Cyanoacrylates are a family of strong, fast-acting adhesives with industrial, medical, and household uses that are derived from ethyl cyanoacrylate and related esters. The cyanoacrylate group in the monomer rapidly polymerizes in the presence of water to form long, strong chains. Specific cyanoacrylates include methyl 2-cyanoacrylate (MCA), ethyl 2-cyanoacrylate (ECA, commonly sold under trade names such as "Super Glue" and "Krazy Glue"), n-butyl cyanoacrylate (n-BCA), octyl cyanoacrylate, and 2-octyl cyanoacrylate (used in medical, veterinary and first aid applications). Cyanoacrylate adhesives are sometimes known generically as instant glue, power glue, or super glue. The abbreviation "CA" is commonly used for industrial grade cyanoacrylate.
Development
The original patent for cyanoacrylate was filed in 1947 by the B.F. Goodrich Company as an outgrowth of a search for materials suitable for clear plastic gun sights for the war effort. In 1942, a team of scientists headed by Harry Coover Jr. stumbled upon a formulation that stuck to everything with which it came in contact. The team quickly rejected the substance for the wartime application, but in 1951, while working as researchers for Eastman Kodak, Coover and a colleague, Fred Joyner, rediscovered cyanoacrylates, then applied for a patent in 1954 which was issued in 1956. The two had realized its true commercial potential, and a form of the adhesive was first sold in 1958 under the name "Eastman #910" (later "Eastman 910"). During the 1960s, Eastman Kodak sold cyanoacrylate to Loctite, which in turn repackaged and distributed it under a different brand name "Loctite Quick Set 404". In 1971, Loctite developed its own manufacturing technology and introduced its own line of cyanoacrylate, called "Super Bonder". Loctite quickly gained market share, and by the late 1970s it was believed to have exceeded Eastman Kodak's share in the North American industrial cyanoacrylate market. National Starch and Chemical Company purchased Eastman Kodak's cyanoacrylate business and combined it with several acquisitions made throughout the 1970s forming Permabond. Other manufacturers of cyanoacrylate include LePage (a Canadian company acquired by Henkel in 1996), the Permabond Division of National Starch and Chemical, which was a subsidiary of Unilever. Together, Loctite, Eastman, and Permabond accounted for approximately 75% of the industrial cyanoacrylate market. As of 2019 Permabond continued to manufacture the original 910 formula.
Polymerization
The most common monomer is ethyl cyanoacrylate. Several related esters are known. To facilitate easy handling, a cyanoacrylate monomer is frequently formulated with an ingredient such as fumed silica to make it more viscous or gel-like. Formulations are available with additives to increase shear strength or creating a more impact resistant bond. Such additives may include rubber, as in Loctite's "Ultra Gel", or others which are not specified. In general, the C=C groups rapidly undergo chain-growth polymerization in the presence of water (specifically hydroxide ions), forming long, strong chains, joining the bonded surfaces together. Cyanoacrylates typically have a relatively long on-part working time as long as two surfaces are not pressed together. Cyanoacrylate adhesives generally have a short shelf life—about one year from manufacture if unopened, and one month once opened, but this can be extended by refrigeration.
General properties Cyanoacrylates are mainly used as adhesives. Thin layers bond effectively, thick layers much less so. They bond many substances, including human skin and tissues, natural fibres, cotton, wool, and leather. Cyanoacrylate glue has a low shearing strength, which has led to its use as a temporary adhesive in cases where the piece needs to be sheared off later. Common examples include mounting a workpiece to a sacrificial glue block on a lathe, and tightening pins and bolts. It is also used in conjunction with another slower, but more resilient, adhesive as a way of rapidly forming a joint, which then holds the pieces in the appropriate configuration until the second adhesive has set. Cyanoacrylate-based glue has a weak bond with smooth surfaces and as such easily gives to friction; a good example of this is the fact that cyanoacrylates may be removed from human skin by means of abrasives (e.g. sugar or sandpaper).
Uses
Medical and veterinary
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