Super glue deserves its name -- a single drop can permanently join your thumb to your index finger faster than you can say "Whoops," and a 1-square-inch bond can hold more than a ton. So how does this remarkable substance work? The answer lies in its main ingredient, cyanoacrylate (C5H5NO2, for you chemistry buffs).
Cyanoacrylate is an acrylic resin that cures (forms its strongest bond) almost instantly. The only trigger it requires is the hydroxyl ions in water, which is convenient since virtually any object you might wish to glue will have at least trace amounts of water on its surface.
White glues, such as Elmer's, bond by solvent evaporation. The solvent in Elmer's all-purpose school glue is water. When the water evaporates, the polyvinylacetate latex that has spread into a material's crevices forms a flexible bond. Super glue, on the other hand, undergoes a process called anionic polymerization. Cyanoacrylate molecules start linking up when they come into contact with water, and they whip around in chains to form a durable plastic mesh. The glue thickens and hardens until the thrashing molecular strands can no longer move.
If you think cyanoacrylate's ability to repair broken knick-knacks is super, wait until you hear about its other tricks. Super-glue fuming is sometimes used in criminal investigations to detect latent fingerprints. It works like this:
- The object to be checked for prints is placed in a heated, airtight container.
- Cyanoacrylate is introduced; it evaporates and is circulated throughout the container by fans.
- The gaseous glue reacts with materials that may have been left behind in fingerprints (such as amino acids and glucose) and makes them visible.
Another interesting application is the use of cyanoacrylate to close wounds in place of stitches. Researchers found that by changing the type of alcohol in super glue, from ethyl or methyl alcohol to butyl or octyl, the compound becomes less toxic to tissue. With further research, the practice may become more widespread and could eventually replace the need for stitching up lacerations.
By the way, if you happen to find yourself in a super-sticky situation, a little bit of acetone nail-polish remover helps to unglue fingers.
Here are some interesting links:
