Burning characteristics in a wide range of pressure and thermal decomposition of AP/PBT solid propellants

An attempt to understand the relation between the burning characteristics and thermal decomposition in a wide range of pressure is made in the present investigation based on solid propellants with ammonium perchlorate as an oxidizer and 3,3-diazomethylepoxybutane and tetrahydrofuran as a fuel binder. The burning rate measurement is carried out in a wide range of pressure: 1.0, 3.0, 7.0, 13.8, 15.0, and 20.0 MPa. The inflection point of the pressure exponent for ammonium perchlorate with and without oxalate and the flame extinguishing point both appear at 13.8 MPa. Various mechanisms of burning rate reduction by the quaternary ammonium salt and oxalate are analyzed by theoretical analysis, thermogravimetric analysis, and differential scanning calorimetry analysis. The burning rate and decomposition of the oxidizer and fuel binder with combustion modifiers and their overall impact on propellant combustion are studied. Due to modifiers, a transition between kinetically controlled combustion and diffusion controlled combustion is found to occur.