Fabric water-repellent/waterproof

A new process of water repelling-waterproofing of fabrics depends in part upon cataphoresis. The Tate electrical process of water-repelling waterproofing, as dis-... 

To impart the required functional properties to fibers, yams, and fabrics, it is customary to subject textile materials to different types of physical and chemical treatments. For example, wash-and-wear finish for a cotton fabric is necessary to make it crease- or wrinkle-free. In a similar way, mercerizing, singeing, flame-retardant, water-repellent, waterproof, antistatic, and peach finishing achieve various fabric properties desired by consumers. 

Most commercial aluminum formate is monobasic aluminum diformate because of the difficulties involved in triformate preparation. The main appHcation is in textile waterproofing. Aluminum formate reacts with casein to form a water-soluble complex, which can emulsify paraffin and certain other waxes. Fabrics immersed in these emulsions are rendered water repellent (26—28). 

Early waterproofing treatments consisted of coatings of a continuous layer impenetrable by water. Later water-repellent fabrics permitted air and moisture passage to improve the comfort of the wearer. Aluminum and zirconium salts of fatty acids, siUcone polymers, and perfluoro compounds are apphed to synthetic as well as natural fibers. An increase in the contact angle of water on the surface of the fiber results in an increase in water repeUency. Hydrophobic fibers exhibit higher contact angles than ceUulosics but may stiU require a finish (142). 

Water Repellency and Water Resistance. Water repeUency is defined as the abihty of a textile fiber, yam, or fabric to resist wetting, whereas water resistance is a general term appHed to a fabric s abiUty to resist wetting and penetration by water (2). A third term, waterproof, is appHed to those fabrics that do not allow any water penetration at all. Waterproof fabrics are generally coated with an impermeable surface layer that does not allow air permeabihty. Water-repellent finishes are hydrophobic compounds that are appHed to fabrics to inhibit water penetration while still allowing air permeabihty. 

Question 7.6 How Is a Fabric Made Water-Repellent or Waterproof ... 

Designing effective water-repellent, water-resistant, or waterproof fabrics to provide protection in inclement weather or during certain outdoor activities requires an understanding of the chemical and physical properties of water. Whether you are sailing in wind-driven rain, hiking in a downpour, or sitting on a wet surface, chemistry can keep you dry ... 

The Teijin Company in Japan developed a fabric named Snper-Microft with high water repellency by emulating the strncture of a lotns leaf. Water rolls like mercnry from the lotus leaf, whose surface is microscopically rough and covered with a waxlike substance with low snrface tension. It was reported that Snper-Microft exhibits good water-repellent dnrability and a high wear resistance, and at the same time it possesses moisture permeability and waterproof characteristics. 

Oil and Water Repellents Several classes of chemical agents exist that impart water and/or oil repellency when applied to textile substrates. Some finishes give water repellency only, whereas other finishes impart both water and oil repellency. Water repellent finishes are those which permit the fabric to continue to breathe after treatment, whereas waterproof treatments completely seal the spaces between individual yarns, as in... 

The main difference between water-repellent and wateiproof fabrics is the greater permeability of the former to water under hydrostatic pressure and to water vapor [2]. Water-repellent fabrics, but not waterproof fabrics, permit passage... 

The oldest repellent finish is to repel water. The purpose of this finish is self evident. Drops of water should not spread on the surface of the textile and should not wet the fabric. The drops should stay on the surface and easily drip off. Similarly, oil repellent finishes should prevent oily fluids from wetting treated textiles. In a similar manner, soil-repellent finishes should protect textiles from both dry and wet soils. In all cases, the air permeability of the finished fabric should not be significantly reduced. Waterproofing treatments will not be covered in depth. A waterproof textile should withstand the hydrostatic pressure exerted by a column of water from at least aim height before the first drops of water penetrate through the fabric. In practice this is mostly achieved with coatings which have the disadvantages of stiff handle, lack of air and vapour permeability and consequently poor wear comfort. 

Waterproof Finishes. Waterproofing results from coating a fabric and filling the pores with film-forming material such as varnish, mbber, nitrocellulose, wax, tar, or plastic. The materials may be appHed as hot melts, eg, waxes or some polymers, as solvent solutions, or as aqueous latexes. The continuity of the film provides the water resistance. Except for tents, tarpaulins, and covers, coated fabrics have beenlaigely replaced by plastics, and by fabrics treated with water and oil repellents that do not reduce pemieabiHty to air and water vapor. Fabrics are also commonly laminated to films, such that the total stmcture is waterproof (15), or ia some cases water-resistant but breathable (16). 

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