Polyurethanes are a family of plastic materials that were initially developed in Germany between World War I and World War II. The driving force was to develop an alternative to nylon that had been developed in the United States by E.I. du Pont de Nemours and Company. The initial nylon that was developed was a fiber grade. Otto Bayer and his coworkers developed a similar fiber based on different chemistry. After the initial fiber development, polyurethane foams were introduced and used in aircraft during World War II.