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Analysis of the testing mechanism of moisture absorption, perspiration and quick drying of textiles



To solve the moisture absorption and perspiration performance of fabrics, you first need to understand the moisture absorption and perspiration process of fabrics. Hygroscopicity a…

To solve the moisture absorption and perspiration performance of fabrics, you first need to understand the moisture absorption and perspiration process of fabrics. Hygroscopicity and water absorption are two concepts that need to be explained: Hygroscopicity refers to the ability of a fabric to absorb gaseous water, which mainly depends on the chemical structure of the fiber and has less to do with the physical structure. Fibers with good hygroscopicity are not prone to static electricity, which is beneficial to textile processing and comfortable to wear. Water absorption refers to the ability of a fabric to absorb liquid water, which means that liquid moisture wets the fiber surface and is absorbed and retained by the pores, cavities and capillaries formed between fibers. The water absorption of fibers is related to not only the chemical structure of the fiber, but also the physical structure and supramolecular structure of the fiber. For hydrophobic fibers, the physical structure of the fiber and the supramolecular structure of the fiber macromolecules contribute more to water absorption.

Usually, in the crystalline region or high-order region of fiber macromolecules, it is difficult for water molecules to diffuse or penetrate, while in the amorphous region or low-order region, as well as regions with rough morphological structure, micropores or more pores, and gaps between fibers, Water molecules are easy to diffuse and are retained, showing good hydrophilicity. In order to avoid cumbersome descriptions, the word “hygroscopic” is used below except when necessary. ​
The human body must sweat when working and exercising while dressed. The process of sweat being transmitted to the outside space through fabrics can be described in two forms: 1) Liquid sweat directly contacts the fabric and transfers the fabric to the fabric in the form of liquid water. The inner surface is moistened and absorbed by the fabric, and is transported to the outer surface of the fabric by relying on the capillary action formed by the gaps between yarns or fibers, and then evaporates into water vapor and diffuses to the outer space; 2) The water vapor evaporated by human sweat is directly formed into the fabric It is absorbed by the fiber surface and condenses into liquid water on the inner surface of the fabric. It is then transmitted to the outer surface of the fabric through the same mechanism, evaporates into water vapor and migrates to the outer space.
Therefore, the realization of sweat absorption, perspiration and quick-drying process must consist of several steps: wetting-moisture absorption-diffusion-evaporation. ​

1Wetting process

That is, the wetting of the surface of fibers and fabrics by water is the first step to complete the functions of moisture absorption, perspiration, and quick drying. For synthetic fibers lacking polar hydrophilic groups, it is also the control step to complete the overall process. The wetting process is mainly controlled by thermodynamic conditions, that is, the ability of water to wet the fiber material. From the perspective of chemical structure, it would be the best solution to introduce hydrophilic groups into the fabric or the fibers constituting the fabric; from the perspective of physical structure, if we try to roughen the fiber surface, specialize the fiber cross-section and make the fiber finer, that is Expanding the contact surface area between water and fiber will be beneficial to the wetting process. ​

2 Hygroscopic (or water absorption) process

It refers to the process in which moisture infiltrates fibers and fabrics and then adsorbs on the surface and interior of fibers and fabrics. Measures to increase the specific surface area, such as hydrophilization of fiber chemical structure, roughening of fiber surface, cross-section specialization and fineness, are undoubtedly beneficial to this process.

3Diffusion process

It refers to the process in which the moisture absorbed by the fabric diffuses from the inner surface to the outer surface of the fabric and the moisture absorption area of ​​the fabric gradually expands. It mainly relies on the cavity in the fiber, the holes in the single fiber, the gaps between the single fibers in the yarn and the fabric. The capillary action formed by the gaps between the yarns. Therefore, fiber cross-section specialization, fiber fineness, and fabric structure compactness are all effective in improving conduction. ​

4Evaporation process

It means that the moisture absorbed by the fabric evaporates to the outer space to achieve the quick-drying process of the fabric. The presence of too many hydrophilic groups in the macromolecular chemical structure of the fiber (such as cotton fiber, viscose fiber, etc.) is not conducive to the realization of quick drying. In terms of physical structure, all measures that can increase the evaporation specific surface area are It is conducive to quick drying; therefore, the diffusion process creates the necessary conditions for the rapid evaporation of water, and the temperature, humidity and air flow rate of the environment outside the fabric also have an important impact on the evaporation process. ​

The development of highly moisture-absorbent, sweat-wicking, quick-drying fabrics is of great significance to improving the comfort of clothing. It is very suitable for high-level sportswear, workwear under high-temperature and high-humidity operating conditions, etc., and is suitable for blending with an appropriate amount of cotton fiber. It can be used in shirts, jeans, underwear, trousers, linings, etc. It can also be used in home textiles such as decorations, bedding and toiletries.

Article source: China Textile Network Forum

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