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<< Lancair Builders' Mail List >>
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>> my Jefco hardner gets darker and darker over time in its
unopened plastic container. <<
Bill, et al,
The Jefco hardener starts out a very light amber color and changes only
slightly in the plastic container. I have one unopened catalyst container
in my shop that is only slightly deeper amber than it started out after 4
years. The color that Bill (Maddox) was talking about is a very deep red,
almost mahogany shade that the catalyst takes on after only a very short
time in the original Michael Engineering dispenser. I, too, have had
discussions with the folks at Jefco about this color change and was told
the same thing, that it would have no effect on the characteristics of the
epoxy after it was cured. Bill's concern (and mine as well) is that there
have been no longevity tests done with the resin system with the hardener
in that particular changed condition, and so we don't really know what's
going to happen after 5 or 10 or more years. Maybe Jefco is 100% correct
in their position, and if that's the case then we're worrying about
nothing. But if they're wrong we could be in for some undesirable
surprises. Anyway, the dramatic color change is obviously a result of some
reaction that is taking place inside the dispenser tub, and is caused by
the check valve assembly. You can test this by putting fresh catalyst into
a CLEAN dispenser tub and let it sit for a few weeks without pumping.... if
you look at the catalyst during that time you'll see a cloud of deeper
color that slowly forms around that check ball. If you leave it sit, the
reaction spreads through the entire contents of the tub and eventually the
entire batch of catalyst turns that dark red/brown color. To make a long
story short, thanks to Bill's and others' discussions with the folks at
Michael Engineering, they have come up with a check valve for the cat side
that is made of a different material which doesn't discolor (ie, react
with) the material. Bill has been testing the prototype valve for the past
month with the pump in a controlled 80 degree environment and the material
is the same light amber color, with no evidence of discoloration having
occurred during that time. Hopefully they (Michael Engrg) will let us know
when they've frozen the new design, the cost of the replacement valve
assembly and when they'll have production versions ready for shipment. I,
for one, will feel much better about my resin system knowing that the only
reactions that are occurring are those that I initiate when I mix the resin
and hardener together prior to doing my layups. I suspect you might feel
the same. I hope that this clarifies this situation.
<Marv>
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LML website: http://www.olsusa.com/mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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