The Effect of Humidity on Polyamide & Stabilization Solutions

Polyamides such as PA66 GF25 offer a powerful combination of strength, stiffness, and thermal stability, making them ideal for high-performance thermal-break systems. However, one inherent characteristic of polyamides—their ability to absorb moisture—significantly affects their mechanical and dimensional behavior. Understanding how humidity influences polyamide properties is essential for achieving long-term stability and producing profiles with predictable, consistent performance.

1. Moisture Absorption and Its Effect on Mechanical Properties

Polyamides naturally absorb moisture from the environment due to their amide bonds. As moisture increases, stiffness decreases while impact strength and flexibility rise. This dual behavior can be beneficial in some applications, but for thermal-break profiles where precision is critical, uncontrolled moisture absorption may cause dimensional changes and alter load distribution.

2. Dimensional Stability in Thermal-Break Applications

In aluminum window and façade systems, dimensional accuracy must remain consistent over years of load and temperature fluctuations. Moisture absorption can lead to slight expansion or swelling in PA66 GF25, which in turn may affect the fit, alignment, and stress state within the assembly. Proper stabilization techniques and material formulations help ensure that the profiles retain their dimensional integrity throughout their service life.

3. Importance of Pellet Drying Before Extrusion

Drying the material before extrusion is crucial. If pellets contain excessive moisture, hydrolysis can occur during melt processing, breaking polymer chains and significantly reducing strength and molecular weight. PA66 GF25 typically requires drying at 80–90°C for at least 6 hours in a dehumidifying dryer. Precise moisture control ensures smooth processing and high-quality surface finish.

4. Post-Extrusion Conditioning for Long-Term Stability

After extrusion, controlled conditioning allows the polymer to reach moisture equilibrium. This step relieves internal stresses, stabilizes material dimensions, and ensures predictable performance in long-term use. Without proper conditioning, the profile may gradually absorb moisture after installation, causing slow dimensional drift. Manufacturers often implement climate-controlled storage and conditioning protocols to prevent this.

Conclusion

Moisture absorption is an unavoidable characteristic of polyamides but can be effectively managed through proper drying, stabilization additives, and post-extrusion conditioning. By controlling humidity at every stage—from pellet preparation to storage—manufacturers can produce PA66 GF25 profiles with high dimensional accuracy and reliable long-term performance in thermal-break systems.