Estimating ambient vapor pressures of low volatility explosives by rising-temperature thermogravimetry

Abstract

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), 1,3,3-trinitroazeditine (TNAZ), triacetone triperoxide (TATP), and diacetone diperoxide (DADP). Ambient temperature vapor pressures were estimated by extrapolation of Clausius-Clapeyron plots (i.e. ln p vs. 1/T). With this information potential detection limits can be assessed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.