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[fabric dying] Water-repellent processing and waterproof processing

2019-01-18 16:37
In waterproof processing, waterproof and water-repellent fabrics should be distinguished.

Waterproof fibers prevent the passage of water as a whole, which is usually only a little moisture transfer while preventing water from passing through, such as rainwater. These are thin film-coated fibers such as urethane. Thus, the raincoat is entirely covered with a plastic film such as vinyl, urethane or synthetic fiber. However, these garments have good water resistance but poor fit.

The role of water repellent fibers is very important. This is because many fibers, such as natural fibers and synthetic cellulose fibers, are extremely absorbent and should be used as water-repellent materials regardless of their compactness. Other fibers, such as thermoplastic fibers, may also be water-repellent, provided that they have a sufficiently high fiber composition ratio for the garment and are sufficiently dense to avoid the passage of water. Mixing of thermoplastic fibers and cotton is very rare, but in recent years, the mixture has become popular so that thermoplastic fibers can be repaired using the property of expanding the cotton when wet. There are various methods of water repellent treatment.

This is found in runner fabrics and is a runner fabric that is fed light mineral oil suitable for items such as shower curtains. This method is rarely used today, but it is also possible to feed heavy military canvas cloth with paraffin wax and metallic salts. In the case of a raincoat, it has some durability for washing and dry cleaning although it has discomfort for clothes.

Another method uses a pyridine salt. It is vulnerable to dry-cleaning but produces some durability. However, this method is new. Fatty acids can also be used to obtain water-repellent surfaces, which can be obtained by the reaction of a metal ion-introduced fiber with an alkaline metal salt of a soap-fatty acid. This is based on the principle of the chemical reaction of soap with a fabric into which metal ions have been introduced as a result of the formation of metallic soaps that are not soluble in water.

Due to the advances in silicon chemistry used in textiles, these methods have become outmoded. The type of silicon that is often blended with most fibers is obtained from chlorosilanes, and silicon forms crosslinks. The cross-linking of cellulose fibers requires heat fixation, which may be used in wool without application of heat. When the silicone reacts with cellulose, it lays side by side on the surface of the fibers, and when a catalyst of the proper concentration is applied, durable water repellency is produced in washing and dry cleaning. Water repellency, now widely popular, lowers the surface tension to prevent water from passing through, but it can be damaged by detergent residues. The new water-repellent treatment uses a fluoropolymer. Although this treatment requires too high a temperature for crosslinking, it is mechanical in popular general processing. It is often provided as a multimeter such as an aerosol. This provides durability to fiber surfaces and fibers covered with fluorine compounds. The application of a strong treatment is required to be waterproof, but such gentle chemistry can be maintained until it wears down to other surfaces. Sometimes, water-repellent aerosols cause the fibers to yellow.