Polyamide 66, or Nylon 66 (PA66) is an engineering-grade thermoplastic. PA66 has higher strength but lower impact resistance than PA6. PA66 is a semicrystalline-crystalline material with one of the highest melting points among commercially available polyamides. PA66 homopolymer is produced by the polymerization of hexamethylene diamine and adipic acid (a dibasic acid). PA66 does absorb moisture after molding, but retention is not as high as PA6. Moisture absorption depends on the composition of the material, wall thickness, and environmental conditions. The grades have strength and stiffness that is retained at elevated temperatures. Dimensional stability and properties are all affected by the amount of moisture absorption, which must be taken into account for product design. Poly (hexamethylene adipamide), Polyamide 66, or Nylon 66 (PA66) is an engineering-grade thermoplastic. PA66 has higher strength but lower impact resistance than PA6. Various modifiers are added to improve mechanical properties; glass fiber is one of the most commonly used fillers. Although it does not flow as easily as PA6, the viscosity of PA66 is low so it flows easily, which enables the molding of thin components. The viscosity is very sensitive to temperature. PA66 is resistant to most solvents, but not to strong acids or oxidizing agents.
