The term waterproof describes something that is unaffected by water or covered with a material that does not allow water in. Such items are suitable for use in wet environments (outdoors) or under water. Waterproofing is the treatment of a surface to prevent the passage of water under hydrostatic pressure, or the process where a building component is made totally resistant to the passage of water and/or water vapour.
Clothing waterproofing includes treatments made to clothing or products during or after the production process, which provides some protection against exposure to water. The extent to which the item is protected can vary by extended exposure, water depth, water composition, salts, chemicals etc., and the quality or method of treatment. Products which are waterproofed can be made so by applying a waterproof spray, such as NIKWAX.
Waterproof fabrics are usually natural or synthetic fabrics that are laminated to or coated in some sort of permanently waterproofing material, such as rubber, polyvinyl chloride (PVC), polyurethane (PU), silicone elastomer, and wax. Examples include the rubberised fabric used in Mackintosh jackets and inflatable boats.
Waterproof breathable fabrics (aka waterproofs, waterproof breathable
and waterproof-breathable) are defined as fabrics that will
withstand over 1000 millimetres of water (9.8 kPa) pressure without leaking
(hydrostatic head), whilst allowing water vapour to pass through. Their most
common use is in outdoor sports clothing and single wall tents, because of
their ability to allow sweat to evaporate while remaining impervious to
Rain room tests show that certain fabrics with less than 1,000 millimetres hydrostatic head can keep you dry. Such garments 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 20,000mm have leaked due to the design of zips, hoods etc. Pressure may not be a good measure for rain wear, as the force of the rain drop on the fabric depends on how much the fabric moves. However, pressure is a good measure for sitting on wet ground or similar situations.
Fabric construction which directs water away from the body can be used to keep the wearer dry, rather than membranes, coatings or laminates. This means that perspiration can be moved away from the body more effectively as both liquid water and water vapour can be directed. These are DirectionalTM or FurTechTM fabrics, which are also breathable in the conventional sense.
The breathability of all waterproof/breathable fabrics is very dependant on conditions. When the fabrics become chilled or humidity is high, the dew point may be reached and condensation will occur.
Some common waterproof/breathable fabrics are:
Gore-Tex (abbreviated GTX) is a registered trademark of W.L. Gore & Associates best known for its use in relation to waterproof/breathable fabrics. The first commercial consumer product using Gore-Tex was a tent called the Light Dimension that was created and sold by the Seattle firm, Early Winters, Ltd., in 1976. Gore-Tex was co-invented by Wilbert L. Gore (1912-1986) Rowena Taylor and his son, Robert W. Gore. For its invention, Robert W. Gore was inducted into the National Inventors Hall of Fame in 2006. WL Gore and Associates is known for its unique corporate structure. It has consistently been placed on the Fortune magazine top 100 companies to work for worldwide.
|Gore-Tex membrane, electron microphotograph|
Robert Gore was granted U.S. Patent in 1976 for a porous form of polytetrafluoroethylene with a micro-structure characterized by nodes interconnected by fibrils. Robert Gore, Rowena Taylor and Samuel Allen were granted a U.S. Patent in 1980 for a "waterproof laminate". Gore-Tex is used for outdoor clothing, gloves, hats and waterproof boots
Gore-Tex materials are typically based
on thermo-mechanically expanded polytetrafluoroethylene (PTFE) and other
fluoropolymer products. They are used in a wide variety of applications such
as high performance fabrics, medical implants, filter media, insulation for
wires and cables, gaskets and sealants.
|Schematic diagram of a
Gore-Tex fabric for outdoor clothing
The best known application for Gore-Tex fabrics is in outdoor activity
In this context, it helps keep the wearer protected from the wind and rain, while nonetheless allowing sweat to evaporate and escape. This is in contrast to traditional plastic raincoats, for example, which lack breathability and therefore promote a build up of humidity in the air inside the coat, preventing sweat from evaporating effectively.
Gore-Tex is also used in surgery as an implant material, patch or membrane, such as in plastic surgery and heart surgery.
Gore requires that all garments made from their material have taping over the seams, to eliminate leaks. Gore's sister product, Windstopper, is similar to Gore-Tex in being windproof and breathable, but (1) has ability to stretch and (2) is not waterproof.