Effect of different crystalline structures on W/O and O/W/O wax emulsion stability

Abstract

Abstract The possibility of emulsion stabilization using mineral and vegetable wax particles only (without surfactant) was investigated. Mineral waxes, paraffin wax and ceresin, and a vegetable wax, carnauba wax, were used. The content of the wax particles and the water to oil proportion were found crucial for the stability of all emulsions. Some emulsions were also produced with a liquid wax (i.e. jojoba oil). The multiple light scattering method was used to determine the stability of emulsion systems during storage. The presence of crystalline structures were confirmed by microscopic analysis. The results show that all tested waxes can independently stabilize emulsion systems. The wax crystallization directly on the droplet surface provided stability against droplet coalescence while the continuous phase wax crystals reduced inter-droplet collisions. However, the effective protection against coalescence and the phase separation takes only place in the presence of appropriate amounts of different waxes and with specific proportions of water to oil phases. The emulsions type was denoted as W/O in the presence of mineral waxes and O/W/O in systems with vegetable wax. Emulsions with jojoba oil and mineral waxes had a similar stability compare to emulsions with the same composition but without the liquid wax. In contrast, phase separation were observed in emulsions obtained with two vegetable components (jojoba oil and carnauba wax). It might have been associated with a high wettability of the carnauba wax surface by jojoba oil that could have made the wax particles unsuitable for Pickering stabilization of emulsion.