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An analysis of permeation of hydrocarbon fuel in thermoplastic multilayer fuel tanks is presented. Measurements of permeability coefficients in indolene of high density polyethylene, HDPE, the ethylene-vinyl alcohol, EvOH, copolymer barrier layer and a maleated linear low density polyethylene, LLDPE, have been incorporated to provide an approximate description of the relative permeability of a fuel tank laminate. The effects of laminate thickness, barrier layer thickness, the incorporation of a regrind layer and laminate construction have been addressed using existing simple theoretical expressions. Particular attention has been focused on the overall permeability of the seam or “pinch off” and a simple description of seam geometry and structure has been applied to estimate the relative contribution to emissions. Results suggest that the seam may contribute considerably more to overall tank emissions than the body of the tank.

The recyclability of co-extruded multilayer fuel tanks, and characterization of the materials used in their manufacture, have been investigated. The ethylene-vinyl alcohol, EvOH, copolymer barrier layer, extruded as a sandwich between two adhesive layers of a maleated linear low density polyethylene, LLDPE, is surrounded by three high density polyethylene, HDPE, layers, one of which is composed of the regrind derived from the waste generated by manufacture. Particular attention has been focused on the mechanism of adhesion between the barrier layer and the adhesive layers. Surface analysis of the in situ surfaces has confirmed the formation of chemical bonds between the two polymers. Morphological information, concerning dispersion of the barrier layer in the HDPE matrix during recycling, has been obtained by scanning (SEM) and transmission (TEM) electron microscopy techniques.