Roy Plunkett with Teflon insulated cable.
DuPont Company
By Jeff Glorfeld
When New Scientist magazine profiled “eight great accidents in scientific discovery” in 2017 it included such unlikely events as a melting chocolate bar leading to the first microwave oven, and how an attempt to develop an insecticide instead came up with an artificial sweetener.
Also on the list was US research chemist Roy Plunkett’s accidental discovery of the material now universally known as Teflon – a story well worth telling.
Born on 26 June 1910 in Ohio, Plunkett studied chemistry and earned a doctoral degree from Ohio State University in 1936. He immediately went to work for the DuPont chemical company in New Jersey, where he remained for his entire working career.
One of his first assignments was to find a non-toxic, non-flammable coolant to be used in refrigerators.
A biography of Plunkett published by the Science History Institute describes how, in 1938, he was researching new chlorofluorocarbon refrigerants, regarded as potential replacements for products such as sulfur dioxide and ammonia, “which regularly poisoned food-industry workers and people in their homes”.
He had produced a quantity of tetrafluoroethylene gas (TFE) and stored it in small cylinders at dry-ice temperatures (minus 78.5 degrees Celsius) before chlorinating it, but when he and his assistant started to prepare a cylinder for use, “none of the gas came out – yet the cylinder’s weight was unchanged”.
“They opened it and found a white powder, which Plunkett had the presence of mind to characterise for properties other than refrigeration potential. He found the substance to be heat-resistant and chemically inert, and to have very low surface friction so that most other substances would not adhere to it.”
Plunkett saw that the TFE had polymerised – “against the predictions of polymer science of the day” – to produce a substance “with such potentially useful characteristics”. He called his discovery polytetrafluoroethylene (PTFE) and received a patent for it in 1941.
DuPont then handed it to scientists with specific experience in polymer research and development to investigate the substance further, while Plunkett moved onto a team developing tetraethyl lead as an additive to boost octane levels in gasoline.
Teflon was trademarked in 1945, but despite its qualities it was expensive to produce, and at the time its value seemed limited to industrial uses.
According to the World of Molecules website, it was important in no less than the Manhattan Project, being used to coat valves and seals in pipes holding highly reactive uranium hexafluoride at the uranium enrichment plant at Oak Ridge, Tennessee.
Teflon might have remained just a functional coating for military and industrial products if not for the French engineer Marc Gregoire, who in 1954 found a way to bond PTFE to aluminium.
At the urging of his wife Colette, who had seen him using the slippery material on his fishing tackle, Gregoire coated aluminium cookware with PTFE. In 1956 they founded the Tefal Corporation, selling coated kitchenware in France.
In 1960 the US Food and Drug Administration approved PTFE for food processing equipment.
Plunkett, meanwhile, became a divisional director of operations at DuPont, before retiring in 1975.
A popular speaker at events, he told audiences that his Teflon “accident” came about because his mind “had been prepared for the challenge by years of education, and that he had succeeded because he was trained to recognise novelty”.
He died on 12 May 1994.