Epoxy Warning

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Ted - 24 Jun 2007 20:50 GMT

I was joining two wing halves yesterday and mixed up a large batch of
30 minute epoxy. The temperature in the garage was about 90 degrees. I
had just finished coating the spar that joins the two halves and had
inserted it into one wing half and was coating the inside edge of the
wing when I noticed the epoxy was already starting to harden. I had
just enough time (about a minute to coat the second half and join the
wings. The meshed together INSTANTLY! I could not even remove the
excess epoxy with alcohol as it had set up so quickly. Word to the
wise here. If you are using epoxy in this hot weather, bring it to
room temperature in the house first. After I set the wing in place I
looked at the epoxy cup and the chemical reaction of the epoxy in
combination with the heat of the garage had melted the cup!

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Terence Lynock - 24 Jun 2007 23:15 GMT

Hi ted,
this works both ways, if you mix slow-set Epoxy and use some
of it you can stick it in the freezer for a few hours and the cold will
stop the reaction dead, then take it out and allow to warm up and it is
ready for use.
I have used this trick for years with excess Epoxy or I havnt been able
to complete a job for some reason, I have used half of the mix and
frozen the other half for three or four hours then thawed it out to
finish off, Epoxy setting times are calculated at around 76 degeees F so
higher air temps speed everything up,

regards, Terry

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Six_O'Clock_High - 25 Jun 2007 04:35 GMT

> I was joining two wing halves yesterday and mixed up a large batch of
> 30 minute epoxy. The temperature in the garage was about 90 degrees. I
[quoted text clipped - 8 lines]
> looked at the epoxy cup and the chemical reaction of the epoxy in
> combination with the heat of the garage had melted the cup!

Check the age of your epoxy. I have finally learned (the hard way - of
course) that old epoxy is the opposite of old CA. It sets up extremely fast
where the CA takes a week or more to cure out when it has been aged. What
you described sure does sound like old epoxy, or at least like my old epoxy.

YMMV

Jim Branaum
AMA 1428

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JJVB - 25 Jun 2007 12:59 GMT

Isn't that a sick, helpless feeling?? My experience has been that if
you are mixing up a big batch of epoxy, it is better to mix it on a
large flat surface such as a coffee can lid, than in a cup. Seems the
deeper the epoxy, the more heat it generates (or can't dissipate) and
the faster it sets up. Just my observations.

John VB

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Mark Daughtry, SR - 25 Jun 2007 13:37 GMT

When epoxy is confined in a small space it will produce heat which will make
it cure all the faster. After mixing up your batch of epoxy in a cup or bowl
pour it out onto a paper plate to spread it out. This will let the heat
"bleed off" without transferring it back to the mixture. As someone else
pointed out cooling will slow the reaction and curing time. To make applied
epoxy cure faster you can use a heat gun. You do have to be careful though
as the epoxy will get a bit runny when the heat is first applied but will
then begin curing at an accelerated rate. Another tip for removal of cured
epoxy is to heat it up with said heat gun and it will become "pasty" enough
to scrape off.

(BTW most of my knowledge of epoxy comes from System 3's Epoxy Book
http://www.systemthree.com/index_2.asp)

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Best regards,
Mark Daughtry, SR

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Model Forum / Radio Controlled / Air Models / June 2007

Epoxy Warning