Burning properties of PBXN-5 - closed vessel testing

Abstract

PBXN-5, a HMX based explosive composition for press filling has been studied in Closed Vessel for characterisation of burning properties. PBXN-5 has been tested as powder and in form of pressed pellets. Pellets have been pressed and tested with four different densities from 1.59 g/cm3 to 1.826 g/cm3. The purpose with the CV-testing was to see if we were able to observe differences in the burning properties as function of differences in density of the pellets. Pressure-time curves of firings with pellets of different density show clearly that as the density of pellets increase the burn time increase. For the loosely packed pellets the burning start on the surface of the pellets, but as the pressure increase the burning also take place inside the pellets. For the pellets of highest density the burning take place only on the surface of the pellets. For PBXN-5 similar burning rates for powder and pellets of high density is obtained. Experimentally obtained impetuses, co-volumes and maximum pressures are in general lower then theoretically calculated ones by use of the Cheetah code. The differences between experimental and theoretical values increase as the pellet density increase. The explanation for this observation is that when the burn time increase, also the loss of energy to the CV increases.