Combustion of magnesium/polytetrafluoroethylene

The combustion of magnesium (Mg) with polytetrafluoroethylene (TF) is a complex oxidation reaction accomplished by physical changes from solid to liquid and to gas. The burning rate characteristics were determined with Mg/TF propellant pellets made of various-sized Mg particles and different mixture ratios of Mg/TF. The adiabatic flame temperature of Mg/TF propellants is the maximum when the weight fraction of Mg particles (£) is 0.33. However, the experimental results indicate that the burning rate increases with increasing £ for the propellants tested (£ = 0.2 ~ 0.7), which shows that the burning rate does not depend on the final flame temperature. Furthermore, the burning rate increases when large Mg particles (200 /*m diam) are replaced with small Mg particles (22 /*m diam) at £ = 0.6. The burning rate is correlated with the total surface area of the Mg particles mixed within the propellants. The burning rate increases with increases in the surface area of the Mg particles within the range of £ tested in this study. The heat produced just above the burning surface has a dominant effect on the burning rate. This heat is generated by the oxidation of the surface layer of the Mg particles with fluorine produced by the thermal decomposition of the TF at the burning surface of the propellants.