Cross-Interface Assembly of Propellants Enabled by Disulfide Bonds: Enhanced Interfacial Mechanical and Combustion Stability

Assembly of modular propellants can greatly enhance production efficiency and propellant flexibility, yet the instability of the assembly interface increases the risk of motor failure. Here, a method enabling cross-interface assembly of modular solid propellants has been developed, significantly enhancing the mechanical and combustion stability at the assembly interface. The method involves incorporating dynamic disulfide bonds into the hydroxyl-terminated polybutadiene binder curing process, thereby reducing slurry viscosity and endowing the resultant binder (named PB–PU binder) with metathesis capability. The submodule propellants are integrated into the monolithic propellant system by applying propellant slurry at interfaces, followed by in situ curing. During curing, PB–PU binder metathesis occurs at the assembly interface, eliminating interface defects while enabling interface fusion and cross-interface assembly. The assembled propellant achieves stable combustion at the assembly interface while maintaining combustion properties consistent with the pristine propellant. Further, the assembled propellant is uniform between the submodule and the interface, achieving 100% mechanical strength (i.e., identical to the pristine propellant’s bulk strength). The PB–PU binder also exhibits excellent processability, featuring a low viscosity of 2.3 Pa·s (40 °C) and a pot life exceeding 24 h. This work provides significant value in enhancing the production efficiency, functionality, and stability of propellants.