Permeability Rate
Mass transfer of water vapor through a unit area of fabric within a specified time frame determines the comfort level of protective clothing. High moisture vapor transmission allows sweat to escape from the body, keeping the wearer dry and preventing heat stress during exertion. This rate depends on the physical structure of the textile, including fiber type and thickness.
Measurement Method
Laboratory assessment of this property typically involves a sealed cup filled with water and covered by the test fabric. This cup is placed in a controlled climate chamber to measure the weight loss over twenty-four hours, which gives the moisture vapor transmission rate in grams per square meter. A faster rate indicates greater breathability and comfort for active use.
Fabric Influence
Fiber blending can optimize this behavior. Natural fibers like wool absorb and release moisture, which increases the moisture vapor transmission of the blended garment.
Testing Standard
Different international test methods can yield widely varying results for the same fabric specimen. Because some tests use an inverted cup and others use a dry desiccant, the reported moisture vapor transmission values are not directly comparable. Specifying the exact test method used allows for a fair comparison between competing product lines.
