Development and evaluation of environmentally benign techniques for polymer film coating of fine particles

Film coating of fine particles (5-20 microns) by polymers has a wide range of industrial applications, yet few techniques are commercially available that are environmentally friendly. In this study, four different techniques are considered with an ultimate goal of developing a reliable technique that is scaleable and is also environmentally friendly. Two of these techniques are fluidization based; magnetically assisted fluidization, and rotating bed or centrifugal bed fluidization. The other two techniques are based on utilizing supercritical fluids, one is a supercritical antisolvent (SAS) process, and the other is an in-situ polymerization process done within a supercritical fluid medium. Several types of fine powders ranging from a few microns to about 20 microns are considered, including energetic material simulants, metal powders, and drug materials. Various polymers are also considered as coating materials, including biodegradable polymers as well as commercial polymers. Electron micrography techniques (FESEM and TEM) are used to characterize the particles before and after coating. It is shown that all of these techniques are capable of coating fine particles, but each one has a different set of advantages and disadvatages. Relative merits of these methods are discussed, including the possibility for their scale-up, and feasibility for use in film coating of energetic materials.