Polymerization of methyl-2-cyanoacrylate
Behaviours[edit]
Cyanoacrylates are mainly used as adhesives. They require some care and knowledge for effective use: they do not bond some materials; their shelf life at room temperature is about 12 months unopened and one month once opened; they do not fill spaces, unlike epoxies, and a very thin layer bonds more effectively than a thicker one that does not cure properly; they bond many substances, including human skin and tissues, almost instantly and can cause harm to people. They have an exothermic reaction to natural fibres: cotton, wool, leather, see reaction with cotton below.
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.
Electronics[edit]
Cyanoacrylates are used to assemble prototype electronics (see wire wrap), flying model aircraft, and as retention dressings for nuts and bolts. Their effectiveness in bonding metal and general versatility have made them popular among modeling and miniatures hobbyists. They are used to re-harden the boxes and shanks of ballerinas' pointe shoes.
Aquaria[edit]
Cyanoacrylate glue's ability to resist water has made it popular with marine aquarium hobbyists for fragging corals. The cut branches of hard corals such as Acropora can be glued to a piece of live rock (harvested reef coral) or Milliput (epoxy putty) to allow the new frag to grow out. It is actually safe to use directly in the tank, unlike silicone, which must be cured to be safe. However, as a class of adhesives, traditional cyanoacrylates are classified as having "weak" resistance to both moisture and heat[5] although the inclusion of phthalic anhydridereportedly counteracts both of these characteristics.[6]
Bonding smooth surfaces[edit]
Most standard cyanoacrylate adhesives do not bond well with smooth glass, although they can be used as a quick, temporary bond prior to application of an epoxy or cyanoacrylate specifically formulated for use on glass.[7] A mechanical adhesive bond may be formed around glass fibre mat or tissue to reinforce joints or to fabricate small parts.
When added to baking soda (sodium bicarbonate), cyanoacrylate glue forms a hard, lightweight adhesive filler (baking soda is first used to fill a gap then the adhesive is dropped onto the baking soda). This works well with porous materials that the glue does not work well with alone. This method is sometimes used by aircraft modelers to assemble or repair polystyrene foam parts. It is also used to repair small nicks in the leading edge of composite propeller blades on light aircraft. The reaction between cyanoacrylate and baking soda is very exothermic (heat-producing) and also produces noxious vapors. See Reaction with cotton below.
Forensics[edit]
Cyanoacrylate is used as a forensic tool to capture latent fingerprints on non-porous surfaces like glass, plastic, etc.[8] Cyanoacrylate is warmed to produce fumes that react with the invisible fingerprint residues and atmospheric moisture to form a white polymer (polycyanoacrylate) on the fingerprint ridges. The ridges can then be recorded. The developed fingerprints are, on most surfaces (except on white plastic or similar), visible to the naked eye. Invisible or poorly visible prints can be further enhanced by applying a luminescent or non-luminescent stain.
Woodworking[edit]
Thin CA glue has application in woodworking. It can be used as a fast-drying, glossy finish. The use of oil (such as boiled linseed oil) may be used to control the rate at which the CA cures. CA glue is also used in combination with sawdust (from a saw or sanding) to fill voids and cracks. These repair methods are used on piano soundboards, wood instruments, and wood furniture.
Medical[edit]
Some rock climbers use cyanoacrylate to repair damage to the skin on their fingertips.[9][10] Similarly, stringed-instrument players can form protective finger caps (in addition to calluses) with cyanoacrylates.
CA glue was in veterinary use for mending bone, hide, and tortoise shell by the early 1970s or before. Harry Coover said in 1966 that a CA spray was used in the Vietnam war to retard bleeding in wounded soldiers until they could be brought to a hospital. Butyl cyanoacrylate has been used medically since the 1970s. In the US, due to its potential to irritate the skin, the U.S. Food and Drug Administration did not approve its use as a medical adhesive until 1998 with Dermabond.[11] Research has demonstrated the use of cyanoacrylate in wound closure as being safer and more functional than traditional suturing (stitches).[12] The adhesive has demonstrated superior performance in the time required to close a wound, incidence of infection (suture canals through the skin's epidermal, dermal, and subcutaneous fat layers introduce extra routes of contamination),[12] and final cosmetic appearance.[13][14]
While standard "superglue" is 100% ethyl cyanoacrylate, many custom formulations (e.g.,, 91% ECA, 9% poly(methyl methacrylate), <0.5% hydroquinone, and a small amount of organic sulfonic acid[15] and variations on the compound N-butyl-cyanoacrylate's for medical applications[12]) have come to be used for specific applications.
Archery[edit]
Cyanoacrylate is used in archery to glue fletching to arrow shafts. The special "fletch-tite" glues are really cyanoacrylate repackaged in special fletching glue kits. Often these tubes have a long thin metal nozzle to aid in better accuracy in the application of the glue to the base of the feather or plastic fletching to ensure a good bond to the arrow shaft.
Cosmetics[edit]
Cyanoacrylate is used in the cosmetology/beauty industry as a "nail glue" for some artificial nail enhancements such as nail tips and nail wraps, and is sometimes mistaken for eye drops causing accidental injury.[16]
Safety issues[edit]
Skin injuries[edit]
CA adhesives may glue skin and eyelids together within seconds. In the course of separating the glued body parts, injuries may occur by ripping off parts of the skin. However, when left alone, the glue will separate from the skin over the course of time (up to four days). The separation process can be accelerated by applying vegetable oil near on and around the glue. In the case of glued eye lids, a doctor should be consulted.[17]
Toxicity[edit]
The fumes from CA are a vaporized form of the cyanoacrylate monomer that irritate sensitive membranes in the eyes, nose, and throat. They are immediately polymerized by the moisture in the membranes and become inert. These risks can be minimized by using CA in well ventilated areas. About 5% of the population can become sensitized to CA fumes after repeated exposure, resulting in flu-like symptoms.[18] It may also act as a skin irritant and may cause an allergic skin reaction. The ACGIH assign a Threshold Limit Value exposure limit of 200 parts per billion. On rare occasions, inhalation may trigger asthma. There is no singular measurement of toxicity for all cyanoacrylate adhesives as there is a wide variety of adhesives that contain various cyanoacrylate formulations.
The United States National Toxicology Program and the United Kingdom Health and Safety Executive have concluded that the use of ethyl cyanoacrylate is safe and that additional study is unnecessary.[19] 2-octyl cyanoacrylate degrades much more slowly due to its longer organic backbone that slows the degradation of the adhesive enough to remain below the threshold of tissue toxicity. Due to the toxicity issues of ethyl cyanoacrylate, the use of 2-octyl cyanoacrylate for sutures is preferred.
Reaction with cotton[edit]
Applying cyanoacrylate t, , o some natural materials such as cotton, leather or wool (cotton swabs, cotton balls, and certain yarns or fabrics) results in a powerful, rapid exothermicreaction. The heat released may cause serious burns,[20] ignite the cotton product, or release irritating white smoke. Material Safety Data Sheets for cyanoacrylate instruct users not to wear cotton or wool clothing, especially cotton gloves, when applying or handling cyanoacrylates.[21] source：http://en.wikipedia.org/wiki/Cyanoacrylate
