Textile Finishing; Stain Repellency and Stain Resistant Finishing

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There are some textile products or fabric those used long time without any types of wash. So some special care must be taken for those materials. Stain Repellency finishing and Stain-Resistant Finishing are those special treatment whish ensure the proper care of the textile material. This types of finishing also cares from oil and wax. 

Stain Repellency finishing: 

Scotchgard and other finishes that repel water and oil may be classified as stain resistant finishes. These finishes decrease the surface energy of the fabric so that water or oil beads up rather than penetrating the fiber. Illustrates this principle with two different stain-repellent finishes: fluorochemical and silicone. The fluorochemical finish, like DuPont’s Teflon finish on cookware, prevents both oil and water from penetrating the fabric surface. The silicone finish, which also coats the fabric, repels water but not oil.Soil-Release Finishes 

Soil-release finishes were developed largely as a result of the tendency of durable press and polyester fabrics to absorb and hold oilborne stains. The soil-releasing finish should not be confused with stain-repellent finishes, although Scotchgard is both stain resistant and soil releasing. Soil-release finishes alter the characteristics that cause soil to bond to the fibers. Agents such as polyethylene glycol derivatives may be added to the polymer solution before extrusion to make the nonabsorbent fibers more hydrophilic (“water loving” or having a strong affinity to water). Other finishes may form hydrophilic grafts on the fiber resulting in improvements in soil release and soil redeposition. Most soil-releasing finishes are applied during the finishing of the fabric and are compatible with durable pres; finishes. 

Some fluorochemical finishes are dual-acting. They are block copolymers of fluorocarbons and polar segments such as esters. In air the fluorocarbon sections come to the surface to repel oily substances. When the finished fabric is immersed in water, however, the polar hydrophilic sections predominate on the surface, attracting water to help release soils. At the same rime that soil-releasing finishes increase the receptivity of fibers to water, a second benefit is gained. Static electricity buildup is decreased as absorbency is increased. 

Increased absorbency also increases the comfort of the garment in warm weather. Fuzzing and pilling seem to be decreased by soil releasing finishes as well, because the finish also lubricates the fabric. Effective soil-releasing finishes should result in fabrics from which common soil is removed during home laundering with normal detergents. Oily stains, often hard to remove from durable press fabrics, should be removable in home laundering. The disadvantage of most of these finishes is that they are gradually diminished through laundering. 

Stain Resistant Finishing: 

Stain-resistant finishes for nylon carpets were developed to increase the resistance of these carpets to food and other common stains. The finishes are generally sulfonated aromatic condensation (SAC) compounds that function essentially as colorless dyes. The stain blockers, which have negative charges, are attracted to the positive sites in the nylon fibers, tie up the dye sires, and set up a barrier layer to staining materials. Many food stains, for example, which are negatively charged like the stain resist molecules, are not absorbed as easily. Today, stain-resistant finishes are used on most nylon carpets for residential use. One trademark is DuPont’s Stainmaster.

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Textile Finishing; Waterproofing finishing, Soil and Water Repellency finishing

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Textile Finishing and Fabric finishing is very important terms in textile manufacturing area. We need some special task with textile material to meet the buyer requirement. We know that natural fibres as well as textile fabric manufactured with natural fibre absorb the water. So it easily passes water with their surface. If we want to protect passing water or making the water proof fabric surface, we need to do some special treatment to surface of the fabric. This could be known as water proofing finishing. This is similar for Soil and Water Repellency finishing. The term water repellent should not be confused with the term waterproof Water-repellent fabrics resist penetration by water but are not completely waterproof. Such fabrics represent a practical alternative to fabrics that keep out water and air.

Waterproofing finishing: 

For a fabric to be truly waterproof, it must be completely sealed with a substance that is insoluble in water. The familiar rubber coated garb of police officers and firefighters is a good example. Modern waterproofing materials include the vinyl resins, which do not oxidize and crack as readily as rubber. Synthetic rubbers are also more durable to outside influences than natural rubber. The fabrics used in most of today’s waterproof materials are cotton and nylon. The latter, coated with vinyl resins, has largely superseded the heavy canvas tarpaulins used to protect merchandise in transit. A fabric that is waterproof allows no water to penetrate from the surface to the underside. Coatings made from rubber or synthetic plastic materials can create fabrics that are completely waterproof; however, these fabrics tend to be warm and uncomfortable because they create a barrier that traps air and perspiration close to the body.

The dilemma of providing protection and comfort was resolved by the development of fabrics that are described as waterproof and breathable (WP/B). The general principle behind these fabrics is that they keep out water from rain and snow but allow the passage of moisture vapor from perspiration. They are promoted for use in outdoor clothing and for active sports. One of the first of these products was Gore- Tex, made by placing a membrane of fluoropolymer underneath a layer of outer fabric. The membrane is porous.

The pores are smaller than a drop of water that contains many water molecules, but they are larger than a molecule of water vapor. This structure keeps out rain but allows moisture from perspiration to escape.

The success of Gore- Tex has led to the production of other products using similar principles. Many of these use polyurethane coatings with microscopic pores. Sympatex, a polyester membrane for lamination, is nonporous but breathable. A charged outer surface attracts polar water molecules which are drawn through the membrane. Also helping to “push” moisture vapor through is the high vapor pressure on the body side (Sympatex 1988).

Soil and Water Repellency finishing:

Soiling results when a textile comes into contact with soiled surfaces or with air- or waterborne soils. Soil is retained either by mechanical entrapment of soil particles within the yarn or fabric structure or by electrostatic forces that bond the soil to the fabric. One way to approach the problem of soiling is to prevent its deposition on the fabric. Another is to seek ways to facilitate its removal. Special finishes have been developed that have taken both of these approaches.

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Fabric Shrinkage Control by Textile Finishing

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Fabric finishing is most effective procedure to maintain the fabric property. Most of the fabric property could be maintained by textile finishing. There are different types of textile finishing. Such as Mechanical finishing, Chemical finishing or other special finishing. 

Fabric shrinkage is one of most important fabric property. Shrinkage property is depending upon the fibre property. It effects in finished garments shape. We know that every style of garments have particular size. The most popular sizes are Small(S), Medium(M), Large(L), Extra Large(XL) etc. size of particular garment indicate by pattern grading. Most probably 1cm to 2 cm varies from one size to another size. Due to shrinkage the size of the garment could be change abnormally. For example Length of a garments increase but chest does not change. So it will be subjected as size mistake but the size was ok during fabric cutting. That’s why shrinkage property of fabric must be controlled by particular finishing method before cutting the fabric. 

A reduction in the length or width of a fiber, yarn, or fabric is known as shrinkage. If fabrics shrink after they have been made into garments or household items, they may decrease in size to such an extent that the item is no longer serviceable. For example, a garment with a 25-inch waist size will decrease by 11\4 inches if it shrinks 5 percent. Growth occurs when a fabric increases in dimension. Some fibers such as wool, cotton, and rayon swell more in water than do others. Fabrics made from these fibers are less dimensionally stable than fabrics made from fibers with lower moisture absorbance. Wetting a fabric causes the tension that has been applied during its manufacture to be relaxed, so that fabrics generally shrink after the first and subsequent launderings. This type of shrinkage is known as relaxation shrinkage. It occurs because the moisture within the fibers allows them to return to the dimensions they occupied before they were stretched during processing. The amount of relaxation shrinkage depends on the amount of stretching the fibers underwent during manufacturing. 

Wool fibre and rayon fibre, which are more extensible, will stretch more and therefore have greater potential for relaxation. Successive heating and drying cycles may produce progressive shrinkage, where the fabric continues to shrink. Woven fabrics generally shrink more in the warp than in the filling direction because the warp yarns are under greater tension during weaving. When the fabric is later subjected to moisture, or heat in the case of thermoplastic fibers, the stresses within the fibers are relieved, and the fabric relaxes. Fibers that are moisture-absorbent absorb a significant amount of water and swell. Accordingly, the yarn diameter increases, and the yarns in each direction must move closer together to accommodate the yarns in the opposite direction. This is a less strained position for the yarns and results in a permanent increase in crimp, especially in warp yarns. 

Knit goods tend to stretch more during manufacture than woven goods, and therefore knit goods are likely to shrink and change shape even more than woven goods. Procedures and solvents used in commercial dry cleaning, as a rule, do not permit fabrics to relax, as washing does, so that items that are dry cleaned may not shrink as readily. Shrinkage in dry cleaning generally results from the high moisture content in the solvent or from steaming the fabric during pressing.

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