Basic Characteristics of Nylon

Chemical Structure: The molecular main chain contains repeated amide groups (–NHCO–), prepared by polycondensation of a diacid with a diamine or by ring-opening polymerization of a lactam.

Common Varieties:
Nylon 6 (PA6): Made by ring-opening polymerization of ε-caprolactam, melting point about 220–225 °C, higher moisture absorption (saturated water absorption 7–9%).

Nylon 66 (PA66): Made by polycondensation of hexamethylenediamine with adipic acid, melting point about 255–265 °C, lower moisture absorption (about 3–4%), higher strength and rigidity.

Physical Properties:
Density: About 0.91–1.09 g/cm³, classified as a lightweight engineering plastic.

Melting Point: PA6 about 220 °C, PA66 about 255–265 °C.
Glass Transition Temperature (Tg): 45–70 °C.

Mechanical Properties:
High Strength: Tensile strength 60–85 MPa, flexural strength 80–120 MPa.

High Toughness: Notched impact strength up to 80–120 kJ/m².
Good Wear Resistance: Low friction coefficient, suitable for gears, bearings, and other friction components.

Moisture Absorption:
Due to the polarity of the amide group, strong moisture absorption (PA6 saturated water absorption 7–9%, PA66 about 3–4%), affecting dimensional stability and electrical properties.

Thermal Stability:
Thermal decomposition temperature >300 °C (PA66 can reach >350 °C), can be used long-term at 80–120 °C, reinforced versions can reach 250 °C.

Electrical Insulation: High volume resistivity (e.g., PA66 reaches 1.83×10¹⁵ Ω·cm), making it an excellent insulating material.

Chemical Resistance:
Resistant to oils, alkalis, and most organic solvents; not resistant to strong acids (e.g., concentrated sulfuric acid can destroy the amide bond).