Meaning
A porous barrier that resists the passage of liquid water while allowing gases and vapors to move through freely provides environmental protection for sensitive electronics. The installation of a hydrophobic membrane in a battery pack allows for pressure equalization during altitude changes without risking moisture ingress. This material relies on low surface energy to prevent droplets from wetting the surface.
Moisture Barrier
Liquid water beads on the surface of the material rather than soaking into the fibers. A hydrophobic membrane protects the internal components of a pack from rain, spray or condensation. This property is measured by the water entry pressure, which defines the maximum depth or force the material can withstand.
A higher pressure rating indicates a more durable barrier for outdoor applications.
Gas Permeability
Air molecules pass through the microscopic openings in the structure to balance the internal and external atmosphere. When a hydrophobic membrane is part of a venting system, it ensures that hydrogen gas can escape safely if a cell malfunctions. The high flow rate prevents the build-up of pressure that could deform the enclosure.
Material Selection
Polytetrafluoroethylene is a common choice for these barriers due to its high chemical resistance. Engineers specify a hydrophobic membrane based on the pore size. This selection maintains the IP rating of the device.
