Fabric Dimensional Stability
In daily life, newly bought clothes, sheets, and other textiles, after water washing once or twice, which are not the original size, greatly affecting our user experience. So how did this happen? And how to prevent this embarrassing phenomenon from happening? This brings us to the dimensional stability of the fabric.
What is the Dimensional Stability of Fabrics?
The dimensional stability of fabric refers to the change of fabric size when it is used or reprocessed due to the properties of a material and the potential thermal contraction force in the process of processing. The fabric with good dimensional stability is worn and washed for many times, the original pleating and shape are unchanged, and the dimensions don’t shrink or elongated, which don’t affect the user experience. The fabric with poor dimensional stability is usually shown as shrinkage, such as shrinkage in sewing, ironing, washing and so on. Among them, the wash shrink is the problem that consumer pays close attention to very much.
Main Factors Affecting Fabric Shrinkage
The moisture absorption of fiber is the direct factor of fabric shrinkage. The tightness of yarn and fabric structure is the indirect factor of shrinkage. The tighter the structure, the expansion of the fiber cause the yarn to swell, then the warp height of the yarn in the fabric increases and the length of the yarn in the buckling state becomes shorter, so the fabric shrinks. Therefore, the higher twist and volume fraction of the yarn, the greater shrinkage of the fabric.
The processing tension of the fabric also has an effect on fabric shrinkage. If the processing tension increases, the fiber deformation increases, the internal stress and the slow elastic deformation increase, then the relaxation and retraction degree of the fabric increases after soaking, which make the shrinkage rate of the fabric increases obviously. Besides, temperature also has a great effect on fabric shrinkage, because the high temperature has the effect of relaxation and expansion, and even heat shrinkage.
Different raw materials of fabrics will affect shrinkage rate and heat shrinkage rate. Under normal circumstance, fabrics with minimum shrinkage rate are synthetic fibers and blended fabrics; secondary is linen fabrics; middle is cotton fabrics; the maximum is viscose fabrics. In addition to this, the shrinkage rate varies from fabrics density, the thickness of yarns, weaving, dyeing and finishing process. Different kinds of fabrics have been prescribed standard of shrinkage rate. In the process of dyeing and finishing, some processes like mercerization and preshrunk can reduce shrinkage rate. Synthetic fiber is easy to deform when heated, especially nylon fabrics, it shrinks more easily when heated, but it can improve its dimensional stability by hot setting.
Treatment of Fabric Shrinkage
By using the thermoplasticity of the fabric fiber, after the shrinkage of the fabric, the shrinkage fiber can be stretched back to its original state and cooling setting under the action of hot steam. This will normally restore shrunken clothing to its original state. In addition, when washing clothes of different materials, you should pay attention to some situations: when washing wool fabrics, you should add a small amount of water or use quality dry cleaning aids, if possible, dry clothes in advance. Do not dry clean PVC or clothing containing polypropylene fiber. The temperature should not be too high when drying clothes.
Fabric Shrinkage Rate Test
Shrinkage rate refers to the percentage that fabrics’ size presents shrink when washed or soaked, which is also an indicator of measuring the degree of fabric shrinkage. The level of fabric shrinkage rate is one of the criteria to measure product quality. The commonly used shrinkage rate test methods are mainly mechanical shrinkage method and dipping method.
A. Mechanical Shrinkage Method
a) Test Apparatus and Materials
Shrinkage Tester (Figure 5), AATCC 1993 Standard Detergent WOB, No Phosphorus ECE Standard Detergent, Oven, Scale, Sewing Thread, Pen, Fabrics, etc.
