<P> Currently, Kevlar has many applications, ranging from bicycle tires and racing sails to body armor, because of its high tensile strength - to - weight ratio; by this measure it is 5 times stronger than steel . It is also used to make modern drumheads that withstand high impact . When used as a woven material, it is suitable for mooring lines and other underwater applications . </P> <P> A similar fiber called Twaron with roughly the same chemical structure was developed by Akzo in the 1970s; commercial production started in 1986, and Twaron is now manufactured by Teijin . </P> <P> Poly - paraphenylene terephthalamide--branded Kevlar--was invented by Polish - American chemist Stephanie Kwolek while working for DuPont, in anticipation of a gasoline shortage . In 1964, her group began searching for a new lightweight strong fiber to use for light but strong tires . The polymers she had been working with at the time, poly - p - phenylene - terephthalate and polybenzamide, formed liquid crystal while in solution, something unique to those polymers at the time . </P> <P> The solution was "cloudy, opalescent upon being stirred, and of low viscosity" and usually was thrown away . However, Kwolek persuaded the technician, Charles Smullen, who ran the spinneret, to test her solution, and was amazed to find that the fiber did not break, unlike nylon . Her supervisor and her laboratory director understood the significance of her accidental discovery and a new field of polymer chemistry quickly arose . By 1971, modern Kevlar was introduced . However, Kwolek was not very involved in developing the applications of Kevlar . </P>

Which of the following is not a product that has been made with kevlar