Fabric air permeability refers to the performance of the gas molecules through the fabric, is the most basic performance fabric permeability, gas permeability will directly affect the fabric to keep warm, wet, windproof, such as performance, in the human body and the environment of energy exchange plays an important role, is an important index for clothing comfort performance evaluation, the fabric after moisture absorption, due to the influence of water, change the indicators, including the air permeability.
Amount of breathable fabric with the increase of moisture content increased first and then decrease, in the process of air permeability, gas through holes and gaps between the fiber yarn fabric cloth two ways, hole as the main way, general with cloth fabric wetting fiber before and after the expansion, but because the fabric is woven by forming coil, the structure is loose, the yarn of the space is larger, not between the yarn have obvious smaller pore, on the contrary, knitted fabric wetting surface hairiness after lodging, fabric thickness decreases, and reduce the length of the ventilation pipe, in the fabric and breathable aperture increases, increase air volume, ventilation quantity increase, namely wet fabric with further increase of moisture content, water mainly exists in the form of free water, occupied the porosity of the knitted fabric, and easy to form a continuous film of water between the fiber, less air quantity.
With the increase of moisture content, the amount of breathable fabric decreases obviously, the woven fabric is vertical with each other by the warp and weft weaving and become, woven fabric after absorbing water, fiber length and cross-sectional area of the expansion, and this expansion showed obvious anisotropy, the expansion of the fiber length direction after moisture absorption is very small, and expansion in diameter direction, lead to yarn in fabric bending degree increase, squeeze each other tight at the same time, reduce the gap between yarn and yarn, fabric shrinkage, water, plus attached gap further blocked in the fabric, breathable fabric quantity decreased obviously.
