The three levels of stabilization in pickering emulsions stabilized by a non-modified bentonite particle: from particle efficiency to emulsion stabilization efficiency

When it comes to Pickering emulsions, the first question that arises is the ability of a particle to position itself at the oil/water interface and then ensure stabilization of the emulsion formed. However, when we try to transpose this type of emulsion to industrial requirements, for example, another question arises: can the sole presence of particles enable us to obtain stable, homogeneous and fully emulsified emulsions? We have been able to prove, for the first time, that pristine bentonite particles, which have not undergone any modification to their surface chemistry, are capable of stabilizing emulsions for at least two years. To this end, we have shown that the emulsification process must be accompanied by very high shear. In fact, only a process in which the particles were subjected to high-energy ultrasound (25–30 kJ) showed this high stabilization capacity. Spectroscopy, surface free energy measurement, and microscopic characterizations confirmed that at this stage these pristine bentonite particles remained unchanged, except for their morphology. A very simple formula containing water, 4 % particles, 20 % Caprylic/Capric Triglyceride and 1 % preservative has demonstrated its ability to form a fully emulsified, homogeneous and stable Pickering emulsion, Rheological and microscopic measurements of the formulated emulsion clearly show that part of the particles are positioned at the interface as expected and moreover that it is through the organization of a 3D network of particles present in excess in the continuous phase that this Pickering emulsion achieves both homogeneity and stability. Our methodology provides a robust approach for explaining the relevant parameters for obtaining a fully emulsified and stable emulsion over time, using pristine, non-modified, bentonite particles for topical applications.