|Density||1.14 g/mL (Zytel)|
|Melting point||542 K|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
Nylon 6-6, also referred to as nylon 6,6, is a polyamide from nylon class. Nylons come in many types, and the two most common for textile and plastics industries are nylon 6 and nylon 6-6. The polymer is made of hexamethylenediamine and adipic acid, which give nylon 6-6 a total of 12 carbon atoms in each repeating unit, and its name.
Synthesis and manufacturing Nylon 6-6
Nylon 6-6 is synthesised by polycondensation of hexamethylenediamine and adipic acid. Hexamethylene diamine and adipic acid are combined with water in a reactor. This produces nylon salt. The nylon salt is then sent to an evaporator where excess water is removed. The nylon salt goes into a reaction vessel where a continuous polymerization process takes place. This chemical process makes molten nylon 6-6. The molten nylon 6-6 undergoes a spinning process, where the nylon 6-6 is extruded and sent through a spinneret, which is a small metal plate with fine holes. The nylon is then air-cooled to form filaments. n HOOC(CH2)4COOH + n H2N(CH2)6NH2 at 553K and high pressure of about 300atm gives -[nylon66]
Nylon's chemical formula is n HOOC-(CH2)4-COOH + n H2N-(CH2)6-NH2 → [-OC-( CH2)4-CO-NH-(CH2)6-NH-] n + 2n H2O and the part -CO-NH- will stick together becoming Nylon 6-6.
Nylon 6-6 is frequently used when high mechanical strength, great rigidity, and good stability under heat is required  It is used for ball bearing cages, electro-insulating elements, pipes, profiles and various machine parts. Other popular applications are: carpet fibres, apparel, airbags, tyres, zip ties, ropes, conveyor belts, hoses and the outer layer of turnout blankets.[clarification needed] Nylon 6-6 is also a popular guitar nut material.