersed droplets. Regarding the techniques used to study the microscale analysis, different approaches have been used in the literature to study this phenomenon; using a droplet formed at a needle tip and forced against a planar interface (that can be considered a large drop) of a bulk liquid phase [15,[39][40][41] or against another droplet [35,42,43], or by using microfluidic devices [22,[44][45][46][47] (Fig.…”