Nylon 66

Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing 6 carbon atoms, hexamethylenediamine and adipic acid, which give nylon 66 its name. Aside from its superior physical characteristics, nylon 66 is attractive because its precursors are inexpensive. Hexamethylenediamine (top) and adipic acid (bottom), monomers used for polycondensation of Nylon 66. Nylon 66 is synthesized by polycondensation of hexamethylenediamine and adipic acid. Equivalent amounts of hexamethylenediamine and adipic acid are combined in water. In the original implementation, the resulting ammonium/carboxylate salt was isolated and then heated either in batches or continuously to induce polycondensation.n(HOOC - (CH2)4 - COOH) + n(H2N - (CH2)6 - NH2) -> [-OC - (CH2)4 - CO - NH - (CH2)6 - NH - ]_n + (2n - 1)H2O Removing water drives the reaction toward polymerization through the formation of amide bonds from the acid and amine functions. Alternatively, the polymerization is conducted on a concentrated aqueous mixture formed of hexamethylenediamine and adipic acid. It can either be extruded and granulated at this point or directly spun into fibers by extrusion through a spinneret (a small metal plate with fine holes) and cooling to form filaments. In 2011 worldwide production was two million tons. At that time, fibers consumed just over half of production and engineering resins the rest. It is not used in film applications as it cannot be biaxially oriented. Fiber markets represented 55% of the 2010 demand with engineering thermoplastics being the remainder. Nylon 66 is frequently used when high mechanical strength, rigidity, good stability under heat and/or chemical resistance are required. It is used in fibers for textiles and carpets and molded parts. For textiles, fibers are sold under various brands, for example Nilit brands or the Cordura brand for luggage, but it is also used in airbags, apparel, and for carpet fibres under the Ultron brand.