Crystallization of High Bulk Density Nitroguanidine

摘要

Nitroguanidine (NQ) is an important high explosive widely used as a propellant. Conventionally, NQ is obtained as a long needle or rod shaped crystal that has a very low bulk density and cannot be used in propellant application. In this work, high bulk density NQ was obtained with a bulk density of 0.81 g/mL by controlled cooling of a supersaturated water solution of NQ containing methylcellulose and partially hydrolyzed polyvinyl alcohol (PVA). The dissolved NQ concentration in water solution containing methylcellulose and PVA was measured by following the absorption of infrared spectra, and the supersaturation level was calculated as the difference between the measured dissolved concentration and the solubility, also measured in the present work. Experiments were also conducted to obtain the kinetics of the crystallization. It appears from the experiments on kinetic studies that without the additives, the growth of the crystals in one direction is many times faster than other directions resulting in needle or rod shaped crystals, while the additives restrict the growth in that direction resulting in a more uniform growth in all directions.