Waterproof Principle of Plastic Waterproof Breathable Valve

Plastic waterproof breathable valves are designed to allow air and moisture vapor to pass through while blocking liquid water. Their waterproof functionality relies on a combination of material properties and structural design.

1. Microporous Membrane Technology:
   Most waterproof breathable valves incorporate a microporous membrane made of PTFE (polytetrafluoroethylene) or ePTFE (expanded PTFE). These membranes contain billions of tiny pores per square centimeter, typically ranging from 0.1 to 10 micrometers in diameter. These pores are small enough to prevent liquid water molecules (due to surface tension) from penetrating, while allowing air and water vapor to escape.

2. Hydrophobic Material Properties:
   The membrane material is inherently hydrophobic, meaning it repels liquid water. This prevents water droplets from spreading and penetrating the valve, even under slight pressure.

3. Pressure Differential Mechanism:
   The valve is designed to open under pressure differences, allowing internal moisture (from condensation or humidity) to escape while maintaining a seal against external water ingress.

4. Laminated or Multi-Layer Structure:
   Some valves use a multi-layer construction, combining a breathable membrane with a protective outer layer to enhance durability while maintaining waterproofing.

5. Elastomeric Sealing:
   The valve housing is often made of flexible plastic (such as silicone or TPU) to ensure a tight seal when closed, preventing water leakage even in submerged conditions.