[NSRCA-discussion] Epoxy Question-Gray's response

[Lance Van Nostrand]

Here's THE answer from "Master Fowler".
NSRCA list dudes..

I have been at home on vacation so I have not check the NSRCA list. Lance 
notified me of the epoxy question so here is my answer.
I did not see the original question but I think I have the general idea. 
Alcohols can be used to thin epoxy resins and their blends. The most 
efficient and fastest evaporating is methanol. Then ethanol and isopropyl. 
All can be used to thin epoxy, but only methanol comes close to having an 
evaporation rate fast enough to be useable. What that means is isopropyl 
will require a long flash time to ensure that no solvent is trapped in your 
epoxy mix, which will seriously degrade the properties. If your epoxy starts 
thickening faster than the solvent evaporation rate you will have a problem. 
The main reason to use an alcohol as an epoxy solvent is because the alcohol 
will not destroy foam cores used for wings. If this is the application of 
the epoxy in question, then use methanol if you can. One real common problem 
with ethanol and isopropyl is they are usually sold not as 100%, but have 
other things in them such as water and other solvents. Water will mess up 
your epoxy and the other solvents may hurt your foam.

It may be difficult to find near 100% pure (99% is okay) alcohols 
(especially ethanol), and methanol is usually the easiest to obtain. If you 
are not on foam the use of acetone, methyl ethyl ketone, lacquer thinner, 
toluene all work better.

Also, the use of any solvent in the epoxy blend must be used as a coating 
(very thin coat) to allow the solvent to flash.

 I have also found that the over use of ethanol during the construction of 
your pattern plane can have detrimental effects on proper alignment.....

Happy Thanksgiving.....speaking of ethanol, my family allows my Aunt's ex 
husband at our TG because he is part owner of a winery, and brings much to 
compensate for his personality.

Gray Fowler
----- Original Message ----- 
From: <patterndude at tx.rr.com>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Cc: "Atwood, Mark" <atwoodm at paragon-inc.com>
Sent: Tuesday, November 20, 2007 3:48 PM
Subject: Re: [NSRCA-discussion] Epoxy Question


> 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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