Novel Preparation and Properties of Microspheres involving a Hydrocarbon‐Perfluorocarbon Solvent Extraction Process

Abstract

Microspheres were prepared using a hydrocarbon-perfluorocarbon solvent extraction process. The effects of solidification conditions on the properties of the microspheres were investigated. The emulsion flow velocity into the solidification vessel was found to have the greatest effect on the final particle size. Smaller particles were formed when the emulsion flow velocity into the solidification vessel was increased. However, mixing conditions during the solidification and the solidification temperature were also found to greatly affect the particle size of the microspheres. The initial droplet size distribution, created in the emulsification step, changed during the solidification phase, which happened partly because the emulsion stability was poor. Increasing the stirrer speed in the solidification vessel led to the production of smaller particles. At higher temperatures, larger particles were formed due, in part, to the particles forming hollow cores. Solidification conditions also strongly affected the compactness of the particles. More compact particles were produced at 10°C than at higher temperatures, i.e., 50°C and 90°C, where hollow particles were mainly produced. More compact particles were produced at 50°C when toluene was added to the PFC used in the solidification step. This result was attributed to the slower mass transfer of toluene from the solidifying droplets into the continuous phase.