Synthesis and properties of nitro-HTPB

To enhance the energy density of hydroxyl-terminated polybutadiene (HTPB) propellants, a series of nitro-functionalized HTPB (NHTPB) binders were synthesized via I₂-Na₂O₂-mediated nitration of HTPB. The chemical structures of the products were characterized by FT-IR and ¹H NMR spectroscopy. Physicochemical properties including nitration degree, viscosity, hydroxyl value, molecular weight distribution, and glass transition temperature (T_g) were then determined. Furthermore, the compatibility of NHTPB with energetic plasticizers was evaluated, while the mechanical and combustion properties of NHTPB-based elastomers were also investigated. The results show that the NHTPB elastomer with a 7.5% nitration degree exhibits excellent mechanical properties, achieving a tensile strength of 1.88 MPa and an elongation at break of 690.6%. Meanwhile, its energy characteristics are significantly improved, combustion heat is increased by 60% and the burning rate at 0.1 MPa is doubled compared with HTPB elastomer. Moreover, NHTPB exhibits good compatibility with Bu-NENA, laying the foundation for its subsequent application in HTPB propellants.