Preparation and characterization of foamed propellants using supercritical fluids

Foaming behaviours of nitrocellulose based propellants with RDX and DNDA were investigated in a batch foaming process using supercritical carbon dioxide as physical blowing agent. SEM pictures show the influence of saturation conditions (pressure and temperature) on the porosity and internal structure of the propellants. An increasing solubility of carbon dioxide in the polymeric matrix of the propellants leads to more porous powders. This means that low temperature (narrow above the critical temperature of CO2) and a preferably high pressure favour the formation of porous propellants.