Super glue, commonly known by its chemical name, cyanoacrylate, is a fast-acting and powerful adhesive used across industrial, medical, and household applications. This liquid adhesive is an acrylic resin that forms a powerful bond almost instantly. Cyanoacrylate’s strength often leads people to wonder how it interacts with the most common of solvents, water. Understanding the unique chemistry of this glue is key to knowing why it behaves the way it does when exposed to moisture and what is required to break the bond.
The Direct Answer: Water Does Not Dissolve Super Glue
Water does not dissolve cured super glue. Once the liquid cyanoacrylate sets, it transforms into a solid polymer that is inherently hydrophobic, meaning it repels water. This cured state is chemically resistant, allowing the adhesive to maintain its strength even when submerged or exposed to high humidity.
Cured super glue is a tough, plastic-like substance. Water molecules lack the necessary chemical properties to break apart its long, interconnected polymer chains. This water resistance makes it an effective choice for repairs that might encounter moisture. Soaking in warm, soapy water can help weaken the physical bond by making the hardened polymer more brittle, but mechanical force, not the dissolving power of the water, aids in separation.
The Role of Moisture in Curing
Water plays an opposite role in the initial setting process of super glue, acting not as a solvent but as a catalyst. Cyanoacrylate adhesives rely on anionic polymerization to cure, initiated by the presence of a weak base. The hydroxyl ions found in trace amounts of water are the initiators for this reaction.
When the liquid adhesive is applied, cyanoacrylate monomers react with moisture present on the surfaces or ambient humidity. This reaction causes the small monomer molecules to link together rapidly, forming long, strong polymer chains that create the solid bond. The process is sensitive; the natural moisture on human skin is enough to cause the glue to set almost instantly.
Optimal curing occurs when the relative humidity is between 40% and 60%. Lower humidity slows the reaction, while excessively high humidity can lead to a less stable, weaker bond. This dependence on moisture explains why super glue is a one-part, solvent-free adhesive that does not require mixing or the evaporation of a carrier fluid. The water is consumed in the polymerization process, transforming the liquid into a water-resistant solid.
What Solvents Actually Break Down Cyanoacrylate?
Since water cannot break down cured cyanoacrylate, specific solvents are required to return the hardened polymer to a manageable state. The most effective and commonly available solvent is acetone, a powerful organic compound often found in nail polish remover. Acetone works by attacking the long polymer chains of the cured glue, causing them to soften, swell, and dissolve.
Commercial super glue removers are often used to break down cyanoacrylate bonds, typically containing acetone or another strong solvent like propylene carbonate. Other industrial-strength solvents, such as nitromethane, dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP), are also effective at dissolving the cured adhesive. These compounds are generally harsher and not readily available to the average consumer.
When using any strong solvent like acetone, it is important to exercise caution, as these chemicals can damage or permanently mar many materials, especially various types of plastics and varnished surfaces. Prolonged contact with the skin should be avoided, and the solvent should be applied only to the affected area to minimize the risk of damaging the underlying material.