Encapsulation of aluminum flakes by dispersion polymerization of styrene in a nonaqueous system with reactive surfactants

Dispersion polymerization of styrene in ethanol was carried out to encapsulate aluminum flakes. The effects of three reactive surfactants, two anionic and one nonionic, were investigated. It was confirmed prior to encapsulation that these surfactants did not polymerize by themselves but did promote polymerization of styrene. The capsules obtained were characterized with respect to the morphology and mean size. The encapsulating efficiency of the polymer of the wall material, the wall thickness, and the molecular weight distribution were measured. The effects of the concentrations of styrene monomer and reactive surfactants on these characteristics were determined and discussed. Aluminum flakes were coagulated to form secondary particles and they were covered with fine polymer particles, which were precipitated in the continuous phase. To improve encapsulation, the auxiliary addition of nonionic surfactant was attempted. By controlling those concentrations, capsules covered with polymer layer were prepared. (C) 2001 John Wiley & Sons, Inc.