Low Permeability

Increasing concern about air pollution over the last decades has forced car manufacturers to control vehicle evaporative emissions. These emissions mainly consist of hydrocarbons or unburned fuel and a considerable amount of them usually escapes from any point in the fuel system. Tests such as the Sealed Housing Evaporative Determination (SHED) test are used to measure pollution caused by fuel evaporation. Since SHED requirements have become stricter, fuel tank manufacturers have been forced to reduce the permeability of their tanks in order to meet the new standards.

It goes without saying that changes made to obtain lower permeability of a tank can affect its weight, price and recyclability. Plastic fuel tanks generally consist of a multilayered structure the permeability of which can be reduced in several ways. Using more layers, making them thicker or modifying their chemical composition may result in a structure which is heavier, more expensive and more difficult to recycle.

Even though a plastic fuel tank may become heavier according to the abovementioned methods, its weight would only increase by a small percentage; however this fuel tank would also still remain lighter than a tank made of steel.

In addition, designing more sophisticated products usually implies additional investments, which should certainly be reflected in their prices. Fuel tanks are no exception to this rule, whether they be made of plastics or steel. Car manufacturers may opt for the cheapest option; however, price is not the only criterion to be considered when choosing a fuel tank and should certainly not be so to the detriment of quality and performance.

Finally, it is true that plastic fuel tanks and systems are complex structures that include various types of component and material, and that one of the main challenges for recycling them has been to be able to remove fuel residues and other coatings. Adding a layer or changing the chemical composition of the material used in plastic fuel tanks could increase the complexity of their recycling process. However, existing recycling methods and technologies are already dealing with complex structures, therefore whatever the number of layers, finding ways to recycle new types of plastic fuel tanks will only be a matter of time.