Why is the fabric shrunk?
Shrinkage is one of the phenomena of the change of length or width in the process of washing, dehydration, drying and so on. The degree of shrinkage involves different kinds of fibers, fabric structure, and different external forces acting on the fabric processing, etc., with different performances.
1. Reasons for the shrinkage of fabrics.
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 their fabrics have different shrinkage degrees, depending on the properties of their fibers, such as cotton, hemp, viscose and other fibers. Hydrophobic fibers have less shrinkage, such as synthetic fibers.
3, fiber in the wet state, puffing, under the action of immersion due to fiber diameter change, such as on the fabric, forcing the fabric of the fiber radius of curvature of the crossing point of increase, causing fabric length is shortened. For example, the cotton fiber bulges under the action of water, the cross-sectional area increases by 40~50%, the length increases by 1~2%, while the synthetic fiber is about 5% or so in the heat contraction, such as boiling water shrinkage, etc.
4. In the heat condition of textile fibers, the morphology and size of the fibers change and shrink, and they cannot be returned to the initial state after cooling, which is called thermal shrinkage of fibers. And the length of the heat shrinkable before and after the thermal contraction percentage is called heat shrinkage rate, general with boiling water shrinkage test, at 100 ℃ in the boiling water, fiber length contraction percentage of said; Also useful hot air way, in more than 100 ℃ hot air of the contraction percentage, also useful steam way, in more than 100 ℃ steam measuring its shrinkage percentage. Fiber due to the internal structure and heated under different conditions, such as temperature, time, performance is also different, such as processing of polyester staple of boiling water shrinkage rate is 1%, whalen boiling water shrinkage rate is 5%, chlorofibre hot air shrinkage rate of 50%. The fiber is closely related to the dimensional stability of textile processing and its fabric, and provides some basis for the design of the post-process
2. Factors that cause shrinkage of fabric.
1. The raw material of the fabric is different, the shrinkage rate is different. Generally speaking, hygroscopic large fiber, the fiber expands after soaking, the diameter increases, the length is shortened, the shrinkage rate is large. For example, the moisture absorption rate of some viscose fibers is as high as 13%, while the moisture absorption of synthetic fiber fabric is poor, and its shrinkage rate is small.
2, yarn (line) is by the fiber through twisting winding shaft alignment, the size of it in the water changes, in addition to related to the nature of the fiber, but also to the structure such as twist, close degree. Generally speaking, fabric yarn is thick and different, the shrinkage rate is also different. The shrinkage rate of yarn is large, and the shrinkage of fabric is small.
3. The density of the fabric is different, and the shrinkage rate is different. If the warp and weft density is similar, the shrinkage rate is close. After the density of the fabric, the shrinkage is large, and vice versa, the weft is larger than the warp. In general, the dimension stability of high-density fabric is better than that of low density.
4. The production process of the fabric is different, and the shrinkage rate is different. Generally speaking, fabrics in weaving and dyeing and finishing process, the fiber wants to stretch many times, processing time is long, the fabric that exerts the tension is large, the shrinkage rate of the fabric is large, and vice versa. In order to control the door width of the cloth, in the actual process, we usually use pre-shrunk to solve the problem (after the previous article).
5. Washing care, including washing, drying and ironing, each step will affect the shrinkage of the fabric. For example, the dimension stability of hand washing is better than machine washing, and the temperature of washing will also affect its dimensional stability. Generally speaking, the higher the temperature, the worse the stability.
According to the composition of the fabric, a suitable ironing temperature can be selected to improve the shrinkage of the fabric. For example, cotton and linen fabrics can be ironed to improve their shrinkage. But the higher the temperature, the better. For synthetic fibers, the high temperature ironing does not improve its shrinkage, but can damage its performance, such as brittle fabric and brittle hair.