Manufacturing process

PTFE membranes are created using the sintering process and then a skiving process. The sintering process uses a combination of heat and pressure to bond the materials together. The objective is not to melt or change the main properties of the material – but to create a customized porous material suitable for the customer’s need. The skiving process involves cutting the sintered form into thinner membranes.

Sintering process

Skiving process

Material

Polytetrafluoroethylene (PTFE)
For applications in need of ultra-hydrophobicity, high temperature tolerances, high chemical resistance, and excellent robustness, sintered and skived PTFE membrane technology is a perfect choice.

Using our wide range of application-specific products, we work closely with your engineering team to define your specifications, and they can help select the best PTFE membrane for your application. 

Physical properties

When incorporating a sintered PTFE membrane into your product, it’s critical to understand several physical properties as they impact the materials and functionality of the part: 

• Air flow rate: This is the desired air flow rate at a given pressure drop through a specific area. This is a critical measure for designing a venting membrane.  One important thing to note – air flow rate will increase through the same vent as the ΔP increases.   

• Water entry pressure (WEP): This is the amount of water pressure required to have water break through the membrane. This is a critical measure when designing a water-resistant venting or filtering membrane. 

• Operating temperature: Operating temperature defines the temperature range at which the part will be required to operate. For Porex Virtek PTFE membrane, this value is 260 °C continuous.

• Other key characteristics:  Porex Virtek PTFE membrane is an extremely versatile material that is used in numerous markets and applications. Other application-specific characteristics can include filtration efficiency, moisture vapor transmission rate, Gurley number, % reflectivity, and dielectric properties that may be required for your application. 

For Electronics & Automotive application – our standard Porex Virtek product offering is below:

For Life Sciences applications, below is another table that shows values across the medical-grade PTFE membrane portfolio:

Chemical properties

Porex Virtek PTFE membrane is one of the most chemically resistant materials available in the market. There are only a handful of fluorinated acids known to attack PTFE, so PTFE is always your safest choice if unknown chemicals may be in contact with the component.

Additive options

Additives and treatments open the door to many possibilities for your PTFE membrane. Below are some additives and treatments commonly used with PTFE:   

• Oleophobic treatment
• Polypropylene scrim support layer
• Adhesive backing
• Screen Printing

Geometric options

Porex Virtek PTFE membrane material begins as a 330 mm wide format (between 0.1 and 3.0 mm thick) and can be cut into porous PTFE sheets and other format options such as:

• Slit rolls (8 – 330 mm)
• Die cut discs and various shapes
• Rotary cut plugs and discs
• Cut discs “in web”
• Water jet cut shapes
• Zoned adhesive disc and other shapes
• Rods & molded or spiral tubes
• Thermoformed shapes
• Porous PTFE sheets

Our engineers can also look at your manufacturing process and assist with which size, shape and dimensions that best fit your application.

Assembly & converting options

Customizable assembly and converting options are endless. Typical options for sintered PTFE include:

• Thermal & ultrasonic welding
• Overmolding
• Die-cutting
• Press fit
• Pressure-sensitive adhesive (PSA)

It’s important to understand how the final product or device will be assembled when talking with our engineers, as sintered plastics can be used to decrease number of assembly steps by combining multiple parts into one custom-engineered part. 

Porex also has a Preferred Converter program for smaller order quantities. Check here to find a converter who is familiar with POREX materials and can convert them into the size and shape that you need.

How to use PTFE membrane

• Vent – The most common area for Porex Virtek PTFE membranes.  Many application and market areas rely on venting for their products to work properly.  From electrical enclosures to container venting to diagnostic and medical device vents – Porex Virtek is the material of choice for durable and reliable venting. 
  
• Reflect – Proper diffuse reflectivity is critical in uniformly distributing light energy. This is particularly critical in UVC disinfection devices, where a highly reflective and even distribution of the UVC energy is critical in insuring proper deactivation of pathogens. No material does this better than Porex Virtek PTFE membrane.
  
• Filter – In the field of healthcare, filtration properties are extremely important. Cross-contamination issues are addressed through several types of filtration, absorption, and ventilation options. Choosing product that offers the most protection is key. One example is filters for sterilization containers. These filters need to resist microbe entry yet allow steam heat to penetrate into the box to fully sterilize the equipment.    
  
• Media Support – Porex Virtek PTFE membrane is unaffected by virtually any chemical. This is important when supporting other media such as in chromatography.  With no fear of contamination or decomposition, PTFE support frits are ideal in this application

• Dielectrics – Having optimal dielectric properties is critical in products such as antennae systems. Porex Virtek PTFE membrane can attain a consistent dielectric constant in the 1.4 range while maintaining a tight thickness tolerances.  

This list of application examples is just a small selection of what is possible. Check out our market pages to see more examples of our porous polymers in action.