Re‐Crystallization of HNS‐IV by Optimization of Solvent/Anti‐Solvent Method through Taguchi Analysis Design
Hamid Reza Pouretedal, Sajjad Damiri, Javad Moslemi
Abstract
Abstract The explosive HNS‐IV has been proven to be insensitive to shock, percussion, heat, and friction among polymorphs of HNS. According to the US military standard MIL‐E‐82903, the surface area of HNS‐IV must be 5.0 to 25.0 m 2 /g. Thus, the micronization of its particles in re‐crystallization process is a key step. The solvent/anti‐solvent method is used for re‐crystallization of HNS‐IV particles because user‐friendly, inexpensive and efficient. A successful re‐crystallization depends on the proper choice of solvent. Among studied solvents, N,N‐dimethylformamide (DMF) is selected based on its solubility for HNS that is obtained 7.23 g per 100 mL at 100 °C. Taguchi experiment design method is used to optimize the solvent/anti‐solvent re‐crystallization process. The three parameters of volume ratio of anti‐solvent to solvent, temperature of solvent and temperature of anti‐solvent are optimized. The bulk density (B.D) of re‐crystallized of HNS‐IV particles is used as a signal for optimization with the concept of “the larger‐the‐better”. The optimized parameters are volume ratio 20 to 1 for anti‐solvent to solvent and temperatures of 100 and 5 °C, respectively, for solvent and anti‐solvent. BET (Brunauer‐Emmett‐Teller) method shows the specific surface area 12.7 m 2 /g for re‐crystallized particles. Also, SEM images indicate a thin platelet with size 5–10 μm for micronized HNS‐IV product.