Ageing properties of polyamide-12 pipes exposed to fuels with and without ethanol |
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Authors: | KJ Kallio |
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Institution: | a Volvo Car Corporation, Polymer Centre, SE-40531 Göteborg, Sweden b School of Chemical Science and Engineering, Fibre and Polymer Technology, Royal Institute of Technology, SE-100 44 Stockholm, Sweden |
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Abstract: | The chemical and physical properties of polyamide-12 (PA12) fuel pipes/lines, aged for ≤2400 h at 110 °C, have been investigated. The pipes, containing fuel with or without ethanol, were either of a single PA12 layer, or of two PA12 layers surrounding a poly(vinylidene fluoride) barrier layer. The molar mass of the inner surface region obtained by size-exclusion chromatography was reduced during ageing, and optical microscopy revealed a surface that was partly dissolved in the presence of ethanol. Infrared spectroscopy revealed a rapid loss of plasticiser, especially in the presence of ethanol, and the fuel contained plasticiser and other polymer related components. Immersion tests at 60 °C showed that the swelling of the pipe and the amount of dissolved material were greatest for the fuels with intermediate ethanol content (50 vol.%). Aged samples experienced an increase in melting point, presumably, to a large extent, due to the loss of plasticiser and/or PA12-related components. In addition, for several samples, the crystallinity seemed to increase with ageing. |
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Keywords: | Polyamide-12 Ageing Fuel lines Pipes Ethanol Swelling |
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