A fundamental study of the microencapsulation procedure utilizing coacervation in a polystyrene-cyclohexane solution.

Coacervation in polystyrene (PS)-cyclohexane solution induced by the lowering of temperature was utilized to investigate the fundamental problems involved in the microencapsulation procedure. Polydispersity of PS played a vital role in determining variables at the critical state of phase separation, such as the composition of coacervate (dense) and lean phases. This also depended on temperature. Observations revealed that microcapsules of glass beads consist of a wall with a thin film of PS covered with a thick shell of talc. Poor utilization of PS may limit practical applications of this system unless effective measures are taken for the recovery of unutilized PS. Controlled release behaviour from microcapsules was successfully investigated by using encapsulated anhydrous sodium sulphate (ASS) particles, and applying the Higuchi model to the estimation of the effective diffusion coefficient of ASS through the composite wall. The values of diffusion coefficient decreased from an order of 10(-7) to 10(-8) cm/s by lowering the encapsulation temperature.