Nylon 6-6, also referred to as nylon 6,6, is a type of nylon. Nylon comes in many types, and the two most common for textile and plastics industries are nylon 6and nylon 6,6.


Nylon 6,6 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.

Physical properties

  1. Nylon 6,6 has a melting point of 265°C, high for a synthetic fiber, though not a match for polyesters or aramids such as Kevlar.[1] This fact makes it resistant to heat and friction and enables it to withstand heatsetting for twist retention.
  2. Its long molecular chain results in more sites for hydrogen bonds, creating chemical “springs”, making it very resilient.
  3. It has a dense structure with small, evenly spaced pores. This means that nylon 6,6 is difficult to dye, but once dyed it has superior colorfastness and is less susceptible to fading from sunlight and ozone and to yellowing from nitrous oxide.

Manufacturing of Nylon 6-6

  1. 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.
  2. The nylon salt goes into a reaction vessel where a continuous polymerization process takes place. This chemical process makes molten nylon 6,6.
  3. 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.
  4. Nylon's chemical formula is nHOOC-(CH2)4-COOH+n H2N-(CH2)6-NH2---->[-OC-( CH2)4-CO-NH-

(CH2)6-NH-] n+2nH2O and the part -CO-NH- will stick together becoming Nylon 6,6.


  1. Carpet fiber
  2. Apparel
  3. Airbags
  4. Tires
  5. Zip Ties
  6. Ropes
  7. Conveyor Belts
  8. Hoses

Nylon 6,6's longer molecular chain and denser structure qualifies it as a premium nylon fiber, specified most often by professional architects and designers for use in commercial settings like offices, airports, and other places that get a lot of wear and tear. It is also an excellent choice for residential carpet applications.