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The Ageing of Fuel Lines Based on Polyamide-12
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
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 [en]
pipes, ethanol
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-12050ISBN: 978-91-7415-552-5 (print)OAI: oai:DiVA.org:kth-12050DiVA: diva2:300445
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
List of papers
1. Ageing properties of polyamide-12 pipes exposed to fuels with and without ethanol
Open this publication in new window or tab >>Ageing properties of polyamide-12 pipes exposed to fuels with and without ethanol
2008 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 93, no 10, 1846-1854 p.Article in journal (Refereed) Published
Abstract [en]

The chemical and physical properties of polyamide-12 (PA12) fuel pipes/lines, aged for <= 2400 h at 110 degrees 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 degrees 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. (C) 2008 Elsevier Ltd. All rights reserved.

Keyword
Polyamide-12, Ageing, Fuel lines, Pipes, Ethanol, Swelling, THERMAL-DECOMPOSITION, ALIPHATIC POLYAMIDES, CHROMATOGRAPHY, DEGRADATION, KINETICS
Identifiers
urn:nbn:se:kth:diva-12043 (URN)10.1016/j.polymdegradstab.2008.07.025 (DOI)000260648800019 ()2-s2.0-52049113185 (Scopus ID)
Note
QC20100722Available from: 2010-02-25 Created: 2010-02-25 Last updated: 2017-12-12Bibliographically approved
2. Ageing properties of car fuel-lines;accelerated testing in “close-to-real” service conditions
Open this publication in new window or tab >>Ageing properties of car fuel-lines;accelerated testing in “close-to-real” service conditions
2010 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 29, no 1, 41-48 p.Article in journal (Refereed) Published
Abstract [en]

The use of ethanol-based fuels and tougher restrictions on fuel emissions put a higher demand on car fuel-line (pipe) systems. In this context, it is important to be able to establish and predict properties based on measurements on pipes exposed to real or “close-to-real” environments. This paper presents a new method to age pipes in accelerated “close-to-real” conditions. In this method, the pipe is exposed to circulating fuel on the inside and to air on the outside. The method/equipment allows for non-destructive mechanical testing on “continuous” pipes. The usefulness of the ageing method/system was illustrated on polyamide-12 (PA12) pipes exposed to fuels with varying ethanol content at 50 °C and 110 °C for a maximum of, respectively, ca 3 years and 100 days. “Non-destructive” three-point bending as well as tensile testing was used to assess the ageing-induced changes in mechanical properties. The most conclusive information was that the lowest pipe extensibility (ductility) of dried, previously fuel-exposed pipes was observed at the end of the ageing periods and at the higher ethanol contents. In fact, optical microscopy showed that the tensile fractured pipes, exposed to 25/30 vol. % ethanol at 110 °C (100 h), showed no signs of macroscopic yielding. The trends were interpreted, based also on findings from previous work, as being due to the loss of plasticiser (possibly also PA12 monomers/oligomers) and material “degradation/annealing” processes, the latter involving possibly stabiliser issues.

 

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
Pipe; Fuel; Polyamide-12; Ageing; Ethanol
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12038 (URN)10.1016/j.polymertesting.2009.09.003 (DOI)000274562800008 ()2-s2.0-72449202605 (Scopus ID)
Note
QC 20110210Available from: 2010-02-25 Created: 2010-02-24 Last updated: 2017-12-12Bibliographically approved
3. Effects of ethanol content and temperature on the permeation of fuel through polyamide-12-based pipes
Open this publication in new window or tab >>Effects of ethanol content and temperature on the permeation of fuel through polyamide-12-based pipes
2010 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 29, no 5, 603-608 p.Article in journal (Refereed) Published
Abstract [en]

A new test method has been developed which enables the fuel permeation properties of polyamide-12 (PA-12) - based pipes to be investigated. Fuel lines were exposed to circulating fuel with equal volume contents of toluene, isooctane and 0, 25 or 85 vol.% ethanol for up to 6 months at 60-110 degrees C. The pipes were either of a single PA12-layer or a multi-layer type, the latter having a poly(vinylidene fluoride) barrier layer between two PA12 sections. With a Thwing-Albert cup attached to the fuel line, it was possible to expose a pipe-section to surrounding air running in a separate pipe loop at a controlled flow-rate. Gas/vapour samples were collected from this loop using a syringe and, subsequently, analysed with a flame ionization detector. It was observed in the case of multi-layer pipes that the presence of ethanol increased the permeability (average values) of the "total" fuel as well as of the individual hydrocarbons. In addition, the 60 degrees C fuel permeability (85 vol.% ethanol) increased after a high temperature (110 degrees C peak) cycle, whereas the ethanol-free fuel flux seemed to decrease.

Place, publisher, year, edition, pages
elsevier, 2010
Keyword
Polyamide-12, ageing, fuel lines, permeation, hydrocarbons, ethanol
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12033 (URN)10.1016/j.polymertesting.2010.03.008 (DOI)000279522000011 ()2-s2.0-77955304821 (Scopus ID)
Note
QC 20100722 Uppdaterad från submitted till published (20110203).Available from: 2010-02-25 Created: 2010-02-23 Last updated: 2017-12-12Bibliographically approved
4. Degradation of Polyamide-12 pipes aged in fuel
Open this publication in new window or tab >>Degradation of Polyamide-12 pipes aged in fuel
(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
Polyamide 12, ageing, fuel lines, ethanol, degradation
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-12035 (URN)
Note
QS 20120327Available from: 2010-02-25 Created: 2010-02-23 Last updated: 2017-12-12Bibliographically approved

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