In situ polymerized fluoropolymer coatings on aluminum particles: Tailored modulation of combustion dynamics and agglomeration suppression in composite propellants

Aluminum powder is widely used as a metal fuel in solid propellants, thermite reactions and other energy-rich materials due to its excellent energetic properties. However, its performance is often hindered by ignition delay, incomplete combustion and particle agglomeration, making the efficient utilization of aluminum a persistent focus of research. In this work, we have used trifluoroethyl methacrylate (TFEMA) to prepare modified aluminum powders (Al@PTFEMA) with different fluoropolymer coating concentrations by in situ polymerization technology and systematically investigated its effect on the ignition and combustion characteristics of aluminum powders and propellants. The experimental results demonstrated that the fluoropolymer coating effectively suppressed surface oxidation of the aluminum powder, reducing surface oxygen content from 25.3 % to 1.8 %. Additionally, the preignition reaction (PIR) generated AlF3 and other gaseous products, enhancing gas production performance. This combination significantly shortened the ignition delay time of the aluminum powder. In the propellant system, the sample PF3 containing 7.5 % Al@PTFEMA (AF3) exhibited optimal performance. At 1 MPa pressure, its burning rate decreased by 32 %. Under 7 MPa, combustion efficiency improved from 76.63 % to 96.61 % compared to the baseline propellant. Furthermore, the particle size of condensed combustion products (CCPs) decreased by 34 %. In addition, the modulation mechanism of Al@PTFEMA on the combustion characteristics of modified aluminum particle and propellant was revealed, providing theoretical support for the application of fluoropolymers in aluminum-based propellants.