Causes of shrinkage in textile fabrics
Synthetic fibers and blended fabrics shrink the least. Then, come woolen and linen fabrics. Cotton fabrics are in the middle. Silk fabrics tend to shrink more. Viscose, rayon, and artificial wool shrink the most. Pre-shrinking does not mean the fabric won’t shrink at all. It means to control shrinkage within acceptable limits.
Effects of Fiber and Fabric Contraction on Shrinkage Rate
When fibers absorb water, they swell to a certain extent. Generally, this swelling causes the fiber length to shorten while increasing its diameter. The dimensional stability is the percent change in fabric length after soaking, compared to its original length. Fabrics that absorb more water swell more. They shrink more and are less stable.
The fabric’s length differs from the total length of the yarn. This is usually shown by the “fabric contraction rate.” Soaking swells the fibers. This further shortens the fabric. Variations in the fabric’s contraction rate affect that.
Impact of Fabric Structure and Weaving Tension on Shrinkage
The fabric’s structural organization and weaving tension affect its contraction rate. Lower weaving tension makes fabrics compact, dense, and less prone to dimensional stability. They contract more, though. Higher weaving tension creates looser, lighter fabrics. They shrink more due to a lower contraction rate.
In dyeing and finishing, pre-shrinking techniques are often used to reduce shrinkage. These methods involve increasing the fabric’s weft density. This will enhance its contraction rate and reduce shrinkage.
Analysis of Shrinkage Causes
Fiber Factors
1.External Forces
Spinning, weaving, and finishing stretch or deform the fibers and yarns in a fabric. This creates internal stress in the fiber and fabric due to external forces. In different states of relaxation, this internal stress is gradually released. This allows the fibers and fabric to return to their initial state.
2.Fiber Characteristics
The level of different fibers and fabrics depends largely on their characteristics. Hydrophilic (water-attracting) fibers, like cotton and linen, tend to shrink more. Hydrophobic (water-repellent) fibers, such as synthetics, generally shrink less.
3.Effect of Immersion
When fibers are wet, they swell due to the liquid, causing their diameter to increase. In fabrics, this swelling increases the curvature of fibers at interlacing points. It shortens the fabric’s length. For instance, cotton fibers can swell in water. Their cross-sectional area can increase by 40–50% and their length by 1–2%. Synthetic fibers tend to shrink more due to heat (e.g., hot water). They usually shrink by about 5%.
4.Heat exposure
When textile fibers are exposed to heat, their structure and size change as they shrink. After cooling, they do not return to their original state. This is called thermal shrinkage. The thermal dimensional stability is the percent change in fiber length after heat exposure. This is often measured by boiling water shrinkage. It subjects the fiber to 100°C water. Or, it uses hot air or steam methods above 100°C to measure shrinkage.
Fabric Factors
1.Fabric Structure
Woven fabrics are generally more stable than knitted ones. And, high-density fabrics are more stable than low-density ones. Among woven fabrics, plain weaves shrink less than flannel fabrics. For knits, plain knits shrink less than rib knits.
2.Manufacturing Process
During dyeing, printing, and finishing, fabrics are inevitably stretched by machines, creating tension. When fabrics encounter water, this tension is easily released, causing dimensional changes after washing. To address this, pre-shrinking techniques are commonly used.
3.Density
The density of a fabric affects its dimensional stability. When the warp and weft densities are similar, their shrinkage rates are also close. Fabrics with a higher warp density tend to shrink more in the warp direction. Fabrics with a higher weft density tend to shrink more in the weft direction.
4.Yarn Thickness
The thickness of yarns also impacts shrinkage. Fabrics made from thicker yarns tend to shrink more, while those with finer yarns shrink less.
5.Production Techniques
Different production techniques result in varying shrinkage rates. Fabrics that stretch, take a long time to process， and are woven and finished under high tension have higher shrinkage rates. Fabrics processed with less tension have lower shrinkage rates.