Compatibility and thermal decomposition kinetics studies between 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtizane and hydroxyl-terminated polyether resin cured with different diisocyanates by thermal techniques

This study investigates the chemical compatibility of energetic compound 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtizane (CL-20) with a hydroxyl-terminated polyether (HTPE) as a polymer binder system, specifically for applications in rocket propellant and cast-cure explosive formulations. The compatibility investigations were undertaken in accordance with the North Atlantic Treaty Organization standard agreement (STANAG) 4147 as a benchmark by employing vacuum stability testing (VST) and differential scanning calorimetry (DSC) techniques. According to the criteria set by STANAG 4147 and the findings from VST and DSC, CL-20 demonstrated a good chemical compatibility with the HTPE binder system cured with different curing agents. The kinetics parameters of pure CL-20 and its mixtures were calculated by the Ozawa, Kissinger, and ASTM E-698 methods, by heating the samples. The apparent activation energy obtained from DSC experiments via the Kissinger method was measured to be 233.4, 254.0, 217.6, and 233.2 kJ/mol for binary mixtures containing MDI, IPDI, TDI, and TMDI, respectively. The experimental findings indicated that the values of activation energies obtained by the ASTM- E698 method are consistent and in good agreement with those obtained from the Kissinger methods. The thermodynamic parameters for all mixtures, including pure CL-20, were evaluated. The ∆G# values for all samples were found to be positive, indicating that the thermal decomposition reactions proceed through a non-spontaneous decomposition process, which reveals high thermal stability.