[NSRCA-discussion] Micoballons

[Gray E Fowler]

Bob
You are right on. 
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.

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.



Gray Fowler
Principal Chemical Engineer
Composites Engineering



Bob Richards <bob at toprudder.com> 
Sent by: nsrca-discussion-bounces at lists.nsrca.org
04/17/2006 11:46 AM
Please respond to
NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>


To
randy10926 at comtekmail.com, NSRCA Mailing List 
<nsrca-discussion at lists.nsrca.org>
cc

Subject
Re: [NSRCA-discussion] Micoballons






I'm not a chemist, so what I am about to say is just an educated guess. 
:-)
 
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.
 
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.
 
Try using longer curing epoxy. :-)
 
Bob R.
 

Glenn Hatfield <randy10926 at comtekmail.com> wrote:

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.
 
This stuff appears to be acting as a catalyst; which really surprised me. 
What is really going on here.
 
randy
_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20060417/1ea0f5a9/attachment-0001.html