Anhydrous Pickering emulsions stabilized by kaolinite and talc clay minerals

Abstract

Anhydrous emulsions, which exclude water from their formulation, are valuable in pharmaceutical applications as they minimize degradation processes such as oxidation and hydrolysis. This approach also aligns with the growing trend toward waterless cosmetics. Kaolinite and talc are natural, cost-effective, and environmentally friendly nonionic clay minerals that have not been extensively explored as Pickering particles in unconventional anhydrous emulsions. The hypothesis focuses on the potential of kaolinite and talc layered particles to stabilize emulsions composed of silicone oil and glycerin. For this purpose, emulsions with varying oil fractions and kaolinite or talc concentrations were developed. Particle-free emulsions exhibited limited and low-stability self-emulsification. In contrast, the addition of Pickering particles increased the emulsified volumes minimizing coalescence, while reducing droplet size, from 60 µm to 47.5 µm for kaolinite and 18 µm to 6.5 µm for talc emulsions. Most kaolinite particle stabilized emulsions are of the silicone oil-in-glycerin, while talc particle stabilized glycerin-in-silicone oil emulsions. Both emulsions type exhibited solid viscoelastic behavior, contributing to long-term stability of up to six months. Among them, kaolinite-based emulsions stood out due to their greater emulsified volumes, enhanced homogeneity, and superior overall stability, making them particularly promising for pharmaceutical and cosmetic applications.