EVAL™ enables to produce lighter fuel tanks with very low evaporative emissions.
Forty years ago, fuel tanks were made of steel. While offering excellent barrier against fuel vapor, they had the disadvantages of heavy weight and the risks of leakage and corrosion. The auto industry started looking for an alternative and turned to plastics.
The first plastic fuel tanks were introduced in Europe during the early 1970s. They were HDPE monolayer tanks and were successful based on:
In the mid-1980s, automobile manufacturers in the United States started replacing the steel fuel tanks with PFTs. Since then, the number of plastic fuel tanks has increased rapidly, with the current US share of plastic fuel tanks at over 90%. Most of the gasoline PFTs in the US are coextrusion multilayer tanks using EVAL™ EVOH barrier materials. EVOH allows these tanks to achieve the stricter permeation levels that are required by the US regulations.
In Japan, 45% of the fuel tanks are plastic. That market has been slower to adopt plastic solutions, but following the global trend, metal tanks continue to be replaced with plastic.
Barrier plastic fuel tank technology started in Europe, and over time the technologies have evolved. Until the implementation of the LEV1 legislation (USA) in 1996, monolayer fluorinated fuel tanks were the preferred technology. After the development of the slosh test in the US, the use of 6-layer fuel tanks with an EVAL™ barrier layer increased dramatically.
In addition to multilayer structures, fluorination continues to be used in Europe. This is mainly because manufacturers can use existing monolayer machines for this technology without the need for new investment. However, from a performance point of view this technology shows some shortcomings. Durability, barrier performance and environmental concerns have limited the attractiveness of fluorination.
Graphics data courtesy of ITB