Characterization of homemade explosives

Joseph Edward Brady, University of Rhode Island

Abstract

Recently criminals have used homemade explosives. Homemade explosives may refer to unconventional explosives (TATP, HMTD, UN, etc.) or conventional explosives (RDX, TNT, PETN, ANFO, etc.) prepared illegally. In order to prevent the use of homemade explosives as weapons, four different studies were performed in order to better understand the physical properties of these homemade explosives for the purposes of enhanced detection and safe destruction.^ The vapor signature of diacetone diperoxide (DADP) and hexamethylene triperoxide diamine (HMTD) were examined by a gas chromatography (GC) headspace technique over the range of 15 to 55°C. Parallel experiments were conducted to re-determine the vapor pressures of 2,4,6-trinitrotoluene (TNT) and triacetone triperoxide (TATP). The TNT and TATP vapor pressures were in agreement with previously reported results. Vapor pressure of DADP was determined to be 17.7 Pa at 25°C, which is approximately 2.6 times higher than TATP at the same temperature. The Clapeyron equation, relating vapor pressure and temperature, was Ln P (Pa) = 35.9-9845.1/T (K) for DADP. Heat of sublimation, calculated from the slope of the line for the Clapeyron equation, was 81.9 kJ/mole. HMTD vapor pressure was not determined due to reduced thermal stability resulting in vapor phase decomposition products.^ Thermal behaviors, vapor pressures, densities, and drop weight impact results, as well as analytical protocols, are reported for three tetranitrate esters: erythritol tetranitrate (ETN), 1,4-dinitrato-2,3-dinitro-2,3bis(nitratomethylene) butane (DNTN), and pentaerythritol tetranitrate (PETN). ETN and DNTN both melt below 100°C and have ambient vapor pressures comparable to TNT. While LC/MS was shown to be a viable technique for analysis of all three tetranitrate esters, only ETN was successfully analyzed by GC/MS. Performance of these nitrate esters as evaluated in lab using the small-scale explosivity device (SSED) suggested RDX >> DNTN > PETN > ETN. Detonation velocities were calculated using Cheetah 6.0. Since the starting material is now widely available, it is likely that law enforcement will find ETN in future improvised explosive devices. This paper with its analytical schemes should prove useful in identification of this homemade explosive.^ Vapor pressure is a fundamental physical characteristic of chemicals. Some solids have very low vapor pressures. Nevertheless numerous chemical detection instruments aim to detect vapors. Herein we address issues with explosive detection and use thermogravimetric analysis (TGA) to estimate vapor pressures. Benzoic acid, whose vapor pressure is well characterized, was used to calculate instrumental parameters related to sublimation rate. Once calibrated, the rate of mass loss from TGA measurements was used to obtain vapor pressures of the 12 explosives at elevated temperature: explosive salts-guanidine nitrate (GN); urea nitrate (UN); ammonium nitrate (AN); as well as mono-molecular explosives hexanitrostilbene (HNS); cyclotetramethylene-tetranitramine (HMX), 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diaza-tetracyclododecane (TEX), cyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate(PETN), 3-nitro-1,2,4-triazol-5-one (NTO), 3-nitro-1,2,4-triazol-5-one (TNAZ), triacetone triperoxide (TATP), and diacetone diperoxide (DADP). Ambient temperature vapor pressures were estimated by extrapolation of Clausius-Clapeyron plots (i.e. ln P versus 1/T). With this information, potential detection limits can be assessed.^

Subject Area

Chemistry, Analytical|Chemistry, Physical

Recommended Citation

Joseph Edward Brady, "Characterization of homemade explosives" (2011). Dissertations and Master's Theses (Campus Access). Paper AAI3465904.
http://digitalcommons.uri.edu/dissertations/AAI3465904

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