Abstract
Low-molecular-weight (Mw) polytetrafluoroethylene (PTFE) micropowder is added to wax for use in automotive equipment and printing machines and is produced by radiation-initiated degradation under atmospheric conditions. However, pentadecafluorooctanoic acid (PFOA) is produced as a by-product in concentrations greater than 25 ppb, which is problematic because PFOA does not degrade in the environment. Herein, we clarify the PFOA-formation mechanism and develop a manufacturing process for a novel low-Mw PTFE micropowder that does not contain PFOA (less than 5 ppb). The process uses combined irradiation and heat treatment in an oxygen-free atmosphere. Furthermore, PFOA-free PTFE micropowder can be produced on the 10-kg scale.
Highlights
Low-molecular-weight (Mw) polytetrafluoroethylene (PTFE) micropowder is added to wax for use in automotive equipment and printing machines and is produced by radiation-initiated degradation under atmospheric conditions
PTFE can be crosslinked by irradiation in its molten state in an oxygen-free atmosphere[6,7], and the chemical structure of the obtained crosslinked PTFE does not contain oxygen according to Fourier-transform infrared (FT-IR) spectroscopy[8,9], X-ray photoelectron spectroscopy (XPS),[9] and 19F solid-state NMR9,10 analysis
Perfluoroalkyl carboxylic acids (PFCAs) group were detected in small amounts of 46 ppb in perfluorobutanoic acid (PFBA: C4), 26 ppb in perfluoropentanoic acid (PFPeA: C5), 20 ppb in perfluorohexanoic acid (PFHxA: C6), and 15 ppb in perfluoroheptanoic acid (PFHpA: C7), respectively
Summary
Low-molecular-weight (Mw) polytetrafluoroethylene (PTFE) micropowder is added to wax for use in automotive equipment and printing machines and is produced by radiation-initiated degradation under atmospheric conditions. Studies of the radical formation and reactivity of P TFE25 have revealed that carbonyl-containing PTFE and alkyl radicals, including a minor components of chain-end radicals, are produced when peroxy radicals trapped in PTFE are heated beyond 353 K under oxygen-free conditions.
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