Decomposition mechanism and kinetic investigation of novel urea burning rate suppressants in AP/HTPE propellants

The combination of urea with ammonium perchlorate (AP) bonding agents displayed superior efficiency in AP/hydroxyl-terminated polyether (HTPE) propellants in our previous work. However, the decomposition mechanism and kinetic investigation of urea-based burning rate suppressants (BRSs) is not enough. The thermogravimetry and differential scanning calorimetry (TG-DSC) have been used to study their influence on AP and HTPE binders. The activation energy dependent on the conversion rate was estimated based on the DSC curves obtained at different heating rates. It was found that with lower activation energies, the BRSs have a better effect on the reduction of burning rates of propellants. The thermogravimetry-Fourier transform infrared spectrometer curves showed that, compared with Schiff base group in BRS-3, the cyano groups in BRS-1 and BRS-2 are easier to generate ammonia so that they had better deceleration effects.