For cosmetic industrial applications, polyurea microcapsules were formed by using hexamethylene diisocyanate biuret low viscosity (HDB‐LV) and three different amines: ethylenediamine (EDA), guanidine (GUA), and hexamethylenediamine (HMDA). Toluene droplets containing dissolved HDB‐LV were formed by an oil‐in‐water emulsion before being poured into a water phase containing the required excess of amine. The pH of the aqueous phase was fitted through time to calculate the kinetic constant k' and the diffusion constant DB through the polyurea shell when possible. At 60 °C, EDA and HMDA follow a pure kinetic regime, whereas GUA follows a combination of kinetic and diffusion regimes. The presented kinetic data shows that HDB‐LV is a promising nontoxic isocyanate for cosmetic encapsulation.

The common chemical ultraviolet (UV) filters such as octyl salicylate that are used in sunscreen cream may cause irritation and other unknown medical conditions. One possible route to avoid the direct contact of UV filters with human skin is to enclose those filters in microcapsules. In this study, microcapsules with a size calibrated at 78 μm via microfluidics but with different shell thicknesses (0.4 to 2.5 μm) are used for the first time, to study the influence of shell thickness of microcapsules on the UV absorption efficiency. The results show that the shell thickness of microcapsules has no obvious influence on the UV absorption efficiency. Besides, a rough model based on the Beer–Lambert law is used to compare the experimental results.