Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals used in various commercial industries and consumer products due to their resistance to breakdown, which results in their persistence long after their intended life cycle [1]. The Environmental Protection Agency (EPA) is pursuing ongoing research to develop methods to detect and quantify PFAS contamination and evaluate potential disposal mechanisms, to include incineration [2]. This technique disposes of chemicals by combustion at high temperatures, upwards of 1000 to 1400 °C. The persistence of any PFAS byproducts in the environment present a challenge due to the abundance of strong carbon-fluorine bonds. Research on the efficacy of incineration is limited, but recent models predict that the combustion of C₁ and C₂ PFAS results in the formation of the products of incomplete combustion (PICs) such as CF₂ and CF₃ radicals [3]. In our study, we analyze the thermal breakdown and degradation products from polytetrafluorethylene (PTFE), polyvinylidene fluoride (PVDF) and polyvinylidene hexafluoropropylene (PVDF-HFP) using Thermogravimetric Analysis from 20 to 1000 °C, coupled to Mass Spectrometry (TGA-MS). The TGA-MS mass channel data provides a signature for possible gaseous degradation products. The separation of individual byproducts and isolation of gaseous byproducts is a challenge. GC-MS will be used for structural confirmation of these gaseous products. This information will be used to develop a complete degradation mechanism for each of the analyzed fluorinated polymers. Our data will help understand the initial oxidation and combustion of the polymers within a range of 200 to 1000 °C, as well as the composition of any remaining post-combustion residue. Fourier-Transform Infrared Spectroscopy (FT-IR) is used to identify differences in chemical functional groups within the polymers before and after combustion. The combined analysis using TGA-MS and FT-IR allows us to identify the gaseous combustion byproducts of these PFAS materials. After incinerating these polymers to 1000 °C using TGA-MS, mass channel data supported the likely presence of harmful fluorinated gaseous byproducts. Future studies aim to investigate additional methods to capture and decisively characterize the gaseous byproducts of the combustion of PFAS to understand their degradation and impact on human health and the environment.

Pamela Sheehan

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