What are the production processes of ePTFE membrane?

1. Raw material selection and preparation:
Select the appropriate PTFE resin as the raw material, and add extrusion aids (such as lubricants) as needed to facilitate the subsequent processing.
2. Extrusion molding:
After mixing the PTFE resin and the extrusion aid, it is extruded into a film through an extruder. During this process, the extruded film can be calendered to obtain the desired thickness and surface properties.
3. Drying treatment:
The extruded film needs to be dried to remove the lubricant and other volatile components in it to prepare for the subsequent stretching and sintering process.
4. Unidirectional or bidirectional stretching:
The dried film is longitudinally stretched at high temperature (usually less than 320°C) to form an ePTFE structure composed of nodes and microfibers. This step is the key to forming the microporous structure of the ePTFE membrane. The stretching process is divided into unidirectional stretching and bidirectional stretching:
Unidirectional stretching: The film is stretched along the machine direction (MD).
Bidirectional stretching: After the film is longitudinally stretched, it is stretched in the transverse direction (TD) to improve the mechanical strength and porosity of the membrane.
5. Sintering fixation: The stretched film is sintered at a certain temperature to fix the microporous structure. Sintering is usually carried out below the melting point of PTFE to ensure partial orientation of the molecules in the stretching direction.
6. Cooling and winding: The sintered ePTFE membrane needs to be cooled to room temperature and then wound into a roll for subsequent processing and application.
7. Post-treatment: The surface of the ePTFE membrane can be plasma treated as needed to change the surface properties, such as making it hydrophilic. In addition, the ePTFE membrane can be given specific application properties by coating or bonding drugs.