| 1. |
- Kallio, Kai J., 1967-, et al.
(författare)
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Ageing properties of car fuel-lines;accelerated testing in “close-to-real” service conditions
- 2010
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Ingår i: Polymer testing. - : Elsevier. - 0142-9418 .- 1873-2348. ; 29:1, s. 41-48
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Kallio, Kai J., 1967-, et al.
(författare)
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Degradation of Polyamide-12 pipes aged in fuel
- 2024
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Ingår i: Polymer degradation and stability. - : Elsevier. - 0141-3910 .- 1873-2321.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 3. |
- Kallio, Kai J., 1967-, et al.
(författare)
-
Effects of ethanol content and temperature on the permeation of fuel through polyamide-12-based pipes
- 2010
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Ingår i: Polymer testing. - : elsevier. - 0142-9418 .- 1873-2348. ; 29:5, s. 603-608
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Kallio, Kai J., 1967-
(författare)
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The Ageing of Fuel Lines Based on Polyamide-12
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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