Date of Award

2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry

First Advisor

Jimmie C. Oxley

Second Advisor

James L. Smith

Abstract

Law enforcement and military personnel must be prepared to deal with explosives, unidentified chemicals, and even chemical warfare agents. This is a vast problem space. The included studies examine issues with characterization, mitigation, and disposal of energetic materials.

Among oxidizers those containing the ammonium cation have the potential of self-oxidization, making them of special hazard. We have examined ammonium nitrite and ammonium chlorate, two ionic compounds with well-known hazard potential, and compare their explosive performance with related materials. A novel protocol for assessment of explosivity on the gram-scale was employed.

Law enforcement and military personnel must deal with scenarios where fast and safe destruction of sensitive materials or chemical warfare agents (CWA)1 and biological threats is required. Any attempt to destroy these threats must ensure the method, itself, does not spread contamination. Flexible plasticized pyrotechnic formulations that burn with high heat release, but without detonation, have been created in order to allow controlled destruction2. The pyrotechnics also provide a safe and fast method for destruction of sensitive information (laptops and documents). In the case of CWA, the pyrotechnic formulation must burn hot enough to melt through lightly cased containers, so that responders do not need to open them. In the cases of biological threats, the pyrotechnic can also release a biocide, e.g., a halogen, in addition to heat3. In rating chemicals in terms of burn rate, heat release or explosive potential, the focus is usually on the anion since it is the species that carries the oxygen. However, in the final formulation the contribution of each species of the oxidizer and the fuel must be considered.

After experimental testing on various polymers (ABS, PLA, PIB) and literature review4-11, a flexible polymer with the appropriate properties was incorporated into an energetic mixture. Oxidizers were vetted for heat release using various forms of thermal analysis: SDT [Simultaneous Differential Calorimetry (DSC) and Thermogravimetric Analysis (TGA)]: and bomb (isoperibol) calorimetry. To achieve biocide generation, species containing releasable halogens were selected (e.g., calcium iodate and magnesium bromate), first by literature review, and then by testing selected materials for generation of molecular halogens12. Several techniques were used for detection/quantification of the halogen, e.g., colorimetric test, UV/VIS, and Raman spectroscopy. The heat release of plasticized formulations was determined with SDT and bomb calorimetry, and the maximum temperature of an open burn was monitored with thermal camera. The viscoelastic behavior of the pure polymer and the plasticized formulation was determined with by rheometry.

Long-term stability of explosives is a matter of concern to all who deal with them. Fluoropolymers have been used as the binder or plasticizer in a number of explosive formulations13,14. Historically, munitions and energetic materials have been destroyed by open burn and open detonation (OB/OD)15. However, concerns have arisen on the effects of these plastics on the environment and on human health and development. These indestructible plastics and their byproducts have been found in air, food sources and the human body16-20. The thermal decomposition of explosive formulations containing such plastics has been examined using SDT; TGA-IR (Thermogravimetric Analysis -Infrared Spectroscopy) and Pyrolysis GC-MS (Pyrolysis Gas Chromatography coupled with Mass Spectrometry). The explosives and polymers were examined independently and mixed (50% HMX- 50%polymer and 95% HMX and 5% polymer, by weight). An actual sample of PBXN-5 (95% HMX and 5% Viton A) was also studied.

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