Abstract:
Slow burning Si-BaSO4 pyrotechnic delay compositions are employed commercially for
intermediate to long time delays. However, there is very little information on this
composition available in open literature. The reactivity of this composition was therefore
characterized and compared to that of Si-CaSO4. The Si-BaSO4 composition supported
combustion in the range of 20 to 60 wt.% Si in the bomb calorimeter. However, burning was
only sustained between 20 and 40 wt.% Si in rigid aluminum tubes, with burning rates of
between 8.4 and 16 mm s1. These values are comparable to those for the Si-CaSO4 system
(6.9 – 12.5 mm s1). However, the CaSO4 based formulations tended to have higher energy
output and produced more transient pressure compared to the barium sulfate compositions.
Both formulations were insensitive to impact, friction and electrostatic discharge stimuli. The
reaction products were a complex mixture that contained crystalline phases in addition to an
amorphous phase. Although barium sulfate is insoluble in water and decidedly non-toxic, the
reaction products produced by the Si-BaSO4 compositions were found to release soluble
barium ions when contacted with water. This ranged from 50 to 140 mg per gram of barium
sulfate reacted.