Epoxy--post cured-- more ethanol resistant?

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#1

I’ve read all over “horror stories” about epoxies and gasoline/ethanol resistance.

In my shop, I have a gasoline/alcohol container with three different epoxies that have been submerged for many months. None show any softening or degradation at all. One of the three samples is a pricey “structural” epoxy while the other two are cheaper, garden variety…I choose to not reveal brands because I do not want the responsibility of someone acting on my mostly anecdotal report here.

I live in Texas and all three of these samples lived through last summer’s 71 days of 100+ temps shop thermometer showed 110+ commonly. They were not officially post cured but certainly did some heat soaking at lower than typical pc temps but for a longer time.

My experiment began purely out of curiosity since I had all sorts of epoxy scraps laying around (polyester too, for that matter).

Anyone have an opinion as to whether this non-intentional posturing increased these epoxies seeming ethanol resistance?

#2

I have been conducting a similar experiment; I have been running a fuel tank on my motorcycle for over a year now without any signs of leakage or degradation. This has seen oxygenated, ethanol, and C12 race fuels at over 100 degree days (which means roughly 130 on track surface + engine heat).

Hardly scientific I realize but the results are there. Sadly I cannot say if this is due to the compound or the post-cure process. I am just glad that I dont have a leaky tank.

I am in process of building another currently and plan on using the same resin. I will post up as things progress.

#3

In general a postcured epoxy means better resistance to chemicals than the same non postcured epoxy.

But I am writing it down, I will be at Huntsman to spend 2 days with the tech guys in mid September, and will ask them as well.

#4

I’m lucky to live in a place where you can get ethanol free 91! If you can find gas that is ethanol free then there is no risk of epoxy destruction… or treat the gas to remove the alcohol.

has anyone ever come across any epoxy degradation without ethanol? I’m sure that all the boat guys only started being concerned about their composite tanks when the oxygenated fuels hit the market…

#5

Most acute problems come from coated metal tanks. the coating disintegrates into small slivers, clogging the fuel filters. At a time it was not uncommon to change fuel filters every week.

#6

I was under the impression that phenolic resins combated the problem, is this no longer the case with regards to ethanol in the fuel?