Development and Performance of Boron Carbide-Based Smoke Compositions

Pyrotechnic smoke compositions for visual obscuration containing boron carbide, potassium nitrate, potassium chloride, and various lubricants are described. Only the waxy lubricants stearic acid and calcium stearate slowed the burning rate into a range suitable for end-burning smoke grenades. For compositions pressed into steel cans, the addition of just 2wt-% calcium stearate was shown to reduce the burning rate from 0.50cms(-1) to 0.09cms(-1). In this system, potassium chloride serves as a diluent that reduces incandesence but also increases slag formation. Compositions containing potassium chloride in the 25-30wt-% range exhibited both acceptably low incandescense and slag formation upon burning, while also producing copious amounts of white smoke. These experimental compositions were loaded into full-size grenade cans; field and smoke chamber testing revealed that they outperform the US Army's in-service M83 TA grenade both qualitatively and quantitatively. The photopic mass-based figures of merit for experimental grenades KCl-25, KCl-30, and a production-run M83 TA grenade were 2.51, 2.19, and 1.44m(2)g(-1), respectively.