Miles McCallum wrote:
>
> > My inspector insists I peel-ply everything. That gives a surface free
> > of amine blush that can be readily abraded to key whatever's going on
> > next, without cutting into the glass.
>
> Amine blush is a function of excess or unmixed hardener - it'll appear on
> peelplied surfaces just as easily - if the peel ply is off.
>
Miles, I 'googled' several mfr's user manuals and tech papers re epoxy
laminating resins, and they say amine blush is oily/waxy/cloudy and a
result of the curing chemistry, aggravated by high ambient moisture,
and varies by product. It is removed with water, cut with some
ammonia. It will be harder to remove if peel ply is used, and they
say _do not_ apply resin or adhesive over any blush. The residue you
describe as due to improper mix they say just condemns the layup, if
not gone in couple days.
Some thus say their product don't blush, and FWIW, I have never seen
any with the Aeropoxy supplied to builders here. Sometimes it isn't
just sales brochure puffery, I guess.
Also re the use of solvents, there's no worry it seems for wax/oil/etc
removal. Chemically pure (CP), or virgin, MEK (unhealthy), lacquer
thinner, or acetone are specified in the docs. And in the States
here, if the can don't say CP or virgin, it is probably 'recovered'
and thus contaminated. MEK is used as test for improperly cured or
mixed resin, and they use a numeric scale (MEK Resistance) in
specifying solvent resistance. A technical doc published the the
Australian Air Force re composite repairs requires cleaning with MEK,
abrasion, then MEK again to remove the dust. I prep'd all my bonding
surfaces that way in mere ignorance. Feel much better now....
One more epoxy factoid. Water(!) can actually weaken epoxy. Not by
dissolution but osmosis, if soaked. Thus, epoxy for boat building
below the water line is formulated to prevent that.
Regards,
Fred F., A063
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