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Hydrocarbon permeation is one of the remaining main sources of vehicle evaporative hydrocarbon emission. However, very little information exists on the role of fuel properties on permeation losses. Therefore, experimental and modeling studies were conducted to determine the relationships between hydrocarbon permeation through HDPE (high density polyethylene) and fuel properties. Half-gallon HDPE bottles without EVOH were used in this study, because they were easily available and because steady state permeation can be measured in a matter of few days instead of several months in the case of HDPE/EVOH bottles. A permeation equation was developed using both theory and experimental data, which shows that permeation increases exponentially with fuel aromatic content, increases linearly with fuel RVP, and increases exponentially with temperature. The equation is useful for predicting how fuel and ambient temperature affect hydrocarbon permeation through vehicle fuel system.

Commingling of fuels containing various concentrations of ethanol can occur in a vehicle fuel tank. It was not possible to estimate the RVPs of commingled ethanol containing fuels because they form complex non-ideal solutions. A nomograph and an equation were developed using the theory and experimental data for estimating the RVP of a commingled ethanol fuel blend from the RVPs of two base fuels containing any amounts of ethanol. The model is also useful for general purpose estimation of vapor pressures of ethanol/gasoline blends such as seasonal blending of E85 fuels with the right vapor pressure gasoline and the right amount of ethanol to meet the seasonal fuel vapor pressure requirement.

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.

Federal standards that mandate improved fuel economy have resulted in the increased use of lightweight materials in automotive applications. However, the environmental burdens associated with a product extend well beyond the use phase. Life cycle assessment is the science of determining the environmental burdens associated with the entire life cycle of a given product from cradle-to-grave. This report documents the environmental burdens associated with every phase of the life cycle of two fuel tanks utilized in full-sized 1996 GM vans. These vans are manufactured in two configurations, one which utilizes a steel fuel tank, and the other a multi-layered plastic fuel tank consisting primarily of high density polyethylene (HDPE). This study was a collaborative effort between GM and the University of Michigan's National Pollution Prevention Center, which received funding from EPA's National Risk Management Research Laboratory.