What is the shrinkage rate of several common textile fabrics?

Shrinkage of fabric is the percentage of fabric shrinkage after washing or soaking. Shrinkage is a textile in a certain state through the process of washing, dehydration, drying and other changes in length or width of a phenomenon. The degree of shrinkage involves different kinds of fibers, the structure of the fabric, fabric processing by different external forces, etc.. Shrinkage rate is the smallest synthetic fibers and mixed textiles, followed by woolen fabrics, hemp fabrics, cotton fabrics in the middle, silk fabrics shrinkage is larger, and the largest is viscose fiber, rayon, artificial wool fabrics. Objectively speaking, cotton fabrics more or less have the problem of shrinkage and fading, the key is the finishing behind. So the general home textile fabrics are pre-shrinking treatment. It is worth noting that after pre-shrinking treatment is not equal to no shrinkage, but refers to the shrinkage rate control within the national standard 3%-4% clothing, especially natural fiber clothing will shrink. Therefore, in the purchase of clothing, in addition to the quality of the fabric, color, pattern selection, the shrinkage rate of the fabric should also have knowledge.

1. Fiber and the impact of weaving shrinkage

When the fiber itself absorbs water, it will produce a certain degree of swelling. Usually the swelling of fibers is anisotropic (except nylon), i.e., the length is shortened and the diameter is increased. Usually the difference between the length of the fabric before and after the water and its original length as a percentage of shrinkage. The stronger the water absorption capacity, the more intense the swelling, the higher the shrinkage rate, 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 difference is usually expressed in terms of the weaving shrinkage.

After the fabric is put into water, the fabric length is further shortened due to the swelling of the fiber itself, which produces shrinkage. The fabric weaving shrinkage rate is different, the size of its shrinkage rate is different. The fabric's own organizational structure and weaving tension is different, the weaving shrinkage rate is different. Weaving tension is small, the fabric is tight and thick, the weaving shrinkage rate is large, the shrinkage rate of the fabric is small; weaving tension is large, the fabric is loose and thin, the weaving shrinkage rate is small, the shrinkage rate of the fabric is large. In the dyeing and finishing process, in order to reduce the shrinkage rate of the fabric, often use the pre-shrinkage finishing to increase the weft density, weaving shrinkage rate in advance, so as to reduce the shrinkage rate of the fabric.

2. Reasons for shrinkage

①Fiber in spinning, or yarn in weaving and dyeing, the fabric in the yarn fiber by external forces and elongation or deformation, while the yarn fiber and fabric structure generated internal stress, in the static dry relaxation state, or static wet relaxation state, or in the dynamic wet relaxation state, full relaxation state, different degrees of internal stress release, so that the yarn fiber and fabric back to the initial state.

② Different fibers and their fabrics, the degree of shrinkage are different, mainly depending on the characteristics of their fibers - hydrophilic fibers shrink more, such as cotton, linen, viscose and other fibers; and hydrophobic fibers shrink less, such as synthetic fibers.

③ fiber in the state of wetting, due to the role of liquid immersion under the effect of expansion, so that the diameter of the fiber becomes larger, such as in the fabric, forcing the fabric of the interweaving point of the fiber radius of curvature increased, resulting in a shorter length of fabric. For example, cotton fibers in the role of water expansion, cross-sectional area increased by 40 ~ 50%, the length increased by 1-2%, while synthetic fibers are shrinkage to heat, such as boiling water shrinkage, etc., generally about 5%.

④ Textile fibers under heat conditions, the shape and size of the fiber changes and shrinkage, cooling can not return to the initial state, known as fiber heat shrinkage. The percentage of length before and after thermal contraction is called thermal contraction rate, generally to boiling water shrinkage test, in 100 ℃ boiling water, the percentage of fiber length contraction as expressed; also useful in the hot air way, in more than 100 ℃ in the hot air to measure the percentage of its contraction, also useful in the steam way, in more than 100 ℃ in the steam to measure the percentage of its contraction. Fibers due to the internal structure and heat temperature, time and other different conditions of performance is also different, for example, the processing of polyester staple fiber boiling water shrinkage rate of 1%, vinylon boiling water shrinkage rate of 5%, chlorine spandex hot air shrinkage rate of 50%. Fiber in the textile processing and its fabric dimensional stability has a close relationship, to provide some basis for the design of the post-process.

The general shrinkage rate of fabrics:

Cotton 4% - 10%.

Chemical fiber 4% - 8%.

Cotton-polyester 3.5% - 5 5%.

Raw white fabric 3%.

Poplin 3-4.5%.

Twill cloth 4%.

Labor cloth 10%.

Synthetic cotton 10%.

3. Reasons affecting the shrinkage rate

·Raw materials

The raw materials of fabrics are different, the shrinkage rate is different. Generally speaking, moisture-absorbent fibers, fiber expansion after immersion, diameter increases, length shortens, shrinkage rate is large. Such as some viscose fiber water absorption rate of up to 13%, while the synthetic fiber fabric moisture absorption is poor, its shrinkage rate is small.

·Density

The density of the fabric is different, the shrinkage rate is also different. Such as warp and weft density is similar, its warp and weft shrinkage rate is also close. By the density of the woven fabric, the warp shrinkage is large, and vice versa, the weft density is greater than the weft density of the woven fabric, the weft shrinkage is also large.

·Production Process

Fabric production process is different, the shrinkage rate is also different. In general, the fabric in the weaving and dyeing process, the fiber to stretch many times, the processing time is long, the applied tension is larger fabric shrinkage, and vice versa is small.

·Fabric structure

In general, the dimensional stability of woven fabrics is better than knitted fabrics; the dimensional stability of high-density fabrics is better than low-density ones. In woven fabrics, the general shrinkage rate of plain fabrics is less than that of facecloth fabrics; and knitted fabrics, the shrinkage rate of flat needle organization is less than that of ribbed fabrics.

·Production process

As the fabric is dyed, printed and finishing process, it will inevitably be stretched by the machine, thus there is tension on the fabric. However, the fabric is easy to lift the tension after encountering water, so we will find the fabric shrinkage after washing. In the actual process, we generally use pre-shrinkage to solve this problem.

·Washing and care process

Washing care includes washing, drying, and ironing, and each of these three steps 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 temperature of washing likewise affects their dimensional stability. In general, the higher the temperature, the less stable it is. Sample drying method on the shrinkage of the fabric is also relatively large impact.

Commonly used drying methods are, drip drying method, metal mesh flat method, hanging dry drying method and tumble drying method. Among them, the drip drying method has the least effect on the size of the fabric, while the rotating cylinder arch drying method has the greatest effect on the size of the fabric, and the remaining two are in the middle.

In addition, according to the composition of the fabric to choose a suitable ironing temperature, can also improve the shrinkage of the fabric. For example, cotton and linen fabrics can be ironed at high temperatures to improve its size shrinkage. But not the higher the temperature is better, for synthetic fibers, high temperature ironing can not improve its shrinkage rate, but will have damage to its performance, such as fabric hard and brittle.