How Super Glue is Made

Super Glue, also Known as Cyanoacrylate (CA), is One of the Five Types of Glue

 

Photo of Super GlueWinter is the perfect time to fix what’s broken inside your home. For quick jobs that require bonding two surfaces (like a broken coffee mug handle), super glue is a common and simple solution.

Of course, super glue isn’t restricted to winter, nor the home. It bonds a wide variety of materials (including fingers) in residential, commercial, medical and industrial applications. From broken eyeglasses to car parts to coffee mugs, super glue provides inexpensive, hassle-free surface bonding wherever – and whenever – you need it.

While many have used super glue, few are likely familiar with its origin, chemical composition or manufacturing process. This In The Mix blog takes a closer look at the history of super glue and how it is made.

What is Super Glue?

There are currently five types of glue: solvent-based, water-based, two-part, animal hide and cyanoacrylate (CA). Super glue is the latter, which is made from synthetic polymers, reacts with moisture on material surfaces and in the air, and is very strong.

Other than the need for moisture, the bonding properties of CA glues aren’t well understood. They are unlike most glues which bond using microscopic hooks and eyes (think Velcro). One theory suggests the polymers in CA glues bond by using the same electromagnetic force that holds all atoms together:

  • A sizeable mass of one substance will electronically repel any other substance.
  • Two atoms of different substances placed in very close proximity will exert a mutually attractive force.

These forces likely explain why a thin film of CA glue works better than a thicker one. When a thin film is applied, electromagnetic forces take over because the materials the CA is bonding are extremely close. A thicker layer of CA does not hold as well because molecules repel one another.

The History of Super Glue
Photo of film roll

Scientists at Kodak, known for it’s photography film and equipment, accidently rediscovered CA during a failed light refraction experiment in the 1950s.

The B.F. Goodrich Company filed the original patent for CA in 1942 for potential applications related to World War II gun sights. Roughly ten years later, Kodak scientists rediscovered CA during a light refraction experiment. The experiment ruined an expensive piece of equipment and was initially deemed a failure. However, the scientists examined the results more closely and discovered they accidently invented a new adhesive.

Kodak took the new adhesive to market in the late 1950s. Many others have entered the CA market since, while Kodak dropped out in the 1960s after selling its CA glue to Loctite.

How Super Glue is Made

CA glues are produced in heated kettles with revolving blades. The kettles can hold several thousand gallons in large scale production environments. Regardless of the production scale, typical CA manufacturing steps include:

  1. Ethyl cyanoacetate is mixed in a kettle with formaldehyde. This triggers condensation, a chemical reaction that produces water.
  2. The kettle is then heated to evaporate the water.
  3. To prevent the CA from curing, nitrogen or another nonreactive gas is added to the kettle to fill the void left by evaporation.
  4. The kettle is reheated to cause thermal cracking of the polymer and create reactive monomers. The monomers are lighter than air and rise. When the finished glue is applied, the monomers recombine to form a bond.
  5. The monomers are piped out of the kettle through a series of cooling coils to form a liquid, which is collected in a second vessel. The process is similar to distilling.
  6. Various chemicals called free radical inhibitors and base scavengers are added to the second vessel (which is effectively the CA) to prevent hardening.
  7. Additives may be used to change the viscosity of the CA for specific applications or to bond materials that earlier CAs could not (e.g., wood).
  8. The CA is put in humidity-free, polyethylene (and sometimes aluminum; other metals may react) tubes for retail sale. If any of the CA is exposed to moisture or an alkaline, the monomers will repolymerize and harden.

As one might expect, quality control is critical in CA production. Should the polymerization of monomers occur at any time, it can’t be stopped until all the glue is polymerized – and potentially thousands of gallons of product are ruined.

For More Information

ProQuip tank agitators are used to manufacture adhesives. For more information on ProQuip mixing solutions for adhesive manufacturing, email applications@proquipinc.com or call us at 330-468-1850.

Sources: Wikipedia, How Products are Made , Starbond