Slurry and Emulsion Explosives: New Tools for Terrorists, New Challenges for Detection and Identification

Abstract

With advantages in cost, safety and ease of use, water gel/slurry and emulsion explosives are rapidly replacing traditional explosives. As a result, cap sensitive versions of each are increasingly encountered in criminal activity and a strategy for their identification and characterization is needed. A water gel/slurry explosive is essentially an aqueous solution of an inorganic oxidizer gelled with a carbonaceous gelling agent. Dispersion of fuel or additional oxidizer in the gel produces a slurry, the “water gel explosive” of commerce. Added sensitizers enhance intiation to a detonator with particular compounds protected by patent and specific to a producer. When intact material is available for examination, sensitizer and other component identification characterizes the explosive type. Emulsion explosives, more efficient than gels, differ in that, emulsifying agents suspend droplets of aqueous oxidizer solution in an oil phase. Chemical sensitizers may be used in emulsion explosives but are less common than in slurry types. Most emulsions are sensitized by microspheres, tiny glass bubbles which both control density and provide “hot spot” initiation. Physical characteristics and composition of typical slurries and emulsions, combined with a systematic analytical approach, are used for the characterization and discrimination of intact gel/slurry and emulsion explosives.