Study of the Effect of DINA on the Polymorphic Transition of epsilon-CL-20 in Composite Modified Double Base Propellants

The polymorphic transition of 2,4,6,8,10,12-hexanitro2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0(5,9).0(3,11)]dodecane (CL-20) is influenced by the materials and conditions used in the preparation of propellants, and limits the application of epsilon-CL-20 in solid propellants. In the present work, the effect of dinitroxydiethylnitramine (DINA) on the polymorphic transition of epsilon-CL-20 in CMDB propellants was investigated by Raman spectroscopy and the Calvet microcalorimeter method. The performance of propellants with CL-20 as affected by DINA was studied by the theoretical prediction of their energetic parameters, stability, combustion, and mechanical tests, respectively. The results showed that the polymorphic transition temperature of epsilon-CL-20 to alpha-CL-20 can be reduced to 75 degrees C by DINA. Expansion of the crystal volume during the process of the epsilon-CL-20 to alpha-CL-20 transition will produce obvious cracks in the surface of the crystals. NC/NG can inhibit the effect of DINA on the polymorphic transition of epsilon-CL-20. The theoretically predicted results indicated that adding DINA will not lower the energy level of CMDB propellants containing CL-20. The DSC and VST results showed that CL-20 has good compatibility and thermal stability with DINA. The burning rate tests revealed that adding DINA decreases the burning rates of CMDB propellants containing CL-20. Mechanical property testing showed that adding DINA can clearly improve the mechanical properties of CMDB propellants containing CL-20. The results of these investigations suggested that DINA has no effect on the crystalline stability of epsilon-CL-20 in the solventless extrusion process, which contributes to a significant understanding of practical applications and provides guidance for applied research on the use of CL-20 in propellants.