如何区别Waterproof Water Repellent Water Resistant

如何区别Waterproof\Water Repellent\Wa ter Resistant\Weather Resistant
Fabrics and garments may be labeled waterproof, water-repellent,
weather-resistant or some combination of these. But what does it all mean? Waterproof
A waterproof fabric is completely impermeable to water.(1) Since all the pores are closed, these fabrics are also impermeable to air and can become hot and uncomfortable as apparel. A vinyl raincoat is an example of a waterproof garment. The wearer remains dry since rain stays outside the coat; it can not soak into or through the fabric. Waterproofness is easy to determine either water can get in or it can not.
Water Repellent
Water repellence and water resistance introduce a lot more uncertainty. Water repellency is the resistance to wetting; water resistance is the resistance to wetting and water penetration.(2) Different fabrics resist wetting (absorbing water) to different degrees and the AATCC Technical Manual includes two methods for determining water repellency. AATCC Test Method (TM) 22, Water Repellency: Spray Test calls for a visual evaluation of the wetting pattern after the fabric is sprayed with water. Manufacturers and retailers must agree on an acceptable level of repellency based on the end-use of each fabric.
A rating of 80-90 (on a scale of 0-100) is generally acceptable for unlaundered samples intended for use as water-repellent outerwear.(3) Water repellency tests measure the amount of water that soaks into the fabric, not the amount that soaks through.
Intended mainly to measure the water-repellent efficacy of finishes, TM 70, Water Repellency, Tumble Jar Dynamic Absorption Test is not intended to predict rain penetration resistance.(4) Specimens are tumbled in water, weighed, and the wet weight is compared to the dry weight.
Water Resistant
AATCC TM 35, Water Resistance: Rain Test and TM 42, Water Resistance: Impact Penetration Test use the weight of the water penetrating the fabric as a measure of resistance. Less than 1 g is usually considered acceptable;3 anything over 5 g is reported as > 5 g and indicates failure as a water-resistant fabric.2 The rain test may be performed at different pressures to simulate different intensities of rain and acceptable values for both tests may vary according to end-use.
Another measure of water resistance is TM 127, Water Resistance: Hydrostatic Pressure Test. Water is directed at one side of the fabric under increasing pressure and the point at which water droplets appear on the opposite side is recorded. This test differentiates between the water resistance of the fabric and the water repellency of the fiber, yarn, and fabric construction. The degree to which the fibers and yarns resist wetting, combined with the size, shape, and number of pores in the fabric construction, influences the overall penetrability of the fabric.(5)
Weather Resistant
Weather resistance, the ability of a material to resist degradation of its properties when exposed to climactic conditions,6 is an even more complicated issue. AATCC TM 186, Weather Resistance: UV Light and Moisture Exposure subjects fabrics to artificial weathering through the use of ultraviolet (UV) light, humidity, and/or water spray. Exposed fabrics are compared to control fabrics in terms of color change and breaking or bursting strength. This test is most appropriate for items which will be placed outdoors for extended periods of time. The test method suggests three cycle options based on end-use梘eneral applications (e.g., outdoor furniture fabrics, and
tent material), architectural applications where thermal shock may be an issue, and automotive exteriors. The UV and humidity/spray conditions for each application vary slightly. TMs 111, 169, and 192 are similar tests, using different combinations of light and/or water to simulate weathering.
So, will your fabric keep you dry?
Waterproof fabric will protect you from rain, but will eventually make you hot and sweaty. A water-repellent fabric will probably keep you dry if you are out in the rain for just a few minutes. Water-resistant fabrics may also keep you dry temporarily and they will be more breathable than waterproof fabrics, but water will eventually soak in, making the fabric heavy and wet. While a
weather-resistant fabric makes no promise to keep you dry, it will continue to look and perform as it was intended even after prolonged exposure to sun and rain.
References
1. Dictionary of Fiber & Textile Technology, KoSa, Charlotte, N.C., U.S.A., 1999, p215.
2. AATCC Technical Manual, Vol. 81, 2006, pp65-67, 85-88.
3. Annual Book of ASTM Standards, Vol. 7.02, West Conshohocken, Pa.,
U.S.A., 2005, p992.
4. AATCC Technical Manual, Vol. 81, 2006, pp99-100.
5. AATCC Technical Manual, Vol. 81, 2006, pp211-212.
6. AATCC Technical Manual, Vol. 81, 2006, pp348-352.
Note: Story by Diana Wyman, AATCC.。