Effects of temperature on the decomposition of PTFE induced by electron beam irradiation

The effect of temperature on the irradiation-induced decomposition of polytetrafluoroethylene (PTFE), a representative fluorocarbon polymer, was investigated to improve the energy efficiency of the recycling process. The weight loss of PTFE was 18 %, 33 %, 64 %, and 91 % by the irradiation with a dose of 7.5 MGy (dose rate:1.0 kGy/s) at 30 °C, 120 °C, 200 °C, and 270 °C, respectively. During the electron beam (EB) irradiation of PTFE powders under an oxygen atmosphere, a greater weight loss of PTFE was observed at higher irradiation temperatures. At 370 °C, PTFE powder is completely converted to gaseous components with an absorbed dose of 5.0 MGy; the primary product was identified as an oxidized fluorocarbon (C_nF_2nO_x). A lower dose rate (0.1 kGy/s) reduced the required absorbed dose for PTFE decomposition to 80 % level. Post-irradiation analyses of the PTFE residues using TGA, SEM-EDX, and FT-IR consistently showed that higher irradiation temperatures accelerated the production of oxidized fluorocarbons and further oxidized gaseous products evaporating from the PTFE residue. XRD analysis showed that high-temperature irradiation also increased the crystallite size to 37 ± 5 nm after irradiation at 270 °C, which is nearly double the size of non-irradiated PTFE (21 ± 2 nm). High-temperature irradiation significantly accelerated the oxidation and weight loss of PTFE, offering a promising method for enhancing the energy efficiency of PTFE recycling.