What Is the Difference Between ePTFE and Sintered PTFE?

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.

The scanning electron microscope (SEM) images below offer a unique glimpse into the microstructures of both expanded PTFE (ePTFE) and sintered PTFE. These high-resolution images allow us to visually grasp the intricate details that set these materials apart. As we explore their differences, we gain valuable insights into how these structural variances influence their performance and suitability for various applications.

Expanded PTFE vs. sintered PTFE

When it comes to protection vents and barriers within devices, PTFE, or polytetrafluoroethylene, plays a pivotal role. However, not all PTFE is created equal, and it’s crucial to grasp the distinctions between two primary variants: expanded PTFE (ePTFE) and sintered PTFE. These two materials may share a common goal of providing breathable barriers, but their differences are evident in durability, support requirements, airflow characteristics, and water-repellent properties. In this section, we dive into the comparative analysis of these materials, shedding light on the factors that influence product design and engineering choices for optimal performance.

Durability

When considering expanded PTFE (ePTFE), picture it as delicate as tissue paper. It’s susceptible to wrinkling, and with frequent handling, the risk of tearing increases significantly.

In stark contrast, sintered PTFE exhibits remarkable strength. This difference is palpable; you can feel the sturdiness of the material. Unlike ePTFE, sintered PTFE retains its integrity even when subjected to physical contact, making it a robust choice for various applications.

Support

Given the touch-sensitive nature of ePTFE, it often necessitates additional support. Consequently, many protective vents utilizing expanded PTFE are laminated to fabric to minimize the risk of damage.

In the case of sintered PTFE, there’s no requirement for extra support. In fact, sintered PTFE can be securely ultrasonically welded to plastic components, simplifying the manufacturing process.

Air Flow

Airflow is a critical consideration, especially in applications where optimal performance relies on it. When ePTFE is touched, airflow experiences a significant drop. This feature can have adverse effects on products where consistent airflow is imperative for functionality.

In contrast, tests have shown that sintered PTFE vents maintain consistent airflow even when subjected to touch or contact. This attribute ensures that the product’s performance remains unaffected.

Water Repellent

While both ePTFE and sintered PTFE are designed to repel water, their methods of handling water differ significantly. When water encounters ePTFE, it forms beads that can be wicked away. However, in some instances, a portion of the water can adhere to the film’s surface. This residual water may pose an issue, potentially being drawn into an enclosure or sensitive components.

In the case of sintered PTFE, water behaves similarly by forming beads that can be wicked away. However, what sets it apart is that it leaves no water droplets behind. This unique property ensures superior protection for the product, minimizing the risk of water-related damage.

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. If you’d like to see the differences, use our Sample Selector to discover Porex Virtek™ firsthand or talk to one of our material science engineers.