PA66 (Nylon 66)
An engineering polyamide (nylon)
Typical values for the temper in the title
PA66 (nylon 66) is similar to PA6, but its melting point is higher (about 260 °C), and it is slightly stronger, harder and more heat resistant. Glass-filled, it is one of the most common materials for under-hood automotive parts.
Like all polyamides, it absorbs water, so design to the conditioned state.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 70-85 MPa | |
| Elongation A | 60% | |
| Modulus of elasticity E | 2.8 GPa | |
| Density ρ | 1.14 g/cm³ | |
| Rockwell hardness | R119 | |
| Machinability | 70% | relative rating in the site database |
Structure and family
| Feature | Value | Meaning |
|---|---|---|
| Type | semi-crystalline polyamide | strength and toughness |
| Tm melting | about 260 °C | |
| Water absorption | high | affects dimensions and properties |
Typical values per producer data sheets.
Grades and versions
In engineering polymers, the choice is between an unfilled grade, filled grades (glass or carbon fiber) and special grades (bearing, medical, food). Filler strongly changes strength, stiffness and expansion.
| Version | Properties | When to choose it |
|---|---|---|
| Unfilled | tough and ductile | general parts |
| Glass-fiber filled (GF30) | much stronger and stiffer, less dimensional change | structural and automotive parts |
| Cast nylon | large rods and plates, high crystallinity | large machined parts |
Applications
- Under-hood automotive parts
- Connectors and electrical parts
- Gears
- Cable ties
- Machine parts
Fabrication
Water absorption
Polyamides absorb water from the air. Water plasticizes the material, reduces strength and stiffness and increases dimensions. For a precision part, design to the conditioned state, not the dry state.
Machining
Use very sharp tools, a feed that does not overheat the material, and good support (the material is flexible and deforms under clamping). For precision parts, stress-relief annealing before final machining is sometimes performed.
Joining
Ultrasonic, hot-plate or vibration welding, and mechanical assembly.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| PA6 (Nylon 6) | 75–80 MPa | Ultrasonic | PA6: similar, lower melting point · material page |
| PBT | 55 MPa | Ultrasonic | PBT: absorbs little water, stable · material page |
| PPS | 165 MPa | Ultrasonic | PPS: chemical and heat resistant, expensive · material page |
Common mistakes
Designing to dry-state properties
Conditioned, strength and stiffness are lower. Design to conditioned data.
Ignoring dimensional change
The part grows slightly as it absorbs water.
Using unfilled PA66 hot and under load
Strength drops when hot. For hot parts, a filled grade.
Equivalents, standards and supply
| ASTM | D6779 |
|---|---|
| Standards | ASTM D6779 / ASTM D4066 |
| Forms | rod · plate · injection |
| Producers | DuPont Zytel · BASF Ultramid · Lanxess |
Learn more
Values are typical for an unfilled grade (unless stated otherwise) and for comparison only. In polymers, properties depend on grade, filler, temperature, moisture and load duration. For design, rely on the producer data sheet for the specific grade. Sources: ASTM classification standards (D8033, D5205, D5204, D6394, D4067 and others), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026