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  • Author or Editor: P. Makashir x
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Abstract  

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 studied, together with its morphology and evolved gaseous products using thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR) and hot-stage microscopy. The kinetics of the thermolysis has been followed by IR after suppressing volatilisation by matrixing and by isothermal TG without suppressing volatilisation to simulate actual user conditions. The best linearity was obtained for Avrami-Erofeev equation for n=1 in isothermal 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 on the initial thermolysis of TNT has also been studied. Evolved gas analysis by IR showed that CO2, NO2, NO and H2O are more dominant than N2O, HCN and CO. The decomposition involves the initial rupture of the C-NO2 bond, weakened by hydrogen bonding with the labile hydrogen atom of the adjacent CH3 group, followed by the abstraction of the hydrogen atom of the methyl group by NO2, generated in the initial step.

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Abstract  

Complexes of nitrocellulose (NC – low and high nitrogen content) with copper oxide (CuO) have been synthesized and studied for morphological behaviour on heating from room temperature to 500°C with the help of hot stage microscopy (HSM). During decomposition, NC:CuO complexes show contraction of fibrous boundaries followed by mass movement of matrix, with the evolution of brown yellow colour gas at higher temperatures as compared to NC alone.

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The kinetics of the thermal decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in condensed state has been investigated by high temperature infrared spectroscopy (IR) and thermogravimetry (TG) in conjunction with pyrolysis gas analysis, differential thermal analysis (DTA) and hot stage microscopy. The decomposition proceeds in two main stages under isothermal conditions and the initial stage involving about 24% loss in weight obeys Avrami-Erofe'ev equation (n= 1), and is governed by an activation energy (E) of 150.58 kJ·mol−1 and log(A in s−1) 12.06. The second stage corresponding to 24 to 90% loss in weight gave best fit for Avrami-Erofe'ev equation,n=2, withE=239.56 kJ·mol−1 and log(A in s−1) 19.88 by isothermal TG. The effect of additives, on the initial thermolysis of TATB has also been studied. Evolved gas analysis by IR showed that NH3, CO2, NO2, HCN and H2O are produced in the initial stage of decomposition. The decomposition in KBr matrix in the temperature range 272 to 311.5°C shows relative preferential loss in the -NH2 to -NO2 band intensity which indicates that the rupture of C-NH2 bond, weakened also by the interaction of the NH2 with the neighbouring NO2 group, appears to be the primary step in the thermolysis of TATB.

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Abstract  

The thermal decomposition of nitrocellulose (NC) 12.1% N, has been studied with regard to kinetics, mechanism, morphology and the gaseous products thereof, using thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy, differential scanning calorimetry (DSC) and hot stage microscopy. The kinetics of the initial stage of thermolysis ofNC in condensed state has been investigated by isothermal high temperature infrared spectroscopy (IR). The decomposition ofNC in KBr matrix in the temperature range of 142–151°C shows rapid decrease in O−NO2 band intensity, suggesting that the decomposition of NC occurs by the rupture of O−NO2 bond. The energy of activation for this process has been determined with the help of Avrami-Erofe'ev equation (n=1) and is ≈188.35 kJ·mol−1. Further, the IR spectra of the decomposition products in the initial stage of thermal decomposition ofNC, indicates the presence of mainly NO2 gas and aldehyde.

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The kinetics of the initial stage of thermal decomposition of N-2,4,6 tetranitro-N-methyl aniline (tetryl) in condensed state has been investigated by high temperature infrared spectroscopy (IR) in conjunction with pyrolysis gas analysis and thermogravimetry (TG). The decomposition in KBr matrix in the temperature range of 131 to 145 °C shows rapid decrease in the N-NO2 band intensity as compared to the C-NO2 band. Decomposition products in the initial stage show mainly NO2 gas and picric acid. The studies show that the initial stage of decomposition of tetryl occurs by the rupture of the N-NO2 bond and the energy of activation for this process is 177 kJ/mol.

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