POLYAMIDES (Nylon Fibers)

Polyamides are the second largest group of synthetic fibers after polyesters.

However, they were the first synthetic fibers that appeared in the market in 1940. This was the result of the work of W. H. Carothers in USA who developed nylon 66. At about the same time nylon 6 was also developed in Germany by I. G. Farben. Both of these nylons still dominate the market for polyamides. However, due to patent restrictions and raw materials considerations, nylon 66 is most extensively produced in USA and nylon 6 is most extensively produced in Europe.

Numbers that follow the word “nylon” denote the number of carbons present within a repeating unit and whether one or two monomers are being used in polymer formation. For nylons using a single monomer such as nylon 6 or nylon 12, the numbers 6 and 12 denote the number of carbons in caprolactam and laurolactam, respectively. For nylons using two monomers such as nylon 610, the first number, 6, indicates the number of carbons in the hexamethylene diamine and the other number, 10, is for the second monomer sebacic acid. Polyamides are produced by the reaction between a dicarboxylic acid and a diamine (e.g., nylon 66), ring openings of a lactam, (e.g., nylon 6) or by the polymerization of w-amino acids (e.g., nylon 11). The production of some important nylons is discussed in the following sections.