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Degradation of Polyamide-12 pipes aged in fuel
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
(English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Other academic) Submitted
Abstract [en]

In this work properties of polyamide-12 (PA12) fuel lines, exposed for ≤2400 h at 110°C and ≤26000 h at 50°C, containing fuels with different ethanol contents, were investigated. Dynamic mechanical thermal analysis indicated a sizeable loss of plasticiser during ageing. Viscosity measurements suggested that chain scission was an important mechanism of degradation at the higher temperature and size exclusion chromatography suggested that this was probably the case also at 50°C after long ageing times. The molar mass and polydispersity data indicated that the most degraded samples were those exposed to high ethanol contents at 110°C. Thermogravimetry showed that the onset temperature of the main degradation stage was 340-410°C (depending on heating rate). X-ray fluorescence spectroscopy and high performance liquid chromatography indicated migration of stabiliser and in the three-layered pipe, having two PA12 layers divided by a poly(vinylidene fluoride) barrier layer, the migration occurred preferentially from the inner pipe layer into the fuel.

Place, publisher, year, edition, pages
Elsevier.
Keyword [en]
Polyamide 12, ageing, fuel lines, ethanol, degradation
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-12035OAI: oai:DiVA.org:kth-12035DiVA: diva2:299744
Note
QS 20120327Available from: 2010-02-25 Created: 2010-02-23 Last updated: 2012-03-27Bibliographically approved
In thesis
1. The Ageing of Fuel Lines Based on Polyamide-12
Open this publication in new window or tab >>The Ageing of Fuel Lines Based on Polyamide-12
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today, the use of bio-fuels for cars is increasing. There is a wide range of biofuelsavailable world wide, in Sweden ethanol containing fuels are favoured.For car manufacturers there is a need to be able to predict short and long termproperties of fuel lines subjected to ethanol containing fuels to ensure properlong term behaviour. The presented method for ageing in “close to real”environment involved circulating fuel inside the tubes and air on the outside attwo temperatures, 50°C and 110°C. The exposure time was extensive in the50°C case, almost 3 years, and the ageing at 110°C was conducted for 100days. Polyamide-12 was chosen as pipe material, which is also used in realparts. Tensile testing was used to assess the mechanical changes caused byageing. Long ageing times and high ethanol levels resulted in low extensibility.In the case of fuel with 25 vol.% ethanol at 110°C (100 days) the samplesshowed no macroscopic yielding. Even at 50°C a time induced loss ofextensibility was observed (80 vol.% ethanol). However, at ethanol levels of 0and 22 vol.% the extensibility was not reduced even after the 3 years of ageing.The changes at short times were interpreted as being due to loss of plasticizer.The changes at long ageing times were thoroughly investigated. The change incrystallinity, pipe swelling, leaching and the decrease in extensibility were allgreatest in the pipes subjected to ethanol. As expected, the molar massdecreased as the ethanol level increased and a good correlation between molarmass and extensibility was observed. A method for determining the fuelpermeation properties was developed. Fuel lines were subjected to circulatingfuels in the same manner as in the ageing tests and the surrounding air wasanalysed for fuel components with a flame ionisation detector. Higher level ofethanol increased the individual fuel component fluxes as well as the total fluxand also the temperature effect on the flux was significant. Finally it should bementioned, that ethanol was not always an unwanted ingredient; adding a smallamount of ethanol to the ethanol-free fuel prevented premature pipe failure at110°C.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 71 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:6
Keyword
pipes, ethanol
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12050 (URN)978-91-7415-552-5 (ISBN)
Public defence
2010-03-19, F3, KTH, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Note
QC20100722Available from: 2010-02-26 Created: 2010-02-26 Last updated: 2010-07-22Bibliographically approved

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