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Nylon 12 resins have been utilized for liquid fuel lines in automobiles for more than 25 years. This resin has proven its suitability in monowall tubing in the chassis environment and in contact with normal fuels. The development of more aggressive fuels (mostly those containing alcohol) and the establishment of new hydrocarbon emission standards by various government agencies have changed this. In response to the changing situation, multilayer tubing has been developed in order to improve the properties of the nylon 12 tubing, primarily the permeation resistance. Hüls has developed two different constructions, both of which contain a fuel-resistant barrier layer in the wall of the Nylon 12 tubing. One utilizes a barrier layer of a specialty polyester resin with good bonding to the outside and interior layers of Nylon 12 without use of an adhesive. The other utilizes a PVDF resin bonded to the Nylon 12 by an adhesive layer.

When hydrocarbon emissions are measured for conformance testing of a vehicle's fuel and vapor handling systems, the test used is the Sealed Housing Evaporative Determination (SHED) procedure. Flame Ionization Detection (FID) techniques are used for those measurements. During development of individual fuel/emissions systems components, however, recirculation procedures described in SAE J1737 are utilized to determine emissions (adsorbancy measurements of permeation are used). The platform engineer needs a correlation between values out of both procedures and to be able to estimate the emissions of the fuel/emission system of his platform based on the lab values available for the individual components. The study was done using alcohol-containing fuels. In addition to permeation measurements for 3 different temperatures, an understanding of speciation of the fuel constituents is necessary.