ENCAPSULATION OF SOLID PARTICLES BY THE CONCENTRATED EMULSION POLYMERIZATION METHOD

The encapsulation of submicron sizes of alumina and fumed silica particles in crosslinked polyacrylamide is described. In a first step, a colloidal dispersion was prepared by dispersing the solid particles in an aqueous monomer (acrylamide) solution containing a water-soluble dispersant, a crosslinking agent, and a suitable initiator. In the second step, a concentrated emulsion was prepared at room temperature by dispersing the above colloidal system in decane containing a suitable surfactant, the volume fraction of the continuous phase being about 0.1. Upon heating at 40°C, polymerization of the dispersed phase of the gel-like emulsion obtained took place, thus encapsulating the solid particles in capsules with a polyhedral shape. Electron microscopy revealed that the solid particles were covered by polymer, and that the sizes of the capsules were around 4-5 μm for alumina and 1.0-1.5 μm for silica. © 1990.