[NSRCA-discussion] Epoxy Question

Bob Richards bob at toprudder.com
Wed Nov 21 08:57:55 AKST 2007 

John,
   
  That is what I do, heat the epoxy and brush it on. However, the fumes really bother me when I do this so I have to use good ventilation. After years of building using CA and epoxy, I develop cold-like symptoms sometimes after using this stuff.
   
  Bob R.
  

John Gayer <jgghome at comcast.net> wrote:
  Sounds as if there is enough data already to stop thinning your epoxy with alcohol. Just heat it gently with a heat gun and brush it on. Just as easy to brush on a thin coat, no loss of strength, faster cure....where's the downside?

John

glmiller3 at suddenlink.net wrote:   
Guys,  I thought the idea was to allow you to spread it thinner so that the end result was lighter.  Let's do a test where we coat a piece of 3 X 6 inch balsa with thinned and unthinned  epoxy and see if the thinned is actually lighter.  I would have done this already but I'm AFW (away from workshop) on vacation this week.      George    ---- Don Ramsey <don.ramsey at suddenlink.net> wrote:     
  
My test with 5 minute expoxy and 70 % alcohol was a disaster.  1 oz expoxy and 1 oz alcohol after curing only lost about a gram in the cup. The mixture was a rubbery substance that crumbled when pressure was applied.  No strength at all.  Spreading thin for the cure would have lost more weight but probably not substantially.  So, I no longer believe the alcohol evaporates and you are only left with expoxy.  The molecular structure changes and not for the better.  I'm not going to thin anything that needs strength.    Don      ----- Original Message -----     From: Bob Kane     To: NSRCA Mailing List     Sent: Tuesday, November 20, 2007 6:32 PM    Subject: Re: [NSRCA-discussion] Epoxy Question        This reminds me of a workshop incident 29 years ago . . . .    I was making a spacer out of 5/8" particle board to put an aftermarket aircleaner on my 1978 Chevy Monza. I decided to "fuelproof" the spacer, but wanted to get it done in a hurry, so I mixed up a batch of 5 minute
 epoxy and thinned it quite a bit with alcohol. I painted the mixture on the spacer and was waiting for it to cure, when all of a sudden an epoxy "snake" started growing out of the mixing cup. It made kind of a hissing, snapping sound, and grew to be about 8 inches long. I figured the epoxy heated up enough to "boil" the epoxy while it was still somewhat pliable. The result was an interesting honey colored rock hard piece of epoxy foam.  The epoxy on the particle board cured fine.         Bob Kane    getterflash at yahoo.com           ----- Original Message ----    From: "patterndude at tx.rr.com" <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 4:48:13 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      ________________________________          _______________________________________________        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            ------------------------------------------------------------------------------    Be a better pen pal. Text or chat with friends inside Yahoo! Mail. See how.      ------------------------------------------------------------------------------        _______________________________________________    NSRCA-discussion mailing list    NSRCA-discussion at lists.nsrca.org    http://lists.nsrca.org/mailman/listinfo/nsrca-discussion      

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