Nylon’s tendency to absorb moisture is perhaps the most important characteristic to understand when designing with this material. Proper design can turn this characteristic from a challenge into a manageable variable.
Why Does Nylon Absorb Water?
Nylon’s molecular structure contains polar amide groups (-CONH-) that form hydrogen bonds with water molecules, causing the material to absorb moisture from humid air or liquid water.
Moisture Absorption by Nylon Grade
| Nylon Grade | Moisture at 50% RH | Saturation in Water | Dimensional Change |
|---|---|---|---|
| PA6 | 2.5-3.0% | 9.5% | 0.5-1.0% |
| PA66 | 2.0-2.5% | 8.0% | 0.4-0.8% |
| PA11 | 0.8% | 1.9% | 0.1-0.3% |
| PA12 | 0.7% | 1.5% | 0.1-0.3% |
| PA6 GF30 | 1.7-2.1% | 6.5% | 0.2-0.4% |
How Moisture Affects Mechanical Properties
Water acts as a plasticizer within the nylon matrix. A PA6 part at 50% RH can lose 20-40% of dry tensile strength and 30-50% of dry flexural modulus.
Impact Resistance Increases
Moisture conditioning improves impact resistance by 2-3x. This is why nylon parts are frequently conditioned before use in impact-critical applications.
Design Strategies for Dimensional Control
- Use glass-filled grades: GF30 absorbs ~30% less moisture
- Select low-moisture grades: PA11/PA12 for critical applications
- Design clearances: Account for swelling in tolerance calculations
- Pre-condition parts: Condition before final machining
- Use symmetrical designs: Symmetrical parts swell more uniformly
Processing Implications
Before processing, nylon must be dried to <0.2% moisture. Insufficient drying results in splay marks, reduced mechanical properties, and inconsistent dimensions.
Drying Recommendations
| Grado | Drying Temp | Time | Target Moisture |
|---|---|---|---|
| PA6 | 80°C | 4-8 hrs | < 0.10% |
| PA66 | 80°C | 4-8 hrs | < 0.10% |
| PA12 | 80°C | 3-4 hrs | < 0.05% |
Our Capabilities
With over 300 CNC machines, we produce more than 10,000 pieces daily with tolerances as tight as ±0.005mm. We accept MOQ from 1 piece, with delivery times ranging from 24 hours to 15 days. We understand nylon’s moisture behavior and design accordingly. Get a quote within 24 hours.
Preguntas frecuentes
Can nylon parts be used underwater?
Yes, but with careful design. PA12 is the preferred grade for continuous water immersion.
How long does it take nylon to reach moisture equilibrium?
Thin parts (1-2mm) may equilibrate in days. Thick parts (10mm+) can take weeks or months.
Does painting or coating prevent water absorption?
Coatings can slow moisture absorption but rarely prevent it entirely. Most coatings are permeable to water vapor over time.
Can I use dried nylon properties for engineering calculations?
No—this is a common mistake. Always use conditioned (equilibrium moisture) properties for design calculations.
