COMBUSTION MECHANISM OF ENERGETIC BINDERS WITH NITRAMINES

The paper describes the results of a combustion study of the binary compositions of nitramines [tetranitrotetraazacyclooctane (HMX), trinitrotriazacyclohexane (RDX), tetranitrotetraazabicyclooctane (Bi-HMX), hexanitrohexaazaisowurtzitane (CL-20)] with two nitro ester binders, in which combustion complies with two different mechanisms; i.e., a gas-phase mechanism for volatile energetic materials and a condensed-phase mechanism. It is shown that in compositions in which the binder is characterized by gas-phase combustion, HMX in concentrations up to 50% acts as an inert additive. Depending on the size and concentration of the HMX particles, three types of combustion of the mixtures can be identified; i.e., combustion along the binder interlayer, combustion as a single system, and combustion with a coolant. At higher nitramine concentrations, combustion control passes to nitramine and the burning-rate controlling reaction occurs in the liquid phase of nitramine. Only two combustion models are realized in the case of the binary compositions of a volatile binder with nitramines, which are less stable and burn faster than HMX (Bi-HMX and CL-20); i.e., the mixtures can burn either by a model with fast-burning additives or as a single unit. For the binary compositions of RDX and HMX with the binder, in which combustion obeys the condensed-phase mechanism, the model with fast-burning additives can be realized for a narrow set of conditions. The compositions mostly burn only as a single unit, and the addition of nitramine increases the burning rate of nitro ester by transferring heat from the overlying zone to the condensed phase.