Sintered or Expanded—Which PTFE Is Best Suited for Your Device?

Medical device manufacturers have relied on ePTFE, or expanded PTFE film, to permit the flow of air and water vapor in their products, all with the goal of improved device performance and patient care. But how does this material really stack up against the other options on the market, and how do device engineers choose the right option? To address this question as well as other common questions often heard with regard to this material, this FAQ was developed to offer perspective on ePTFE and why it may not be the preferred material choice. A new sintered PTFE that more effectively vents, diffuses, and filters air and water is proving to be a better fit for some device manufacturers in ostomy and urology care, injection therapy, and other life sciences applications.
 
Q: Isn’t ePTFE the industry standard? Are there issues with it?
A: Expanded PTFE, as the name implies, involves stretching the material to the point at which it becomes porous. This process allows for air and water molecules to penetrate the material—a positive when it comes to maintaining proper moisture levels—but also places stress on the film, leaving it weak and highly susceptible to damage.
 
In addition, there is a misconception with the sustainability of ePTFE. Due to its thin nature, manufacturers often view ePTFE as eco-friendlier, utilizing fewer raw materials to create each unit. While this is true, ePTFE typically requires a scrim to bolster it, rendering it less ecofriendly and less pure. The thinness of ePTFE is also what causes it to wear out quickly, requiring frequent replacement, which in turn consumes more materials and more production resources. A similar comparison could be made to consumer goods made of paper and metal, where paper is often championed as a greener material despite metal’s distinct benefits of infinite recyclability and its ability to be reused time and time again with no reduction in quality or loss of properties. Analogous to metal, porous PTFE filters can be reused in autoclave sterilization applications for a practically “infinite” number of recycles. The material can significantly reduce total economic costs as well as ecological costs for superior functional performance.
 
Q: What is sintered PTFE?
A: Sintered PTFE is a membrane featuring an open-celled, omnidirectional 3D-pore structure that is design-flexible and can be tailored in thickness, porosity, and volume to individual device needs. This unique composition results in a network of well-controlled particles that together offer robust strength, making the porous PTFE components or membranes more durable and reliable, while potentially prolonging their lifespan. The strong porous material also retains its specified characteristics and structure even after enduring high-speed medical device assembly manufacturing processes. The proprietary manufacturing process used to create sintered PTFE is also highly reproducible, meeting quality standards for medical device manufacturing.
 
Q: How do I know when I should be using sintered PTFE?
A: If you’re experiencing performance challenges with your medical device, the problem likely lies much deeper and is at the core of your material integrity. Often, simply finding the right material can elevate the functioning and reliability of your device and transform outcomes by providing better venting, diffusing, or filtering performance. When designing a new device, establishing quality requirements can also help to zero-in on the right material option. If your device requires bacterial filtration efficiency of up to 99.9999 percent, superior hydrophobicity, and high temperature and pressure stability, sintered medical-grade PTFE is the preferred option. The material also features ease of component assembly and integration, and requires no supporting layers (or scrims), which is not possible for an ePTFE film.
 
Q: What applications can use sintered PTFE?
A: The uses for sintered medical-grade PTFE are wide-ranging, but some of its applications include:
 

• Infection control: The material serves as a vent in sterilization containers, enabling pressure equalization during the sterilization process and blocking bacteria under storage containers.
• Urology and ostomy care: The media speeds urine disposal during drainage procedures and prevents water penetration in ostomy pouches during water immersion activities. It also serves as a vent for pressure equalization in urine collection bags and gas release in ostomy pouches.
• Injection therapy: The material acts as a vent to pass gas and air through IVs and safety catheters and as a flash plug for hydrophobic membranes. It also helps to block blood bypass in flashback chambers and reduce blood-borne pathogen exposure.
• Medical and pharmaceutical packaging: The material harmonizes air flow and provides a superior sterile barrier for products.

 
Q: What do I do if I don’t even know what type of material my device needs?
A: The best place to start is to prioritize the goals of your device and to become informed on which of the functional performances—including venting, diffusing, or filtering—impacts those goals. Knowing what operational needs your device has can determine the level of porosity and the type of structure you need in a porous PTFE film. Finding the right partner in innovation is key for this understanding, adding critical material and applicational expertise to your design process.

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Jack Chan is the global marketing director for Porex’s medical market with more than 20 years serving the medical device industry. He is responsible for driving Porex’s biomedical marketing strategy through his extensive experience in working with medical grade polymers used in medical devices. Chan received his Ph.D. in physical chemistry of polymers from the University of Texas—Austin, a Master’s in Science in polymer science and engineering from the University of Massachusetts in Amherst, and double Bachelor’s of Science degrees in polymer science and chemistry from the University of Southern Mississippi.