One of the common justifications for the space race was that mankind benefited from the technology spin-offs. ‘Teflon’ is the usually quoted as an example. Everyone knows what ‘Teflon’ is, right? Nothing sticks to it – that’s what people say. But what exactly is it? What gives it those non-stick and other useful properties?
‘Teflon’ is a proprietary brand name. It actually pre-dates the space race by almost 30 years. It was invented as long ago as 1938 by Roy Plunkett at DuPont (which owns the brand name). Invented is perhaps the wrong word – it was observed during some other research, in much the same way that penicillin was discovered.
The word ‘Teflon’ has passed into our everyday lexicon and is used to describe anything slippery – especially politicians, of whom Ronald Reagan was the first to enjoy the dubious distinction.
What Properties Make Teflon Non-Stick?
Teflon is DuPont’s Tradmarked brand name for PTFE – polytetrafluoroethylene, a polymer. It is a long chain polymer, one of the biggest known to science. It is a solid fluorocarbon, and is hydrophobic. This means that it ‘rejects’ water. It is very stable and inert, due the high strength of the carbon-fluorine bonds, but its properties do degrade with temperature.
‘Slipperiness’ is measured by a material’s coefficient of friction. It has a ‘waxy’ feeling to the touch. Only two other solids are more slippery – aluminium magnesium boride, and diamond. Both these are very hard materials, unlike PTFE.
‘Stickiness’ is due to what are known as Van Der Waals forces. These forces operate at a molecular level between materials. They give the Gecko its ability to climb walls – unless of course they are coated with Teflon. Teflon is unique in this respect. The pads on a Gecko’s feet have a relatively high Van der Waals force (actually a sum of three different forces), but Teflon’s are very low. So, there is little attraction – or ‘stickiness’.
Its other properties include ‘creep’. This is the ability to stretch without relaxing to its previous dimensions when strain is removed. It makes PTFE ideal for seals. Hence, it is loved by plumbers. (ie Tape Dope)
It is subject to wear where surfaces have regular relative movement, despite its slippery nature. It is now being combined with lubricants such as molybdenum disulphide which result in advanced composites which are ideal for hi-tech bearings typically used in aerospace applications.
Uses of Teflon
Its early uses focused on its chemical inertness and creep – it was used for gas-tight seals in the production of enriched uranium for the first atomic bomb in 1945.
Since then, many other interesting properties have been identified. The list of applications is amazingly wide:
- Gore-Tex, a water repellent materials used for outdoor clothing and even as a roofing material.
- Rocket ignition and flares – when mixed with certain combustible compounds, it can act as a catalyst.
- Instruments in optical and radio physics – it has useful properties relating to its ability to diffuse electromagnetic radiation.
- As an electrical insulator in cables, circuit boards and other components
- Coating bullets – this reduces wear of the rifling in a gun’s barrel and prolongs life (and reduces corrosion).
- Incinerators – used as a cleaning agent in heat exchangers
- Lab containers and chemical transport systems – anti corrosive and inert, it protects containers from attack by the chemicals they hold
- Air filtration systems to remove dust.
- Insect containment – used to prevent climbing insects from escape (or entry)
- Cooking utensils – the first one was created in France in 1954.
Carcinogenic by-products can be released when it is heated beyond 260 Centigrade. This rarely happens in practice.
DuPont’s original production process used a toxic chemical known as PFOA but alternatives are now available and the use of the chemical is being phased out.
The Future of Teflon
New uses are still being found for it, and its utility is being extended by combining it with other chemicals.
China is now the world’s biggest producer (and consumer). DuPont produced 900 tons a year in 1948 and worldwide production is forecast to reach 240,000 tons by 2017. So, despite its properties, Teflon is likely to stick with us for many years to come.