Charles Smith wrote:

Group,

I have data for a four day immersion on two different epoxy samples in
oxygenated fuel.

Sample 1 was pure Aeropoxy PR2032/PH3660 resin cured for at least three
months at room temperature.
Sample 2 was an epoxy/glass laminate coated with Jeffco 9700 (supplied by
Bill Schertz).

Both samples were nominal 1X1 inch squares.  The fuel mixture was ASTM Fuel
C/Ethanol blend 85/15 by volume.  ASTM Fuel C is a high aromatic fuel blend
intended to simulate premium gasoline and is 50/50 (v/v) iso-octane and
toluene.  The ethanol was added at 15% to make the fuel mix as aggressive as
it gets.  Only methanol blended at this ratio would be worse.

After four days, the pure Aeropoxy volume changed by +12% and its weight
changed +9%.
The Jeffco sample volume change was +10% and its weight change was +5%.

If these samples were elastomers, I would think the results quite good; on
the order of what I would expect to see using 70 Shore A durometer
fluoroelastomer.  However, they are materials which should have considerably
higher crosslink density than elastomers and I could hope for better
results.  I am not raising any red flags.  The fuel mix is extremely
aggressive and represents worse case and these are quite low volume changes.
I haven't tested avgas yet and would expect much, much milder results.  I
have put the samples back into the fuel mix and will pull them out when they
reach one month duration and measure again.

I did speak with Scott the tech service chemist at PTM&W and he tells me
that the Aeropoxys have not been tested or certified for fuel contact.  He
advised coating tanks with a polysulfide sealant and I have asked them to
mail me their literature on coatings they recommend.  I'll be happy to share
that with the group if any are interested.

Charlie Smith
Cruiser 4021

 
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