Nylon PA66 properties
Nylon PA66 (polyamide 6,6) is a semi-crystalline thermoplastic from the polyamide family, synthesized by polycondensation of hexamethylenediamine and adipic acid, both monomers with six carbon atoms. Its typical density is 1.15 g/cm³, combining high mechanical strength, good thermal stability, and excellent wear resistance — characteristics that make it one of the most widely used engineering materials in the automotive, electrical, and consumer goods sectors.
Chemical composition and molecular structure
Section titled “Chemical composition and molecular structure”The molecular formula of the repeating unit is (C₁₂H₂₂N₂O₂)ₙ. The polymer is formed by amide bonds alternating with hexamethylene segments, resulting in a linear chain with high crystallization capability and strong intermolecular hydrogen bonds.
| Component | Formula | Molar ratio |
|---|---|---|
| Adipic acid | C₆H₁₀O₄ | 1 |
| Hexamethylenediamine | C₆H₁₆N₂ | 1 |
| Water (byproduct) | H₂O | 2n-1 |
Mechanical properties
Section titled “Mechanical properties”Freshly molded dry Nylon PA66 exhibits a tensile strength of 82 MPa / 11.9 ksi and a modulus of elasticity between 2.0 and 3.6 GPa / 290 and 522 ksi. Exposure to moisture reduces mechanical strength and stiffness but significantly increases toughness and elongation at break.
| Property | Dry state (0.2% moisture) | Conditioned state (2.5% moisture) |
|---|---|---|
| Tensile strength | 82 MPa / 11.9 ksi | 60 MPa / 8.7 ksi |
| Tensile modulus (Young) | 2.0 – 3.6 GPa / 290 – 522 ksi | 1.2 – 1.8 GPa / 174 – 261 ksi |
| Elongation at break | 40 % / 40 % | 150 – 300 % / 150 – 300 % |
| Flexural strength | 105 MPa / 15.2 ksi | 45 MPa / 6.5 ksi |
| Izod impact strength (23 °C) | 45 J/m / 0.84 ft·lb/in | 110 J/m / 2.06 ft·lb/in |
| Rockwell hardness | R120 / R120 | R100 / R100 |
Physical properties
Section titled “Physical properties”The density of unreinforced PA66 is 1.14 g/cm³ / 71.2 lb/ft³, placing it among medium-weight engineering thermoplastics. Its equilibrium water absorption at 23 °C and 50% relative humidity is 2.5% by weight, a property that must be considered in the dimensional design of precision components.
| Property | Value |
|---|---|
| Density | 1.14 g/cm³ / 71.2 lb/ft³ |
| Water absorption (24 h, 23 °C) | 1.2 % / 1.2 % |
| Water absorption at saturation (23 °C) | 8.5 % / 8.5 % |
| Dynamic coefficient of friction (against steel) | 0.30 – 0.40 / 0.30 – 0.40 |
| Melt volume index (275 °C, 5 kg) | 12 cm³/10 min / 0.73 in³/10 min |
Thermal properties
Section titled “Thermal properties”The crystalline melting temperature of Nylon PA66 is 264 °C / 507 °F and the dry glass transition temperature is 70 °C / 158 °F. The maximum continuous service temperature in air is 100 °C / 212 °F, with peaks up to 180 °C / 356 °F for short periods under no load.
| Property | Value |
|---|---|
| Melting temperature (Tm) | 264 °C / 507 °F |
| Glass transition temperature (Tg) | 70 °C / 158 °F |
| Maximum continuous service temperature | 75 – 100 °C / 167 – 212 °F |
| Heat deflection temperature (HDT, 1.8 MPa) | 75 °C / 167 °F |
| Heat deflection temperature (HDT, 0.45 MPa) | 200 °C / 392 °F |
| Coefficient of linear thermal expansion | 80 x 10⁻⁶ /K / 44 x 10⁻⁶ /°F |
| Thermal conductivity | 0.25 W/m·K / 0.14 BTU·ft/h·ft²·°F |
| Specific heat | 1.67 kJ/kg·K / 0.40 BTU/lb·°F |
Electrical properties
Section titled “Electrical properties”PA66 is an excellent electrical insulator, with a volume resistivity of 10¹⁵ ohm·cm and a dielectric strength of 14 kV/mm / 356 V/mil. Its dielectric constant at 60 Hz is 4.5, a value that remains stable under dry conditions but increases with moisture absorption.
| Property | Value |
|---|---|
| Volume resistivity | 10¹⁵ ohm·cm / 10¹⁵ ohm·cm |
| Dielectric strength | 14 kV/mm / 356 V/mil |
| Dielectric constant (60 Hz) | 4.5 / 4.5 |
| Dissipation factor (60 Hz) | 0.014 / 0.014 |
| Arc resistance | 120 s / 120 s |
Applications by industry
Section titled “Applications by industry”The versatility of PA66 makes it a reference material in applications requiring stiffness, thermal resistance, and toughness. The ease of processing by injection molding and extrusion, and the ability to reinforce it with glass fiber, further expand its field of use.
| Industry | Typical applications |
|---|---|
| Automotive | Intake manifolds, valve covers, radiator tanks, mirror housings, gears for electrical systems, fasteners and clips. |
| Electrical & electronics | Connectors, switches, power tool housings, cable ties, wire ducts, terminals and terminal blocks. |
| Consumer goods | Zippers, brush bristles, appliance components, vacuum cleaner housings, kitchen utensil handles. |
| Textile & industrial | High-tenacity fabrics (Cordura), conveyor belts, ropes, industrial sewing threads, high-traffic carpets and rugs. |
| Sports & leisure | Ski bindings, bicycle components, skate wheels, racquets, helmets and protective gear. |
Comparison with similar materials
Section titled “Comparison with similar materials”Compared to other polyamides, PA66 stands out for higher stiffness and better thermal behavior than PA6, although with lower resilience under wet conditions. With respect to general-purpose thermoplastics such as polypropylene, it offers much higher mechanical and thermal performance at the expense of higher density and cost.
| Material | Density (g/cm³ / lb/ft³) | Tensile strength (MPa / ksi) | Tensile modulus (GPa / ksi) | Melting temperature (°C / °F) |
|---|---|---|---|---|
| Nylon PA66 | 1.14 / 71.2 | 82 / 11.9 | 2.0 – 3.6 / 290 – 522 | 264 / 507 |
| Nylon PA6 | 1.13 / 70.5 | 78 / 11.3 | 2.0 – 3.0 / 290 – 435 | 220 / 428 |
| Polypropylene (PP) | 0.90 / 56.2 | 33 / 4.8 | 1.4 / 203 | 165 / 329 |
| Polyoxymethylene (POM) | 1.41 / 88.0 | 70 / 10.2 | 2.8 / 406 | 175 / 347 |
| PET (semi-crystalline) | 1.33 / 83.0 | 80 / 11.6 | 2.8 / 406 | 255 / 491 |
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the difference between Nylon PA66 and Nylon PA6?
Section titled “What is the difference between Nylon PA66 and Nylon PA6?”The main difference lies in the chemical structure and melting point. PA66 has a melting temperature of 264 °C compared to 220 °C for PA6, which provides better dimensional stability at high temperature and greater stiffness. PA6, on the other hand, offers better impact resistance in the conditioned state and a slightly wider processing range.
Is Nylon PA66 resistant to chemicals?
Section titled “Is Nylon PA66 resistant to chemicals?”It exhibits excellent resistance to oils, greases, gasoline, aliphatic hydrocarbons, dilute alkalis, and most organic solvents. Strong mineral acids, phenols, formic acid, and benzyl alcohols attack it and should be avoided.
Can Nylon PA66 be recycled?
Section titled “Can Nylon PA66 be recycled?”Yes, PA66 is thermoplastic and therefore recyclable through grinding and re-extrusion processes. Injection and extrusion grades can accept high percentages of reprocessed material, although it is recommended to dry the material properly before each processing to avoid hydrolytic degradation.
What is the heat deflection temperature of Nylon PA66?
Section titled “What is the heat deflection temperature of Nylon PA66?”The heat deflection temperature (HDT) under a 1.8 MPa load is approximately 75 °C / 167 °F for unreinforced material. With 30% glass fiber reinforcement, the HDT can exceed 250 °C / 482 °F.
Why does Nylon PA66 absorb moisture and how does it affect its properties?
Section titled “Why does Nylon PA66 absorb moisture and how does it affect its properties?”Moisture absorption, which can reach between 2.5% and 8.5% depending on conditions, is due to the polar amide groups in the polymer chain. The absorbed water acts as an internal plasticizer: it reduces tensile strength and stiffness but significantly improves impact resistance and elongation at break.
What processing techniques are used with Nylon PA66?
Section titled “What processing techniques are used with Nylon PA66?”The main techniques are injection molding, extrusion of profiles, monofilaments, and sheets, and blow molding. In all cases, pre-drying of the granulate to a moisture content below 0.2% is essential, typically at 80 °C for four to eight hours.