Study on thermal decomposition of HNTW by in-situ FTIR spectroscopy

The thermal decomposition of hexanitrohexaazaisowurtzitane (HNIW) was studied by In-situ FTIR spectroscopy. The spectra of condensed-phase reactant and its decomposition products were recorded from room temperature to 450°C. The absorption bands of the condensed-phase decomposition products were assigned. The results of the subtraction FTIR spectra show that a nitro group on six-membered ring homolyzes in the range of the crystal transformation temperature 110°C to 150°C. This homolysis causes a series of cleavage reactions to form compounds contained αβ-unsaturated aldehyde and αβ-unsaturated nitroso-group. Above 155°C, a nitro group on five-membered ring begins to homolyze and form five-membered ring lactam. Above 165°C, more cleavage reactions and self-oxidations occur. Above 190°C, oxidation reactions between product molecules dominantly happens besides self-oxidations. A lot of decomposition products are formed, such as dioxoimidazole, dioxopiperazine, acid anhydride, cyanuric acid, ammonium, four, five and six-membered ring lactam etc. Carbodiimide appeared in residues at temperatures higher than 300°C is attributed to the decomposition of amine compounds. Above 400°C, chief components in the residue are melem and its polymers such as melon etc.