Shrinkage Rates of Common Textile Fabrics and Influencing Factors

Shrinkage is a phenomenon where textiles change in length or width after washing, dehydration, and drying. The degree of shrinkage involves different types of fibers, fabric structure, and the external forces applied during fabric processing.

"Synthetic fibers and blended fabrics have the lowest shrinkage rates, followed by wool, linen, and cotton fabrics in the middle. Silk fabrics shrink significantly, while viscose, rayon, and artificial wool fabrics shrink the most."

Objectively speaking, all cotton fabrics experience some degree of shrinkage and fading; the key factor is the finishing process. Therefore, most home textile fabrics undergo pre-shrinking treatment. It's important to note that pre-shrinking treatment does not mean no shrinkage, but rather that the shrinkage rate is controlled within the national standard of 3% to 4%. Underwear fabrics, especially those made of natural fibers, will shrink.

Shrinkage rates of common fabrics:

Cotton: 4%~10%;

Synthetic fibers: 4%~8%;

Cotton-polyester blend: 3.5%~5%;

Natural white fabric: 3%;

Poplin: 3~4.5%;

Twill: 4%;

Dairy fabric: 10%;

Rayon: 10%.

The Influence of Fiber and Fabric Shrinkage

Fibers themselves swell to a certain extent after absorbing water. Usually, fiber swelling is anisotropic (except for nylon), meaning the length shortens and the diameter increases. The shrinkage rate is usually defined as the percentage difference in length between the fabric before and after washing compared to its original length. The stronger the water absorption capacity, the more intense the swelling, the higher the shrinkage rate, and the worse the dimensional stability of the fabric.

The length of the fabric itself differs from the length of the yarn (silk) used; this difference is usually expressed by the fabric shrinkage rate. Shrinkage (%) = [Yarn (filament) length - Fabric length] / Fabric length

After washing, the fabric length shortens further due to fiber swelling, resulting in shrinkage. Different shrinkage rates result in different shrinkage rates. The fabric's weave structure and weaving tension also affect the shrinkage rate. Lower weaving tension results in a tighter, thicker fabric with a higher shrinkage rate and lower shrinkage.

Higher weaving tension results in a looser, lighter fabric with a lower shrinkage rate and higher shrinkage. In dyeing and finishing processes, pre-shrinking treatment is often used to increase weft density and pre-increase the shrinkage rate, thereby reducing the fabric's shrinkage.

Causes of Shrinkage

1. During spinning, weaving, and dyeing, the yarn fibers in the fabric are subjected to external forces, causing them to elongate or deform. Simultaneously, internal stress is generated in the yarn fibers and fabric structure. Under static dry relaxation, static wet relaxation, dynamic wet relaxation, or full relaxation conditions, the release of this internal stress to varying degrees allows the yarn fibers and fabric to return to their initial state.

2. Different fibers and their fabrics exhibit different degrees of shrinkage, primarily depending on the fiber's characteristics. Hydrophilic fibers, such as cotton, linen, and viscose, shrink more; while hydrophobic fibers, such as synthetic fibers, shrink less.

3. When fibers are wetted, they swell under the influence of the soaking liquid, increasing their diameter. In fabrics, this forces an increase in the radius of curvature of the fibers at the interlacing points, leading to a shortening of the fabric length. For example, cotton fibers swell in the presence of water, increasing their cross-sectional area by 40-50% and their length by 1-2%, while synthetic fibers shrink under heat, such as from boiling water, typically by about 5%.

4. When textile fibers are heated, their shape and size change and they shrink, and they cannot return to their initial state after cooling; this is called fiber thermal shrinkage. The percentage of length before and after thermal shrinkage is called the thermal shrinkage rate, usually expressed as the percentage of fiber length shrinkage in boiling water at 100°C.

Alternatively, hot air shrinkage is used, measuring the percentage shrinkage in hot air exceeding 100°C, and steam shrinkage is used, measuring the percentage shrinkage in steam exceeding 100°C. Fibers exhibit different shrinkage rates depending on their internal structure and the temperature and time of heating. For example, the boiling water shrinkage rate for processed polyester staple fiber is 1%, for vinylon it is 5%, and for chlorofiber it is 50%. Fibers have a close relationship with the dimensional stability of textile processing and fabrics, providing a basis for the design of subsequent processes.

Factors Affecting Shrinkage Rate:

1. Raw Materials: Different raw materials result in different shrinkage rates. Generally, fibers with high hygroscopicity expand when soaked in water, increasing in diameter and shortening in length, leading to greater shrinkage. For example, some viscose fibers have a water absorption rate as high as 13%, while synthetic fiber fabrics have poor hygroscopicity and therefore lower shrinkage rates.

2. Density: Different fabric densities result in different shrinkage rates. If warp and weft densities are similar, their warp and weft shrinkage rates will also be similar. Fabrics with higher warp density experience greater warp shrinkage, and vice versa.

3. Yarn Count: Different yarn counts result in different shrinkage rates. Fabrics with coarser yarn counts shrink more, while those with finer yarn counts shrink less.

4. Manufacturing Process: Different fabric manufacturing processes result in different shrinkage rates. Generally, during the weaving and dyeing process, fibers are stretched multiple times, resulting in longer processing times and higher shrinkage rates. Conversely, fabrics subjected to greater tension have higher shrinkage rates, and vice versa.

5. Fiber Composition: Compared to synthetic fibers (such as polyester and acrylic), natural plant fibers (e.g., cotton, linen) and regenerated plant fibers (e.g., viscose) are more prone to moisture absorption and expansion, leading to higher shrinkage rates. Wool, due to its scaly fiber surface structure, is prone to felting, affecting its dimensional stability.

6. Fabric Structure: Generally, woven fabrics have better dimensional stability than knitted fabrics; high-density fabrics have better dimensional stability than low-density fabrics. Among woven fabrics, plain weave fabrics generally have lower shrinkage rates than flannel fabrics; while among knitted fabrics, plain knit weaves have lower shrinkage rates than rib knit weaves.

7. Production and Processing: During dyeing, printing, and finishing processes, fabrics inevitably experience machine stretching, resulting in tension within the fabric. However, this tension is easily released when the fabric comes into contact with water, leading to shrinkage after washing. In practice, pre-shrinking is generally used to address this issue. 8. Washing and Care Process: Washing and care includes washing, drying, and ironing, each of which affects fabric shrinkage. For example, hand-washed samples have better dimensional stability than machine-washed samples, and washing temperature also affects dimensional stability. Generally, the higher the temperature, the worse the stability. The drying method also has a significant impact on fabric shrinkage.

Common drying methods include drip drying, flat-laying with a metal mesh, hanging drying, and tumble drying. Drip drying has the least impact on fabric dimensions, while tumble drying has the greatest impact, with the other two being intermediate.

Additionally, choosing an appropriate ironing temperature based on the fabric composition can also improve shrinkage. For example, cotton and linen fabrics can have their dimensional shrinkage improved by high-temperature ironing. However, higher temperatures are not always better. For synthetic fibers, high-temperature ironing not only fails to improve shrinkage but can also damage their properties, such as making the fabric stiff and brittle.