Graphene Oxide-Modified Hydroxy-Terminated Polybutadiene Liner for Suppressing Plasticizer Migration: Molecular Dynamics Simulation and Experimental Study

In solid rocket motors, the liner serves as a critical interfacial material between the propellant and insulation, and its resistance to plasticizer migration directly affects the long-term structural stability of the propellant grain. In this study, hydroxyl-terminated polybutadiene (HTPB) was used as the matrix and isophorone diisocyanate (IPDI) as the curing agent to prepare composite liners with varying graphene oxide (GO) contents (0, 0.1, 0.3, and 0.5 wt%). The ability of the liners to suppress the migration of dioctyl sebacate (DOS) was systematically investigated. Molecular dynamics (MD) simulations were also conducted by constructing two amorphous cell models, namely DOS/HTPB/IPDI and GO/DOS/HTPB/IPDI, to calculate binding energy and migration coefficient and elucidate the role of GO at the molecular level. Immersion experiments revealed that the incorporation of GO significantly lowered the migration rate of DOS in the liner, with the optimal anti-migration performance achieved at a GO content of 0.3 wt%, which exhibited the lowest equilibrium migration concentration. MD showed that the incorporation of GO reduced the binding energy between DOS and the matrix from 290.998 to 229.264 kcal/mol, while the migration coefficient of DOS decreased from 6.52 × 10−11 m2/s to 5.52 × 10−11 m2/s, corresponding to a reduction of approximately 15.3%. The combined experimental and simulation results indicate that an appropriate amount of GO forms a two-dimensional physical barrier within the HTPB/IPDI matrix, effectively extending the diffusion pathway of DOS molecules and weakening their affinity with the matrix, thereby significantly enhancing the anti-migration performance of the liner. This work provides both experimental and molecular-level insights for the development of high-performance liner materials with enhanced resistance to plasticizer migration.