Scientist invented several of the thermoplastics prior to WWII. Some plastics sat on a shelf, trying to find the purpose of their existence while others, such as, nylon found an immediate market. Du Pont invented the miracle fiber nylon, to an enthusiastic crowd during the 1939 World's fair. The Du Pont rep declared it to be stronger than steel. As war broke out, the miracle material was about to help the Allies - it was used for parachutes, cords and airplane tires.