Cyanoacrylate

Source: Wikipedia, the free encyclopedia.

Structure of the backbone of a cyanoacrylate polymer.

Cyanoacrylates are a family of strong fast-acting adhesives with industrial, medical, and household uses. They 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.[1]

Specific cyanoacrylates include

2-octyl cyanoacrylate
(used in medical, veterinary and first aid applications). Cyanoacrylate adhesives are sometimes known generically as instant glues, power glues or superglues. The abbreviation "CA" is commonly used for industrial grade cyanoacrylate.

Development

Harry Wesley Coover Jr. shortly before being awarded the National Medal of Technology and Innovation in 2010

The original

Eastman Kodak
, Coover and a colleague, Fred Joyner, rediscovered cyanoacrylates. The two realized the true commercial potential, and a form of the adhesive was first sold in 1958 under the title "Eastman #910" (later "Eastman 910").

During the 1960s, Eastman Kodak sold cyanoacrylate to

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.[4] As of 2019 Permabond continued to manufacture the original 910 formula.[5]

Polymerization

Chemical structure of ethyl cyanoacrylate, the precursor to many commercial adhesives

The most common monomer is

viscous or gel-like. More recently, formulations are available with additives to increase shear strength, 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

hydroxide ions), forming long, strong chains, joining the bonded surfaces together. Because the presence of moisture causes the glue to set, exposure to normal levels of humidity in the air causes a thin skin to start to form within seconds, which very greatly slows the reaction; hence, cyanoacrylates are applied as thin coats to ensure that the reaction proceeds rapidly for bonding. 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.

Polymerization of methyl 2-cyanoacrylate

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

A tube of "Super Glue", a cyanoacrylate glue

Medical and veterinary

The arm of a child with a small cut, with a shiny layer of adhesive covering the cut region
An incision wound closed with Dermabond, a cyanoacrylate-based medical adhesive

Cyanoacrylate glue is widely used in human and veterinary medicine.[6] It was in veterinary use for mending bone, hide, and tortoise shell by the early 1970s or before. A cyanoacrylate spray was used in the Vietnam War to reduce bleeding in wounded soldiers until they could be taken to a hospital.[7]

n-Butyl cyanoacrylate has been used medically since the 1970s. In the US, due to its potential to irritate the skin, the

suturing (stitches).[9] Although cyanoacrylates are widely used for sutureless wound repair, "existing adhesives still lack sufficient adhesion strength to completely replace sutures and staples."[6]

Some rock climbers use cyanoacrylate to repair damage to the skin on their fingertips.[10][11] Similarly, stringed-instrument players can form protective finger caps (typically, when they lose their calluses due to inactivity or accidents) with cyanoacrylates. While the glue is not very toxic and wears off quickly with shed skin, applying large quantities of glue and its fumes directly to the skin can cause chemical burns.[12]

While standard "superglue" is 100% ethyl 2-cyanoacrylate, many custom formulations (e.g., 91% ECA, 9% poly(methyl methacrylate), <0.5% hydroquinone, and a small amount of organic sulfonic acid,[13] and variations on the compound n-butyl cyanoacrylate for medical applications[9]) have come to be used for specific applications. There are three cyanoacrylate compounds currently available[where?] as topical skin adhesives. 2-Octyl cyanoacrylate is marketed as Dermabond, SurgiSeal, and more recently LiquiBand Exceed. n-Butyl cyanoacrylate is marketed as Histoacryl, Indermil, GluStitch, GluSeal, PeriAcryl, and LiquiBand. The compound ethyl 2-cyanoacrylate is available as Epiglu.[14]

The ester substituent has several effects upon the biocompatibility of the adhesive. Longer side chains result in higher flexibility of the cured adhesive allowing a better match for the flexibility of skin, and can result in a slower release of formaldehyde after curing.[15] Alkoxy-ethyl substituents have also been investigated and have shown some promise as a medical adhesive.[16]

Forensics

Cyanoacrylate is used as a

latent fingerprints on non-porous surfaces like glass, plastic, etc.[17]
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.

Cosmetics

Cyanoacrylate is used in the cosmetology and beauty industry as an eyelash extension glue, or a "nail glue" for some

eye drops causing accidental injury (chemical eye injury).[18]

Niche and hobbies

Cyanoacrylates are used to assemble prototype

miniatures hobbyists.[19]

Cyanoacrylate glue's ability to resist water has made it popular with marine aquarium hobbyists for fragmenting 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 fragment to grow out. It is 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[20] although the inclusion of phthalic anhydride reportedly counteracts both of these characteristics.[21]

Cyanoacrylate glue is also used frequently in

boiled linseed oil, may be used to control the rate at which the cyanoacrylate cures. Cyanoacrylate 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. Cyanoacrylate glue is also used in the finishing of pen blanks (wooden blanks for turning pens) that have been turned on a lathe by applying multiple thin layers to build up a hard, clear finish that can then be sanded and polished to a glossy finish.

Some hobby applications call for cyanoacrylate glue mixed with inorganic fillers such as baking soda (sodium bicarbonate)[23] and calcium oxide.[24]

Arrow glues

Cyanoacrylate is used in archery to glue fletching to arrow shafts. Some special fletching glues are primarily cyanoacrylate repackaged in special fletching glue kits.[25] Such tubes often have a long, thin metal nozzle for improved precision in applying the glue to the base of the fletching and to ensure secure bonding to the arrow shaft.

Fencing

Cyanoacrylate is used in

epee or foil.[26]

Safety issues

Skin injuries

Cyanoacrylate adhesives may adhere to body parts, and injuries may occur when parts of the skin are torn off.[27][28] Without force, however, the glue will spontaneously separate from the skin in time (up to four days). The glue can also cause chemical burns, and exposed skin should be washed with soap and warm water.[29] Separation can be accelerated by applying vegetable oil near, on, and around the glue.[30] If glue gets in eyes, serious injuries can occur. In any case of adhesives getting in or around the eyes, the eye(s) should be rinsed with lukewarm water for 15 minutes and medical care obtained.[29]

Toxicity

Heating causes

parts per billion. On rare occasions, inhalation may trigger asthma
. There is no singular measurement of toxicity for all cyanoacrylate adhesives because of the large number of adhesives that contain various cyanoacrylate formulations.

The United Kingdom's Health and Safety Executive and the United States National Toxicology Program have concluded that the use of ethyl cyanoacrylate is safe and that additional study is unnecessary.[32] The compound 2-octyl cyanoacrylate degrades much more slowly due to its longer organic backbone (series of covalently bonded carbon molecules) and the adhesive does not reach the threshold of tissue toxicity. Due to the toxicity issues of ethyl cyanoacrylate, the use of 2-octyl cyanoacrylate for sutures is preferred.[33]

Reaction with cotton, wool, and other fibrous materials

Applying cyanoacrylate to some natural materials such as

Material safety data sheets for cyanoacrylate instruct users not to wear cotton (jeans) or wool clothing, especially cotton gloves, when applying or handling cyanoacrylates.[35]

Solvents and debonders

gamma-butyrolactone.[39] Commercial debonders are also available, many based on propylene carbonate
.

Shelf life

Cyanoacrylate adhesives have a short shelf life. Date-stamped containers help to ensure that the adhesive is still viable. One manufacturer supplies the following information and advice:

When kept unopened in a cool, dry location such as a refrigerator at a temperature of about 55 °F (13 °C), the shelf life of cyanoacrylate will be extended from about one year from manufacture to at least 15 months. If the adhesive is to be used within six months, it is not necessary to refrigerate it. Cyanoacrylates are moisture-sensitive, and moving from a cool to a hot location will create condensation; after removing from the refrigerator, it is best to let the adhesive reach room temperature before opening. After opening, it should be used within 30 days. Open containers should not be refrigerated.

freezer, and allowing the contents to reach room temperature before use.[42]
Opening a container while chilled may cause moisture from the air to condense in the container; however, reports from hobbyists suggest that storing cyanoacrylate in a freezer can preserve opened cyanoacrylate indefinitely.

As cyanoacrylates age, they polymerize, become thicker, and cure more slowly. They can be thinned with a cyanoacrylate of the same chemical composition with lower viscosity.[31] Storing cyanoacrylates below 0 °F (−18 °C) will nearly stop the polymerization process and prevent aging.

References

  1. .
  2. ^ US 2467927, Alan E. Ardis, "Preparation of monomeric alkyl alpha-cyano-acrylates", issued 19 April 1949, assigned to B.F. Goodrich Company. 
  3. ^ "Inventor of the Week Archive". Lemelson-MIT Program. September 2004. Archived from the original on 3 May 2009. Retrieved 21 September 2021.
  4. ^ HBS, "Loctite Corporation: Industrial Product Group," 15 July 1991, p.3
  5. ^ "Permabond 910 Technical Datasheet" (PDF). www.permabond.com. 6 August 2020. Retrieved 22 August 2021.
  6. ^
    S2CID 231761847
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  7. ^ Harris, Elizabeth A. (28 March 2011). "Harry Coover, Super Glue's Inventor, Dies at 94". The New York Times. Retrieved 30 June 2018.
  8. S2CID 29869951
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  10. ^ "Bouldering" Archived 27 November 2010 at the Wayback Machine. climbingaction.com. Retrieved 19 February 2011.
  11. ^ Anahad O'Connor (4 December 2007). "The Claim: Super Glue Can Heal Wounds". The New York Times. Retrieved 19 February 2011.
  12. ^ "Document: Cyanoacrylate adhesives (GOLD)". Chemwatch.
  13. ^ Safety data for ethyl cyanoacrylate Archived 11 February 2009 at the Wayback Machine from the Physical and Theoretical Chemistry Laboratory of the University of Oxford
  14. ^ "Topical skin adhesives. DermNet NZ". www.dermnetnz.org. Retrieved 29 June 2016.
  15. PMID 27322731
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  16. .
  17. ^ Eric W. Brown "The Cyanoacrylate Fuming Method" Archived 20 October 2007 at the Wayback Machine
  18. PMID 11302128
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  19. ^ "Metal adhesive guide". Adhesiveplatform.com. Retrieved 20 May 2020.
  20. .
  21. .
  22. ^ "Fine Woodworking: Super Glue to the Rescue". 30 March 2016. Retrieved 30 June 2018.
  23. ^ "Propeller Field Repair". www.eaavideo.org. Archived from the original on 31 January 2018. Retrieved 30 January 2018.
  24. ^ "S-FIXX APX4 Ultra Strength Superglue Adhesive and Powders Kit".[permanent dead link]
  25. ^ "ds-archery". ds-archery. website. Retrieved 11 January 2017.
  26. ^ "Leon Paul Fencing || Foil Tip Maintenance". YouTube.
  27. PMID 21481658
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  28. .
  29. ^ a b "Super Glue". Missouri Poison Center. Retrieved 21 April 2023.
  30. ^ "7 methods to get super glue off the skin". www.medicalnewstoday.com. 31 October 2018. Retrieved 4 February 2024.
  31. ^ a b "CA PLUS Adhesives, Inc". Archived from the original on 8 July 2011. Retrieved 3 August 2009.
  32. ^ Methyl Cyanoacrylate and Ethyl Cyanoacrylate from inchem.org
  33. PMID 6683097
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  34. .
  35. ^ "Material Safety Data Sheet" (PDF). accumetricinc.com. Archived from the original (PDF) on 19 February 2009. Retrieved 9 June 2008.
  36. S2CID 21241200
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  37. ^ "BSI Un-Cure Safety Data Sheet" (PDF). bsi-inc.com. Retrieved 10 January 2021.
  38. S2CID 33126572
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  39. .
  40. ^ Palm Labs Adhesives: Cyanoacrylate Adhesive Shelf Life Archived 14 July 2014 at the Wayback Machine
  41. ^ "MASTER BOND MB SERIES CYANOACRYLATES: Technical Data Sheet" (PDF).
  42. ^ "WEICON Contact Cyanoacrylate Adhesives". Archived from the original on 25 May 2014.

Further reading

External links