What Makes Super Glue So Super?
Harry W. Coover receives from the National Medal of Science in the East Room of the White House, November 17, 2010. © Olivier Douliery/Pool/Corbis
Super Glue inventor Dr. Harry Coover died Saturday at his home in Kingsport, Tennessee. He was 94. Matt Soniak looks back at Coover's famous adhesive.
A Sticky Situation
In 1942, American scientists at Kodak Laboratories were looking for materials to make extra-clear plastic gun sights for infantry rifles. Harry Coover and Fred Joyner stumbled upon a few acrylate monomers (esters of acrylic acid that can bind to each other to form chains of molecules) that showed promise, but the monomers stuck to everything they touched. They wouldn’t do any good, so Coover shelved the formulas.
Nine years later, Coover was working at the research labs of the Tennessee Eastman Co., trying to find a tough, heat-resistant material for making jet canopies. He pulled out his old formulas from the war years and gave them another spin. They were, of course, sticky as ever. One researcher spread one of them between the prisms of a machine to see how refractive it was. He got the measurement he needed, but then couldn’t pull the prisms apart. He had to go to Coover with his tail between his legs and report that he had ruined a very expensive instrument. But Coover was delighted—he realized he had a unique adhesive on his hands.
The lab accident became a marketable product in 1958, when Kodak began selling the first cyanoacrylate glue, Eastman #910. Coover himself got to show off the first “super glue” the next year when he went on the TV show I've Got a Secret and used the glue to lift the show’s host completely off of the ground.
Through the years, there have been plenty of cyanoacrylate adhesives, like #910, Loctite Quick Set, Super Bonder, Super Glue and Krazy Glue.
All of these glues get their power from cyanoacrylate polymers. A polymer is what happens when a bunch of monomers get together and attach to each other in repeating units. They form a chain or other structure that resists breaking and grabs any microscopic roughness it can find on other objects it touches. The only trigger cyanoacrylate polymers need to form is water—specifically, the hydroxide ions in it. Since there are minute traces of water on almost any surface, it’s easy for the glue to start a polymeric reaction anywhere. Once this reaction starts, it’s pretty difficult to stop, and the resulting molecular bonds don’t come undone easily.
Super glue can do more than stick things together, and it’s become a valuable tool in law enforcement. When you get cyanoacrylate warmed up, it releases fumes. When these fumes touch the moisture residue from fingerprints, white polymers are formed and fingerprints that might have otherwise been hard to see become plainly visible for analysis.
Speaking of warming cyanoacrylate up, super glue spontaneously combusts when enough of it makes contact with cotton or wool. See it in action here.