Effect of crystallization parameters and presence of surfactant on ammonium perchlorate crystal characteristics
ABSTRACT Ammonium perchlorate is an exceptional oxidizer in composite solid rocket propellant formulations. Crystallization is the most critical step in the manufacture of ammonium perchlorate, which determines the size, shape, morphological characteristics, crystal strength, grinding characteristics, and thermal characteristics of the crystals. Attempts are made in the present study to establish the effect of crystallization parameters such as cooling patterns, agitator rpm, retention of crystals in the mother liquor, and presence of surfactant, on the morphological, thermal, and physical characteristics of ammonium perchlorate crystals. Based on the trials conducted in a 5 L capacity laboratory glass crystallizer, it is found that spherical, transparent, and smooth surface crystals are obtained by crystallization having a slow cooling pattern and an agitator rpm of 600. Irregular shaped crystals are obtained under fast cooling pattern and/or lower agitator rpm. It is also seen from XRD patterns that ammonium perchlorate crystals made in the present study do not have any amorphous phase on the surface. Porous nature of the crystals made in the presence of surfactant was verified by scanning electron microscopy images, bulk density, transparency of crystals, and change in the low temperature decomposition pattern in Differential Scanning Calorimeter (DSC) curves.