Decomposition and combustion of 4,4'-bis4-aminofurazan- 3-yl-azoxy-3,3'-azofurazan and its macrocyclic analog

摘要

Thermal decomposition of two azoxyfurazans, 4,4'-bis[4-aminofurazan-3-yl-azoxy]-3,3'-azofurazan (ADAAF) and its macrocyclic analog tetra(diazenoxidofurazan) (TOATF) has been investigated under isothermal and non isothermal conditions using the thin-walled glass manometer of the compensation type and DSC, correspondingly. Changing the ratio of the sample weight to the vessel volume the kinetic parameters of ADAAF decomposition preferential in the solid state (k = 10~(13)exp(-42200/RT), s~(-1)) and the gas phase have been measured. The comparison of the ADAAF decomposition rate constants obtained under isothermal conditions with those obtained in DSC experiments shows that due to presence of autocatalysis during decomposition the DSC experiments cannot allow obtaining the kinetic data, which describes the initial step of ADAAF decomposition. The kinetic parameters of ADAAF decomposition in the solution (k = 6.810~(11) exp(-35600/RT), s~(-1)) and TOATF in the melt (k = 4.4 10~(15)exp(-49800/RT), s~(-1)) have been measured. Burn rate characteristics of ADAAF and TOATF have been investigated in the pressure interval of 0.05-15 MPa. The temperature distribution in the combustion waves of ADAAF and TOATF has been measured at pressures 0.1-1 MPa. Based on the burn rate and thermocouple measurements data, rate constants of ADAAF and TOATF decomposition in the molten layer at 500-900 °C have been derived from a condensed-phase combustion model (k = 6.710~(9)-exp(-32000/RT) and k = 1.4-10~(17)-exp(-51800/RT), s~(-1)), which are in a good agreement with kinetic data obtained in the solution or melt at 180-270 °C. The kinetic data obtained shows that transfer from linear ADAAF to macrocyclyc TOATF changes decomposition mechanism. Linear polyazo and azoxyfurazans decompose via concerted mechanism, whereas initial step of decomposition of the macrocyclyc analog is unimolecular rupture of C-N bond. Possible reason of such alteration is that the decomposition of azo compounds proceed via trans-to-cis isomerization of azo group, that occurs more difficult in macrocycle due to steric hindrance. A comparison of the rate constants of liquid-phase decomposition of ADAAF and TOATF with HMX shows that TOATF is considerably more stable than HMX, while stability of ADAAF is close to stability of HMX.