Synthetic Fibers
. Synthetic fibers derived from natural cellulose were first developed at the end of the 19th century and became known as rayons . In a typical rayon-making process, natural cellulose made from wood pulp is treated with chemicals to form a thick liquid. This liquid is then extruded as filaments into a weak acid bath that converts the filaments back into pure cellulose. Rayons are not, therefore, completely synthetic but are actually regenerated fibers. Acetates and triacetates, which are true synthetic fibers, were developed shortly after rayon. They are derived from cellulose acetate (see Esters ) in a process similar to that used for making rayon. Most synthetic fibers are now derived from organic polymers , materials consisting of large organic molecules. Most of them are thermoplastic—that is, they are softened by heat. The first commercially successful organic synthetic fiber, nylon (polyamide), dates from 1938. Since then many other fibers, including acrylic (polyacrylonitrile)