Design and preparation of a novel nano-composite coating for desensitization of CL-20

Although 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is one of the best high-energy explosives, its application is severely limited by its high sensitivity. Herein, a composite wax-film with interfacial crosslinking anti-falling was designed and fabricated to desensitize CL-20. It was filled with nano-silica powder (n-Si), nano-graphenes (n-GPNs) and multi-walled carbon nanotubes (MWCNTs) as insensitive enhancers. A unique and stable core-shell composite explosive was prepared, and characterized by DSC, SEM, TEM, XRD, XPS as well as mechanical sensitivity tests. The results suggested that the functional group interaction and structural strengthening between enhancers and microcrystalline wax (MW) further enhanced the desensitization ability of the composite film for CL-20. Because of the hydrogen bonding and thickening enhancement, the CL-20 crystal was uniformly coated with a nano-composite film. Three enhancers were demonstrated to be highly compatible with CL-20. In comparison with MW@CL-20, The Ea, Tp0 and Tb of the composites containing n-GPNs increased by >375.27 kJ·mol−1, 21.04 °C and 18.27 °C, respectively. The SEM and XPS results showed that the composite performed a complete core-shell structure with thermal softening resistance and superior coverage (98.20 %). The insensitive enhancer was also distributed and embedded in the MW-film matrix. Besides, the anti-fall and cross-linking properties of the film enable the mechanical sensitivity of the composite explosive to reach to a level better than that of WO3/Al nanothermite with 5 wt% polyaniline and polymer-bonded explosive (PBX) with 95 wt% LLM-105 and 5 wt% ternary composite. The heterogeneous composites demonstrated excellent mechanical safety and high energy performance. These findings can provide a reference for the efficient desensitization of CL-20.