Shrinkage is a phenomenon in which the length or width of a textile undergoes washing, dehydration, and drying processes in a certain state. The degree of shrinkage involves the structure of different types of fibers and fabrics, the different external forces acting on the fabric during processing, and so on. The performance of the research is now examined one by one.
The first reason for the shrinking phenomenon:
(1) When the fiber is spinning, or when the yarn is weaving and dyeing, the yarn fibers in the fabric are elongated or deformed by an external force, and the internal stress is generated in the yarn fiber and the fabric structure, and the static dry relaxation occurs. In the state, or in the state of the static wet relaxation, or in the state of the dynamic wet relaxation and the full relaxation, the release of stress in different degrees restores the yarn fibers and the fabric to the initial state.
(2) Different fibers and fabrics have different degrees of shrinkage depending on the characteristics of their fibers - hydrophilic fibers have a relatively large degree of shrinkage, such as cotton, hemp, viscose and other fibers; and hydrophobic fibers. Less shrinkage, such as synthetic fibers.
(3) When the fiber is in the wet state, it expands due to the action of the immersion liquid, which causes the fiber diameter to become large. For example, on a fabric, the radius of curvature of the fiber at the interweaving point of the fabric is increased, resulting in a shortened length of the fabric. For example, the cotton fiber Extruded under the influence of water, the cross-sectional area increases by 40 to 50%, and the length increases by 1 to 2%, while the synthetic fiber shrinks by heat, such as boiling water shrinkage, which is generally about 5%.
(4) Under the condition of heat of textile fiber, the shape and size of fiber will change and shrink. After cooling, it will not return to the initial state. It is called fiber thermal shrinkage. The percentage of the length before and after heat shrinkage is called the thermal shrinkage rate. The boiling water shrinkage test is generally used.
In 100 °C boiling water, the percentage of fiber length shrinkage is expressed;
It also uses hot air method to measure the percentage of shrinkage in hot air over 100°C. It also uses the steam method to measure the percentage of shrinkage in the steam exceeding 100°C. The fiber has different conditions due to internal structure, heating temperature and time. The performance is also different.
For example, the boiling water shrinkage rate of processed polyester staple fiber is 1%, the shrinkage rate of vinylon boiling water is 5%, and the hot air shrinkage rate of acrylic fiber is 50%. The fiber has a close relationship in the textile processing and the dimensional stability of the fabric. The design provides some evidence.
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