Heat generation of propellants and explosives

The self heating of an explosive due to chemical decomposition reactions determines its 'cook-off' behavior and its tendency to thermal explosion. Critical storage temperatures can be calculated with the theory of Frank-Kamenetzkii. This is demonstrated for the solid rocket propellant HV5. The necessary values for the heat generation as function of temperature were measured with an isothermal-isoperibolic microcalorimeter. By using an adiabatic calorimeter, e.g. the 'Accelerating Rate Calorimeter' (ARC), it is possible to determine the characteristic data of the self heating directly. The self heat rates and the pressure increase rates of the following explosives and propellants were measured: PETN, NQ (Nigu), TAGN, RDX, TNT, pure AN, single base GP A5020, LOVA type GP KHP 230 and KHP 281, energetic binder GAP and solutions of GAP in toluene and dioxane. The onset temperature of the self heating was always much below the corresponding deflagration temperature measured at 5 Cel/min heat ing rate of Wood's bath. All substances, except AN and the solutions, deflagrated after a 'controlled' self heating. These transition temperatures were also below the deflagration temperatures. The activation energy for the decomposition of GAP, soluted in toluene and dioxane was determined from the self heat rates of these solutions. The values are 168.9 kJ/mol in toluene and 170.2 kJ/mol in dioxane and agree well with the data of pure GAP.