Interfacial Polymerization Kinetics of Polyurea Microcapsules Formed Using Hexamethylene Diisocyanate Biuret Low Viscosity Isocyanate

Abstract 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 D B 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.