Shrinkage is a phenomenon that occurs when the length or width of textiles changes in a certain state after washing, dehydration, drying, etc. The degree of shrinkage involves different kinds of fibers, the structure of the textiles, and different external effects during the processing of textiles. The degree of shrinkage involves different kinds of fibers, fabric structure, fabric processing by different external forces, etc., has a different performance.
Objectively speaking, cotton fabrics generally have the problem of shrinkage and discoloration, so the home textile fabrics are pre-shrinkage treatment. It is worth noting that after the pre-shrinkage treatment is not the same as not shrinking, but refers to the shrinkage rate control in the national standard 3% -4% or less. In the purchase of fabrics, in addition to the quality of fabrics, color, pattern selection, the shrinkage rate should also have an understanding.
What is the shrinkage rate？
The fiber itself absorbs water, will produce a certain degree of swelling. Usually, the swelling of fibers is anisotropic (except nylon), i.e., the length is shortened and the diameter is increased. The difference between the length of the fabric before and after it has been exposed to water, as a percentage of its original length, is usually called the shrinkage rate. The stronger the water-absorbing capacity, the more intense the swelling, the higher the shrinkage rate, the poorer the dimensional stability of the fabric.
“Shrinkage, formally known as “rate of dimensional change in washing”, is the percentage of shrinkage of a textile after washing or immersion in water.
Shrinkage rate = (size before washing – size after washing)/ size before washing x 100%.
Reasons for shrinkage
1, fiber in the spinning, or yarn in the weaving and dyeing and finishing, the fabric of the yarn fibers by the external forces and elongation or deformation, while the yarn fibers and the fabric structure generates internal stress, in the static dry relaxation state, or static wet relaxation state, or in the dynamic wet relaxation state, the full relaxation state, the release of different degrees of internal stress, so that the yarn fibers and the fabric back to the initial state.
2, different fibers and their fabrics, the degree of shrinkage are different, mainly depends on the characteristics of its fibers – hydrophilic fibers shrinkage is greater, such as cotton, hemp, viscose and other fibers; and hydrophobic fibers shrink less, such as synthetic fibers and so on.
3, the fiber in the wet state, due to the role of the liquid produced under the expansion, so that the diameter of the fiber becomes larger, such as in the fabric, forcing the fabric of the interweaving point of the fiber radius of curvature increases, resulting in shortening the length of the fabric. For example, cotton fiber expansion under the action of water, the cross-sectional area increased by 40 to 50%, the length increased by 1 to 2%, and synthetic fibers are heat shrinkage, such as boiling water shrinkage, generally about 5%.
4, textile fibers under thermal conditions, the shape and size of the fiber changes and contraction, cooling can not return to the initial state, known as fiber heat shrinkage.
General fabric shrinkage
Cotton 4% – 10%;
Chemical fiber 4% – 8%;
Cotton polyester 3.5% – 5 5%;
Native white fabric is 3%;
Wool blue cloth is 3-4%;
Poplin is 3-4.5%;
3-3.5% for floral fabric;
4% for twill cloth;
10% for labor cloth;
10% for rayon.
What are the factors affecting shrinkage?
Raw material
Different raw materials have different shrinkage rates. Generally speaking, the hygroscopicity of the fiber, after immersion in water, fiber expansion, diameter increase, length shortening, shrinkage rate is large. Such as viscose fiber water absorption rate of up to 13%, while the synthetic fiber fabric moisture absorption is poor, its shrinkage rate is small.
Density
Fabric density is different, shrinkage is different. If the density of the warp and weft to the similar, the warp and weft to the shrinkage rate is also close. Warp density of fabrics, warp shrinkage is large, on the contrary, weft density is greater than the warp density of fabrics, weft shrinkage is also large.
Yarn thickness
Fabric yarn thickness is different, shrinkage rate is also different. Coarse yarn fabric shrinkage rate is large, yarn fine fabric shrinkage rate is small.
Production process
Fabric production process is different, shrinkage rate is also different. In general, the fabric in the weaving and dyeing and finishing process, the fiber to stretch many times, processing time is long, the fabric shrinkage rate of the larger applied tension is large, and vice versa is small.
Fiber composition
Natural plant fibers (such as cotton, hemp) and plant regenerated fibers (such as viscose) compared with synthetic fibers (such as polyester, acrylic), easy to absorb moisture and expansion, so the shrinkage rate is larger, while wool is easy to felt due to the scaled structure of the fiber surface, affecting its dimensional stability.
Fabric structure
In general, the dimensional stability of woven fabrics is better than that of knitted fabrics; the dimensional stability of high-density fabrics is better than that of low-density ones. In woven fabrics, the general shrinkage rate of plain fabrics is less than that of facecloth fabrics; and in knitted fabrics, the shrinkage rate of flat needle organizations is less than that of ribbed fabrics.
Production process
As the fabrics are dyed, printed and finishing process, it is inevitable that they will be stretched by the machine, thus there is tension present on the fabrics. However, the fabric can easily release the tension when it meets water, so we will find that the fabric shrinks after washing. In the actual process, we generally use pre-shrinkage to solve this problem.
Washing care process
Wash care includes washing, drying, and ironing, and each of these three steps affects the shrinkage of the fabric. For example, the dimensional stability of hand-washed samples is better than that of machine-washed samples, and the temperature of the wash also affects its dimensional stability. In general, the higher the temperature, the worse the stability. The way the sample is dried also has a greater impact on the shrinkage of the fabric.
