Common textile fabric shrinkage rates and influencing factors



Shrinkage is the change in length or width of textiles after washing, dehydration, drying and other processes in a certain state. a phenomenon. The degree of shrinkage involves dif…

Shrinkage is the change in length or width of textiles after washing, dehydration, drying and other processes in a certain state. a phenomenon. The degree of shrinkage involves different types of fibers, the structure of the fabric, the different external forces exerted on the fabric during processing, etc.

“Synthetic fibers and blended fabrics have the smallest shrinkage, followed by woolen fabrics, linen fabrics, and cotton fabrics in the middle. Silk fabrics have a larger shrinkage, and viscose has the largest shrinkage rate. Fiber, artificial cotton, artificial wool fabrics. ”

Objectively speaking, all cotton fabrics have the problem of shrinkage and fading. The key is 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 within the national standard of 3% to 4%. Underwear materials, especially natural fiber 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.

Shrinkage of general fabrics

Cotton: 4%~10%;

Chemical fiber: 4%~8%;

Cotton-polyester: 3.5%~5 5%;

Natural white cloth: 3%;

Poplin: 3~4.5%;

Twill: 4%;

Labor cloth: 10%;

Rayon: 10%.

The influence of fiber and weaving shrinkage

After the fiber itself absorbs water, it will produce a certain degree ofof swelling. 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 is different from the length of the yarn (silk) used. The difference between the two is usually expressed by the shrinkage rate. . Shrinkage (%) = [Yarn (silk) line length – Fabric length] / Fabric length

After the fabric is put into water, due to the swelling of the fiber itself, the 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. The weaving tension is small, the fabric is tight and thick, the weaving shrinkage is large, and the shrinkage of the fabric is small.

If the weaving tension is large, the fabric will be loose and light, and if the weaving shrinkage is small, the shrinkage of the fabric will be large. In the dyeing and finishing process, in order to reduce the shrinkage of the fabric, pre-shrinkage finishing is often used to increase the weft density and increase the weaving shrinkage in advance, thereby reducing the shrinkage of the fabric.

Causes of shrinkage

 1. When the fiber is spinning, or when the yarn is weaving, dyeing and finishing, the yarn fibers in the fabric are elongated or deformed by external forces. At the same time, the yarn fibers and the fabric structure generate internal stress. In the static state In the dry relaxation state, or the static wet relaxation state, or in the dynamic wet relaxation state, or the full relaxation state, the internal stress is released to varying degrees, causing the yarn, fiber and fabric to return to their original state.

 2. 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. For example, fibers such as cotton, linen, and viscose; while hydrophobic fibers shrink less, such as synthetic fibers.

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

4. When textile fibers are heated, the shape and size of the fibers change and shrink, and they cannot return to shape after cooling.Returning to the initial state is called thermal shrinkage of the fiber. The percentage of length before heat shrinkage and after heat shrinkage is called heat shrinkage rate. It is generally measured by boiling water shrinkage. In boiling water at 100°C, the percentage of fiber length shrinkage is expressed.

There is also a hot air method, which measures the shrinkage percentage in hot air exceeding 100°C, and a steam method, which measures the shrinkage percentage in steam exceeding 100°C. The percentage of its shrinkage. Fibers behave differently due to internal structure and heating temperature, time and other conditions. For example, the boiling water shrinkage rate of polyester staple fiber processing is 1%, the boiling water shrinkage rate of vinylon is 5%, and the hot air shrinkage rate of chlorine fiber is 50%. Fibers are closely related in textile processing and the dimensional stability of fabrics, which provides some basis for the design of post-processes.

Causes affecting shrinkage

1. 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.

2. Density

The density of the fabric is different, and the shrinkage rate is also different. If the longitudinal and latitudinal densities are similar, the longitudinal and latitudinal shrinkage rates are also similar. Fabrics with a high warp density will have a large shrinkage in the warp direction; conversely, fabrics with a weft density greater than the warp density will have a large shrinkage in the weft direction.

 3. Thickness of yarn count

  The thickness of fabric yarn count is different, and the shrinkage rate is also different. Fabrics with a thicker yarn count will have a greater shrinkage rate, while fabrics with a finer yarn count will have a smaller shrinkage rate.

4. Production process

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

5. Fiber composition

Natural plant fibers (such as cotton, linen) and plant regeneration Fibers (such as viscose) are more likely to absorb moisture than synthetic fibers (such as polyester, acrylic)Swells, so the shrinkage rate is large, while wool is easy to felt due to the scale structure on the fiber surface, affecting its dimensional stability.

6. Fabric structure

Generally speaking, the dimensional stability of woven fabrics is better For 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.

7. Production and processing process

Since the fabric is in the process of dyeing, printing and finishing , it will inevitably be stretched by the machine, so tension exists on the fabric. However, fabrics easily release tension when exposed to water, so we may notice shrinkage in the fabric after washing. In actual processes, we generally use pre-shrinking to solve this problem.

8. Washing care process

Washing care includes washing, drying, and ironing. Each of the 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 washing 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.

In addition, 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 damage its performance, such as making the fabric hard and brittle.

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Author: clsrich

 
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