The shrinkage is the smallest is synthetic fiber and blended textiles, followed by wool, linen, cotton fabrics in the middle, silk fabric shrinkage is larger, and the largest viscose fiber, Rayon, man-made wool fabrics.
Objectively speaking, more or less all cotton fabrics have the problem of shrinkage fading, the key is the finishing behind. So the fabric of General Home Textile is preshrunk after processing.
It is worth noting that the pre-shrinkage treatment is not equal to no shrinkage, but refers to shrinkage rate control in the national standard 3%-4% underwear materials, especially natural fiber fabrics will shrink. Therefore, in the purchase of clothing materials, in addition to the quality of the fabric, color, pattern selection, the shrinkage of the fabric should also have some knowledge.
- Effect of fibre and shrinkage
After the fiber itself absorbs water, it will produce a certain degree of swelling. Usually the swelling of the fiber is anisotropic (except for Nylon) , that is, the length is shortened and the diameter is increased. Usually the fabric before and after the length of the difference and its original length as a percentage of shrinkage. The stronger the water absorption, the more intense the swelling, the higher the shrinkage, the worse the dimensional stability of the fabric.
The length of the fabric itself is different from the length of the yarn (silk) used and the shrinkage is usually used to indicate the difference.
Shrinkage (%) = [ yarn (silk) thread length-fabric length ]/fabric length
Fabric in the water, due to the swelling of the fiber itself, so that the fabric length is further shortened, resulting in shrinkage. The shrinkage of a fabric varies with the shrinkage of the fabric. The shrinkage is different with the fabric structure and the weaving tension. The weaving tension is small, the fabric is compact and thick, the shrinkage is big, the shrinkage is small; the weaving tension is big, the fabric is loose and light, the shrinkage is small, the shrinkage is big. In dyeing and finishing, in order to reduce the shrinkage of the fabric, pre-shrinkage finishing is often used to increase the weft density and increase the shrinkage in advance, thus reducing the shrinkage of the fabric.
- Causes of shrinkage:
1) when the yarn is spinning, or when the yarn is weaving, dyeing or finishing, the yarn fibers in the fabric are stretched or deformed by external forces, while the yarn fibers and the fabric structure are under internal stress in either a static state of dry relaxation or a static state of wet relaxation, or in the dynamic state of wet relaxation, full relaxation, different degrees of stress release, so that the yarn fiber and fabric back to the initial state.
2) Different fibers and their fabrics have different degrees of shrinkage, depending mainly on the characteristics of their fibers-hydrophilic fibers have a higher degree of shrinkage, such as cotton, hemp, viscose and other fibers, while hydrophobic fibers have a lower degree of shrinkage, synthetic fibers, for example.
3) When the fiber is wetted, it expands under the action of the soaking liquid, which increases the diameter of the fiber. For example, on the fabric, the radius of curvature of the interlacing point of the fabric increases and the length of the fabric is shortened. For example, cotton fiber expanded in the role of water, cross-sectional area increased 40 ~ 50% , length increased 1 ~ 2% , and synthetic fiber is on the heat shrinkage, such as boiling water shrinkage, generally about 5% .
4) Under the heating condition of textile fiber, the shape and size of the fiber change and shrink, after cooling can not return to the initial state, called the fiber heat shrink. The percentage of the length before and after the thermal shrinkage is called the thermal shrinkage rate, which is usually measured in boiling water and expressed as the percentage of the length of the fibre in boiling water at 100 °C, the percentage shrinkage is measured in hot air above 100 °C or in steam above 100 °C. For example, the boiling water shrinkage of pet staple fiber is 1% , the boiling water shrinkage of vinylon is 5% , and the hot air shrinkage of PVC fiber is 50% . The dimensional stability of fibers in textile processing is closely related to the dimensional stability of fabrics, which provides some basis for the design of post-processing.
- The shrinkage of general fabrics is:
Cotton 4%-10% ,
chemical fiber 4%-8% ,
cotton polyester 3.5%-55% ,
natural color white cloth 3% ,
wool blue cloth 3-4% , poplin 3-4.5% ,
cotton cloth 3-3.5% ,
twill cloth 4% ,
labor cloth 10% ,
man-made cotton 10% .
4. REASONS FOR SHRINKAGE:
The shrinkage of fabrics is different with the raw materials. In general, hygroscopicity of the fiber, soaked after the fiber expansion, diameter increases, length shortened, shrinkage is large. If some viscose fiber water absorption rate as high as 13% , and synthetic fiber fabric hygroscopicity is poor, its shrinkage is small.
The shrinkage of the fabric varies with its density. If the Longitudinal and latitudinal densities are similar, the Longitudinal and latitudinal shrinkage rates are also close. Warp density of the fabric, warp shrinkage will be large, conversely, weft density is greater than warp density of the fabric, weft shrinkage is also large.
3） Yarn Count
The shrinkage of the fabric is different with the yarn thickness. The shrinkage of the fabric with thick yarns is large, and that of the fabric with thin yarns is small.
The shrinkage of fabric is different with different production process. Generally speaking, the fabric in the weaving and dyeing and finishing process, fiber to stretch many times, processing time is long, the application of tension larger fabric shrinkage, otherwise small.
Natural plant fiber (such as cotton, hemp) and plant regeneration fiber (such as viscose) are easier to absorb moisture than synthetic fiber (such as polyester, acrylic) , so the shrinkage rate is larger, while wool is easier to felting because of the scale structure on the surface of the fiber, affect its dimensional stability.
In general, the dimensional stability of woven fabric is better than that of knitted fabric, and the dimensional stability of high density fabric is better than that of low density fabric. In woven fabrics, the shrinkage of plain weave fabric is less than that of flannel fabric, while in knitted fabrics, the shrinkage of plain weave is less than that of rib fabric.
As the fabric in dyeing, printing, finishing process, will inevitably be stretched by the machine, there is tension in the fabric. However, the tension of the fabric can be easily relieved when it meets water, so we will find that the fabric will shrink after washing. In the actual process, we generally use pre-shrinkage to solve this problem.
8） Washing process
Washing care includes washing, drying and ironing, each of which 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 washing temperature also affects the dimensional stability. In general, the higher the temperature, the worse the stability. The drying method of the sample also has a great influence on the shrinkage of the fabric.
Commonly used drying methods are, drip drying, Metal Mesh paving method, hanging drying and rotary drying method. Among them, the drip drying method has the least influence on the fabric size, while the drum drying method has the most influence on the fabric size, and the other two methods are in the middle.
In addition, selecting a suitable ironing temperature according to the composition of the fabric can also improve the shrinkage of the fabric. For example, cotton and linen fabrics can be ironed at high temperatures to improve their dimensional shrinkage. However, the higher the temperature, the better, for synthetic fiber, high-temperature ironing can not improve its shrinkage, but will damage its performance, such as fabric hair hard brittle and so on.
Post time: Jun-08-2022