Morphology and properties of CL-20/MTNP cocrystal prepared via facile spray drying

Abstract

Cocrystal of 2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-3,4,5-trinitropyrazole (CL-20/MTNP) in a 1:1 molar ratio is a promising energetic material, since it combines the superior detonation performance of CL-20 and good mechanical sensitivity of MTNP. In order to promote its progress to practical use, a rapid, facile and candidate large-scale manufacture method-spray drying was used to prepare the CL-20/MTNP cocrystal in this study. The morphology, crystal structure and thermodynamic behavior of the resulted CL-20/MTNP-SD cocrystal, raw materials and the cocrystal prepared via solvent evaporation method (CL-20/MTNP-E) were systematically studied by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD) and differential scanning calorimetry (DSC), respectively. The resulted CL-20/MTNP-SD cocrystal shows a regular spherical shape with diameter narrowly distributed from 0.2 µm to 2 µm. This morphology is different from the rod-like shape of CL-20/MTNP-E cocrystal. The crystal structure and thermal behavior CL-20/MTNP-SD is similar to the CL-20/MTNP-E cocrystal, and totally different to the raw materials. Additionally, the initiation temperature and activation energy for thermal decomposition of the CL-20/MTNP-SD cocrystal are slightly lower than the CL-20/MTNP-E cocrystal. The short pulse slapper sensitivity of cocrystals have been investigated. The spray drying method endows CL-20/MTNP cocrystal with the ability of being initiated by short-duration impulse. And the slapper impact initiating threshold of CL-20/MTNP-SD cocrystal is even lower than the commonly used initiating explosive 2,2′,4,4′,6,6′-hexanitrostilbene (HNS). This result evokes a prospective application of CL-20/MTNP-SD cocrystal as an initiating explosive for short impulse shockwave.