A manufactured fiber in which the fiber-forming substance is any long chain synthetic polymer composed of at least 85% by weight of an ester of dihydric alcohol and terephthalic acid (FTC definition). The polymer is produced by the reaction of ethylene glycol and terephthalic acid or its derivatives. Fiber forms produced are filament, staple, and tow. The process of production resembles that of nylon. temperature, using a vacuum by one of two methods. (1) The glycol and a terephthalate ester react to form a polymer chain, releasing methanol; or (2) the glycol and terephthalic acid react directly to form the polymer with water as the by-product. As with nylon, the filaments are spun in a melt-spinning process, then stretched several times their original length, which orients the long chain molecules and gives the fiber strength.