Durable Water Repellent
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Durable water repellent, or DWR, is a coating added to
fabrics Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
at the factory to make them
water-resistant Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...
(''
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, th ...
''). Most factory-applied treatments are
fluoropolymer A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon ...
based; these applications are quite thin and not always effective. Durable water repellents are commonly used in conjunction with waterproof breathable fabrics such as
Gore-Tex Gore-Tex is a waterproof, breathable fabric membrane and registered trademark of W. L. Gore & Associates. Invented in 1969, Gore-Tex can repel liquid water while allowing water vapor to pass through and is designed to be a lightweight, waterpr ...
to prevent the outer layer of fabric from becoming saturated with water. This saturation, called 'wetting out,' can reduce the garment's breathability (moisture transport through the breathable membrane) and let water through. As the DWR wears off over time, re-treatment is recommended when necessary. Many spray-on and wash-in products for treatment of non-waterproof garments and re-treatment of proofed garments losing their water-repellency are available. Older methods for factory application of DWR treatments involve applying a solution of a chemical onto the surface of the fabric by spraying or dipping. More recently the chemistry is applied in the vapor phase using
chemical vapor deposition Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (substra ...
(CVD) machinery. The advantages of CVD include eliminating the use of hazardous and environmentally harmful solvents in the application process; requiring less chemical; and an extremely thin waterproof layer that has less effect on the natural
look and feel In software design, the look and feel of a graphical user interface comprises aspects of its design, including elements such as colors, shapes, layout, and typefaces (the "look"), as well as the behavior of dynamic elements such as buttons, boxes ...
of the fabric. Some researchers have suggested that the use of PFASs in water-repellent clothing is over-engineering, and comparable performance can be achieved using specific silicon- and hydrocarbon-based finishes.


Re-treating garments

Certain types of fabrics need to be re-treated to maintain water-repellency, as fluoropolymers
decompose Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ...
over time when exposed to water and chemicals. Washing the garment with harsh detergents usually accelerates DWR loss; in addition, soaps often leave a residue which attracts water and dirt. On the other hand, rain water or salt water affects DWRs less significantly. Affected garments can be treated with a 'spray-on' or 'wash-in' treatment to improve water-repellency. In some cases heat treatment can reactivate the factory applied repellent finish and aid in the repelling of water, and other liquids such as oils. On the other hand, some DWR products do not require heat treatment to be activated, and sometimes DWR treatments can be revitalized simply by washing the fabric with a suitable cleaner.


Cravenette

Cravenette was an old process to make cloths water-repellent. It was a performance finish that repelled water. Various U.S.-based suppliers, such as A. Murphy, W.G. Hitchcock, and H. Herrmann, were offering Cravenette-treated cloths in the early 20th century.


See also

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P2i P2i is a nanotechnology development company that works with manufacturers to produce liquid repellent nano-coating protection to products for the electronics, lifestyle, life sciences, filtration and Energy, and military and institutional sectors. ...
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Perfluorobutanesulfonic acid Perfluorobutanesulfonic acid (PFBS) is a chemical compound having a four-carbon fluorocarbon chain and a sulfonic acid functional group. It is stable and unreactive because of the strength of carbon–fluorine bonds. It can occur in the form of ...
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Perfluorooctanoic acid Perfluorooctanoic acid (PFOA; conjugate base perfluorooctanoate; also known colloquially as C8, for its 8 carbon chain structure) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes an ...
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Scotchgard Scotchgard is a 3M brand of products, a stain and durable water repellent applied to fabric, furniture, and carpets to protect them from stains. Scotchgard products typically rely on organofluorine chemicals as the main active ingredient along ...
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Finishing (textiles) In textile manufacturing, finishing refers to the processes that convert the woven or knitted cloth into a usable material and more specifically to any process performed after dyeing the yarn or fabric to improve the look, performance, or "hand" ...
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Nikwax Analogy Nikwax Analogy is a two-component fabric system for weatherproof clothing based on "biomimicry" of fur (the system was originally called "Nikwax Biological Analogy"). Technology The key to the system is the inner "pump" layer which is designed to ...


References

{{reflist Technical fabrics Textile chemistry Textile treatments