Date of Award

2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Jimmie Oxley

Abstract

This thesis focuses on the handling and detecting of improvised explosives, specifically erythritol tetranitrate (ETN). ETN is a nitrate ester with the unusual property of melting at a temperature significantly below its decomposition temperature. For this reason the first two manuscripts probe the potential usefulness of ETN as a military explosive and the long-term stability of this material. The third manuscript examines x-ray detection, a technique that readily reveals covert military explosives. Discussed are ways to evaluate detection capability without actually employing the explosive.

With the recent availability of erythritol as an artificial sweetener, the synthesis of ETN has become economically feasible. This dissertation examines eutectics of ETN, to establish if it can be a useful component in melt-casted explosive formulations. To this end we report three novel ETN-energetic eutectics with trinitroazetidine (TNAZ), dinitroanisole (DNAN), and 2,3-hydroxymethyl-2,3-dinitro-1,4-butanediol tetranitrate (SMX). We also report adjusted ratios and melt-temperatures for two previously reported ETN eutectics with 2,4,6-trinitrotoluene (TNT) and with pentaerythritol tetranitrate (PETN), and examine a new eutectic composed of insensitive explosives, DNAN-TNAZ. Finally, we examined the eutectic of TNT-PETN as a reference to confirm the validity of our other results. Melting was examined on a differential scanning calorimeter (DSC) and eutectic properties were determined by constructing phase diagrams and Tamman plots. Theoretical eutectic properties were calculated using the van’t Hoff equation and a more recently published equation for predicting eutectics specifically of energetic compounds. Experimental results are consistent across analysis metrics but did not correspond with the theoretical results.

With the increased ease of synthesizing ETN, and because we have been examining the usefulness of ETN, its complete characterization, especially its stability, is of great interest. This work examines the thermal decomposition of ETN and compares it to the well-studied nitrate ester PETN, both through experimental methods and computational theory.

ETN was aged isothermally at temperatures of 60, 80, 110, 120, and 140 °C for multiple time points. At each point, the amount of ETN remaining was quantified using liquid chromatography mass spectrometry (LCMS). Kinetic parameters of decomposition were found by fitting this data to the integrated first order rate law equation, the obtained rate constants were then fit the Arrhenius equation to calculate the activation energy (Ea) and pre-exponential factor (A). It was found that ETN is less thermally stable than PETN, however ETN is more thermally stable than results from our previous DSC kinetics study would indicate. In addition to these kinetic parameters, decomposition products were examined to elucidate the decomposition pathway of ETN. These products were also studied using LCMS and consisted primarily of erythritol trinitrate, along with minor quantities of the dinitrate and mononitrate, presumably generated by the loss of NO2 from ETN.

In addition to our work with ETN, a new approach to develop non-hazardous materials that simulate explosives, and other related threats, on x-ray detection equipment is presented in this work. Simulants for x-ray detection are needed to confirm proper working order of detection instruments in areas where actual threats cannot be examined (airports, vendors’ facilities, etc.). Rather than trying to make universal simulants, which often do not provide adequate matches across multiple instruments, this method focuses on making accurate simulants specific to the instruments on which they are designed. This is accomplished by matching the end signal output of these instruments rather than trying to match the properties inherent to x-ray interactions with materials. Our original methodology was developed on a liquid bottle screener on which we created simulants for five concentrations of hydrogen peroxide, four concentrations of nitric acid, and nitrobenzene. The methodology was applied to a computed tomography baggage scanner to make three hydrogen peroxide simulants and prove the applicability of the simulant development method. The method was tested for its applicability to solid threats and was found to require significant additional tweaks before moving on from liquid threats.

Available for download on Saturday, May 11, 2019

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