Long-term performance of a polyamide-12-based fuel line with a thin poly(ethylene-co-tetrafluoroethylene) (ETFE) inner layer exposed to bio- and petroleum diesel

• The long-term performance of a polyamide-12 (PA12)-based (bio)diesel fuel line/pipe with a thin poly(ethylene-co-tetrafluoroethylene) (ETFE) inner layer was investigated in “close to real” and high-temperature isothermal conditions with fuel on the inside and air on the outside of the pipe. The inner carbon-black-containing ETFE layer resisted fuel attack, as revealed by the small fuel uptake, the very low degree of oxidation, and the unchanged electrical conductivity, glass transition and melting behaviour. The properties of the ETFE layer remained the same after exposure to all the fuel types tested (petroleum diesel, biodiesel and a blend of 80% diesel with 20% biodiesel). Because of the presence of the ETFE layer on the inside, the fuel pipe experienced noticeable changes only in the outer PA12 pipe layer through migration of plasticizer, annealing and slight oxidation. The evaporation of plasticizer was found to be diffusion-controlled and it led to an increase in the glass transition temperature of PA12 by 20 °C. This, together with a small annealing-induced increase in crystallinity, resulted in a stiffer and stronger pipe with an increase in the flexural/tensile modulus and strength. The oxidation of PA12 remained at a low level and did not lead to an embrittled pipe during the simulated lifetime of the vehicle. This study reveals that fluoropolymers have a great potential for use as fuel-contacting materials in “demanding” motor vehicle fuel line systems. 

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering (hsv//eng)

Nyckelord

Ageing

Biodiesel

Diesel

Fuel pipe

Plasticizer loss

Poly(ethylene-co-tetrafluoroethylene)

Polyamide

Carbon black

Diesel fuels

Ethylene

Fluorine containing polymers

Gasoline

Glass

Oxidation

Plasticizers

Polyamides

Reinforced plastics

Electrical conductivity

Fuel pipes

High temperature

Isothermal conditions

Long term performance

Tetrafluoroethylene

Glass transition

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