Guest post by Rowena Fletcher-Wood

Some people are said to be luckier than others, but can the same lucky chance happen twice, to the same person? Harry Coover was a serial inventor, patenting more than 460 inventions in his 94-year life, but his most famous product was discovered by accident.

Superglue in use (©iStock)

In 1951, whilst trying to come up with a heat resistant polymer to make jet canopies from, Harry Coover and Fred Joyner accidentally created a substance that glued two refractometer prisms together with an obstinacy not to be resisted. Joyner began to panic – the prisms were very expensive – but Coover did not: he had seen this reaction before. He had made it.

During the second world war , Coover had been a practising scientist developing clear plastic gun sights. One group of materials he tested were the cyanoacrylates, because they were transparent, but they had proved far too sticky. At the time, Coover had abandoned the persistently sticky cyanoacrylates, but as he said himself, ‘serendipity [gave him] a second chance.’ Knowing chance was unlikely to strike a third time, Coover immediately began investigating the cyanoacrylates – by rushing round the laboratory sticking together everything he could find. Although he probably destroyed a lot of laboratory equipment, he did learn some interesting things about the properties of this ‘super’ glue.

The exothermic process which creates the powerful chemical bonds between materials was a polymerisation reaction, initiated by moisture and, in particular, hydroxide ions. The resultant polymer bonds firmly to the surfaces and to itself, forming a hard, transparent plastic. Cyanoacrylates are so sensitive to moisture that the moisture in the air is enough to make it set hard, and this is why tubes of glue slowly harden, becoming unusable approximately one month after being opened. Under airtight conditions, however, such as an unopened tube or tube left over silica drying beads, superglue stays sticky for a whole year.

Not everything has moisture in it, so not everything bonds to superglue, but most materials do – and when they do the strengths of the chemical bonds are incredible: one radio station who decided to put the product to the test were able to lift a car by using a small area of superglue to attach it to a crane. But tough as it is, it’s not chemically impervious – if you do need to unstick superglue, use acetone (nail varnish remover); acetone depolymerises the superglue, weakening the bond.

Harry Coover also discovered that cyanoacrylate was non-toxic and apparently harmless to humans. This led to another profound discovery: since we naturally have moisture in our bodies, the glue efficiently binds human tissues together. Only a few years after it was patented, superglue was used as an emergency medical spray in the Vietnam War to hold together wounds before soldiers could reach a hospital to receive stitches. It was brought onto the market in 1958.

Only the smallest amount needs to be used, which is in itself lucky, since the exothermic reaction can even cause small burns or ignite cotton wool if used in excess. Medical applications of superglue persist, and new uses have been discovered, such as forensic definition of fingerprints, where fumes of superglue react with the moisture left by fingerprints to produce visible, white prints on surfaces.

It’s hard to say whether Harry Coover’s inventive methods would have inevitably led him back round to cyanoacrylates, or whether luck really did strike the same man twice. A sticky problem.

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