[NSRCA-discussion] Epoxy Question

[Don Ramsey]

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

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