Molecule of the Month: Teflon: The non-stick myth that stuck: Did you think that your hi-tech frying pan was a spin-off from the space race? John Emsley explains that the truth is the other way around
Monday 18 July 1994
This assertion was widely believed, and is currently to be read in adverts for Camel Lights cigarettes. But it is a myth.
In reality it was the non-stick frying pan that made the moon landing possible. We have Teflon to thank for that giant leap, not the other way about.
Teflon is one of the trade names for the polymer PTFE (short for polytetrafluoroethylene) that had first been made 30 years before the moon visit. It was discovered by a 27-year-old chemist, Dr Roy Plunkett, at the Du Pont research laboratories at Deepwater, New Jersey. Plunkett died in May this year, aged 83. His polymer was destined to change the world - its first big role was in the production of the atomic bombs that fell on Hiroshima and Nagasaki in 1945.
The story began on the morning of 6 April 1938 when Plunkett opened a cylinder of tetrafluoroethylene which he was using to make CFCs. He was puzzled why a cylinder supposedly holding 1,000 grams of the gas only released 990 grams. The explanation was to be found in 10 grams of a curious white powder which he fished out with the help of a piece of wire. Plunkett realised that this was a new polymer, formed when molecules of the gas string together in chains of about 100,000 carbon atoms long, each carbon atom having two fluorine atoms attached.
The new plastic had some remarkable properties: it was not attacked by hot corrosive acids; it did not dissolve in solvents; it could be taken down to -240C without becoming stiff and up to 260C without affecting its performance; it could be heated to over 500C without burning; and it had a peculiarly slippery feel. This was to be the secret of its commercial success, and worldwide production is now about 50,000 tonnes per year, with a value of pounds 400m.
Du Pont named the new plastic Teflon, but it is known by other trade names such as Fluon, the ICI variety. 'All the PTFE manufactured in Britain is Fluon,' says ICI's Dr Glyn Hughes. 'It is made by ICI at Hillhouse, near Blackpool, and we export 80 per cent of our output.' PTFE starts life as the blue mineral fluorspar, which is mined in Derbyshire. Fluorspar is calcium fluoride, which with sulphuric acid yields hydrofluoric acid. When this is reacted with chloroform, and the product is heated to 600C, it forms the tetrafluoroethylene gas from which PTFE is made.
ICI is about to market a new form of PTFE which it calls Fluoroplus, and which, according to Dr Hughes, overcomes many difficulties experienced by the polymer when used in moving parts. PTFE has excellent lubricant features, but can still suffer wear. Fluoroplus is a blend of Fluon and a patented mixture of 'fillers' that prevent this.
The non-stick frying pan was a technological triumph, achieved by Louis Hartmann back in the Fifties. He sought to bond PTFE to aluminium, and found a way to do it: treat the metal surface with acid, apply PTFE as an emulsion, and then bake at 400C for a few minutes. The polymer melts and forms a film over the surface. The French company that solved the problem was Tefal, and it went on to dominate the world's non- stick cookware market. Its first non- stick frying pans went on sale 10 years before the trip to the Moon.
This year also sees the 25th anniversary of the PTFE fabric, Gore-tex. In 1969 Dr Bob Gore found a way of expanding PTFE by heating and stretching the polymer to form a membrane. This created invisible pores in the film - billions per square inch - and these are small enough to keep water droplets out, but big enough to allow water molecules of sweat to escape. The Gore-tex film is sandwiched between the outer fabric and the inner lining and is widely used for wet-weather gear and sportswear.
Gore-tex is ideal for golf suits, but players may also have expanded PTFE inside their bodies as well. Artificial veins and arteries made of Gore-tex are a standard treatment for cardio-vascular disorders.
Other ways in which PTFE enters our everyday life are as fabric roofing for sports arenas; as stain-repellants for clothes, chair-covers and carpets; as plumber's tape for sealing joints in water pipes and central heating; on the underside of irons; and as dental floss. As you read this article your fingers will be picking up PTFE from the page. The scrap PTFE from industry is re-used by grinding it to a microfine powder and adding it to printer's ink to make it flow more smoothly.
Not all PTFE uses have been so innocent. Shortly after its discovery, it was in demand for the Manhattan Project, the aim of which was to make an atomic bomb. Its chemical inertness meant that it could stand up to fluorine gas, the most reactive of all molecules. Large quantities of this were needed to make uranium hexafluoride, from which the fissionable isotope uranium-235 can be extracted. By 1942, and despite its cost, Teflon was being manufactured to make gaskets and other items, and today the chemicals industry relies on PTFE-coated tanks and vessels to hold corrosive chemicals.
Another project where money was of secondary importance was the race into space in the Sixties. The environments of extreme cold, low pressures, and the corroding effects of activated oxygen in the upper atmosphere required a material with unearthly properties, and PTFE was the only plastic suitable for space. Without it there could have been no voyage to the Moon. That this led to the non-stick frying pan is a legend that won't stick.
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