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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The education and value of this forum (and
by definition from its members) never ceases to amaze me. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>-Mark<o:p></o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Gray E Fowler<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, April 17, 2006 2:46
PM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">NSRCA
Mailing List</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion]
Micoballons</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
</span></font><font size=2 face=sans-serif><span style='font-size:10.0pt;
font-family:sans-serif'>Bob</span></font> <br>
<font size=2 face=sans-serif><span style='font-size:10.0pt;font-family:sans-serif'>You
are right on. </span></font> <br>
<font size=2 face=sans-serif><span style='font-size:10.0pt;font-family:sans-serif'>Rule
of thumb......for every 12 degrees F increase, epoxy cure time is cut by 50%.
So as the mixture exotherms the balloons insulate the heat.</span></font> <br>
<br>
<font size=2 face=sans-serif><span style='font-size:10.0pt;font-family:sans-serif'>Pot
life is defined as 100 grams of mixed material in a mass such as a cup starting
at 25degrees C (77F) and the time it is still usable. It is not unreasnable to
realize that the potlife of a neat resin blend is different than a mixture of
fillers or even a solvent such as a coating.</span></font> <br>
<font size=2 face=sans-serif><span style='font-size:10.0pt;font-family:sans-serif'><br>
<br>
<br>
Gray Fowler<br>
Principal Chemical Engineer<br>
Composites Engineering</span></font> <br>
<br>
<o:p></o:p></p>
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<p class=MsoNormal><b><font size=1 face=sans-serif><span style='font-size:
7.5pt;font-family:sans-serif;font-weight:bold'>Bob Richards
<bob@toprudder.com></span></font></b><font size=1 face=sans-serif><span
style='font-size:7.5pt;font-family:sans-serif'> </span></font><br>
<font size=1 face=sans-serif><span style='font-size:7.5pt;font-family:sans-serif'>Sent
by: nsrca-discussion-bounces@lists.nsrca.org</span></font> <o:p></o:p></p>
<p><font size=1 face=sans-serif><span style='font-size:7.5pt;font-family:
sans-serif'>04/17/2006 11:46 AM</span></font> <o:p></o:p></p>
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respond to<br>
<st1:PersonName w:st="on">NSRCA Mailing List</st1:PersonName>
<nsrca-discussion@lists.nsrca.org></span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=1 face=sans-serif><span style='font-size:
7.5pt;font-family:sans-serif'>randy10926@comtekmail.com, <st1:PersonName
w:st="on">NSRCA Mailing List</st1:PersonName> <nsrca-discussion@lists.nsrca.org></span></font>
<o:p></o:p></p>
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<p class=MsoNormal align=right style='text-align:right'><font size=1
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<p class=MsoNormal><font size=1 face=sans-serif><span style='font-size:
7.5pt;font-family:sans-serif'>Re: [NSRCA-discussion] Micoballons</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br>
<br>
I'm not a chemist, so what I am about to say is just an educated guess. :-) <br>
<br>
Epoxy gets warm as it cures, and cures quicker as it gets warm. A thick mass of
epoxy will cure quicker than a thin film since there is less surface area
through which the heat can escape. <br>
<br>
Microballons are hollow glass spheres, and probably act as a thermal insulator.
This insulation property is possibly preventing the heat of the curing process
from escaping, and causes the epoxy to cure quicker in the center since the
heat can't escape. <br>
<br>
Try using longer curing epoxy. :-) <br>
<br>
Bob R. <br>
<br>
<b><i><span style='font-weight:bold;font-style:italic'><br>
Glenn Hatfield <randy10926@comtekmail.com></span></i></b> wrote: <br>
</span></font><font face=Arial><span style='font-family:Arial'><br>
I recently used micro-ballons in an epoxy for the first time. I was
really surised how much the cure time changed with just a small ratio of
micro-ballons. I was able to feel the expoxy warming up in the mixing
cup. As an experiment I mix a small batch and tried to go for the max
ratio; but ended up with a hot spot in the middle that set before I could
finish the mixing.</span></font> <br>
<font face=Arial><span style='font-family:Arial'> </span></font> <br>
<font face=Arial><span style='font-family:Arial'>This stuff appears to be
acting as a catalyst; which really surprised me. What is really going on
here.</span></font> <br>
<font face=Arial><span style='font-family:Arial'> </span></font> <br>
<font face=Arial><span style='font-family:Arial'>randy</span></font> <br>
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