ian lanc
Senior Airman
Just what exactly is that stuff in glass bottles that makes super glue cure all most instantly ?
Ian.
Ian.
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See?The correct chemical designation for the CA glue is ethyl 2-cyanoacrylate. An acronym ECA is also used in chemistry. The actual composition of most commercial glues is typically: 91% ethyl 2-cyanoacrylate, 9% polymethylmethacrylate, <0.5% hydroquinone and a trace of organic sulfonic acid.
The cyanoacrylate glue hardens very quickly when trapped between two surfaces. The reaction is caused by the condensed water vapor on the surfaces (namely the hydroxyl ions in water). The water comes from the surrounding air, so obviously the air humidity is a factor that may affect bonding capabilities, or cause them to differ from application to application. The curing reaction starts at the surface of the bonded material and develops towards the centre of the bond. Because of this, thick seams or large blobs of glue may harden less satisfactorily than surface-to-surface bonds with good fit. In a thick blob of glue, a polymerization reaction may stop before it reaches the centre of the blob. A rule of thumb is that seams thicker than 0,25 mm should be avoided. Thick seams will also take longer time to cure. Thus a thick superglue-filled seam will allow adjustment of the parts, but will bond instantly and definitely when they are pressed together, so that the gap decreases below 0.25 mm. Pressing the parts harder against each other will make the glue cure instantly.
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.
Besides water, cyanoacrylate polymerizes 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 polymerization 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.
I live in a very simple world.All the time I spent on that, and all I had to do was reply..... Magic??
I use CA glue and baking soda as a filler on a regular basis. A word of caution. If you are going to sand it don't dilly dally. The mixture will cure very quickly but will still take some time to go off and harden completely. Sand as soon as the initial hardening,which is almost instant,or you'll find that the filler is much harder than the surrounding plastic making for a much tougher job.
Wherever possible I use this filler from the inside where it won't be seen and sanding on the outside is minimal.
Also be aware that some heat will be given off as the glue cures.
I usually apply the glue and then sprinkle the baking soda on top.
To add to the accelerant question,simply blowing on the join/CA will work due to the moisture in your breath.
Cheers
Steve
Bingo!Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke