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General control line discussion => Open Forum => Topic started by: Dick Pacini on June 05, 2011, 11:42:16 PM
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Why is it that CA will sometimes give off a whiff of smoke during application and other times it doesn't?
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Normally, superglue in the tube is made up of lots of little units (monomers), which, when the glue cures, link up to become long chains of those units (polymers).
In order to start the reaction off some water is normally needed.. damp things stick better/quicker than dry ones and the glue goes hard faster on a humid day.
Only about 40% of the volume of a piece of balsa is solid substance. To give a balsa tree the strength it needs to stand in the jungle, nature pumps each balsa cell full of water until they become rigid - like a car tire full of air. Green balsa wood typically contains five times as much water by weight as it has actual wood substance, compared to most hardwoods which contain very little water in relation to wood substance - it is then klin dried.
Since the reaction gives out heat, the balsa therefore gets hot (and as it becomes hotter so the reaction goes faster - there would be a reaction occuring faster than normal visable via smoke )
I wouldn't like to guess what the fumes might be, as I don't know which out of the cyanoacrylate or the balsa would break down first, and to what extent any nasties would be burnt before evaporating. The gas might be C02 and some other carbon/hydrogen molecules, maybe H2O as well.
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The 'smoke' is CA monomers. The bonding reaction gives off heat, if it goes fast enough then un-reacted CA will evaporate, then immediately condense as monomers. Hence the smoke, and the smell even if you don't see smoke.
See http://en.wikipedia.org/wiki/Cyanoacrylate, "reaction to cotton" for an extreme example.
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Heh heh heh, time to test "reaction to cotton" VD~
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Well, that didn't do squat....
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A very small dab of CA won't smoke. A large (too large) quantity will, when it finally "goes off". Many things help set the glue "off", including humidity (exhale on it), sanding dust, baking soda, micro balloons, "kicker", etc. If you have the right combination of too much CA, some sanding dust and high humidity, you've got "CA smoke" coming your way. Don't inhale that chit! It's bad for you, even badder than gluing your finger in your ear. LL~ Steve
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CA usually only smokes during the fire season in the fall. Oh, you were referring to the glue, not the state! LL~
We do have seasons: Earthquake, Flood, Fire and Riot.
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Heh heh heh, time to test "reaction to cotton" VD~
And strangely enough, the instructions for the P40 ARF said to use Q-tips to remove excess CA. I saw no reaction, other than the dang Q-tips would glue themselves to the bench (or me) when I put them down. I tell you, the whole concept of instant adhesives is really something to get used to. In the days of yore, glue was liberally applied and then sometimes, an extra blob was issued to the joint. After all, if you didn't have glue oozing out of all the joints, it wasn't going to be a very strong airplane. HB~> Learning to replace that glue loogie with a tiny drop of CA that scoots into the joint, never to be seen again, is a brain boggler.
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Years ago a rep from Pacer Zap came to our club meeting and told us that only one thing kicks off CA glues that was raising the PH of the glue. That's why way back then we used baking soda to get the glue to set when the wood was too dry. For what it's worth I still use baking soda.
Andy
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Dick,
Back in the day we did not smoke CA. We had grass.