Poly (hexamethylene adipamide), Polyamide 66, or Nylon 66 (PA66) is an engineering-grade thermoplastic. PA66 has higher strength but lower impact resistance than PA6.
Competes with PA6 for most applications.
If the material is sealed before molding, drying is not required. If the containers are left open, dry in a hot air oven at 85 C [185 F]. If the moisture content is > 0.2%, vacuum dry at 105 C [220 F] for 12 hours.
80 C [176 F] suggested. Mold temperature affects crystallinity level which in turn affects physical properties. In thin-walled parts, crystallinity changes with time when mold temperatures of less than 40 C [104 F] are used. In such cases, annealing can be required to retain dimensional stability.
Generally between 75MPa 125 MPa, depending on material and product design.
High (slightly lower for reinforced grades)
The gate location is important because of fast freeze-off times. Use any type of gate. Make the aperture not less than half the thickness of the part. When hot runners are used, the size of the gates can be smaller than when cold runners are used, because premature freeze-off is prevented. When using circular tapered gates, use a minimum diameter of the gate of 0.75 mm.
The polymerization of hexamethylene diamine and adipic acid (a dibasic acid) produces PA66. PA66 is a semicrystalline-crystalline material with one of the highest melting points among commercially available polyamides. The grades have strength and stiffness that is retained at elevated temperatures. 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 amount of moisture absorption affects dimensional stability and properties, which must be taken into account for product design.
Various modifiers are added to improve mechanical properties; glass is one of the most commonly used fillers. The addition of elastomers, such as EPDM or SBR, improves impact resistance.
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 sensitive to temperature.
Shrinkage is of the order of 0.01 0.02 mm/mm [1 2%]. The addition of reinforcing glass fibers reduces the shrinkage to 0.2 1%. Differential shrinkage in the flow and cross-flow directions is high. Mineral fillers yield more isotropic moldings.
PA66 is resistant to most solvents, but not to strong acids or oxidizing agents.