THERMAL-DECOMPOSITION OF ENERGETIC MATERIALS .46. THE FORMATION OF MELAMINE-LIKE CYCLIC AZINES AS A MECHANISM FOR BALLISTIC MODIFICATION OF COMPOSITE PROPELLANTS BY DCD, DAG, AND DAF

The gas products from dicyandiamide (DCD), diaminoglyoxime (DAG), and diaminofurazan (DAF) heated at dT/dt greater-than-or-equal-to 100-degrees-C/s, under pressure up to 1000 psi Ar have been determined. Contrary to the behavior of most materials, large, thermally stable cyclic azines (melamine and melon) form in addition to common low-molecular-weight gases NH3, CO2, HCN, and N2O. The structural isomer of DCD, ammonium dicyanamide, NH4[N(CN)2] also vaporizes from DAG and DAF. The cyclic azines are proposed to contribute to the burn-rate suppression and the lowering of the pressure exponent when DCD, DAG, and DAF are formulated in composite propellants. The azines are proposed to form on the burning surface and reduce the heat and mass transfer in this region. DCD, DAG, and DAF liberate NH3 as part of the cyclization process that may also contribute to burn-rate suppression.