Creep and drainage in the fast destabilization of emulsions

Abstract

The destabilization of emulsions is important for many applications but remains incompletely understood. We perform squeeze flow measurements on oil-in-water emulsions, finding that the spontaneous destabilization of emulsions is generally very slow under normal conditions, with a characteristic time scale given by the drainage of the continuous phase and the coalescence of the dispersed phase. We show that if the emulsion is compressed between two plates, the destabilization can be sped up significantly; on the one hand, the drainage is faster due to the application of the squeezing force. On the other hand, creep processes lead to rearrangements that also contribute to the destabilization.

Is there a difference between surfactant-stabilised and Pickering emulsions?

“…The preparation of SDS-stabilised emulsions is described previously. 38 The continuous phase is prepared by dissolving 1 wt% of SDS (Sigma-Aldrich) in a 50 : 50 mixture of glycerol and demineralised water. Nile red (Sigma-Aldrich) is added to the silicone oil (VWR Chemicals, viscosity 500 cSt) as a dye.…”

“…From these observations, we can consider that the Pickering emulsions destabilise in a similar way as surfactant-stabilised emulsions since both require low energy input to induce destabilization. 38,59 Intriguingly, to induce coalescence in surfactant-stabilised emulsions, the emulsion needs to be squeezed quite significantly. Our ECNP-stabilised Pickering emulsion, however, already destabilises when putting a drop on a microscope slide and simply placing a cover slide on top of it.…”

Testing and Evaluation of the Emulsifying Properties of Compound Oil Displacement Agents

“…During the destabilization process of the emulsion, the emulsion droplets located in the lower part of the sample container float up. During the ascent, they aggregate with other droplets, coalesce into large droplets, and the large droplets continue to float and eventually merge into the upper oil phase, gradually realizing oil–water stratification. , For the binary system, the whole sample container was all-emulsion at the beginning, the light transmittance was poor, and the backscattered light intensity was high. With the progress of the destabilization process, the intensity of the backscattered light in the lower part of the sample decreased greatly, and the light transmittance became better, indicating that the water content of the emulsion here increased, the emulsion droplets began to float, and the lower part gradually transformed into the water phase.…”