Multilayer fuel tube features inner layer of low extractable PA 612

The use of fuels that contain alcohol, for example biofuels containing ethanol, can lead to the extraction of substances from the inner walls of conventional plastic gasoline lines. Under certain extreme conditions these substances can clog the fuel injection nozzles in the latest, sensitive fuel systems, which use small-diameter nozzles to create an atomized spray of gasoline and air for fuel injection in order to decrease fuel consumption. To reliably counteract this, the automotive industry is looking for new fuel line materials with significantly reduced extraction.

For many years, Evonik (Essen, Germany) has been offering its MLT 7440 multilayer structure, a conductive system that fully meets the requirements. This system employs a Vestamid polyamide (PA) 12 outer layer, PA adhesive layers, an EVOH barrier layer, and a Neoflon EFEP conductive inner layer that is exposed to the fuel. Neoflon is a fluoropolymer supplied by Japan’s Daikin Industries. Conductive systems are commonly used in North America.

Evonik has now supplemented this offering with its new MLT 4800 non-conductive system. It is based on the MLT 4300 system, which employs an outer layer of Vestamid polyamide 12 and a barrier layer of ethylene vinyl alcohol (EVOH) to prevent fuel permeation. In the MLT 4800 system, however, the PA 6 inner layer of the proven 4300 system has been replaced by a newly developed, low extractable Vestamid polyamide 612, which meets the latest requirements of automobile manufacturers. The mechanical characteristics, chemical resistance, and permeation behavior are on the same level as the MLT 4300, which is the most adopted MLT in Europe at present on account of its lower cost versus conductive systems.

Evonik will be introducing the technology at the K 2016 Show (Hall 6, Stand B28).