Development of a precipitation method intended for the entrapment of hydrated salt

Microcapsules loaded by sodium phosphate dodecahydrate (DSP) were prepared according to the solvent evaporation–precipitation method using chloroform as solvent and cellulose acetate butyrate (CAB) cross-linked by methylene diisocyanate (MDI) as coating polymer. The effects of the preparation conditions on the capsule morphology and the entrapment efficiency of water-soluble materials were investigated. A mechanism of the process of wall formation material is also suggested depending on the ratio of CAB/MDI introduced. A competition between the hydroxyl functions of CAB and water to react with an isocyanate might occur to form the microcapsule shell. An increase of the amount of MDI promoted urethane linkages whereas urea and urethane linkages decreased by increasing the CAB amount. Furthermore, the encapsulation yield was found to be linked to the CAB and MDI concentrations and optimal when the ratio (MDI to CAB) was in the range of 0.4–1.