Polyamide is widely and successfully used for products in the electrical and electronics industries. Thanks to its excellent mechanical and physical properties over a wide range of application temperatures and its very good weather resistance, polyamide can be used to make products for interior and external use that meet the most stringent of demands.
As a hygroscopic material, polyamide has the ability to absorb moisture in molecular form into the plastic matrix. As the moisture content goes up, product properties may change slightly, displaying increased toughness and lower rigidity for example.
The following table shows how the moisture content of polyamides comes into balance with the ambient air in a normal climate of 50% relative humidity and 23 °C:
Material
|
in air (23°C/50% rh)
|
| Polyamide 6 |
2 ... 3% by weight |
| Polyamide 12 |
0.8 ... 1.2% by weight |
To maintain a balanced moisture content, PMA recommends storing products under the following conditions:
| Storage temp. |
Processing temp. |
Rel. humidity |
| 18 °C ... 30 °C |
>18 °C |
>30% |
At lower processing temperatures and in particular when subjected to unnatural drying, corrugated pipes display increased flexural rigidity.
In the very dry winter months the moisture balance may go down slightly as the material releases moisture to the environment (owing to lower rel. humidity).
Compared to natural outdoor conditions* at around 0 °C (40 … 80% rh), the humidity in heated rooms may
drop by half to below 20% rh if no humidification is present. (Even extremely dry regions such as the Sahara Desert record average humidity of 20% to 60% rh.) * Central European climate.
If products from an outside environment are brought into a heated processing area, the change in climate may suddenly cause temporary demoisturization around the edges. After one or two days in the processing area a natural balance will be restored. Most PMA products have been modified to make them immune to climate changes of this kind.
Observing this storage recommendation ensures optimum processability and material properties.