Making Use of the Formulation−Composition Map To Prepare Highly Concentrated Emulsions with Particular Rheological Properties

Abstract

The effects of the formulation and dispersed-phase weight fraction on rheological properties of highly concentrated water-in-oil emulsions are reported. Because the surfactant concentration is kept constant, emulsion characteristics may be represented on a formulation−composition bidimensional map. The formulation variable is the hydrophilic−lipophilic balance (HLB) number of the nonionic surfactant or surfactant mixture which ranges from 4.3 to 10. Highly concentrated water-in-dodecane emulsions are prepared using a semibatch process, with a dispersed-phase weight fraction ranging from 0.90 to 0.98. Two major effects are observed in relation to the formulation influence: First, elastic modulus (G′) remarkably decreases in the vicinity of optimum formulation whenever the affinity of the surfactant for the oil and water phases is exactly balanced (HLB = 10.5). Second, the elastic modulus value passes through a maximum, concomitant to a minimum drop size, at some distance of the so-called optimum formulation (HLB = 7.7). Hence, the use of a bidimensional formulation−composition map allows one to control and to modulate the final rheological properties of highly concentrated emulsions.

Evaluation of the repartition of the particles in Pickering emulsions in relation with their rheological properties

“…However, the average diameter of the droplets diminishes with the dispersed water volume fraction. This behavior corresponds well with previously published results since the general trend reported in the literature is to obtain a decrease of the droplet sizes with the increase of the dispersed phase fractions [36][37][38][39][40]. The improvement of the dispersed phase fraction produces an increase of the viscosity and the shearing of the droplets becomes more efficient [39,40].…”

Analysis of the Princen and Kiss Equation To Model the Storage Modulus of Highly Concentrated Emulsions

“…The values of G ′ were determined via small amplitude oscillatory tests at a frequency of 10 rad/s, into the linear viscoelastic domain of the samples, one hour after the end of the emulsion preparation process. Elastic modulus of the prepared emulsions is essentially independent of the frequency (ω), as discussed in greater detail in a previous publication …”

“…For this formulation, G ′ values are always smaller than for the other HLB numbers. This behavior is due to the influence of the formulation, particularly to the proximity of the so-called optimum formulation, that bring a decrease of interfacial tension (see Table ), as discussed with more details in a previous work . To analyze the dispersed-phase volume fraction (φ) dependence of the storage modulus of our highly concentrated emulsions, the different models proposed in the literature were tested against our experimental data.…”

Nanoparticle-stabilized carbon dioxide-in-water foams with fine texture

“…In foams, the droplets of the dispersed phased (CO 2 ) become compressed and deformed, resulting in thin lamella of the external phase (water) separating them [36]. The ratio of phases influences the favored continuous phase [37] and the viscosity of the emulsion/foam [36]. Stability is imparted to emulsions and foams with nanoparticles by retarding destabilization mechanisms such as drainage of the liquid in the lamella, coalescence of neighboring bubbles (lamella rupture), and Ostwald ripening [38].…”