Mechanism of PSAN effect on slow cook-off response of HTPE propellant

Due to safety requirements, insensitive behavior under slow cook-off conditions is the desirable behavior for HTPE propellant. As a low sensitivity oxidant, PSAN is used to partially replace for AP in HTPE propellant formulation to improve the slow cook-off behavior further. But the effect of PSAN on the slow cook-off behavior of propellant is inconclusive. So, in this paper, two kinds of HTPE composite propellant contained either AP as oxidant or a mixture of AP and PSAN were manufactured, named HTPE/AP/Al propellant and HTPE/AP/PSAN/Al propellant respectively. Then the slow cook-off behavior of the two propellants were tested. The results indicated that the slow cook-off response of HTPE/AP/PSAN/Al propellant was much more violent than the response of HTPE/AP/Al propellant. Then the possible mechanism was proposed. It expressed that, during the slow cook-off test, the PSAN decomposed much more than AP, the crack and hole produced in propellant grain; meanwhile the decomposition of PSAN also accelerated the decomposition of HTPE binder, the the crack and hole or AP particles could not be covered effectively by the liquefied decomposition product of HTPE binder; if the ignition occurred, the combustion of thermal damaged propellant was sensitive to pressure, leading a violent response to slow cook-off.