Cooperative Effects of Ni Catalyst and Radiation on Thermal Decomposition Behavior of Poly(tetrafluoroethylene)

This study investigated the impact of a Ni-complex catalyst on the thermal decomposition of irradiated poly-(tetrafluoroethylene) (PTFE) through thermogravimetric analysis and spectroscopic techniques. This catalyst, comprising Ni and NiO particles on a microporous SiO₂/Al₂O₃ support, was incorporated into PTFE powder via mechanical grinding. The Ni-loaded PTFE exhibited nearly 50% weight loss at temperatures 370-400 °C, which is 153-123 °C lower than the decomposition temperature of untreated PTFE (523 °C). The thermal stability of PTFE declines significantly above its melting point. Following electron beam irradiation, approximately half of the irradiated PTFE residue was degassed at relatively low temperatures (100-140 °C), likely due to thermal reactions of the decomposed products or chemically modified PTFE components. FTIR and XPS analyses of the Ni-loaded PTFE residue revealed that both the Ni catalyst and irradiation promoted C-F bond cleavage along with the formation and breakdown of oxidized PTFE fragments and fluorocarbons (C _<i>n</i> F_2<i>n</i> O _<i>x</i> ). Additionally, the Ni catalyst enhanced PTFE oxidation, promoting the conversion of oxidized PTFE moieties to gaseous products such as CO, CO₂, and COF₃. Furthermore, the catalyst supplies oxygen for oxidation and decomposes unoxidized PTFE components during irradiation and subsequent thermal treatment. The combined effects of the Ni catalyst and irradiation notably reduced the thermal decomposition temperature of PTFE, showing great potential for expansion to applications involving the recycling of all per- and polyfluoroalkyl substances.