Effect of Block Structure of Copolyether Binder on Slow Cook-Off Response of Composite Propellant

As the typical insensitive propellants, hydroxyl-terminal block copolyether (HTPE) and hydroxyl-terminal block copolyether (PET) propellant all belong to copolyether propellants. The two binders of propellants have different arrangements of copolyether structure. But, the effect of copolyether structure arrangement on the slow cook-off behavior of propellants and its possible mechanism has been unknown. So, in this paper, the slow cook-off behaviors of HTPE and PET propellants were tested. The result showed PET propellant responded more violently than HTPE propellant. Then, the changes of mass loss, explosion heat, and combustion performance of propellants during the cook-off test were studied. Combined with the slow cook-off behavior of AP and binders, the mechanism of block structure effect on slow cook-off response of propellant was proposed. It expressed that, the binders of HTPE and PET propellant all degraded into liquid products due to the copolyether structure; but the block structure has a significant effect on the chain scission process of copolyether binder, which makes slight degradation and the mild response to slow cook-off for HTPE propellant. While the binder of PET propellant with the random structure degraded seriously, making more mass loss, bigger explosion heat, and worse combustion performance, the PET propellant responds violently to slow cook-off.