P 1957 (OTTO) Poly(1,4-butylene terephthalate) Cas 24968-12-5 - used for housings in electrical engineering, but also in automotive construction as plug connectors and in households for example in showerheads or irons. It is also found processed into fibers in toothbrushes, false eyelashes and is used in the keycaps of some high end computer keyboards because the texture is highly resistant to wear and discoloration due to UV radiation.