Non‐aqueous, surfactant‐free antifoam emulsions: Properties and triggered release

Abstract

Processing convenience and formulation flexibility frequently require the delivery of the silicone oils as emulsions. The shelf life of the latter is achieved kinetically, in the most cases via the addition of surfactants. On the other hand, surfactants are the subject of increasing scrutiny with regard to their environmental impact. The goal of this study is to formulate silicone oils in surfactant‐free emulsions and to demonstrate the controlled release of the active silicone material. A non‐aqueous silicone emulsion comprising of a continuous phase of a polar organic liquid, having droplets of silicone antifoam compound dispersed therein, have been developed. These systems are stabilised by (fractal) waxy particles which play a dual role. They act as Pickering stabilisers and in the same time they form an elastic network in the continuous phase, providing a creaming stability of more than a year. A triggered release of the (antifoam) silicone active can be achieved via heating above the melting temperature of the waxy particles. This is demonstrated by the fact that no antifoam activity has been observed at temperatures below ca. 60°C, while at temperature of above 65–70°C a strong antifoam effect has been obtained.

Advances and Opportunities of Oil-in-Oil Emulsions

“…As such, any desorption of particles from the fluid–fluid interface is driven by a decrease in surface area between two immiscible liquids. ,, In practice, protruded particles adsorbed at the surface of droplets provide additional steric hindrance that stops coalescence, Ostwald ripening, and other emulsion breakdown processes (Figure ). ,− The formation of Pickering emulsions depends upon the surface chemistry of solid particles and the method from which emulsions are made. − However, only limited work has addressed o/o Pickering emulsions, as summarized in Table . , …”

“…The prepared emulsions were temperature sensitive, which enabled them to release the silicone upon triggering by heat. The composition of the emulsion was 81, 10, and 9 wt % PLU, silicon oil, and wax, respectively …”

“…Most emulsions are thermodynamically unstable and thus require the presence of surfactants at the interface to prevent or retard coalescence of droplets of the dispersed phase and access a stable system (Figure ). Stabilization of the oil–water interface in emulsions can be realized using small molecules, block copolymers (BCPs), or particles. One of the most important features that gives information about the type of small molecule emulsifiers and the respective emulsions they stabilize is known as the hydrophilic–lipophilic balance (HLB), which is the balance between the size and strength of the two components of the emulsifier, i.e., hydrophilic and lipophilic components. − HLB values have mainly been explored for small molecule surfactants , but have also found application in the case of amphiphilic macromolecules .…”

Light-Triggered Release from Pickering Emulsions Stabilized by TiO2 Nanoparticles with Tailored Wettability

“…From a practical point of view, the design of emulsions with the ability of on-demand triggered release in response to external stimuli is still a challenge. Recently, temperature , and pH-sensitive Pickering emulsions stabilized by some “smart” particles have been proposed for stimuli-response release. However, change of the system environment is inevitabe in most of these approaches, which is unfavorable for fragile and sensitive cargoes.…”

Non-aqueous Isorefractive Pickering Emulsions

“… 4 − 10 Literature examples of so-called Pickering 11 non-aqueous emulsions are rather rare. 12 − 14 However, adsorbed particles may offer an important advantage over surfactants in this context because the much higher adsorption energies of the former should lead to significantly more stable non-aqueous emulsions. 1 …”