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An innovative multi-layer plastic fuel tank construction has been developed. This new structure meets the most stringent evaporative emissions requirements of PZEV vehicles, while still offering the advantages of plastic fuel tanks (crash worthiness, design flexibility, low weight, excellent chemical and corrosion resistance). The construction incorporates a new polyamide/HDPE alloy barrier material as the inner layer, processes easily on conventional 6-layer blow moulding equipment, and reduces evaporative emissions, especially at the pinch-off line. Further, it complies with the LEV 2 evaporative durability requirement of 15 years or 150,000 miles.

New regulations on Hydrocarbon (HC) emissions have set more stringent requirements for fuel systems evaporative emissions. This creates a need for developing new and more efficient material structures able to offer enhanced barrier properties to fuels. Such low levels of permeation rates have proven to reach the lower detection limits of most of the existing test equipment or methods, and have required the development of innovative techniques in order to characterize new materials or structures by measuring their permeability coefficients, or to be able to compare various constructions for components or sub-assemblies of the fuel system. A new device has been designed and built in our Technology Center in Rastatt (Germany) and proves to offer an outstanding precision capability in measuring ultra-low permeation rates (less than 0.5 mg/day). Its operating process and the easy control on key input parameters offer a large flexibility in terms of measurement resolution and time.

Thanks to their low density, to their excellent processability and recyclability, and to their outstanding chemical resistance and specific mechanical strength, polymers are now the best materials to be applied in fuel tank systems. In that field, High Density Polyethylene (“HDPE”) is regarded as the best compromise between economical and technical requirements. But, basically, because of its chemical nature and structure, HDPE offers a poor barrier to hydrocarbons, especially light ones composing gasoline. Then, in order to meet to more and more demanding regulations on air quality and emissions, professionals from the Fuel Tank System area have developed several technologies in order to cope with that property of HDPE. The aim of that article is to present the different technologies that have been industrially developed and to compare their performance in terms of barrier properties.