Controlled Release of Structural Bed of Coated Particles Filled with Wax Dispersing Starch

Abstract

Encapsulated particles for controlled release generally show a diffusion-type release pattern. However, a release curve of sigmoid type could be useful for various applications. Therefore, a structural bed was prepared by filling voids among encapsulated particles with fine particles dispersed in the filler in order to obtain sigmoid-type release curves. Then, the effects of the volume fraction of fine particles, the packing structure of encapsulated particles and the structural bed height on the release rate were studied. As a result, it was possible to obtain sigmoid-type release curves with the structural bed. The initial release rate decreased with decreasing volume fraction of fine particles and increasing voidage among encapsulated particles, but it was independent of the bed height.