The decomposition, boiling and explosion of trinitrotoluene at high temperatures

Abstract

The instability of z : 4 : 6-trinitrotcluene (TNT.) at high temperatures, as exemplified by its spontaneous explosion, is well known, but few detailed observations of the thermal decomposition and vaporisation preceding the explosion are to be found in the literature. Such data are, however, of some interest in the fundamental study of the thermal sensitiveness of explosives. Experimental.Material.-A commercial TNT., m.p. 80-5O c., containing approximately g g yo of a-TNT, was used for the decomposition and ignition experiments. a-TNT. was prepared from this by repeated recrystallisation from conc. H,SO,.Measurement of Decomposition Rate .-The decomposition preceding explosion was examined in Pyrex glass reaction bulbs, nitrogen, hydrogen or air being present at atmospheric pressure to reduce distillation of the liquid from the hot zone. The methods for rapid heating of the sample of explosive and for recording rapid pressure changes were those described previous1y.l Measurement of Boiling-point .-The induction period before the explosion of TNT. a t its boiling point is sufficiently long (about 20 sec.) t o enable a direct measurement of the b.p. t o be made before the explosion. The sample of TNT. was introduced by an electromagnetic arrangement into a vertical Pyrex tube 1-5 cm. internal diam. immersed to a depth of 2-3 cm. in a bath of fused nitrates maintained a t a temperature usually about 30" c. above that of the boiling point to be measured, and containing air or nitrogen a t the required pressure. The hot junction of a platinum-platinum-rhodium thermocouple was fixed about 3 mm. above the surface of the TNT. to measure the temperature of the condensing vapour. This particular thermocouple has no catalytic effect on the decomposition of TNT. The E.M.F. was measured with a potentiometer and shortperiod galvanometer, the thermocouple being calibrated by direct immersion in a nitrate bath, and the resulting curve checked a t four points by determining the boiling points of benzoic acid, phthalic anhydride, benzophenone and anthracene by the method used with the TNT., the values found being within ri0 c.of the accepted values. The b.p. of benzoic acid was also found a t 12 cm. pressure and a value obtained in close agreement with the vapour pressure 1 Larger quantities than 50 mg. were then required for explosion.

Decomposition kinetics of manganese tris (carbohydrazide) perchlorate (MnCP) derived from the filament control voltage of the T-jump/FTIR spectroscopy

“…(3) cannot be solved under nonisothermal, nonadiabatic conditions. Under adiabatic conditions (λ∇ 2 T = 0), such as time-to-explosion or time-to-exotherm experiments [15,18], the activation energy can be calculated from Eq. (4), where t x is the time-to-exotherm value at temperature T .…”

“…It is widely agreed that the overall process is modeled by a first-order rate expression [15,16] (Eq. (2)), where α is the amount of sample decomposed at time t. Attempts to measure k(T ) are usually made under adiabatic or isothermal conditions whose relationship to k(T ) for a first-order process is given by the heat balance Eq.…”

Kinetics and mechanisms of thermal decomposition of nitroaromatic explosives

“…The measurement by Urbanskii and Rych-ter86 gives the lowest Ea value of all probably because the temperature exceeds the boiling point of TNT (345 °C). 44 Wenograd's low value of Ea was determined at high temperature and high heating rate on a semiconfined sample.2 It is nearly impossible to achieve sufficiently rapid heat transfer and temperature sensing under Wenograd's conditions to obtain an accurate value of EaP In fact, global activation energies determined at high heating rates and high temperature frequently are smaller than those at lower heating rate and lower temperature,88-89 probably because the rate of heat transfer is important. The value of Brill and James87 was obtained at 2000 °C/s under 30 atm Ar to suppress evaporation and does not suffer this problem.…”

“…While N02(g) is not liberated to any great extent from decomposition of trinitroaromatic explosives at temperatures below about 700 °C, N02 or NO from thermal decomposition in the bulk phase may be attacking the aromatic ring producing CO and C02. Maksimov63 examined the decomposition of TNB vapor and noticed first a rise and then a drop in the NO concentration, which was attributed to the reaction of a nitrosoaromatic compound, RNO, with NO according to eq 44. The NO consumption occurs as C02 is fanned, RNO + 2NO -*• R' + N2 + N03* (44) perhaps owing to the reaction of the nitrate radical with R\63 The energy released by the propagations reactions of polynitroaromatic explosives is sometimes reflected in the relative concentrations of the gaseous products that are liberated after the exotherm. These reactions may have a role in the sensitivity, in addition to their important role in the performance of the explosive.…”

Sensitivity of Explosives.

“…1. Isothermal kinetics Isothermal kinetic measurements (31,49,101,102,103,104,135) require working at relatively low temperatures, not above 200°C. for sensitive high explosives such as Tetryl, RDX, EDNA, or the like, and not above 300°C.…”