The kinetics and mechanism of the initial stage of thermal decomposition of
2,4,6-trinitro toluene (TNT), a widely used high explosive, have been stud
ied, together with its morphology and evolved gaseous products using thermo
gravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy
(IR) and hot-stage microscopy. The kinetics of the thermolysis has been fo
llowed by IR after suppressing volatilisation by matrixing and by isotherma
l TG without suppressing volatilisation to simulate actual user conditions.
The best linearity was obtained for Avrami-Erofeev equation for n=1 in iso
thermal IR and also in isothermal TG. The activation energy was found to be
135 kJ mol(-1), with logA (in s(-1)) 12.5 by IR. The effect of additives o
n the initial thermolysis of TNT has also been studied. Evolved gas analysi
s by IR showed that CO2, NO2, NO and H2O are more dominant than N2O, HCN an
d CO. The decomposition involves the initial rupture of the C-NO2 bond, wea
kened by hydrogen bonding with the labile hydrogen atom of the adjacent CH3
group, followed by the abstraction of the hydrogen atom of the methyl grou
p by NO2, generated in the initial step.