What is the shrinkage rate of textile fabrics

The shrinkage of fabric refers to the percentage of fabric shrinkage after washing or soaking in water. Shrinkage is a phenomenon in which the length or width of fabrics changes after cleaning, dehydration, drying and other processes in a certain state. The degree of shrinkage involves different types of fibers, the structure of the fabric, the different external forces exerted on the fabric during finishing, etc.

Synthetic fiber and blended chemical fiber fabrics have the smallest shrinkage, followed by woolen fabrics, linen fabrics, and cotton fabrics in the middle. Silk fabrics have the largest shrinkage, and the largest ones are viscose fiber, artificial cotton, and artificial wool. Fabric. Objectively speaking, Cotton fabrics have the problem of shrinking and fading to some extent. The key lies in the subsequent finishing. Therefore, most home textile fabrics are preshrunk. It is worth noting that pre-shrinking does not mean that there is no shrinkage, but that the shrinkage rate is controlled below the national standard of 3%-4%. Underwear materials, especially natural fiber clothing materials, will shrink.

Therefore, when purchasing clothing materials, in addition to selecting the quality, color, and pattern of the fabric, you should also understand the shrinkage rate of the fabric.

1. The influence of fiber and weaving shrinkage

After the fiber itself absorbs water, it will swell to a certain extent. Usually the swelling of fibers is anisotropic (except for nylon), that is, the length shortens and the diameter increases. The percentage of the length difference between the fabric before and after it is washed and its original length is usually called shrinkage. The stronger the water absorption capacity, the more intense the swelling, the higher the shrinkage, and the worse the dimensional stability of the fabric.

The length of the fabric itself and the length of the yarn (silk) used are different, and the shrinkage rate is usually used to express the difference between the two.

Weaving shrinkage (%) = [yarn (silk) thread length – fabric length]/fabric length

After the fabric is put into the water, due to the swelling of the fiber itself, the length of the fabric is further shortened, resulting in shrinkage. Different shrinkage rates of fabrics result in different shrinkage rates. The fabric’s own organizational structure and weaving tension are different, and its shrinkage rate is different. If the weaving tension is small, the fabric will be tight and thick, and if the weaving shrinkage rate is large, the shrinkage rate of the fabric will be small; if the weaving tension is high, the fabric will be loose and light, if the weaving shrinkage rate is small, the shrinkage rate of the fabric will be large. In dyeing and finishing, in order to reduce the shrinkage of the fabric, pre-shrinking and post-finishing are often used to increase the weft density and increase the weaving shrinkage in advance, thereby reducing the shrinkage of the fabric.

2. Reasons for shrinkage

When fibers are spinning, or when spinning yarns are weaving, dyeing and finishing, the spinning fibers in the fabric are elongated or deformed by external forces. At the same time, the spinning fibers and fabric structure produce Internal stress, in a static dry relaxation state, a static wet relaxation state, or in a dynamic wet relaxation state, or a full relaxation state, is released to varying degrees, causing the spinning fibers and fabrics to return to their original state.

Different fibers and their fabrics have different shrinkage degrees, which mainly depend on the characteristics of the fibers – hydrophilic fibers shrink to a greater degree, such as cotton, linen, viscose and other fibers; and Hydrophobic fibers shrink less, such as synthetic fibers.

When the fiber is in a wet state, it will swell due to the action of the soaking liquid, making the fiber diameter larger. For example, on a fabric, it forces the fiber curvature radius at the intersection point of the fabric to increase, resulting in a shortening of the length of the fabric. . For example, cotton fiber expands under the action of water, and its cross-sectional area increases by 40-50% and its length increases by 1-2%, while synthetic fibers shrink by heat, such as boiling water, generally about 5%.

When fabric fibers are heated, the shape and size of the fibers change and shrink, and they cannot return to their original state after cooling, which is called thermal shrinkage of the fibers. The percentage of length before and after heat shrinkage is called heat shrinkage. It is generally measured by boiling water shrinkage. In boiling water at 100°C, the percentage of fiber length shrinkage is expressed. It can also be expressed by hot air method, in hot air exceeding 100°C. To measure the shrinkage percentage, you can also use the steam method to measure the shrinkage percentage in steam exceeding 100°C. Fibers behave differently due to their internal structure and heating temperature, time and other conditions. For example, the boiling water shrinkage rate of polyester staple fibers is 1%, the boiling water shrinkage rate of vinylon is 5%, and the hot air shrinkage rate of chlorine fiber is 50%. Fiber��There is a close relationship between fabric finishing and the dimensional stability of the fabric, which provides some basis for the design of subsequent processes.

3. The shrinkage rate of general fabrics

Cotton 3%-10%

Chemical fiber 4%-8%

Cotton polyester 3.5%-5.5%

Natural white cloth is 3%

Main blue cloth is 3-4%

Poplin is 3-4.5%

Fabric cloth is 3-3.5%

Twill is 4%

Labor cloth is 10%

Artificial cotton is 10%

4. Reasons affecting shrinkage

Raw materials

Different raw materials of fabrics have different shrinkage rates. Generally speaking, fibers with high hygroscopicity will expand when soaked in water, increase in diameter, shorten in length, and have a large shrinkage rate. For example, the water absorption rate of some viscose fibers is as high as 13%, while synthetic fiber fabrics have poor hygroscopicity and their shrinkage rate is small.

Density

The fabric has different densities and different shrinkage rates. If the longitudinal and latitudinal densities are similar, the longitudinal and latitudinal shrinkage rates are also similar. Fabrics with a higher warp density will shrink more in the warp direction; conversely, fabrics with a higher weft density than warp density will shrink more in the weft direction.

Yarn count and thickness

The fabric yarn count and thickness are different, and the shrinkage rate is also different. Fabrics with coarse yarn counts will have a greater shrinkage rate, while fabrics with fine yarn counts will have a smaller shrinkage rate.

Production process

Different fabric production processes have different shrinkage rates. Generally speaking, during the weaving, dyeing and finishing process of fabrics, the fibers have to be stretched many times, and the finishing time is long. The shrinkage of fabrics with greater tension will be greater, and vice versa.

Fiber content

Natural plant fibers (such as cotton, linen) and plant regenerated fibers (such as viscose) are more likely to absorb moisture and expand than synthetic fibers (such as polyester, polyacrylonitrile fiber), so the shrinkage rate is larger , while wool is simply felted due to the scale structure on the fiber surface, which affects its dimensional stability.

Fabric Structure

Generally, 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 fabrics. Among woven fabrics, the shrinkage rate of plain weave fabrics is generally smaller than that of flannel fabrics; while among knitted fabrics, the shrinkage rate of plain knitted fabrics is smaller than that of ribbed fabrics.

Production and finishing process

As the fabric is inevitably stretched by the machine during the process of coloring, printing, and finishing, tension exists on the fabric. However, fabrics easily lose tension when exposed to water, so we will notice shrinkage of the fabric after cleaning. In actual processes, we generally use pre-shrinking to solve this problem.

Cleaning and care process

Cleaning care includes washing, drying, and ironing. Each of these three steps will affect the shrinkage of the fabric. For example, the dimensional stability of hand-washed samples is better than that of machine-washed samples, and the cleaning temperature will also affect its dimensional stability. Generally speaking, the higher the temperature, the worse the stability. The drying method of the sample also has a relatively large impact on the shrinkage of the fabric.

Commonly used drying methods include drip drying, metal mesh laying, hang drying and drum drying. Among them, the drip drying method has a small impact on the size of the fabric, while the drum drying method has a large impact on the size of the fabric, and the other two are in the middle.

Others, choosing an appropriate ironing temperature based on the composition of the fabric can also improve the shrinkage of the fabric. For example, the dimensional shrinkage of cotton and linen fabrics can be improved by high-temperature ironing. But it is not that the higher the temperature, the better. For synthetic fibers, high-temperature ironing will not only not improve its shrinkage, but will also damage its performance, such as making the fabric hard and brittle.

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