waterproof breathable membrane/waterproof breathable cap

II. Core Working Principle
Its technical core lies in the use of a microporous membrane made from ePTFE (expanded polytetrafluoroethylene) or other polymer materials.

1. Microporous Structure:
This membrane contains tens of thousands of micro-scale or even nano-scale pores.
2. Surface Tension and Hydrophobicity:
   · These pores are much smaller than water droplets (water molecules are small but exist in droplet form).
   · Due to the material's extreme hydrophobicity (water-repellency), water molecules cannot wet or penetrate this membrane. The surface tension of water causes it to form droplets that cannot pass through the micropores.
   · Similarly, it effectively blocks oils and other contaminants.
3. Gas Molecules Pass Freely:
Air molecules (e.g., O₂, N₂, CO₂) are very small and can easily pass through these microporous channels, enabling instantaneous pressure equalization.

III. Main Functions and Advantages
1. Pressure Equalization:
Prevents the formation of a pressure differential (positive or negative pressure) between the inside and outside of a sealed cavity.
   · Avoids the "Pump Effect": For example, an automotive headlight heats up when turned on, causing internal air to expand. Without a vent, pressure would force its way out through the weakest seal; upon turning off and cooling, a vacuum forms, drawing in moisture and dust through seals. The vent eliminates this phenomenon.
   · Prevents Envelope Deformation or Damage: Excessive negative pressure can cause plastic housings to collapse, while excessive positive pressure can lead to seal failure or connector leakage.
2. Water and Dust Protection:
Provides high-level IP (Ingress Protection) ratings, commonly IP67, IP68, etc., ensuring reliable operation of equipment in harsh environments (e.g., rain, snow, splashing water, dusty environments).
3. Prevents Condensation:
By balancing pressure, it avoids the formation of internal condensation due to temperature changes, protecting internal precision circuits from corrosion and short circuits.
4. Extends Product Lifespan:
Protects internal components from moisture, corrosive liquids, and pollutants, significantly improving equipment reliability and service life.
5. Enhances Sealing Performance:
Allows for the use of more comprehensive and economical sealing solutions without worrying about pressure buildup.