High-Flow waterproof ePTFE Pressure Relief Vent Membrane，Customizable

Water ingress into sealed housings, condensation and fogging, and internal/external pressure differentials can lead to device failure or performance degradation. There is a need to balance protection with breathability/sound transmission.

With the ePTFE Pressure-Relief Balanced Membrane – IP68 Fast Pressure Equalization, Customizable, we achieve IP-level protection while maintaining breathability/sound transmission. We support custom die-cutting, adhesive backing, and specifications tailored to your structure.

Shenzhen Sandeli Precision Technology Co., Ltd. produces ePTFE Pressure-Relief Balanced Membranes using expanded polytetrafluoroethylene microporous film as the substrate. Through precise control of pore size and porosity, the membrane achieves dynamic pressure balancing between the interior and exterior of sealed cavities. When pressure differentials occur due to temperature changes, altitude variations, or internal heating, the membrane allows gas molecules to exchange freely, rapidly eliminating pressure differentials, while blocking water, dust, and salt spray ingress, with protection ratings up to IP67/IP68. The product is available in roll stock, sheet stock, and die-cut with adhesive backing, widely used in sealed cavity applications requiring internal/external pressure balancing, such as automotive electronics, outdoor communications, power batteries, and LED lighting fixtures.

An automotive Tier 1 supplier found that during durability testing of ECUs under thermal cycling (-40°C~125°C) for 500 hours, some samples showed condensation traces inside, leading to a decrease in circuit insulation resistance. The cause was that at high temperatures, the sealing ring expanded and sealed well, but at low temperatures, the seal contracted and external moisture was drawn in. After installing Sandeli's Pressure-Relief Balanced Membrane (airflow rate 2000 ml/min/cm², temperature resistance -40°C~125°C), no condensation occurred during 1000 hours of thermal cycling testing. The solution passed OEM certification and has entered mass production.

During GB 38031 standard testing of a new energy battery pack, it was found that under high-temperature and high-speed operating conditions, cell expansion caused internal air pressure to rise, creating a leakage risk due to compression of the sealing ring. Sandeli provided a Pressure-Relief Balanced Membrane (airflow rate 3500 ml/min/cm², IP68 protection) installed at the battery pack's pressure relief valve, balancing internal and external air pressure while maintaining the protection rating. After passing testing, this solution has been adopted in their 63kWh battery pack products.

Sandeli provides full-process services for customers in automotive, communications, new energy, and other industries, from pressure equalization solution evaluation and airflow rate selection to die-cut prototyping. We can collaborate with customers on reliability testing including thermal cycling, salt spray, and water immersion. Regular specifications can be sampled within 3 working days, and custom pressure-relief solutions within 5 working days. For cavity pressure equalization and breathable solution selection needs, please contact our engineering team to discuss specific operating parameters.

What is the difference between the Pressure-Relief Balanced Membrane and the regular Waterproof Breathable Membrane?

The Pressure-Relief Balanced Membrane has a higher airflow rate (1800–5000 ml/min/cm²) and is specifically designed for scenarios requiring rapid pressure equalization, such as high-power lighting fixtures, battery packs, automotive ECUs, etc. The regular Waterproof Breathable Membrane has a lower airflow rate (300–1000 ml/min/cm²) and is suitable for small-cavity products such as phones and watches. In short: the larger the cavity and the faster the temperature change, the more you need a Pressure-Relief Balanced Membrane.

Will the battery pack still get water ingress after installing this membrane?

No. Sandeli's Pressure-Relief Balanced Membrane maintains IP68 waterproof protection while allowing breathability, with hydrostatic pressure ≥80kPa (equivalent to 8 meters water depth pressure). It passes 72-hour salt spray testing with no penetration, meeting the protection requirements of automotive Tier 1 suppliers and battery manufacturers.

Is higher airflow rate always better?

Not necessarily. The airflow rate just needs to be sufficient—too high may allow excessive air exchange, bringing in more moisture and contaminants. Correct selection is based on calculating the required airflow rate from cavity volume and temperature change rate. Sandeli offers free airflow rate calculation services to help you find the optimal specification.

Will outdoor lighting fixtures still fog up after installation?

It will be significantly improved. The main cause of fogging in lighting fixtures is internal moisture condensation caused by temperature differences between the housing interior and exterior. The Pressure-Relief Balanced Membrane reduces the probability of fogging by balancing air pressure and reducing external moisture inhalation. If the fixture already contains significant internal moisture, we recommend filling it with dry air or nitrogen during assembly before sealing.

1.  Determine Opening Size & Structure

   Provide the diameter or length/width dimensions of the housing opening to confirm membrane specifications, adhesive type, and die-cut shape.

2.  Confirm Protection Level Requirements

   Select IP65, IP67, or IP68 based on your application scenario. The protection level determines the membrane material and lamination process.

3.  Identify Operating Environment

   Factors such as temperature, humidity, oil contamination, or chemical exposure influence material selection and service life evaluation.

4.  Define Performance Priorities

   Rank key indicators—such as airflow rate, acoustic transmission, and water pressure resistance—according to your actual application to avoid over-engineering.

5.  Request Free Sample Testing

   Provide structural drawings and test conditions. Our technical team will deliver a tailored solution within 48 hours and send samples for your verification.

• Rapid Pressure Equalization to Prevent Condensation

  The ePTFE microporous membrane's airflow rate can be customized from 500 to 5000 ml/min/cm² @ 70 mbar as needed, and internal/external pressure differentials can be balanced within seconds, effectively preventing condensation short-circuit failures caused by moisture ingress due to negative pressure.

• Waterproof and Dustproof Without Compromise

  Maintains IP67/IP68 protection while allowing pressure equalization, with hydrostatic pressure ≥80kPa, and passes 72-hour salt spray testing with no penetration, suitable for high-humidity and high-salt environments such as automotive engine compartments and coastal base stations.

• Wide Temperature Range and Long Service Life

  Temperature resistance from -40°C to 125°C. The microporous structure of the membrane remains stable and undeformed under thermal cycling shock, with service life covering the full life cycle requirements of automotive components.

• Flexible Die-Cutting Adaptability

  External dimensions from 2mm to 120mm, with tolerances controlled within ±0.1mm. Can be laminated with PET support layers, non-woven fabric liners, or acrylic/silicone adhesive layers to meet the high-efficiency feeding requirements of automated assembly lines.

• Automotive Electronics

  Pressure-relief balanced protection for ECU control units, headlight and taillight assemblies, millimeter-wave radar housings, and ABS/ESP controller cavities to prevent seal failure due to thermal shock.

• Power Batteries

  Battery pack pressure relief and balancing valve components, maintaining internal/external pressure equilibrium during cell charge/discharge thermal expansion and contraction, preventing housing deformation or sealing ring stress fatigue.

• Outdoor Communications & Sensors

  Pressure-relief breathable protection for 5G base station filter cavities, outdoor surveillance cameras, and environmental sensor housings, addressing pressure differentials caused by day-night temperature variations and altitude changes.

• LED Lighting Fixtures

  Cavity protection for high-power outdoor LED modules, expelling internally generated expanding gases to prevent lamp housing gaskets from being pushed out or water vapor ingress causing fogging.