[NSRCA-discussion] Epoxy Question

[patterndude at tx.rr.com]

Mr Fowler is out saving the world through explosives, but as a foot soldier in the cause, here's my understanding (and experience):
Alcohol and acetone both mix into the resin/hardener solution.  This makes is harder for crosslinking to occur and it separates the epoxy molecules trapping the alcohol.  THe resulting solid will be a bit rubbery because of the trapped alcohol.  Acetone is a more powerful solvent than alchohol and is beter for cleaning and thinning, but is also better for making rubber.  
  The answer to the original question is really somewhat obvious.  Alcohol is volatile and will evaporate from the surface of the liquid in your mixing cup.  As the epoxy cures, it exotherms (heats up) and this will also increase the evaporation.   However, not all will evaporate.  Whatever doesn't will be bound into the final rubbery solid.  THe amount left behind is a variable affected by the size of the cup, heat in the room, amount of epoxy mixed, speed of cure, etc.
  The one time alcohol is OK to leave in the mix is when glassing.  The very thin layer allows virtually all the alcohol to evaporate.

Also, Mike says he is using 91% alcohol.  That means 9% water. Water is never good.  He should go to home depot and buy a gallon of Denatured Alcohol.  This is pretty close to 100% pure and it is less than half the price.

--Lance
 
---- "Atwood wrote: 

=============
Actually...my thought goes the other direction.  That if indeed the
alcohol actually MIXES with the epoxy, then it would truly bind and in
some way harden as part of the overall mixture.   Epoxy "cures"...rather
than flashing, so my guess...and it's truly a guess...is that it would
be much closer to the original total weight of 2 oz.   

 

Still waiting patiently for our resident epoxy deity, previously
referred to as Master Fowler to take away the mystery and lead us oh so
graciously to the light...

 

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of wgalligan
Sent: Tuesday, November 20, 2007 9:52 AM
To: Don Ramsey; NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Epoxy Question

 

OK,  I'll take a stab.  After the alcohol evaporates you would have the
same mass or weight of epoxy that you started with.  AND to reiterate
what I learned from the Master Fowler, thinning epoxy, if I remember
right, changes the molecular structure weakening the mixture.  It will
also cause the epoxy to shrink over time. BTDT.

 

Wayne Galligan

 

waiting for Master to speak

	----- Original Message ----- 

	From: Don Ramsey <mailto:don.ramsey at suddenlink.net>  

	To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>


	Sent: Tuesday, November 20, 2007 8:53 AM

	Subject: [NSRCA-discussion] Epoxy Question

	 

	Breaking news.  Here's something from Mike Harrison that will be
of interest to the list.

	Don

	 

	 

	Ok, think about this, take 1 oz epoxy and thin with 1 oz alcohol
(91%).?  After curing how much do you think it weighs and tell me why.

	 

	Mike

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