PTFE

PTFE was discovered accidentally in 1938 by a young scientist looking for something else. Roy Plunkett was a chemist for Du Pont whose area was refrigerants. Many chemicals that were used as refrigerants before the 1930s were dangerously explosive.
Du Pont and General Motors had developed a new type of non-flammable refrigerant, a form of Freon called refrigerant 114. Refrigerant 114 was tied up in an exclusive arrangement with General Motor's Frigidaire division, and at the time could not be marketed to other manufacturers. Plunkett endeavored to come up with a different form of refrigerant 114 that would get around Frigidaire's patent control. The technical name for refrigerant 114 was tetrafluorodichloroethane. Plunkett hoped to make a similar refrigerant by reacting hydrochloric acid with a compound called tetrafluoroethylene, or TFE.
TFE itself was a little known substance, and Plunkett decided his first task was to make a large amount of this gas. The chemist thought he might as well make a hundred pounds of the gas, to be sure to have enough for all his chemical tests, and for toxicological tests as well. He stored the gas in metal cans with a valve release, much like the cans used commercially today for pressurized sprays like hair spray. Plunkett kept the cans on dry ice, to cool and liquefy the TFE gas. His refrigerant experiment required Plunkett and his assistant to release the TFE gas from the cans into a heated chamber. On the morning of April 6, 1938, Plunkett found he could not get the gas out of the can. To Plunkett and his assistant's mystification, the gas had transformed overnight into a white, flaky powder. The TFE had polymerized.

Polymerization is a chemical process in which molecules combine into long strings. One of the best known polymers is nylon, which was also discovered by researchers at Du Pont. Polymer science was still in its infancy in the 1930s. Plunkett believed that TFE could not polymerize, and yet it had somehow done so. He sent the strange white flakes to Du Pont's Central Research Department, where teams of chemists analyzed the stuff. The polymerized TFE was curiously inert. It did not react with any other chemicals, it resisted electric currents, and it was extremely smooth and slick. Plunkett was able to figure out how the TFE gas had accidentally polymerized, and he took out a patent for the polymerized substance, polytetrafluoroethylene, or PTFE.

PTFE was initially expensive to produce, and its value was not clear to Plunkett or the other scientists at Du Pont. But it came into use in World War II, during the development of the atomic bomb. Making the bomb required scientists to handle large amounts of the caustic and toxic substance uranium hexafluoride. Du Pont provided PTFE-coated gaskets and liners that resisted the extreme corrosive action of uranium hexafluoride. Du Pont also used PTFE during the war for making nose cones of certain other bombs. Du Pont registered the trademark name Teflon for its patented substance in 1944, and continued to work after the war on cheaper and more effective manufacturing techniques. Du Pont built its first plant for the production of Teflon in Parkersburg, West Virginia in 1950. The company marketed Teflon after the war's end as a coating for machined metal parts. In the 1960s, Du Pont began marketing cookware coated with Teflon. The slick Teflon coating resisted the stickiness of even scorched food, so cleaning the pans was easy. The company marketed Teflon for a variety of other uses as well. Other related fluoropolymers were developed and marketed in ensuing decades, some of which were easier to process than PTFE. Du Pont registered another variant of Teflon in 1985, Teflon AF, which is soluble in special solvents.