Al@PTFE core-shell composites with tunable shell thickness: Effects on ignition and propellant combustion

The ignition process of aluminum powder significantly affects propellant combustion and agglomeration, making the control of ignition through adjusting the surface coating thickness an effective strategy. In this study, core-shell Al@PTFE composites with tunable PTFE shell thickness were successfully synthesized via plasma pretreatment combined with emulsion polymerization. Characterization results demonstrate that the PTFE shell thickness in Al@PTFE can be precisely regulated from 58 nm to 286 nm, corresponding to a mass fraction range of 4.6 wt% to 16.7 wt%. It was found that the PTFE coating not only effectively lowers the laser ignition threshold and shortens the ignition delay of aluminum but also enhances its ignition performance under high-temperature conditions. The underlying mechanism is that the abundant reactive fluorine species released during the thermal decomposition of PTFE can remove the surface Al₂O₃ oxide layer to form AlF₃, thereby significantly reducing both the ignition temperature and delay time. However, in propellant applications, although Al@PTFE composites significantly mitigate aluminum particle agglomeration during combustion, they simultaneously lead to a decrease in the overall burning rate and combustion temperature of the propellant. The tunable shell thickness strategy demonstrated here opens a new avenue for developing high‑performance aluminum fuels with controllable ignition and agglomeration characteristics for solid rocket propulsion.