Ethyl cyanoacrylate (ECA) is the primary active ingredient in what is commonly known as “super glue” or instant adhesive. This colorless, low-viscosity liquid forms an exceptionally strong bond almost instantaneously upon contact with moisture. Its rapid curing time and impressive adhesive strength have made it a ubiquitous fixture in households and industries globally. ECA functions chemically, relying on a fast reaction to transition from a liquid monomer to a solid polymer, creating a durable bond.
The Chemical Identity and History
Ethyl cyanoacrylate (ECA) is an acrylic resin monomer belonging to the cyanoacrylate family, with the molecular formula C6H7NO2. It is an ester of 2-cyano-acrylic acid, and its structure makes it highly reactive. The compound was first discovered unexpectedly in 1942 by chemist Harry Coover Jr. while working on a wartime project at B.F. Goodrich. The team was synthesizing clear plastics for gun sights, but the resulting sticky formula was initially dismissed.
The compound was rediscovered in 1951 when Coover, then at Eastman Kodak, was researching heat-resistant polymers for jet canopies. A colleague, Fred Joyner, accidentally glued two glass prisms together while testing the substance. Coover recognized its commercial potential, and after further development, the adhesive was introduced to the public in 1958 under the trade name “Eastman 910.”
The Mechanism of Instant Bonding
The fast-acting nature of ethyl cyanoacrylate results from a chemical process called anionic polymerization. The liquid adhesive consists of small molecules, called monomers, which are stabilized by an acidic inhibitor added during manufacturing. Polymerization begins when the liquid contacts trace amounts of a weak base. In most scenarios, this weak base is the hydroxyl ion (OH-) found in water molecules present in atmospheric humidity or on surfaces.
The hydroxyl ion attacks the carbon double bond in the cyanoacrylate monomer, immediately starting a rapid chain reaction. Monomers link together, transforming the liquid into long, strong polymer chains. This highly efficient process occurs within seconds, transitioning the adhesive to a solid, plastic-like state. Cyanoacrylate adhesives must be applied in a thin layer to ensure moisture can effectively reach and trigger all the adhesive molecules.
The reason ethyl cyanoacrylate bonds readily to human skin is the abundant presence of natural moisture and oils on the surface. This moisture acts as the perfect catalyst, instantly initiating the polymerization process upon contact. The hydroxyl ions are immediately available to trigger the chain reaction, linking the resulting polymer to the skin’s microscopic crevices. This rapid curing process is also exothermic, releasing a small amount of heat as the bond forms.
Commercial and Specialized Applications
Ethyl cyanoacrylate’s speed and strength have led to its adoption across a vast range of commercial and specialized fields. In the consumer market, it is the main component in general-purpose household adhesives, sold in small tubes for quick repairs of plastic, metal, rubber, and ceramic items. It is also popular in the cosmetic industry, used as the adhesive base for false nail application and professional eyelash extensions.
Industrially, ECA is a mainstay in manufacturing processes, especially for assembling small or complex parts. It is widely used in the electronics industry for securing components on circuit boards and in the automotive sector for bonding various plastics and rubbers. Its versatility streamlines production by eliminating the need for mechanical fasteners or heat curing.
While ECA was historically used in early medical applications, its short-chain chemical structure causes it to degrade relatively quickly, releasing trace amounts of formaldehyde that can cause tissue irritation. Therefore, medical-grade tissue adhesives, often referred to as “liquid stitches,” typically use longer-chain cyanoacrylates such as octyl or butyl cyanoacrylate. These variants are preferred in clinical settings because their longer molecular chains offer greater flexibility and lower toxicity, making them safer and more compatible for wound closure on living tissue.
Handling Precautions and Removal
Handling ethyl cyanoacrylate requires specific safety precautions due to its rapid polymerization mechanism. The vapors released during curing are irritating to the eyes, nose, and respiratory system. Proper ventilation is recommended when working with the adhesive, especially in confined spaces. Users must avoid eye contact, as the adhesive bonds instantly to the moist surface of the eyeball.
A particular hazard involves contact with fibrous materials like cotton, wool, or leather. This contact can cause a highly accelerated, intensely exothermic reaction. This rapid polymerization generates enough heat to cause a thermal burn or even ignite the material.
If the liquid adhesive bonds instantly to the skin, do not pull the skin apart forcefully, as this can cause tearing. The most effective removal method is using acetone, the primary solvent in many nail polish removers. Acetone chemically breaks down the polymer chains, allowing the adhesive to be gently peeled or rolled off. If acetone is unavailable or the skin is sensitive, soaking the affected area in warm, soapy water or applying petroleum jelly or vegetable oil can soften the bond for removal.