The most common knowledge of shrinking textile fabrics!

2019.06.18SOURCE:

The smallest shrinkage is synthetic fiber and mixed textiles, followed by wool, hemp, cotton, centered, silk fabric shrinks, and the largest is viscose, rayon, artificial wool fabric.
Objectively speaking, there are some problems in shrinking and fading of cotton fabrics. The key is the finishing. Therefore, the fabrics of general home textiles are pre-shrinked.
It is worth noting that the pre-shrinking treatment does not mean that it does not shrink, but that the shrinkage rate is controlled at 3%-4% of the national standard, and the underwear material, especially the natural fiber, will shrink.
Therefore, in the purchase of clothing, in addition to the selection of fabric quality, color, pattern, the shrinkage rate of the fabric should also be known.
1. The influence of fiber and weaving
After the fiber itself absorbs water, it will have a certain degree of swelling. Generally, the swelling of the fibers is anisotropic (except for nylon), that is, the length is shortened and the diameter is increased.
The percentage difference between the length of the fabric before and after the water is taken and its original length is usually referred to as the shrinkage rate. The stronger the water absorption capacity, the more intense the swelling, and the higher the shrinkage rate, the worse the dimensional stability of the fabric.Hebei Hanlin Textile Co., Ltd.are yarn dyed shirts wholesale.
The length of the fabric itself is different from the length of the yarn (filament) used, and the difference in the weaving ratio is usually used to indicate the difference between the two.
Knitting ratio (%) = [yarn (silk) thread length - fabric length] / fabric length
After the fabric is launched, the length of the fabric is further shortened due to the swelling of the fibers themselves, resulting in a shrinkage rate. The weaving rate of the fabric is different, and the shrinkage rate is different.
The fabric structure and the weaving tension of the fabric itself are different, and the weaving rate is different. The weaving tension is small, the fabric is tight and thick, the weaving rate is large, and the shrinkage rate of the fabric is small; the weaving tension is large, the fabric is loose and light, the weaving rate is small, and the shrinkage rate of the fabric is large.
In the dyeing and finishing process, in order to reduce the shrinkage rate of the fabric, the pre-shrinking finishing method is often used to increase the weft density, and the weaving rate is increased in advance, thereby reducing the shrinkage rate of the fabric.
2. Reasons for shrinkage:
(1) When the fiber is spun, or when the yarn is woven and dyed, the yarn fiber in the fabric is stretched or deformed by an external force, and the yarn fiber and the fabric structure generate internal stress, and the static dry state is relaxed. , or static wet relaxation state, or in the dynamic wet relaxed state, full relaxation state, the release of different degrees of internal stress, the yarn fiber and fabric return to the initial state.
(2) Different fibers and their fabrics have different degrees of shrinkage, mainly depending on the characteristics of the fibers - the hydrophilic fibers have a greater degree of shrinkage, such as cotton, hemp, viscose and the like; and the shrinkage of hydrophobic fibers Lesser, such as synthetic fibers.
(3) When the fiber is in a wet state, it is puffed by the action of the immersion liquid, so that the fiber diameter becomes large. For example, on the fabric, the fiber radius of curvature of the interlaced point of the fabric is forced to increase, resulting in a shortened fabric length. For example, cotton fiber puffs under the action of water, the cross-sectional area is increased by 40~50%, the length is increased by 1-2%, and the synthetic fiber is about 5% for heat shrinkage, such as boiling water shrinkage.
(4) Under the heating condition of textile fiber, the shape and size of the fiber change and shrink, and it cannot return to the initial state after cooling, which is called fiber heat shrinkage.
The percentage of length before and after heat shrinkage is called the heat shrinkage rate, generally measured by boiling water shrinkage, expressed as a percentage of fiber length shrinkage in boiling water at 100 ° C; also used in hot air, hot air at over 100 ° C The percentage of shrinkage measured in the middle is also measured by steam, and the percentage of shrinkage is measured in steam exceeding 100 °C. The fiber also has different performances due to internal structure and heating temperature and time. For example, the boiling water shrinkage rate of the processed polyester staple fiber is 1%, the shrinkage of the vinylon boiling water is 5%, and the shrinkage ratio of the polyvinyl chloride hot air is 50%.
Fiber has a close relationship with the dimensional stability of textile processing and fabrics, providing some basis for the design of the post-process.
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