PVC and Teflon

The two derivatives of ethene polymerise in the same way as ethene itself.

Polychloroethene — polyvinyl chloride (PVC)

Polychloroethene is formed by the polymerisation of chloroethene. In short:

Polytetrafluoroethene (Teflon)

Polytetrafluoroethene is formed by the polymerisation of tetrafluoroethene. In short:

Why one pattern makes three plastics

Look at the three drawings side by side. The backbone is identical every time — a long chain of carbons joined by single bonds, formed by opening the C=C bond. Only the atoms hanging off the chain change: all hydrogen in polythene, one chlorine in every unit of PVC, all fluorine in Teflon. Those side atoms decide the properties. The chlorine makes PVC stiffer and helps it resist burning; the fluorine clings so tightly to the carbon that almost nothing sticks to or reacts with Teflon. So by choosing the monomer, chemists choose the plastic.

Where you meet them

PVC is the grey or white pipe that carries water to your tap, the conduit that hides electrical wiring along a wall, and the rainwear that keeps you dry. Teflon is the dark, slippery coating inside a non-stick frying pan. Both began as the same kind of small molecule — ethene with some hydrogens swapped — and both became long chains the same way. Notice also how a polymer is named: put poly-, meaning many, in front of the monomer's name. So polythene is many ethenes, polychloroethene many chloroethenes, and polytetrafluoroethene many tetrafluoroethenes.