Encapsulation of oxidizers: Efficient method by spout-fluid bed

Abstract

In composite solid propellants, the oxidizer in the form of particles is embedded in a polymeric matrix. In general, these oxidizers consist in inorganic salts that are hygroscopic, chemically incompatible or sensitive to friction or impact, so that microencapsulation can be applied as a mean to provide a protective coating layer. This work aims to assess the effectiveness of the spout-fluid bed method to perform microencapsulation of ammonium perchlorate particles with acrylic-based resin. The formed coating integrity was assessed by an optical stereomicroscope for samples with one, two and four layers of coating before and after dissolving the cores in water. The parameters utilized in this method provided a complete and individualized encapsulation with sufficient integrity. Therefore, the spout-fluid bed method proved to be effective, particularly with the application of multiple layers.