Temperature dependence of gas evolution from polyolefins on irradiation under vacuum

Seguchi, Tadao; Haruyama, Yasuyuki; Sugimoto, Masaki

doi:10.1016/j.radphyschem.2012.10.009

Cited by 13 publications

(9 citation statements)

References 11 publications

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“…Thus, the use of airtight polymer bags, such as polyamide or polyethylene terephthalate (PET), is appropriate to secure an oxygen-free environment. When the polymer material is irradiated by ionising radiation under oxygen-free conditions, hydrogen-based decomposition gases are emitted, as reported previously 28 – 31 . The use of a polymer bag would trap the hydrogen emitted upon irradiation under oxygen-free conditions, in turn quenching the trapped radicals in PTFE as a secondary effect.…”

Section: Resultssupporting

confidence: 64%

Pentadecafluorooctanoic-acid-free polytetrafluoroethylene and mechanism of PFOA formation by γ-irradiation

Oshima

Tanaka

Nakaya

et al. 2020

Sci Rep

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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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Section: Resultssupporting

confidence: 64%

Pentadecafluorooctanoic-acid-free polytetrafluoroethylene and mechanism of PFOA formation by γ-irradiation

Oshima

Tanaka

Nakaya

et al. 2020

Sci Rep

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“…The additives mixed in SiR would not be effective in radiation ageing. The decay of tensile properties with dose was almost same between RT and 100 0 C irradiation, but the decay at 155 0 C irradiation was much increased, whereas the thermal degradation at 155 0 C was small for an ageing time less than 800 h. The enormous effect of irradiation temperature above about 120 0 C could be caused by the temperature effect on the radiation chemistry, that is, the radical yield on radiation increased for temperatures above 120 0 C. For the radiation chemistry of PE and EPR under vacuum, the yield of products increased sharply with irradiation temperature above a certain temperature, and the reason was attributed to an increase of radical yield [15]. As the decay of tensile properties was induced by the crosslinking of SiR molecules, the elongation at break for SiR-A is plotted on a log scale for ageing time or dose under different ageing conditions in Figure 5.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Degradation mechanisms of silicone rubber (SiR) by accelerated ageing for cables of nuclear power plant

Shimada

Sugimoto

Kudoh

et al. 2014

IEEE Trans. Dielect. Electr. Insul.

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The degradation behavior of SiR for the cable insulation by accelerated thermal and radiation ageing was studied and the degradation mechanism was proposed. The degradation was observed by the change of tensile properties, the distribution of crosslinking, and the change of weight. The chemical reaction under the both ageing in oxidation conditions was crosslinking and the oxidation mechanism was found to be the same between thermal and radiation ageing. The yield of crosslinking was proportional to the ageing time and also the dose. The effect of irradiation temperature on oxidation was accelerated with an increase of temperature above around 120 0 C, which might be due to the specific radiation chemical reactions. Therefore, the degradation by simultaneous ageing at higher temperatures above 155 0 C was much higher than that for sequential ageing, such as irradiation followed by thermal ageing or thermal ageing followed irradiation. At a high temperature, the degradation by thermal ageing under vacuum (without oxidation) was more progressed than that for the ageing in air (with oxidation). The reason was assumed to be the thermal decomposition of crosslinks between SiR molecules formed by the chemical crosslinking agent. The hardness (Shore hardness) reflected well the degradation of the SiR material for any ageing conditions.

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“…The gases produced by radiolysis have been widely studied for various polymer materials (Chapiro, 1962;Hegazy, Sasuga, Nishii, & Seguchi, 1992;Perera & Hill, 1999). For both XLPE and EPR, aged when oxygen is absent, the gases yielded are mainly H 2 and low-molecular-weight hydrocarbons such as CH 4 and C 3 H 8 (Seguchi, Haruyama, & Sugimoto, 2013). The yield of gas is usually much higher if the irradiation is carried out at higher temperatures and particularly if the polymer is irradiated above its glass transition temperature (Clough, Gillen, Campan, Gaussens, Schonbacher, Wilski, & Machi, 1984).…”

Section: Gas Evolutionmentioning

confidence: 99%

Aging Mechanisms and Monitoring of Cable Polymers

Bowler

Liu

2020

IJPHM

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Aging mechanisms of two polymeric insulation materials that are used widely in nuclear power plant low-voltage cables; cross-linked polyethylene (XLPE) and ethylene propylene rubber/ethylene propylene diene terpolymer (EPR/EPDM), are reviewed. A summary of various nondestructive methods suitable for evaluation of cable insulation is given. A capacitive sensor capable of making local nondestructive measurements of capacitance and dissipation factor on cable polymers, and potentially suitable for in situ cable monitoring, is introduced.Correlating values of elongation-at-break, indenter modulus, capacitance and dissipation factor measured on a set of 47 aged flame-resistant EPR samples shows a higher correlation between indenter modulus and dissipation factor than between indenter modulus and elongation-at-break.

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Temperature dependence of gas evolution from polyolefins on irradiation under vacuum

Cited by 13 publications

References 11 publications

Pentadecafluorooctanoic-acid-free polytetrafluoroethylene and mechanism of PFOA formation by γ-irradiation

Pentadecafluorooctanoic-acid-free polytetrafluoroethylene and mechanism of PFOA formation by γ-irradiation

Degradation mechanisms of silicone rubber (SiR) by accelerated ageing for cables of nuclear power plant

Aging Mechanisms and Monitoring of Cable Polymers

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