Combustion mechanism of nitro ester binders with nitramines

The combustion of binary compositions of nitramines (HMX, RDX, Bi-HMX, and CL-20) with two nitro ester binders, one of which is characterized by gas-phase combustion, and the other by the burning-rate controlling reaction in the condensed phase, was studied in the pressure range 2–15 MPa. It is shown that in compositions with the binder characterized by gas-phase combustion, HMX in concentrations up to 50% acts as an inert additive. Depending on the size and concentration of HMX particles, three types of combustion of the mixtures can be identified: combustion along the binder layers, combustion as a single system, and the model of 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. For Bi-HMX and CL-20 nitramines, which are less stable and more fast burning than HMX and in a mixture with a binder characterized by gas-phase combustion, only two combustion models are observed: the model with fast burning additives or combustion as a single unit. In compositions of the nitramines RDX and HMX with a binder burning by the c-phase mechanism, the combustion model with fast burning additives is applicable only in a narrow range 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.