Burning properties of H-764 and PETN

Two explosives used in MP (Multipurpose) projectiles have been study in closed vessel for characterisation of burning properties. The two explosives are H-764, a HMX based explosive composition for press filling, and PETN. Both explosives are filled into the projectile by press loading. The obtained press density of the loading can vary and will have effect on the reaction rate of the filling. Loosely packed powder ignition will spread very rapidly to all grains or crystals. Solid pellets may burn only on the surface. To be able to observe the effect on the burning properties of differences in density of explosive fillings have we prepared cylindrical pellets of different densities and tested these in closed vessel at different loading density. For H764 in addition to powder, pellets of three different densities have been tested. For PETN powder and one pellet density have been tested. PETN pellets pressed to a density of 1.63 g/cm3 burns only on the pellet surface. For the highest pellet density of H-764 the burning start on the pellet surface, but spreads to all single crystals when the pressure increases.