Study on the Co-crystal Transition Process and Mechanism of CL-20 and HMX in Propellant Formulation

Abstract The integration of CL-20 into solid propellants to enhance their energy levels has emerged as a focal point in the research of high-energy solid propellants and the use of CL-20 as a partial substitute for traditional oxidizers in propellant formulations has emerged as a viable method for propellant modification. However, research indicates that the microstructure and crystal form of CL-20 and HMX may undergo changes due to external stimuli and energy induction, resulting in significant deterioration of the propellant’s mechanical and combustion properties, as well as its safety. We were surprised to find that CL-20 and HMX can form co-crystal not only in the nitric ester plasticizer like DOS but also in some specific binders, such as GAP and HTPE, and revealed that the solvent’s capacity to dissolve two explosives is the key determinant in the formation of co-crystal.