Experimental Study of the Effect of Ammonium Perchlorate Oxidizer Particle Size Distribution on Physical, Mechanical and Combustion Properties of HTPB-Based Composite Solid Propellant Containing 19 wt.% of Aluminum

The composite solid propellant based on the three main components AP/Al/HTPB containing 19 wt.% of Aluminum has special physical, mechanical and combustion properties due to the high solid load. Increasing the solid load is done in order to improve the performance properties of solid propellant, such as specific impulse and volume combustion heat, which are requirements of space missions. On the other hand, increasing the solid load (reducing the binder system) leads to limitations in the production process, such as increasing the viscosity, reducing the pot life, and reducing the processability of the propellant slurry, and also reducing the quality of other propellant properties such as mechanical properties. In this study, the effect of ammonium perchlorate (AP) as one of the key parameters on the physical, mechanical and combustion properties of composite solid propellant has been studied experimentally. The results showed that by reducing the average size of AP particles, the density does not change significantly, the tensile strength and modulus increase and the elongation decreases, and the burning rate of the propellants increases slightly. The average density of propellants is 1792 kg/m3, For the propellant sample with the NCO/OH ratio = 0.88 and the mass average AP particle size equal to 251 μm, the ultimate tensile strength is 0.523 MPa, the maximum elongation is 35.1%, the modulus is 1.5 Mpa, and the burning rate at 65 bar is equal to 6.9 mm/sec.