Breathability

Ability of fabric to transfer moisture vapor Breathability of fabric is the ability of a fabric to allow moisture vapor to be transmitted through the material. Mechanism Air permeability is the ability of a fabric to allow air to pass through it. While air permeable fabrics tend to have relatively high moisture vapor transmission, it is not necessary to be air permeable to be breathable. Moisture Vapor Transfer (MVT) in waterproof fabrics occurs by two processes: Physical: Hydrophobic (water fearing) are waterproof, yet steam permeable -microporous coatings or laminations have pores that are so small that liquid water cannot go through. However, vapor water molecules are many times smaller than the liquid state and can pass through these “micro pores”. Chemical: Hydrophilic (water loving) / non-porous lamination or coating move moisture by chemical diffusion. The water molecule is positively charged and the hydrophilic PU is negatively charged, attracting the water through the intermolecular gaps of the PU. Because the ionic bond is relatively weak, the water then gets pushed through the gaps until the water vapor passes all the way through. Driving Force is the difference in t