Ammonium-nitrate-(AN-) based composite propellants prepared with a hydroxyl-terminated polybutadiene (HTPB)/polytetrahydrofuran\r\n(PTHF) blend binder have unique thermal decomposition characteristics. In this study, the burning characteristics of\r\nAN/HTPB/PTHF propellants are investigated. The specific impulse and adiabatic flame temperature of an AN-based propellant\r\ntheoretically increases with an increase in the proportion of PTHF in the HTPB/PTHF blend. With an AN/HTPB propellant, a\r\nsolid residue is left on the burning surface of the propellant, and the shape of this residue is similar to that of the propellant.\r\nOn the other hand, an AN/HTPB/PTHF propellant does not leave a solid residue. The burning rates of the AN/HTPB/PTHF\r\npropellant are not markedly different from those of the AN/HTPB propellant because some of the liquefied HTPB/PTHF binder\r\ncover the burning surface and impede decomposition and combustion. The burning rates of an AN/HTPB/PTHF propellant with\r\na burning catalyst are higher than those of an AN/HTPB propellant supplemented with a catalyst. The beneficial effect of the blend\r\nbinder on the burning characteristics is clarified upon the addition of a catalyst. The catalyst suppresses the negative influence of\r\nthe liquefied binder that covers the burning surface. Thus, HTPB/PTHF blend binders are useful in improving the performance of\r\nAN-based propellants.
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