Abstract:The boron based fuel-rich propellant is considered as one of the ideal fuel for solid rocket ramjet owning to the high gravimetric and volumetric heating value of boron. However, the amorphous boron powder could react with the terminal hydroxyl groups of the binder, causing increase of apparent viscosity and pot-life of the slurry shortening. The theoretical volumetric heating values of three boron-based propellants were calculated, in which hydroxyl-terminated polybutadiene (HTPB), 3,3-bis (azidomethyl) oxetane and tetrahydrofuran copolyether (PBT) and gycidyl azide polymer (GAP) was used as the binder. The rheological properties and infrared characteristics of B/HTPB, B/PBT and B/GAP at high shear rate were studied by the co-rotating twin screw rheometer and Fourier transform infrared spectrometer, respectively. The reactivity of terminal hydroxyl groups for the three binders was analyzed. At a rational designed composition of 50∶20∶30, the volumetric heating values exceeded 64.00 MJ·dm-3 for B/PBT/AP and B/GAP/AP, which was higher than B/HTPB/AP system (61.08 MJ·dm-3). At shear rate of 355.56 s-1 and 55 ℃, the apparent viscosity for B/HTPB slurry with 25% boron rapidly increased to 260Pa·s and reached gel state after 110 min mixing. After 7 h under same condition, the apparent viscosity increased from 3.63 Pa·s to 10.6 Pa·s for B/PBT with 40% boron, whereas reduced from 5.96 Pa·s to 0.33 Pa·s for B/GAP with 55% boron. For B/HTPB slurry, enhanced B—O vibration absorption and gradually weaken C—O vibration absorption were detected during mixing, which were unchanged for B/PBT and B/GAP slurries. Therefore, considering reacting with the acidic impurities on the surface of boron particles, the reactivity of terminal hydroxyl groups of PBT and GAP were much lower than that of HTPB, which would facilitate processing of boron-based propellant.