Comparison study of the reaction and combustion characteristics of various fluoropolymer/n-Al composites via the reactive molecular dynamics simulation coupled with experimental verification

The combustion mechanisms of nano-aluminum (n-Al) with fluoropolymers are critical for designing advanced energetic materials, yet the distinct roles of non-fluorine elements (O, H, C) within the polymer structure remain poorly understood at the atomic level. In this study, reactive molecular dynamics (RMD) simulations coupled with experimental validation were employed to systematically investigate the combustion of core-shell n-Al particles with three classes of fluoropolymers: oxygen-containing (Flus-O), pure-fluorine (Flus-F), and hydrogen-containing (Flus-H). The simulations revealed a reactivity hierarchy of Flus-O > Flus-F > Flus-H. Oxygen-containing fluoropolymers (e.g., PFPE) exhibit the highest reactivity, driven by an O-F synergistic effect that promotes rapid alumina shell rupture and deep fluorination. Pure fluoropolymers (e.g., PTFE) undergo a direct and continuous fluorination mechanism, resulting in thermodynamically stable AlF 3 crystalline products. Hydrogen-containing fluoropolymers (e.g., PVDF) display the slowest kinetics due to hydrogen's dual inhibitory role: competing for active fluorine to form H-F and passivating Al surfaces by forming Al-H bonds. A critical finding is the mechanism of carbon inhibition, particularly in hydrogen-containing systems, where slow reaction kinetics lead to the accumulation of a carbonaceous layer on the particle surface, acting as a physical diffusion barrier. These simulation predictions were experimentally validated through the analysis of condensed combustion products (CCPs), where elemental analysis, XRD, and SEM/EDS confirmed the high carbon content in PVDF/Al products and the formation of crystalline AlF 3 in PTFE/Al and PFPE/Al systems. This work provides a comprehensive, atomic-scale understanding of how the composition of fluoropolymers dictates combustion pathways, offering a theoretical basis for optimizing energy releasing performance of fluoropolymers/Al energetic composites by controlling elemental ratios and molecular structures. • RMD simulations and experiments systematically investigated the combustion of Flus-O, Flus-F, and Flus-H, establishing a reactivity order of Flus-O > Flus-F > Flus-H. • Carbon layers act as physical diffusion barriers, severely inhibiting Flus-H kinetics. • Product analysis (XRD/SEM) confirms the predicted carbon deposition and AlF 3 formation.