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Next PostPrevious PostTech Posts > Problem Solving > Fuel Tank Blistering/Warping - A Straw Poll

Posts: 2375
Daytona 955i (99-01)

12 Sep 2011 02:52

The newest commercial PA 6 grade offering permeation resistance is Technyl C 536XT, says Gary Kachin, market development manager. The first monolayer applications went into full production in Europe in 2007--a motorcycle gas tank and a tank for a moped made for the U.S. The grades for multilayer applications are still in testing and will probably take several years to qualify since they are for automotive. Kachin notes that Rhodia hasn't formally commercialized any of these new materials.

"We're positioning these products for automotive and nonautomotive markets," Kachin says. He reports that Rhodia is working with a major global manufacturer of automotive fuel tanks to qualify one of the PA 6 grades as a barrier layer, but adds, "It's going to take a long time to replace EVOH in automotive." (Kachin declines to identify the company.)


Acerbis is possibly the "major global manufacturer", based in Europe.

New plastics, specifically tested for ethanol only becoming available within the last 2-3 years. I guess the earlier generation of PA6's used an EVOH barrier layer.

PA6 does absorb moisture, presumably an ethanol fuel mix can contain higher amounts of water.

The rippling effect may be due to the expansion of the fuel tanks in a dimensionally constrained environment combined with a markedly lower strength as temperatures raise. (eg. flexural strength drops from around 45 MPa @ 23 deg C to 20 MPa @ 65 degrees C.).

Source: BASF ULTRAMID 8281 HS.

I don't have data for the Rhodia product.

In short..if your tank hasn't rippled yet, ensure to relieve any stress by redrilling mounting holes. If you find that fitting the tank is a struggle, then the tank is under stress once bolted up.
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