Polyamide resin (PA6PA66) Nylon 6-66, also referred to as PA6, PA66, Polyamide resin, is a type of nylon. Nylon comes in many types, the two most common for textile and plastics industries are: nylon 6 and nylon 6, 6. Nylon 6, 6 has a melting point of 265°C, high for a synthetic fiber’ this fact makes it resistant to heat and friction and enables it to withstand heat-setting for twist retention. Its long molecular chain results in more sites for hydrogen bonds, creating chemical “springs”, making it very resilient; 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.