Low-molecular-weight (M w) 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-M w 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. Pentadecafluorooctanoic acid (C 7 F 15 COOH, PFOA), its salts, and PFOA-related compounds have excellent surfactant properties and are used to give textiles water repellency and antifouling properties, as well as to prevent the scorching of kitchenware. However, they are not degraded in the natural environment and have high bioaccumulation properties. Thus, they are a cause of concern in relation to environmental pollution and human health damage. The Registration, Evaluation, Authorisation and Restriction of Chemical (REACH) legislation in the European Union (EU) will apply to the manufacture and sales of PFOA-containing products in the EU from July 4, 2020; hence it is necessary to reduce PFOA contamination to less than 25 ppb and that of PFOA-related compounds to less than 1,000 ppb 1. Moreover, in the Stockholm Convention on Persistent Organic Pollutants (POPs), regulations concerning PFOSs are under consideration by the POPs Review Committee 2 and will be added to Annex A at the ninth meeting of the Conference of the Parties to the Stockholm Convention (COP9) 3. Low-molecular-weight (low-M w) polytetrafluoroethylene (PTFE) micropowder is a powerful additive used in diverse industrial applications. With its high surface lubricity and anti-blocking properties, its micropowder is becoming accepted in industries that include food, textiles, pharmaceuticals, and electronics, and its global market was worth US$ 400 million in 2018 4. PTFE micropowder is produced industrially by the chain scission of its polymerised powder or moulded scraps induced by 60 Co γ-rays, electron beam (EB) from accelerator or EB conversion X-rays irradiation in air. However, PFOA is produced at concentrations of more than 25 ppb as a by-product of radiation processing 5. For this reason, PTFE micropowder does not comply with regulations and may cause serious problems in industrial applications. Therefore, to comply with regulations, a method for the manufacture of low-M w PTFE with low PFOA contents (< 25 ppb) is required. Furthermore, its formation mechanism needs to be elucidated. In this paper, we clarify the formation mechanism and report a manufacturing process for a novel low-M w PTFE with < 25 ppb PFOA. Note that 'PFOA-free' means below the detection limit (< 5 ppb) when analysed by liquid chromatography/mass s...

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