GAS PHASE POSSIBLE HETEROGENEOUS REACTIONS HEAT PRODUCTS + HEAT PRODUCTS + HEAT

oxidizer particle-polymeric binder interface steep temperature gradient is established in the solid This gradient extends to a depth of several microns, depending upon the external heat-flux rate As the propellant surface layers approach 150°C, the intermosaic blocks of the oxidizer particles8 decompose, and gaseous products diffuse to the oxidizer particle-fuel interface From ammonium perchlo-rate decomposition studies, the over-all reaction for the low-temperature decomposition has been shown to be9 NH4C104 JO, + 2H20 Thus, oxidizing gases are generated at the propellant surface and in the surface layers from decomposition of the solid oxidizer, as shown schematically in Fig 2 Under these conditions, oxidizing species react heterogeneously with the adjacent fuel to generate a source of heat Once these reactions reach runaway conditions, ignition has been achieved Hence, the heterogeneous reactions between the oxidizer decomposition products and the fuel control the internal response of the propellant to the external heat flux The model explains the observed effects on the ignition delay time of heat flux, pressure, initial temperature, and catalyst content Although the description herein has been made for composite propellants that contain ammonium perchlorate, it is completely general and applies to all com-posite and double-base propellants Details of the theory and confirming experimental evidence will be presented in a subsequent publication 1