Effect of addictives on polymorphic transition of ε-CL-20 in castable systems

In order to explore the law of polymorphic transformation in the process of preparing hexanitrohexaazaisowurtzitane (CL-20)-based composite explosives in cast-cured method, the polymorphic transition of CL-20 crystal under heat stimulation was investigated by X-ray diffraction and differential scanning calorimetric method, respectively, and the effects of different addictives (mainly involved in castable systems) on polymorphic transition of CL-20 were elaborately explored. The transition mechanism was systemically analyzed from the point of view of kinetic and thermodynamic. The experiment results showed that the polymorphic transition was closely related to temperature and ambient surroundings, and the influence of different additives was not consistent in the process of polymorphic transition. In addictives with higher dipole moment or solubility of CL-20, ε-form could easily be polarized and tend to transform into γ-form and the process occurred in fluid medium was much easier than that in solid matrix. The investigation contributes to comprehend the polymorphic transformation mechanism of CL-20 and provides guidance for effective control on the CL-20 polymorphs in preparing CL-20-based composite explosives.