<br><font size=2 face="sans-serif">Mixed viscosity is about 250 centpoise
at 77F. Glass transisiton is about 128F. But can be increased to 165F......IF
it is cured or post cured at 160F. A Tg of 109F is not possible in an epoxy
without the application of about 210F heat. Any manufacturer that tells
you otherwise is either ignorant or a liar.</font>
<br><font size=2 face="sans-serif">A 128F Tg DOES NOTmean degredation of
the epoxy itself, it means where structural strength is lost and this is
reversable.</font>
<br>
<br><font size=2 face="sans-serif">Gummy is the result of water or bad
mix ratio. If you apply during high humidity the top surface can be sticky,
This is just the very top of the cured epoxy and does not affect the structural
integrity, yet is a pain for us. There are chemicals that I can formulate
in the blend to make the cure less sensitive to this problem. </font>
<br><font size=2 face="sans-serif"><br>
<br>
<br>
Gray Fowler<br>
Senior Principal Chemical Engineer<br>
Radomes and Specialty Apertures<br>
Technical Staff Composites Engineering<br>
Raytheon</font>
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<td width=40%><font size=1 face="sans-serif"><b>"Mike Hester"
<kerlock@comcast.net></b> </font>
<br><font size=1 face="sans-serif">Sent by: nsrca-discussion-bounces@lists.nsrca.org</font>
<p><font size=1 face="sans-serif">11/26/2007 10:50 AM</font>
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<div align=center><font size=1 face="sans-serif">Please respond to<br>
NSRCA Mailing List <nsrca-discussion@lists.nsrca.org></font></div></table>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">"NSRCA Mailing List" <nsrca-discussion@lists.nsrca.org></font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
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<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">Re: [NSRCA-discussion] epoxy question-I
am back</font></table>
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<br><font size=2 face="Arial">I'm interested...what kind of viscosity and
what will be the transitional temp? Most of the resins I have run across
for this purpose have a transitional temp that is really too low. If you
take a temp reading of your plane's surface in the summer time, some of
the darker colors can approack 190 degrees f. On a wood fuse this can mean
bubbling, delamination etc. </font>
<br><font size=3> </font>
<br><font size=2 face="Arial">What Id like to see is a transitional temp
of at least 190+ and a viscosity of around 200cps. One that actually cures
HARD and not gummy without reducer.</font>
<br><font size=3> </font>
<br><font size=2 face="Arial">I'd buy it by the gallon =)</font>
<br><font size=2 face="Arial">-Mike</font>
<br><font size=3> </font>
<br><font size=3>----- Original Message ----- </font>
<br><font size=3><b>From:</b> </font><a href=mailto:gfowler@raytheon.com><font size=3 color=blue><u>Gray
E Fowler</u></font></a><font size=3> </font>
<br><font size=3><b>To:</b> </font><a href="mailto:nsrca-discussion@lists.nsrca.org"><font size=3 color=blue><u>NSRCA
Mailing List</u></font></a><font size=3> </font>
<br><font size=3><b>Sent:</b> Monday, November 26, 2007 10:23 AM</font>
<br><font size=3><b>Subject:</b> Re: [NSRCA-discussion] epoxy question-I
am back</font>
<br>
<br><font size=2 face="Arial"><br>
1. "Thinning the epoxy saves no weight by evaporation. There
is virtually no evaporation and no weight loss-a big time erroneous assumption
on my part. So if you mix 2 ounces of epoxy and add 2 ounces of thinner
and put it all on the airplane, you have added 4 ounces to the airplane.
"</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
After seeing the real question I expected a weight increase of at least
9% (how much water in the mix). If you put 1oz (by weight) of solvent in
1 oz of epoxy, and apply it as a coating , thin, you will eventually end
up with 1 oz of epoxy. Mike, your solvent got trapped, and now it will
have less adhesion, less tensile, Compression and flexure strength, and
will now shrink slowly as the alcohol exits the cured epoxy, over a year
or so (see Wayne's answer).</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
None of the solvent's listed will react with any epoxy blend. Exotherm
is negligible when applied as a thin coating, but significant in mass.
The ability to have the solvent evaporate out of the epoxy coating is directly
related to the mixed viscosity of the neat epoxy blend and the cure rate
of the epoxy. Those of you who ran experiments with 5 minute epoxy reported
bad results because of high viscosity and fast cure rate.The high viscosity
(even Mike's blend is apparently too high) will cause a skin effect where
the solvent evaporates from the surface first, creating a high viscosity
skin, then the epoxy starts to cure increasing viscosity even more, thus
trapping the solvent. Using fiberglass makes this even worse. MIKE- in
one year from now your wings will weigh less.</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
So it sounds like the the Pattern Dudes of the world need a solution. What
AeroSlave can do is provide a super low viscosity epoxy for sale. This
will be 100% solids (which means NO solvents). Chances are, as a mixed
epoxy, the viscosity will be lower than even blends with some solvent in
them. This can be used to apply fiberglass to wings or as a general laminating
resin.</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
How much interest would there be for such a a product? It would probably
cost about $50/ quart, $25/ pint. It would absolutely require an accurate
scale (+/- 1 gram) to WEIGH the epoxy and hardener into the appropriate
mix ratio. AND I offer no warranty, simply because you guys are the biggest
bunch of experimenters in the world, and I cannot control, nor anticipate
how this could get screwed up.</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
1. Operator cannot operate a scale.</font><font size=3> </font><font size=2 face="Arial"><br>
2. Operator has a crappy scale.</font><font size=3> </font><font size=2 face="Arial"><br>
3. Operator added solvent anyway because thats how he has always done it...since
1976</font><font size=3> </font><font size=2 face="Arial"><br>
4. Operators basement is 100% realative humidity..condensation on the wing.</font><font size=3>
</font><font size=2 face="Arial"><br>
5. Operator added "more" hardener to make it cure faster.</font><font size=3>
</font><font size=2 face="Arial"><br>
6. Operator......(enter F/U here).</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
As you can see there is one common theme to all of these possible problems,
Operator, i.e. customer.</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
So if you are STILL interested please respond and Lance and I will take
it under advisement.</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
</font><font size=3> </font><font size=2 face="sans-serif"><br>
<br>
<br>
<br>
Gray Fowler<br>
Senior Principal Chemical Engineer<br>
Radomes and Specialty Apertures<br>
Technical Staff Composites Engineering<br>
Raytheon</font><font size=3> <br>
<br>
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<td width=46%><font size=1 face="sans-serif"><b>"Dr. Mike Harrison"
<drmikedds@sbcglobal.net></b> <br>
Sent by: nsrca-discussion-bounces@lists.nsrca.org</font><font size=3> </font>
<p><font size=1 face="sans-serif">11/23/2007 01:57 PM</font><font size=3>
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<div align=center><font size=1 face="sans-serif">Please respond to<br>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td width=86%><font size=1 face="sans-serif">"NSRCA Mailing List"
<nsrca-discussion@lists.nsrca.org></font><font size=3> </font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
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<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">[NSRCA-discussion] epoxy question</font></table>
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</font><font size=2 face="Arial"><br>
I have read with interest all the comments and some of you have educated
me on this issue. If I may, I will share what I have learned.</font><font size=3>
<br>
</font><font size=2 face="Arial"><br>
1. Thinning the epoxy saves no weight by evaporation. There
is virtually no evaporation and no weight loss-a big time erroneous assumption
on my part. So if you mix 2 ounces of epoxy and add 2 ounces of thinner
and put it all on the airplane, you have added 4 ounces to the airplane.
</font><font size=3> </font><font size=2 face="Arial"><br>
2. The properties of the epoxy are changed-it becomes rubbery.</font><font size=3>
</font><font size=2 face="Arial"><br>
3. Changing the properties is not an issue regarding finishing the
airplane(painting)</font><font size=3> </font><font size=2 face="Arial"><br>
4. Using thinned epoxy is fine for applying glass cloth.</font><font size=3>
</font><font size=2 face="Arial"><br>
5. I have tried MEK(epoxy thinner), denatured alcohol, 91%alcohol,
acetone. My preference is denatured alcohol because it is the safest
and most economical, I think. I thought MEK would be the answer.
It is the worst of the bunch. </font><font size=3> </font><font size=2 face="Arial"><br>
6. The best way to glass surfaces is to thin the epoxy and apply
as sparingly as possible. A way to do that is to apply and wipe off
excess with paper towels. </font><font size=3> </font><font size=2 face="Arial"><br>
7. It is almost exactly 2 ounces to glass a wing panel complete,
so 4 ounces for a whole wing. About 2 ounces for a stab. Properly
done wings and stab glassed and painted is 2-2.5 times the weight of monokote.
</font><font size=3> </font><font size=2 face="Arial"><br>
8. A second thinned coat of epoxy on the glassed wing is .75 ounces
each wing panel-1.5 oz total.</font><font size=3> <br>
<br>
</font><font size=2 face="Arial"><br>
Pick your poison.</font><font size=3> <br>
</font><font size=2 face="Arial"><br>
Later,</font><font size=3> </font><font size=2 face="Arial"><br>
Mike</font><font size=3> <br>
</font><font size=2><tt>_______________________________________________<br>
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NSRCA-discussion@lists.nsrca.org<br>
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</font>
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