Polymorphism of CL-20 and the Modification and Inhibition Strategies for Its Crystal Transformation

Polymorphism is widespread in energetic materials and has an important influence on the properties of energy materials. 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is a typical representative of third-generation energetic materials and the most advanced non-nuclear single explosive currently available, with great potential and application prospects in the charge of new weapons and equipment. In this article, the polymorphic phenomenon and the structure and property of energetic materials are briefly elaborated. Meanwhile, the thermodynamic relationship and phase transition mechanism of the polymorphs are deeply analyzed. Moreover, the research progress of CL-20 polymorphic transformation and its effect on performance is reviewed. The modification and inhibition strategies of CL-20 polymorphic transformation such as coating technology, additive technology, and cocrystal technology are mainly introduced. Furthermore, based on the control method of drug polymorphs, the development trend and the promising perspectives of energetic crystal materials, especially CL-20, are also discussed and proposed.