PREPARATION OF FINE AMMONIUM-PERCHLORATE BY FREEZE-DRYING

In order to prepare Ammonium Perchlorate (AP) composite propellant wit h a high burning rate, fine AP, of which mean diameter is less than 10 x 10(-6) m, is required. In this study, an attempt was made to prepar e fine spherical AP with safety through a freeze-drying method. O/W em ulsion was prepared by emulsifying with organic solvent as dispersed p hase and AP solution as dispersion medium. Organic solvents used in th is study barely dissolve AP and water. The emulsion was frozen with li quid nitrogen and the frozen emulsion was freeze-dried. The mean diame ter (D-av[m]) of AP prepared depends on the interfacial tension (sigma [N.m(-1)]) between organic solvent and AP solution. In the case of 0.5 x 10(-2) N.m(-1) less than or equal to sigma less than or equal to 4. 9 x 10(-2) N.m(-1), the relationship between D-av and sigma is express ed by the following equation. D-av = 0.18 sigma x 10(-3) The addition of surface active agents is effective for a decrease in sigma. However , foam formed on the emulsion during the preparation for all of the or ganic solvents used in this study except toluene. Consequently D-av de viated from the above equation and there was little spherical AP prese nt. It was proved that the freeze-drying method is applicable as a saf e preparation method for fine spherical AP.