Polytetrafluoroethylene

Polytetrafluoroethylene is better known by the trade name Teflon®. It's used to make non-stick cooking pans, and anything else that needs to be slippery or non-stick. PTFE is also used to treat carpets and fabrics to make them stain resistant. What's more, it's also very useful in medical applications. Because human bodies rarely reject it, it can be used for making artificial body parts.

Polytetrafluoroethylene, or PTFE, is made of a carbon backbone chain, and each carbon has two fluorine atoms attached to it. It's usually drawn like the picture at the top of the page, but it may be easier to think of it as it's drawn in the picture below, with the chain of carbon atoms being thousands of atoms long. 

PTFE is a vinyl polymer, and its structure, if not its behavior, is similar to polyethylene. Polytetrafluoroethylene is made from the monomer tetrafluoroethylene by free radical vinyl polymerization.

And for those of you who are wondering, the monomer tetrafluoroethylene looks like this:

Fluorine is a very strange element. When it's part of a molecule, it doesn't like to be around other molecules or even the fluorine atoms on other molecules. But it likes other kinds of molecules even less. So a molecule of PTFE, being just chock full of fluorine atoms as it is, would like to be as far away from other molecules as it can get. For this reason, the molecules at the surface of a piece of PTFE will repel the molecules of just about anything that tries to come close to it. This is why nothing sticks to PTFE.

Because it's non-stick, PTFE means you can fry things without grease or butter. This means less fat and cholesterol, for a healthier heart.

he question remains then: If nothing will stick to this stuff, how does it stick to the surface of the frying pan? DuPont knows, but they're not telling!

So, a while back we had a "What do you think?" section here, and we asked: "If you were designing frying pans, and you had to make non-stick PTFE stick to frying pans, how would you do it?"

We received a bunch of neat ideas from nice smart people just like you. You can read some of the ideas and our input, too, right here.

Before you go there, though - think about it first - how would you get PTFE to stick to the pan? (And here's a hint: melting PTFE doesn't help. First, because you'd have to heat it to over 300 o to melt it, which is impractical for making something cheap like frying pans. Second, melting PTFE doesn't make it stickier. It just turns form a solid that nothing sticks to into a molten goo that nothing sticks to. And a third hint, roughening the surface of the pan won't help, either, because that only increases the area of the two surfaces which will repel each other, increasing the repulsive force.)

How to be Inert

PTFE is more than just slippery. It's also useful because it won't react with anything. Why, you ask? First of all, if it repels everything, then no molecule can get near it to react with it! PTFE is kind of like a sad person who tries protect him or herself from emotional pain by never opening up to anyone.

Then there's the fact that the bond between the fluorine atom and the carbon atom is just really, really strong. The bond is almost bullet proof! It's so stable that nothing will react with it. Even when it gets as hot as a frying pan, not even oxygen will react with it!

Polytetrafluoroethylene is another of those amazing accidental discoveries of science. In the late 1930s, when PTFE was discovered in DuPont's laboratories, DuPont was not at all concerned with nonstick frying pans or artificial heart valves. What they were really interested in was refrigeration. At the time, refrigerators used things like ammonia and sulfur dioxide as refrigerants. These are pretty nasty things to have leaking out of your refrigerator and into your kitchen. The quest was on, then, to make a non-toxic refrigerant. One of the compounds being investigated was tetrafluoroethylene.

One chemist at DuPont who was working on the project was named Roy Plunkett. Know him? He once had a roommate named Paul Flory. One day Roy Plunkett opened up a brand new tank of tetrafluoroethylene gas, and nothing came out! He weighed it, and sure enough it was full. So he sawed the tank open and found a white powder where the gas was supposed to be. That powder, of course, was PTFE, polymerized from tetrafluoroethylene gas.

This is the kind of accident that makes science fun. There are kinds of accidents in science which aren't fun, say, those that involve large explosions and huge clouds of toxic gasses, but we won't talk about those right now. The fun kind of accident, which all scientists hope for, is an unexpected discovery which opens up a whole new area of investigation. This kind makes you famous and gets you lots of research grants, if you work at a university. If you work for a chemical company, it makes a lot of money for the corporate shareholders, and then you get to keep your job when downsizing time comes.