How was Teflon discovered?

Answer

Chemist Roy Plunkett found a gas cylinder had turned into a waxy white solid, polytetrafluoroethylene.

Context

In April 1938, Roy Plunkett, a young chemist at DuPont's Jackson Laboratory in New Jersey, was investigating new refrigerant gases based on fluorine. He had stored tetrafluoroethylene gas in pressurized cylinders. When he opened one, no gas came out even though the weight of the cylinder indicated it was not empty. Cutting it open, he found a white, waxy powder inside: the gas had polymerized, with the molecules linking into long chains of polytetrafluoroethylene, or PTFE.

The new material turned out to have unusual traits. It was extremely slippery, resisted attack by nearly all chemicals, and withstood high temperatures. The slipperiness comes from the strong carbon-fluorine bonds and the sheath of fluorine atoms around the carbon backbone, which makes it very unreactive. DuPont patented it and trademarked the name Teflon.

Its first major use was secret: during World War II it was used in the Manhattan Project for gaskets and coatings that could tolerate corrosive uranium hexafluoride. Cookware coated with PTFE appeared in the 1950s and 1960s. Later, concerns about related fluorinated chemicals used in manufacturing, notably PFOA, led to regulatory action and phase-outs; that issue concerns production chemicals, and a separate question from the PTFE polymer itself.