Determination of the shell permeability of microcapsules with a core of oil-based active ingredient

An experimental and theoretical methodology is proposed to calculate the permeability of microcapsules that contain a core of oil-based active ingredient. Theoretical analysis is performed considering the polydispersity of the measurable capsule size, which allows the estimation of the permeability polydispersity via three different methods. The models proposed were applied in order to determine the permeability of melamine-formaldehyde microcapsules with hexyl salicylate as core oil. Release experiments were performed with four different co-solvents (ethanol, propan-1-ol, propan-2-ol and 1,3-butanediol) of different concentration. Permeability values were found to be constant, despite a two order magnitude of difference in the solubility concentrations.