Relationship between the morphology of granular cyclotrimethylene-trinitramine and its shock sensitivity

The sensitivity of explosives has been shown to be critically dependent on their morphology as well as their chemical properties. A critical hotspot can be seen as one end of the temperature distribution produced in a heterogeneous material by a shock. Studying shock sensitivity in a granular explosive thus allows insight into the temperature distribution produced by a shock in a granular material. In the case of cyclotrimethylene-trinitramine (RDX), a commonly used explosive, no consensus exists on the dominant features which promote critical hotspots. We present an investigation of the morphology and sensitivity of seven batches of RDX in two size classes and with a range of morphologies. Both the individual crystal morphology and the bulk granular morphology were studied and the features likely to interact with a shock in a granular material to form a critical hotspot are identified. We find that the internal void count does not correlate with the sensitivity of a granular bed and that crystals with defects can be insensitive in such a charge. Sensitivity in our tests was correlated with the presence of surface dimples for particles which are 10-30 mu m in size. For larger particles (100-300 mu m in size), more angular crystals were more sensitive. (c) 2007 American Institute of Physics.