Date of Award
Master of Science in Chemistry
Trace explosive detection is the primary way for quick and easy sampling of various surfaces in a check-point environment, e.g. an airport. The swabs used for commercial explosive detectors, such as ion mobility spectrometers, are made of various materials. The difficulty in collection and analysis of explosive traces is that the swabs must be effective at adsorbing as well as desorbing materials, i.e. pickup from the surface and release into the detection device. This dichotomy results in a tradeoff for development of new swabs. Generally, desorption is considered to be the more desirable property; therefore, Teflon is one choice for commercial swabs. It would be ideal to develop a swab with both enhanced adsorption and desorption. One way to accomplish this is to apply an electrostatic charge to commercial swabs. This enhances their attraction to explosive particles, but once the swab is placed in the inlet of commercial detection instrument, the charge is dissipated, and desorption of the particles into the instrument proceeds as usual.
Methods of generating electrostatically charge swabs was determined; triboelectric charging vs corona charging was compared examining magnitude of the charge, reproducibility and stability, and effects of humidity. The magnitude of charge necessary for enhanced collection of particles was evaluated using an electrostatic voltmeter to measure charge and various means to measure particle pickup. Corona charging was determined to be more effective. Enhancement of collection was judged by comparing results of corona charging swabs to those achieved by contact swabbing. Two variables were examined: the analyte and the substrate from which the analyte is removed. The swab material was Nomex. In each case but three, collection of an analyte by an electrostatically enhanced swab outperformed the traditional contact swabbing. Evaluation was determined by a rigorous quantification by mass spectrometry of the analyte picked up by the swab and the analyte remaining on the substrate after swabbing. When analytical protocol was not amenable to a particular analyte or substrate a commercial explosive trace detection instrument was used. It was found that the substrate morphology played a bigger role in pickup of analyte than the particular analyte.
In order to eliminate biological warfare agents, both heat and halides are used. Ideally, these agents would be destroyed without dispersing them. The approach to create a polymeric-sprayable matrix would allow dispersion of an iodine-producing pyrotechnic, without dispersing the biological weapon, and when initiated would produce both heat and iodine gas. This matrix will provide iodine vapor and a long-lasting flame, not an explosion, to control dispersion of the threat.
A two-part foam was formulated based on polyurethane chemistry, i.e. a diisocyanate combined with polyol to produce a urethane linkage. Each component of the foam (e.g. isocyanate, polyol, catalyst, blowing agent, surfactant) was experimentally adjusted to achieve the best foam based on expansion, structural integrity, and cell uniformity. Since the polyol is the most adjustable component in the foam, an investigation of commercial and synthesized energetic polyols was performed. The structures of the energetic polyols were verified by LC-MS and FTIR and characterized for heat flow by DSC. Once the structures of the energetic polyols had been proven, it was formulated into a polyurethane foam which was characterized for heat of decomposition, by SDT, for heat of combustion by bomb calorimetry, and structurally by FTIR. Documenting heat flow with SDT helped to determine that the structural modification increased heat release and lowered ignition temperature compared to the standard polyurethane foam. The formulated polyurethane foam was then tested for expansion against increased solids loading. When optimal solids loading was determined (>70%), the pyrotechnic foam was ignited in a bomb calorimeter. The heat released and iodine production was quantified.
Levine, Rebecca M., "Interactions of Polymers and Energetic Materials" (2017). Open Access Master's Theses. Paper 1026.
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