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On existence of formic and isocyanic acids in detonation products

The calculation of the composition of detonation products at a given p, V, T condition is a starting point of all thermochemical equilibrium codes that are used for theoretical prediction of detonation properties of explosives. It was reported by many authors that along with main detonation products (such are H2O, H2, CO2, CO, N2, C(s), etc.), some less common, larger molecules, may also exist in significant amounts and affect the accuracy of calculations. The existence of formic acid (CH2O2) as an important detonation product has been a controversial topic for more than two decades. Kerley was amongst the first (1985) who claimed that formic acid is an important detonation product for PETN, RDX and HMX. Baker et al. and Suceska et al. (2010) also reported that formic acid is one of the major products formed at higher pressures. Contrary to them, Fried et al. (2003) concluded that isocyanic acid (HNCO) is a major detonation product for RDX and HMX, not formic acid. It is obvious that opinion on this issue is still divided. Since experimental techniques are still unable to reliably measure the composition of detonation products in the reaction zone and at the Chapman-Jouquet (C-J) state, this topic is studied based on results of thermochemical calculations and molecular dynamics calculations. In this paper we studied the existence of formic acid and isocyanic acid in detonation products using thermochemical equilibrium code EXPLO5. We have found that concentrations of formic and isocyanic acids depend on the equations of state of these two compounds, i.e. values of interaction potential parameters in EXP-6 fluid equation of state used in the calculations. Experimental detonation parameters for studied explosives can be reproduced accurately only by taking formic acid and/or isocyanic acid as major detonation products. Further detailed experimental investigation of the equation of state of these two compounds is required in order to clarify the existence of formic acid and/or isocyanic acid in detonation products of some explosives.

detonation products ; formic acid ; isocyanic acid ; thermochemical code

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