What is the difference between ePTFE and sintered PTFE?

By Avi Robbins, VP of Global Product Development and R&D
Dec. 13, 2019

Inside many common products, like cell phones and headlights, live unseen protection vents (sometimes called protective vents). The vents are made out of a durable, versatile material called PTFE, or polytetrafluoroethylene.

In general, porous PTFE is a material that allows air and other gases to pass through while keeping larger molecules, like water, out. Its unique composition makes it ideal for protection vents. Inside a cell phone, for example, a thin, dime-sized PTFE film sits behind the microphone and acts as a vent, allowing air to flow through while repelling contaminants like water and dust.

There are actually two types of porous PTFE: expanded PTFE – or ePTFE – and sintered PTFE. What’s the difference? Let me explain.

Here’s what an SEM image of ePTFE looks like:

ePTFE

And here’s what an SEM image of sintered PTFE looks like:

POREX Virtek sintered PTFE

Expanded PTFE vs. sintered PTFE

The purpose of both types of PTFE is to offer a breathable barrier, but here’s how they differ:

  • Durability

Think of ePTFE material like a tissue. It’s easy to wrinkle and the more you handle it, the more likely it is to rip.

Sintered PTFE is stronger. You can see and feel the difference in the material, and unlike ePTFE, it will not break down when it’s touched.

  • Support

Since ePTFE material is touch-sensitive, it often requires support. As a result, many expanded PTFE films used in protective vents are laminated to fabric to minimize damage.

With sintered PTFE, additional support isn’t required. In fact, sintered PTFE can be ultrasonically welded to plastic.

  • Air flow

When ePTFE material is touched, air flow drops dramatically. Think about what that could do to a product where air flow is imperative to performance.

Tests shows air flow in a sintered PTFE vent, however, remains unaffected when touched.

  • Water repellent

PTFE is meant to repel water, but ePTFE and sintered PTFE handle water differently. When water meets ePTFE it beads up and can be wicked away, but some of the water often sticks to the film. The remaining water could pose a problem, and be sucked into an enclosure, for example.

When water meets sintered PTFE it also beads up and can be wicked away, but water droplets aren’t left behind, and as a result, provide superior product protection.

Wrap up

Protection vents made from PTFE components can be found in a variety of electrical, industrial, medical, and consumer applications. As engineers create products, it’s important to understand the difference between ePTFE and sintered PTFE. To compare ePTFE material to POREX Virtek™ sintered PTFE, check out this video, or request a sample to see how we can protect your product.