Molecular-Level Insights into the Improvement Mechanism of the Bonding Agent MAPO on the Mechanical Properties of the AP/HTPB-TDI Cross-Linked System
Jun‐Jie Zhang, Peicheng Luo
Abstract
Reliable mechanical properties are necessary to ensure safety during practical application of solid propellants. In this work, molecular dynamics (MD) simulation is conducted to investigate the strengthening mechanism of the bonding agent methyl-aziridinyl phosphine oxide (MAPO) for the mechanical properties of the hydroxyl-terminated polybutadiene (HTPB) propellant. The modeling method was first developed to adapt to the construction of a long-chain polymer model with a high cross-linking degree, and the influence of both MAPO and the cross-linking degree on the ammonium perchlorate/HTPB-toluene diisocyanate (AP/HTPB-TDI) cross-linked system was investigated. MAPO molecules can tightly adsorb to the AP surface with a pyramid conformation, and the formation of a dimer is favorable for strengthening the interfacial interaction. The cross-linking degree has an antagonistic effect on the mechanical properties of the propellant. A high cross-linking degree can increase the mechanical properties of the binder matrix but weaken the interfacial interaction. Moreover, the MAPO droplet as an intermediate layer can improve the wetting behavior between the hydrophilic AP particles and the hydrophobic binder. Finally, MAPO molecules involved in curing reactions can enhance the mechanical properties of the binder matrix, especially in low-temperature environments. The results obtained in this work deepen the understanding of the mechanical properties of bonding agent reinforced propellants from a microscopic perspective, which contributes to the targeted design and effective application of high-performance bonding agents and propellant formulas.