Автор: PolarBear
Дата: 13-06-11 12:31
.......
Standard laboratory testing protocols define the performance of these fabrics. Water resistance is measured by the amount of water, in mm, which can be suspended above the fabric before water seeps through. Breathability is measured by the rate at which water vapor passes through, in grams of water vapour per square meter of fabric per 24 hour period (g/m2/d), often abbreviated to just "g". In recent years some, but not all, sporting goods manufacturers have begun including this information on their product labels. Typical mid-range fabrics tend to have values of 5,000 mm of water resistance and 5,000 g of breathability; the best materials have 20,000 mm and 20,000 g.
One specific definition of "waterproof/breathable" requires the fabric to withstand over 1,000 millimetres of water (9.8 kPa) pressure without leaking (see hydrostatic head)[citation needed].
These values should be taken with some caveats. Rain room tests show that some fabrics with less than 1,000 mm of water resistance keep water out sufficiently for practical purposes. Garments made from these fabrics tested in the Leeds University Rain Room show no signs of leakage after 4 hours of heavy simulated rain, 5 times heavy British rain. However, some garments made from fabrics that exceed 20 000 mm have leaked through zips, hoods, and seams. Pressure may not be a good measure for rainwear, as the force of the rain drop on the fabric also depends on how much the fabric moves. However, pressure is a good measure for sitting on wet ground or similar situations. In addition, the breathability of nearly all waterproof/breathable fabrics is very dependent upon weather conditions, especially temperature and humidity.
.....
|
|