Re: Epoxy ?

Charles Morrill

I’ve observed some outgassing as epoxy cures so anything that interferes with that is not a good idea.  Also curing epoxy generates heat which is usually of little concern in our model building unless you are casting thick parts.  One other point: epoxy – paint – metal/wood etc.  is only as strong a joint as the paint is.

From: 'Hunter, James R.' jhunter@... [STMFC]
Sent: Friday, December 29, 2017 12:17 PM
To: STMFC@...
Subject: Re: [STMFC] Epoxy ?



I always leave epoxy out  "to the air" to cure.  I learned from experience years ago, that especially anything inside a house car, like weights, must be left open or the car will warp.  Secondly, I would never combine epoxy with anything else or paint it before it is cured.


Jim Hunter

From: STMFC@... on behalf of jimbetz@... [STMFC]
Sent: Friday, December 29, 2017 12:44 PM
To: STMFC@...
Subject: [STMFC] Epoxy ?

Hi guys,

  I know the basics of epoxy - combine epoxy and hardener to cause

a chemical reaction that causes it to form a strong bond to the

surface(s) it is contact with - and to itself).  But I'm not a chemist

and don't know how it works.  I know that the epoxy reacts with

the hardener and "cures" and that, for hobby products, the

amount of 'available' hardener in Part B controls/determines

how long the curing takes.  And that once cured epoxy can't

be "uncured". Uncured epoxy does not have much physical

strength and an object in it will tend to "sag" due to gravity

(or other forces).


  All that is fine but what I want to know is the answer to

questions such as:


  1) Does the epoxy use/need anything from the environment

      during the curing process.!   For example oxygen or ___

      from the air?


  2) Related to #1 - is "open to the air" important to the

      curing process?


  3) Would the presence of water, acrylic paint, or lacquer

       paint on the surface of -curing- epoxy affect how well

       it cures?  Faster?  Slower?  Inhibit full cure?  Inhibit/

       only affect the layer in contact with the curing epoxy?


  4) Is it a bad idea to paint over epoxy, before it is cured,

      with acrylics?


  5) Would using a white glue, such as KK, over epoxy

      -while it is curing- affect the cure?


  I have always waited until the epoxy was -fully- cured.

I know that's safe.  Is it just a good id! ea or is it required?


                                                                           - Jim B.


P.S. Yes, this is related to a build project on a STMFC


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