Properties and applications of two melt-cast cocrystal carriers

To further investigate the feasibility of cocrystal explosives as melt-cast carriers, two types of energetic cocrystals were studied: 2,4-dinitroanisole (DNAN)/2-nitroaniline (NA) and ammonium dinitramide (ADN)/urea. The synthesis of these cocrystal materials was confirmed by comparing their X-ray diffraction (XRD) patterns with single-crystal simulation curves. Thermal stability was assessed using differential scanning calorimetry (DSC). <i>In situ</i> XRD was used to analyze the changes in the crystal structure of the two cocrystal carriers across varying temperatures. Additionally, the solubility and polymorphic transformation of ε-hexanitrohexaazaisowurtzitane (ε-CL-20) within these cocrystal carriers were analyzed using high performance liquid chromatography (HPLC) and XRD. The results reveal that the two cocrystal carriers exhibit satisfactory thermal stability. Their melting points are 69.3 °C and 71.9 °C and their decomposition temperatures are 319.8 °C and 201.9 °C, respectively. Additionally, they remain in their cocrystal phases after undergoing melting-solidification thermal cycles within the temperature range of 30-70 °C. The solubility of CL-20 in the DNAN/NA and ADN/urea cocrystal carriers is 3.274 g and 1.046 g, respectively, both significantly lower than that in DNAN. Additionally, it was observed that the polymorphic transformation of ε-CL-20 did not occur during the melting and casting process. Therefore, the DNAN/NA and ADN/urea cocrystals hold promise as novel melt-cast explosive carriers.