Many types of nylon are commercially available. The most popular type is nylon 6/6, followed by nylon 6, then nylon 6/12, nylon 11 and nylon 12. Nylon 6/6 offers an excellent balance of properties and is the strongest of the nylons.
Nylon 6 has improved creep resistance over nylon 6/6 but has a lower modulus. Nylon 6 absorbs moisture more rapidly but has improved processability. Compared to Nylon 6/6 it can be molded about 80 degrees F (45 degrees C) lower with less mold shrinkage because it is slightly less crystalline.
Nylons absorb more moisture from the air than most other polymers. This has an effect on processability, dimensional stability and physical properties. Moisture acts as a plasticizer, reducing tensile strength and stiffness and increasing elongation. But, while absorbed moisture reduces many properties, nylon owes part of its toughness to the plasticizing effect of moisture. As moisture content rises, significant increases occur in impact strength and general energy absorbing characteristics. Properly recognized and accounted for, the effect of moisture on the processing and properties of nylon need not be of great concern.
Glass-reinforced nylon results in materials possessing tensile strengths up to 32,000 psi, approximately 200% better than the base resin. Heat deflection temperatures increase from 160 degrees F to 500 degrees F (71 degrees C to 260 degrees C).
Carbon fiber-reinforced nylons excel over their base resin and glass-reinforced nylons with improved tensile and flexural strengths — comparable to some die casting alloys. Nylon 6/6 has up to 36,000 psi tensile and 50,000 psi flexural strength; lower expansion; better dimensional stability; and improved thermal conductivity and electrical conductivity. Nylon 6/6 has static dissipative characteristics when reinforced with carbon fiber.
Because of their high modulus, good wear resistance and static electricity discharge characteristics, carbon fiber-reinforced nylons have potential for replacement of die cast metals, such as those used in moving textile machine parts.