Friday, January 4, 2013

Fabric Shrinkage Control by Textile Finishing

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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