How PTFE is made

PTFE is made from chlorodifluoromethane, a widely used refrigerant liquid known as Freon 22. The American engineer Dr Roy Plunkett discovered that heating Freon 22 produces the gas tetrafluoroethene. Under a pressure of about 45-50 atmospheres and in the presence of a peroxide catalyst, this gas undergoes a chemical change, and the result is PTFE […]

How the US Navy launched the zip fastener

The US Navy pioneered the use of zip fasteners in 1918 when it ordered 10,000 of them to do up ‘wind-cheating’ flying suits. The first slide fastener – the ancestor of the zip – had been devised by an American engineer, Whitcomb Judson, in 1893. He designed a ‘clasp locker’ as a quick method of […]

Electronic slot machines

The latest generation of slot machines check coins electronically. As soon as a coin is inserted, its conductance – its ability to pass electric current – is tested. Broadly acceptable coins then pass through a gate and are allowed to run down a ramp and between two magnets. Once again, the speed at which they […]