CA Glue Setting Mechanism - Which is it?

[Glen Blanchard]

I watched a Lyle Jamieson video recently and in it he mentioned that CA cures by being in an oxygen-free environment. He went on to suggest that one might want to leave their bottles of CA uncapped so as to prevent setting in the bottle. This morning I was watching a You Tube video and the presenter made mention that CA sets as a result of exposure to moisture. Needless to say, I am a bit perplexed.

So which is it? Is it the lack of oxygen or the presence of moisture that initiates the setting of CA?

[John Coloccia]

Moisture will certainly kick it off, and it reacts with other things as well. If it set in an oxygen free environment, how does the stuff at the bottom of the bottle stay liquid? :) I think sometimes CA glues get confused with things like Loctite under the assumption that Loctite is just weak CA. In fact, Loctite is an anaerobic adhesive and requires both lack of oxygen and metal ions to cure. This is the only thing I can think of.

[Thom Sturgill]

I always understood that cellulose was a trigger for CA to set off. However, according to an article at IPMSStockholm.org (http://www.ipmsstockholm.org/magazine/2004/10/stuff_eng_tech_ca_glue.htm):

The hardening reaction can be described like this. The cyanoacrylate is a polymer which contains its own hardener compound. However, a weak acid is added acting as an inhibitor, preventing the reaction and “holding apart” the molecules which accounts for the liquid consistency of the compound. When exposed to water, the acid is dissolved. It triggers a chain reaction and the compound cures to the solid state.
Manufacturers use the inhibitor to control the curing time of the glue. Slow-setting superglues have a larger proportion of inhibiting acid in the basic mixture.

Accelerators Besides water, cyanoacrylate polymerises also in presence of alcohol and basic compounds (including weak amines). The latter can be used to produce a superglue “kicker” – a compound which triggers quick polymerisation of the glue.

Baking soda is one well-known substance with this effect. If you apply a layer of superglue to a seam and gently pour baking soda over it, the glue will cure very quickly. It makes for most effective filler for smaller jobs, and the baking soda results in a slightly rough surface which is good for sanding.

[Glen Blanchard]

If it set in an oxygen free environment, how does the stuff at the bottom of the bottle stay liquid?

A question I had already asked myself.

[Scott Hackler]

Water is definitely a curing agent for CA. If you have super dry fingers and get some on them, they will generally not stick together....but if they are wet..they will stick almost instantly! Same goes with wet wood vs dry wood. You generally need to spray dry wood with either water or activator to get CA to stick.

I don't buy the oxygen free deal, because of the bottles no setting up on the bottom. Oh, and I rarely ever cap my CA. Mostly because I loose the darn caps.

[Glen Blanchard]

I have started leaving my CA bottles uncapped as well, Scott. But for a different reason - to prevent them from bonding to the bottle!

[robert baccus]

I used to think that 02 removal was necessary for curing but data presented on this forum convinced me otherwise. I am still confused--our RH here in the south is very high and my uncapped bottles last very well without hardening but wetting is never used here.

[John Terefenko]

Lots of answers in here. http://www.caglue.com/Frequently-Asked-Questions-about-CA-glue-from-Satellite-City-Instant-Glues_ep_42.html