Posted for "Justin Hawkins"
<JustinH@lancair.com>:
We heated it back up and made test samples. The samples did harden and
possibly structural but it
took an extra day for it to fully cure. So in
are opinions it just may not be worth using for structural bonding, but
hey it is
experimental and you can do as you wish.
May not want to mention it during aircraft insurance inspection time.
Justin
Hawkins
Lancair Airframe & Technical Support
Lancair Int. Inc.
250 SE Timber AVE
Redmond, OR
97756
justinh@lancair.com
541-923-2244 ext 121
-----Original Message-----
From: gary hunter
[mailto:lucyliu22@mac.com]
Sent: Friday, April 10, 2009 9:46 AM
To: Valin & Allyson Thorn; Valin Thorn
Cc: Justin
Hawkins; lml@lancaironline.net; marv@lancair.net
Subject: Re: [LML] Re: Jefco
WOE JUST A MINUTE
FOLKS....
If we are talking about Jeffco laminating resins ... You need to listen
up.
Just
because the resin is crystallized, it does not mean it has gone
bad. It
is perfectly normal for the resin to crystallize. Epoxy
resins at
ambient
temperature is a "super cooled" liquid. What that means is, that below
it's
melting
point... ~ 130F...the product remains a liquid. A dust
partical, a
seed crystal and cool temperatures (like the floor of
your garage) will
accelerate crystal formation. The most pure resins, crystalize
fastest.
Using the
material in the crystallized state is a no no. If the resins
is
hazy..that is an indication it has begun to
crystallize.
HOWEVER, the resin can be "Reconstituted" by heating it above the
melting
point of the
crystals. Once the product becomes clear, free of haze and
crystal material, it can be cooled back down the room
temperature. The
resin is good as new and has not suffered any degradation what so ever.
The important part is
to Reconstitute the entire contents of the
container.
The epoxy resin formulations we use can be mixtures of different
types
of
resins to get the best overall properties. Some of these different
types of
resins, are not
super cooled liquids and do not crystallize. So the
resin
portion that crystallizes is more dense, and settles to the
bottom of
the
container. If you pour off the liquid part sitting on top of the
crystallized part, it will not be
the same composition of the original
mixture. So, if you find a container of resin that is not clear all
the
way
to the bottom. Heat the whole container to melt all the crystals. Stir
or
shake it
little to mix things back up, then you can pour off what you
need.
The safest way to heat the resin is the seal the
container tightly, and
place it into a bucket of hot tap water Keep refreshing the hot tap
water
until the resin
is sufficient hot to melt the crystals.
If it is a 5 gallon can, I highly recommend you invest in a
silicone
heating
strap from McMaster Carr or some outfit like that. Some of you
innovative
types may find a
cheaper way.
It is not necessary, but some builders find it handy to keep their resin
in
a hot box...like an
Igloo cooler with a 40W light bulb in it. This keeps
the
resin nice and warm and prevents crystal formation. The warm resin
wets
out
the fabric faster, but it will shorten the working time.
Storing you resin on the concrete floor will
speed up the crystal
formation
process. Place a couple 2X4's between the container and the floor.
Some
of you may know me, Jeff Bassman of Jeffco does.. He was one of my
customers in the past. I am an epoxy resin chemist of 30+
years,
currently
working for Dow Chemical Company formulating resins systems for various
composite
applications.
If any of you have any questions on epoxies for homebuilders... Feel
free to
email me. I
provide the same type help for the various canard builders
too.
Gary Hunter
Gary Hunter Composites
117
Mesquite St.
Lake Jackson, TX 77566
281-433-8478
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