09/10/2026
Did you know that the layers inside a fuel tank are designed to perform different jobs?
From the outside, a plastic fuel tank appears to have one continuous wall. In a conventional coextruded fuel system, however, different materials are processed together to form an integrated multilayer structure.
High-density polyethylene contributes to the tank's structural properties. Regrind makes it possible to return suitable production material to the manufacturing process. Ethylene vinyl alcohol (EVOH) provides an important barrier function that helps reduce the permeation of hydrocarbons through the tank wall.
An additional but often overlooked layer is the tie layer. Because EVOH is a polar material and HDPE is a non-polar material, they do not naturally bond to one another. The tie layer, typically a chemically modified LLDPE, acts like an adhesive that enables the EVOH barrier layer to be integrated into the multilayer structure.
The performance of the tank therefore depends not only on the individual materials, but also on how the layers are arranged and processed together. The complete structure must support the required balance of durability, emissions performance, manufacturability, and long-term functionality.
One tank wall, several specialized functions, and one integrated material system.