How to improve the air permeability of ePTFE membrane?

Optimize the preparation process:

1. Raw material selection: Select high-quality polytetrafluoroethylene dispersion resin as the basic raw material to ensure that it has a suitable molecular weight and particle size distribution.

2. Mixing and plasticization: Accurately control the type and amount of additives and fillers. Additives can improve the processing properties of the resin and the performance of the membrane. For example, choosing a suitable lubricant can reduce the friction of the resin during processing and make the mixing more uniform; the addition of fillers can adjust the pore structure and performance of the membrane.

3. Molding: Select a suitable molding method according to actual needs, such as calendering, casting, etc. Parameters such as pressure, temperature and speed during the molding process have an important influence on the structure and performance of the membrane.

4. Stretching and expansion: This is a key step that affects the air permeability of the ePTFE membrane. Parameters such as stretch ratio, stretch speed and stretch temperature need to be precisely controlled. A higher stretch ratio can usually increase the porosity and air permeability of the membrane, but too high a stretch ratio may cause the strength of the membrane to decrease or cause hole defects. Therefore, it is necessary to optimize the stretching process parameters through experiments to find the best balance between air permeability and membrane strength.
5. Sintering and cooling: The control of sintering temperature and time is crucial to the performance of the membrane. Appropriately increasing the sintering temperature can enhance the bonding force between molecules and make the structure of the membrane more stable, but too high a temperature may cause the pore structure of the membrane to be destroyed or contracted, thereby reducing the air permeability. Therefore, it is necessary to optimize the sintering process parameters according to the specific material formula and membrane requirements. The cooling process also needs to control the cooling speed to avoid stress concentration in the membrane due to too fast cooling, which affects the performance and air permeability of the membrane.
Post-processing method:
1. Heat setting: By heating the ePTFE membrane at a certain temperature, the internal stress generated by the membrane during the preparation process can be eliminated, making the structure of the membrane more stable and regular, thereby improving the air permeability. The temperature and time of heat setting need to be optimized according to the specific situation of the membrane. Generally speaking, the temperature range is between 200-300℃, and the time ranges from a few minutes to tens of minutes.
2. Surface treatment: Treating the surface of the membrane by physical or chemical methods can improve the surface properties of the membrane, such as hydrophilicity, hydrophobicity, etc., and thus affect the air permeability.
3. Composite modification: Compounding the ePTFE membrane with other materials can combine the advantages of the two materials and improve the performance of the membrane.
Other measures:
1. Control the thickness of the membrane: Generally speaking, within a certain range, the thinner the thickness of the membrane, the better the air permeability. However, a too thin membrane may affect the strength and waterproof performance of the membrane. Therefore, it is necessary to reasonably control the thickness of the membrane according to the specific use requirements to achieve a balance between air permeability and other properties.
2. Optimize the use environment: The air permeability of the ePTFE membrane will also be affected by the use environment.
3. Combine with other technologies: The ePTFE membrane can be combined with other ventilation or breathable technologies to further improve the overall air permeability effect.