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Potential PFAS products from thermal decomposition of munitions: a DFT analysis of pyrolysis products of fluoropolymers in the presence of energetic compounds
Triumph, Zachary C.
Triumph, Zachary C.
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2023
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Abstract
Per- and polyfluoralkyl substances (PFAS) are one of the most recalcitrant anthropogenic chemicals
that can bioaccumulate and have carcinogenic properties. Their ubiquity in environmental matrices and
resistance toward traditional disposal techniques pose a serious threat to the environment and public
health. This thesis serves as a preliminary analysis of a novel source of PFAS, the disposal of munitions.
Most munitions contain energetic compounds, to serve as the source of energy in detonation events, and
fluoropolymers, to bind formulations as a means of stabilization, to seal the formulation away from the
elements, or to serve as a fluorine source in pyrolants. Energetic compounds degrade through a variety of
pathways, but the major pathways involve the formation of radicals and extreme heat. Despite the extreme
recalcitrance of fluoropolymers, the conditions of detonation events are more than sufficient to initiate
thermal decomposition in even the most robust fluoropolymers. The thermal decomposition of
fluoropolymers involves highly reactive radical intermediates too. Since both energetic compounds and
fluoropolymers undergo radical degradation mechanisms, PFAS radical recombination products are
expected to be formed. There is little known about such potential PFAS products since they contain
functionalities not seen in other sources of PFAS, so a summary of the synthesis and degradation reactions
that these species are known to undergo from synthesis work is provided. This work also contains a
detailed computational investigation of chemical bonding in such potential PFAS products from the
pyrolysis of fluoropolymers in the presence of energetic compounds. Such investigations provide insight to
the mechanisms of PFAS production and the types of functional groups to expect which provide guidance
to the future analytical work by narrowing the scope of the system. The more that computational work is
able to mimic experimental results, the more efficient future laboratory work will be. Thus, this thesis
concludes by proposing possible future directions for this work, which includes a wide variety of ways to
expand the system to be a more comprehensive representation of reality.
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