Interfacial polymerization encapsulation of a viscous pigment mix: emulsification conditions and particle size distribution

Abstract

A viscous organic phase, containing up to 65 per cent solid pigment, was dispersed into water with an emulsifier by a rotor-stator homogenizer and the droplets formed were encapsulated by interfacial polymerization. Microcapsules with volume median diameters d₅₀ ranging from 10 to 25 μm and geometric standard deviation (GSD), from 1.25 to 1.65, were obtained depending on emulsification conditions. Larger impellers gave smaller d₅₀ and slightly narrowed GSD; d₅₀ decreased and GSD increased as volume fraction of dispersed phase is decreased. Higher homogenizer speed and emulsifier concentration decreased d₅₀ but slightly increased GSD. Increasing pigment content in dispersed phase decreased d₅₀ but had little effect on GSD. These effects were assessed quantitatively by fitting an empirical model to the data.