Shrinkage is a phenomenon of length or width change in the process of washing, dehydration and drying of textiles in a certain state.Shrinkage involves different kinds of fibers, fabric structure, different external forces on the fabric during processing, etc.
Synthetic fibers and blends have the smallest shrinkage rate, followed by wool, linen and cotton. Silk has a large shrinkage rate, while rayon, rayon and wool have the largest shrinkage rate.Objectively speaking, the number of cotton fabrics are shrinking and fading problems, the key is the finishing behind.So the fabric that general home spins is through preshrink processing.It is worth noting that pre-shrinkage treatment is not equal to no shrinkage, but refers to the shrinkage rate control within the national standard 3%-4%.Therefore, in the purchase of hotel linen, in addition to the quality of the fabric, color, pattern selection, shrinkage rate of the fabric should also be understood.
One, the reason of fabric shrinkage
1, fiber during spinning, or yarn in weaving and dyeing and finishing, the fabric of the yarn fiber elongation by external force or deformation, stress in fiber yarn and fabric structure at the same time, in the static dry relaxation state, or static wet relaxation condition, or in a dynamic wet relaxation condition, total relaxation condition, different degree of internal stress release, make the yarn fiber and fabric back to its original state.
2. Different fibers and fabrics have different degrees of shrinkage, mainly depending on the characteristics of their fibers -- hydrophilic fibers have a large degree of shrinkage, such as cotton, hemp, viscose and other fibers;Hydrophobic fibers, such as synthetic fibers, shrink less.
3. During the wetting state, the fiber bulks under the action of the dip, making the diameter of the fiber larger, such as on the fabric, forcing the curvature radius of the woven point of the fabric to increase, leading to the shortening of the length of the fabric.For example, cotton fiber expanded under the action of water, the cross-sectional area increased by 40~50%, the length increased by 1~2%, and synthetic fiber thermal shrinkage, such as boiling water shrinkage, generally about 5%.
4. Under the condition of textile fiber being heated, the shape and size of the fiber change and shrink, and it cannot return to the initial state after cooling, which is called fiber thermal shrinkage.And the thermal shrinkage before and after the thermal shrinkage of the length percentage known as thermal shrinkage, generally with boiling water shrinkage test, in 100℃ boiling water, fiber length shrinkage percentage for expression;Also useful hot air way, in more than 100℃ hot air measure its shrinkage percentage, also useful steam way, in more than 100℃ steam measure its shrinkage percentage.For example, the shrinkage of boiling water of polyester staple fiber is 1%, the shrinkage of boiling water of vinylon is 5%, and the shrinkage of hot air of chlorofiber is 50%.There is a close relationship between the size stability of the fabric and the fiber in textile processing.
Second, fabric shrinkage factors
1, the fabric of different raw materials, shrinkage rate is different.Generally speaking, the hygroscopic fiber, after soaking in water fiber expansion, diameter increase, length shorten, shrinkage rate is large.If some viscose fiber water absorption rate as high as 13%, and synthetic fiber fabric moisture absorption is poor, its shrinkage rate is small.
2, yarn (thread) is made of fiber through twist around the yarn axis, its size in the water, in addition to the nature of the fiber, but also its structure such as twist, tightness, etc.Generally speaking, the shrinkage rate is different with different yarn count and thickness.The shrinkage rate of cloth with coarse yarn is large, while that of fine yarn is small.
3, fabric density is different, shrinkage rate is different.If the longitude and latitude density is similar, its longitude and latitude shrinkage rate is close.Fabrics with high warp density will shrink more in warp direction, and those with higher weft density will shrink more in warp direction.In general, the dimensional stability of high density fabric is better than that of low density.
4, fabric production process is different, the shrinkage rate is different.Generally speaking, in the process of weaving and dyeing, the fiber has to be stretched many times and the processing time is long.In order to control the width of the fabric, in the actual process, we usually use pre-shrinkage to solve this problem.
Washing care, including washing, drying, ironing, each of these three steps will affect the fabric shrinkage.For example, the dimensional stability of hand washing is better than that of machine washing, and the washing temperature will also affect its dimensional stability.In general, the higher the temperature, the worse the stability.
Choosing an appropriate ironing temperature based on the fabric composition can also improve the shrinkage of the fabric.For example, cotton and linen fabrics can be ironed at high temperatures to improve size shrinkage.But the higher the temperature, the better.For synthetic fiber, high temperature ironing does not improve its shrinkage, but will damage its performance, such as fabric hard and brittle.
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