Cyanoacrylate is the generic name for substances such as methyl-2-cyanoacrylate, which is usually sold under the trademarks Superglue and Krazy Glue, and 2-octyl cyanoacrylate, which is used in medical glues such as Dermabond and Traumaseal. Cyanoacrylate adhesives are sometimes known as "instant adhesives". The acronym "CA" is quite commonly used for industrial grades.
History
Cyanoacrylate was discovered during World War II when searching for a way to make synthetic gun-sights (a substitute for spider silk). It did not solve this problem, since it stuck to all the apparatus used to handle it. Later it was developed into a more useful form by the Eastman Kodak company in 1958. The term is now used to refer to a range of adhesives based on similar chemistry.
Properties
In its liquid form, cyanoacrylate consists of monomers of cyanoacrylate molecules, (C5H5NO2) CH2=C(CN)COOCH3, and has molecular weight equal to 111.1.
Its burning point lies at 79 ºC and its density is 1.1 times the density of common water (H2O).
It is an acrylic resin which rapidly polymerises in the presence of water (specifically hydroxyl ions), forming long, strong chains, joining the bonded surfaces together. During setting, it exudes concentrated acetic acid, making a strong smell of vinegar. Because the presence of moisture causes the glue to set up, exposure to moisture in the air can cause a tube or bottle of glue to become unsable over time. To prevent an opened container of glue from drying out before use, store it in an airtight jar or bottle with a package of silica gel.
Another important trait is that cyanoacrylate sets up fast, often in less than a minute. A normal bond reaches full strength in two hours, and is waterproof. There are also accelerants that can force a set-up as fast as two or three seconds, at some loss of strength.
Acetone, which is found in nail polish remover, is a commonly available solvent capable of softening cured super glue.
Cold temperatures cause cyanoacrylate to become brittle. Cyanoacrylate's bond can be weakened, allowing disassembly, by placing a glued object in a household freezer for several hours.
Uses
Cyanoacrylate is a tenacious adhesive, particularly when used to bond non-porous materials or those that contain minute traces of water. As such it is very good at bonding body tissue, and while this effect can be a nuisance (or even dangerous) for everyday use, it has been exploited for the benefit of suture-less surgery. Its major polymerization byproduct, acetic acid, is biocompatible. Cyanoacrylates are used in orthopedic surgery to glue metal appliances to bone. They are often used, for example, to glue artificial hip appliances to femurs and pelvic girdles.
Cyanoacrylates are often used to assemble prototype electronics (see wire wrap), flying model aircraft, and as retention dressings for nuts and bolts.
One non-adhesive use for cyanoacrylate is as a forensic tool. Fumes from (warmed) CA can develop latent fingerprints on surfaces. The invisible fingerprint residues react with the CA fumes and atmospheric moisture to become visible and can then be recorded.
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