Combustion of Silicon/Teflon/Viton and Aluminum/Teflon/Viton Energetic Composites

The combustion of Si- and Al-based systems using polytetrafluoroethylene (PTFE) as the oxidizer and Fluorel FC 2175 (a copolymer of hexafluoropropylene and vinylidene fluoride) as a binder has been studied. Experimental data were obtained using two methods: 1) instrumented tube burns and 2) pressed pellets inside a windowed pressure vessel. Loose-powder burning rates were seen to optimize at slightly-fuel-rich mixture ratios for Si/PTFE/FC-2175 (SiTv). Al/PTFE/FC-2175 (AlTV) burning rates optimized near a stoichiometric ratio. Pressures calculated by assuming constant-volume combustion equilibrium were seen to match experimental values from burn-tube experiments when burning rates were at or near peak values. The pressure dependence of SiTV and AlTV pellet burning rates was also characterized and compared with reported Mg/PTFE/Viton (MTV) results. SiTV showed power-law dependence with a constant-pressure exponent over the experimental range of pressures. AlTV was shown to exhibit nonconstant-pressure exponent behavior. SiTV burning rates optimized at mixture ratios similar to that of the tube burns. AlTV burning rates increased well past a stoichiometric ratio and decreased at a fuel-rich ratio, which is a similar trend to MTV burning rates.