Investigation of PBT-AP Interactions in PBT-Based Solid Propellants: A Combined Density Functional Theory and Molecular Dynamics Study

Poly(3,3-bis(azidomethyl)oxetane(BAMO)-tetrahydrofuran(THF)) copolymer (PBT) and ammonium perchlorate (AP) are critical components of solid rocket propellants, where their interfacial bonding mechanisms and temperature-dependent mechanical properties are pivotal to propellant reliability. In this study, density functional theory (DFT) calculations were employed to evaluate the adsorption energies between common AP crystal surfaces and PBT units, identifying the most energetically favorable adsorption configurations. The atomic configurations and charge transfer characteristics at the PBT-AP interface were systematically analyzed. Molecular dynamics (MD) simulations were further conducted to determine the thermally stable operating range of the PBT-AP system. The results reveal a strong temperature dependence of mechanical performance, with viscous failure mechanisms and damage thresholds during static tensile processes investigated across varying temperatures. Notably, mechanical properties remain stable below 60 °C but deteriorate significantly above this temperature. This study elucidates the influence of a PBT-AP interfacial microstructure and temperature on mechanical performance and tensile fracture damage boundaries, providing crucial insights for the design, formulation, and safe application of PBT-based solid rocket propellants.