Studies of the Effect of Hivelite and Other Boron Compounds on Nitramine Decomposition by Pyrolysis GC-FTIR (Fourier Transform Infrared)

The traveling charge gun propulsion concept is being explored at the Ballistic Research Laboratory. A traveling charge is one in which the propellant is attached to the projectile, and for which burning rates in the range of 100- 500 m/s are required. The role of borohydride compounds in very high burning rate (VHBR) materials has been studied using two nitramines (cyclotrimethylene trinitramine, or RDX, and cyclotetramethylene tetranitramine, or HMX) and three boron compounds (the potassium and tetramethylammonium salts of the B12H12-2 anion and NaBH4). Pyrolysis products of these materials have been separated by capillary gas chromatography, GC, and characterized by Fourier transform infrared (FTIR) spectroscopy. Two-component and three-component nitramine/ borohydride combinations, as well as pressed propellant formulations previously tested in the closed bomb, have been studied in order to determine which reaction products of the nitramines are modified by the boron compounds. In addition to the permanent gas products typically observed, larger molecular weight species including amides and nitroso compounds have been identified. The product distributions suggest that the rate of energy release is greater in the nitramine/boron systems than that of either borohydride or nitramine alone, and that decomposition occurs at a lower temperature in the nitramine/borohydride mixtures than with the nitramine alone. These conclusions are also supported by DSC results. Keywords: RDX, HMX, Hivelites, TAGN, Thermal analysis, FTIR, Pyrolysis gc.