Factors Affecting Hydroxyl-Terminated Polybutadiene Pyrolysis Product Chemistry on μs Time Scale Probed with Photoionization Mass Spectrometry

High Resolution Image Download MS PowerPoint Slide We report μs time scale pyrolysis of hydroxyl-terminated polybutadiene (HTPB), a critical component of solid rocket propellants, using a molecular beam platform with pulsed laser surface heating. This approach achieves high heating rates and short reaction time scales, addressing gaps left by prior long time scale experiments and computational studies. We demonstrate that surface composition strongly controls product distributions: graphite-containing rods promoted the production of diverse C4-sized species and hydrogen transfer reactions; metal rods favored dehydrogenation and altered product size distributions. Tungsten uniquely catalyzes secondary association chemistry, yielding C6–C8 products without polycyclic aromatic hydrocarbon (PAH) formation. The unusual further association chemistry was ascribed to the reaction of this metal with oxygen, followed by the insertion/addition of either the oxygen atom or an H 2 O molecule to the multiple bonds of unsaturated hydrocarbon intermediates. Variation in HTPB deposition thickness and residence time further modulates hydrogenation patterns and association chemistry. These findings underscore the role of surface effects in rocket fuel combustion modeling; they highlight tungsten-mediated catalysis as a promising route for PAH suppression and improved polymer recycling strategies.