A friend of mine told me that CA glues (superglues, Zap-A-Gap, etc.) will severely weaken their bonds over time and may eventually turn to white powder. Can anyone out there confirm or deny the above statement?

From the Henkel Consumer Adhesives site:
Cyanoacrylates are extremely rapid curing adhesives known as instant adhesive or Super glue. These adhesives were discovered by accident by Dr. Harry Coover´s group at Eastman Chemical Company while doing some basic research on characterizing certain polymers derived from a chemical called ethylene. A cyanoacrylate adhesive is a very rapid curing adhesive also from the acrylic family tree, but having a completely different cure system. Cyanoacrylate monomer is made from a complex chemical process. The monomer produces a very reactive polymerization. The reaction or polymerization process is stabilized and the monomer kept in the liquid state by the addition of a small amount of an acid stabilizer material.

When a drop of cyanoacrylate adhesive is put on the surface of a part, the acid stabilizer molecules react with the water molecules present on the surface of the part from the relative humidity in the air. The reaction of the water and acid causes the acid stabilizer to be neutralized. The cyanoacrylate molecules then react with each other and form polymer chains without crosslinking.

The amount of stabilizer molecules in cyanoacrylate is very small-measured in parts per million--and very little moisture molecules are required to cause rapid polymerization. Cyanoacrylates begin to form polymer chains immediately on contact with the water vapor on the surface of the part. If parts are moved during initial contact, the polymerization process and polymer chains are stopped. The process must start again at a new catalyzed site."

After its discovery the good people at Eastman derived a number of early applications, including several in the space program and non-sutured wound closures.

I suspect that the conflicting stories about cyano either becoming brittle or not can be explained by reference to the chemical base of the particular brand of glue that was used.
{Dan Pariser}

Regarding CYA's. I am a coatings chemist that uses CYA's frequently. Couple of points to remember about CYA's is that they are soluble in many organic solvents (acetone, methanol) and WATER. Also, if the glue is cured too quickly (by using too much "accelerator") the heat generated will cause the glue to foam and reduce its strength. I have had CYA joints exposed to methanol glow fuels fail, but I have never seen the glues I have used degrade over time. However, it is very possible that years of high humidity, sunlight, or solvent exposure could destroy CYA.
{Dave Seuferling}
I've got two ship models, wood, plank on bulkhead, that I put together in the winter of 1982-83. I used regular Crazy Glue on both and reinforced the joints between the bulkheads and strakes with white glue. All the rest of the glue joints were strictly Crazy Glue. No joints have separated so far, and neither of the models are in a glass case, so they are exposed to whatever the ambient room conditions are. I used the same glue on a double planked hull, still far from finished, and one outer layer strake has separated at the bow (no big deal to fix it).

Two out of three of the above hulls have extreme compound curves at both bow and stern, so the joints had to have been under some stress, even though I hot bent them during construction.

I have a fourth that I started in 84 and am still working on that I used Crazy Glue - wood and leather on. The hull is fully nailed (2000+ nails), so even if the glue lets go, I don't think the planks are going anywhere. This version of Crazy Glue turned out to be a lot better to work with than the original. It's a bit thicker, so its more forgiving about slight gaps or irregularities in the joints, takes a bit longer to set up so tricky pieces can be coaxed into place a bit easier than the "instant" bond of the original allowed.

Even if you don't want to use it as a construction glue, one place this stuff really shines is in threading small blocks when you're doing the rigging and setting the knots and fastenings to belaying pins and cleats. A bit of glue on the end of a piece of string firms it up so it becomes its own needle. A long diagonal cut through the glued string creates a very fine point, and passing the string through the tiny hole in a block is no problem at all. Rat lines and other knotted crossings of lines stay put if you dab a bit of glue on them, and if you use the original formula for this purpose, it disappears completely into the thread. The W&L formula sometime stays visible if you use too much.

Be aware that some shops that sell models don't accept cryo based glues though, so if you're building to market, check with the shop before you spend a lot of time building a boat they won't want.
{Jack Silvia}

One thing I have noticed is that a lot of people are claiming to have built models of various types using CA adhesives that are 20 years old and aren't falling apart.

One thing that has become more prevalent in the use of CA Adhesives is the use of "accelerators" and "ZIP Kickers" with the slower curing varieties of CA. This can produce quite different results than the traditional methods of using CA. The availability of accelerators has also allowed people to use CA as a filler as well as an adhesive.

Problems can occur when an accelerator is used on a thick application of CA. The accelerator can instantly cure the surface of the application, but the center stays liquid, and may not be able to cure properly if the surface hardening completely seals the center off from air. This results in a soft core that may never fully cure, and is not structurally sound as an adhesive.

I ran into this when I used CA to fill all of the windows in a Heller 1/72 Constellation in order to convert it to a C/EC-121. Some of the windows fills retained a "bubble" of uncured CA.

It is better to do this type of operation in multiple thin applications, than trying to do it in one thicker one and use accelerator!

I wonder how many CA problems are related to the one I had! Hopefully, we all learn from our mistakes.
{Steve Kennedy}

I've recently had a very strange experience with them that has me baffled, and I'd like to learn how to not repeat it....

A couple of days ago, I was coating the interiors of cardboard model rocket tubes with CA in order to strengthen them. I was using a store brand (I can give you the manufacturer if you need it) that was a couple of months old. At first I was using medium, but then I ran out and switched to thick. My finger was covered with the stuff, and a bit after I switched to the thick, I started feeling a sharp pain in that finger. I thought it would go away, but it just getting stronger and stronger -- it started feeling like my finger was on fire.

I put my finger under water, which seemed to help. But a few minutes after I would take my finger out of the water, the heat would start coming back. The glue was too thick to wash off, and not set enough to peel off, so my husband tried cleaning it off with paint thinner. That hurt too much, so he got some debonder, and eventually we got it all off, put some burn medicine on, and wrapped my finger in a bandage. Everything was fine after that....

I know it wasn't an allergic reaction because my husband got some on his finger while he was cleaning me up, and he started burning too. I also know that CA generates heat when it cures -- but my husband didn't have that much on his finger.... So, I was curious if you might have any ideas on what caused it to burn so much? Do you think it might have been mixing the medium and thick (both from the same manufacturer)??? Could it have been the age of the stuff??? Or could it just have been something with the brand???? Or could it have been the fact that I had so much on my finger????

As I said, I'd like to avoid this in the future (and warn others about it too), but unless I know what exactly happened, there's not much that I could do that makes sense.....
{Paul & Victoria Heisner}

CA was developed as a way to "stitch" wounds together fast in the field, that's why you shouldn't get it on your fingers, and the chemical reaction involved probably caused the burning of your finger. In short, don't get it on your skin!
{Olaf Kievit}
Bottom line -- Don't rely on a glue joint alone (ANY type of glue)... pin the pieces together as well (using screws, nails, dowels, splines, etc., if at all possible.

Take care when using CA...it was originally developed as an alternative to sutures in surgery.

However, it is handy to have something set almost instantly... I regularly use it in conjunction with other glues (white and yellow) to tack pieces together until the "slow" glue can set up -- instant clamps!
{John O. Kopf}

On the subject of super glues being dangerous, there is one thing that you should watch out for. I learned this by experience. If you are going to sand or shape the area of a joint that you have sealed with any of the super glue types, make sure you let it dry for a long time. On a few occasions, not having been smart enough to learn from the first time, I have attempted to sand or shape such an area with my Dremel tool. The friction from the sanding bit actually turned pockets of undried glue into a gas much like a tear gas. It burnt the nose, throat, and eyes even through goggles. Effect lasted for a good two minutes and I am sure could be much worse for some people with allergies etc. Just a word of caution let it dry well when doing this.
{Tom Dean}
One important point seems to be overlooked in the current round of discussion, that is the heat given off by the glue as it cures. A recent accident reminded me; I spilled some CA onto my work table, then tried to mop it (carefully) with kitchen paper. Of course I was instantly bonded to the paper (though not to the table). The problem was the volume of glue versus the amount of moisture available. Two of my fingers rapidly heated up (there was smoke and acrid CA fumes!). I did not reach the cold faucet fast enough, and received some small but painful chemical burns.

I've been using the stuff for close to 20 years and this was my first bad accident (I don't include all the times I became glued to my ship model!). But beware, it could happen to you too!

I work in a museum where we use this glue a lot to repair fossils! According to the safety literature we have, the glue and its fumes are not considered toxic (it is not a good idea to inhale), and the main dangers have to do with heat production on contact with moisture. And I know people who have successfully replaced a loose tooth crown with a drop of CA.
{John Maisey}

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