Est. 1998 — 27 years of woodworking knowledge
Question on chemistry of Epoxy and CA
J Barrett Irby Jr
Watching a video on prepping a table that has epoxy fill and then touching up tiny places with CA glue colored with the same dye/powder in the epoxy. The guy slips into the habit of calling the CA "epoxy."
They are not the same....Right? Related??? Compatible???
Re: Question on chemistry of Epoxy and CA
Bill Tindall, E.Tn.
Their chemical structure and how they work are entirely different. Epoxy is a two part system where a low molecular weight resin with epoxide groups is mixed with an amine that crosslinks the whole of it by bridging the epoxy groups together.
Cyanoacrylate is a monomer that is primed to polymerize when set off by almost anything, moisture for example. This small molecule rapidly becomes a polymer that is not cross linked. Therefore it can be dissolved in some solvents, unlike cured epoxy that is insoluble in everything known to man.
Re: Question on chemistry of Epoxy and CA
NickinMass
Not at all related. CA is cyanoacrylate and the reaction is driven by water, while epoxy is a resin with epoxide groups and the reaction is driven by a catalyst (usually the second part of two-part epoxy). CA is pretty brittle and not good at gap filling, while epoxy is great at gap filling and can be a lot more flexible (depending on the product)
Re: Putting It Simply
Mark Mandell - Gone Round In New Jersey
Filling the holes in epoxy with colored CA will not survive. The fill with not bind well with the epoxy surface and will fall out over time. Faster yet if you get it wet.
I get air bubbles in my fills. They get filled with more epoxy and sanded flush. Easy
If you bud has issues with mixing small amounts of resin and hardener, tell him to get a 2-gram scale and use the little solo cups you get with take-out. Most of the epoxies get mixed for weight at 100x45 portions.
nit picking and a chemistry lesson
Bill Tindall, E.Tn.
reaction is driven by a catalyst
A catalyst is not used in curing epoxy. The second component, the amine, reacts with epoxy component and becomes part of the cured resin. It is the bridge that links the epoxy resin part together to cross link it.
A catalyst speeds up a reaction without becoming part of the product. The red stuff one mixes with Bondo is a metal catalyst that speeds the cure reaction. Ditto for the metal catalyst that makes "boiled linseed oil" cross link upon exposure to air.
There is a third category of stuff, initiator. Water and amines initiate, that is get it started, the polymerization of cyanoacrylate adhesive. Once started the reaction takes off, no catalyst required.
One does not need to know any of this stuff to use these products as illustrated in their directions. Depart from directions and one better have an understanding of the chemistry involved.
Re: Question on chemistry of Epoxy and CA
Joe in a Cleveland suburb
"it can be dissolved in some solvents"
Which solvents will dissolve CA? In case you glue your fingers together.
A friend recently had this happen and went to the ER. The doc used some kind of very thin file to separate the fingers.
Thanks.
Re: Question on chemistry of Epoxy and CA
John K Jordan
>>>Which solvents will dissolve CA? In case you glue your fingers together.
A friend recently had this happen and went to the ER. The doc used some kind of very thin file to separate the fingers.
I've used acetone. Soaking in plain, soapy water for skin.
But when I glued the tips of thumb and forefinger together on my left hand I took a scalpel and very carefully cut through the bond, a little at a time, to separate my fingers. Not for those with shaky hands or without vision enhancement. I've done this a couple of times over the years and have never cut through my skin. I pull apart then use a new (sharp) scalpel with a #11 blade. (I have some practice with scalpels.) This method probably wouldn't work for the larger a hand glued to a non-flexible surface.
I've read that MEK will dissolve CA but I'd hate to get it near skin or breathe the vapors.
JKJ
Ditto on acetone
Tim Greif - West of Chicago
Acetone will undo the CA bond if you get your fingers stuck. Don't have a can of acetone in the cabinet? Ask your wife for some fingernail polish remover. It's acetone.
Re: Question on chemistry of Epoxy and CA
Bill Tindall, E.Tn.
Your friend needed a chemist not a surgeon!
I was in on the invention of this stuff. We had a grand time tricking people into gluing their fingers together. Stick hand in water and they will come apart. This stuff does not play well with moisture. It breaks down into little molecular pieces.
Re: Question on chemistry of Epoxy and CA
Bill Tindall, E.Tn.
Making the water basic with soap or baking soda will hasten the breakdown of this adhesive. I don't think soap itself will do anything useful.
Re: Question on chemistry of Epoxy and CA
John K Jordan
>>>I don't think soap itself will do anything useful.
It makes my hands clean. That can be useful on occasion. 
Re: Question on chemistry of Epoxy and CA
Jerry Nicholson
I remember Eastman 910 back in the very early 60s. Then it seemed like something too good to be true but the technicians in our electronics lab enjoyed playing tricks on each other with it.
Re: Question on chemistry of Epoxy and CA
Barry Irby
Someone I knew glued his index finger to his eyelid. He did not seem to think it was as funny as I did. Laid down and soaked it with water in a cloth.