Views: 1000 Author: Site Editor Publish Time: 2023-07-17 Origin: Site
The lower the crystallinity of the fiber, the better the moisture absorption capacity. Under the same degree of crystallinity, the size of microcrystals also has an influence on hygroscopicity. In general, smaller crystals are more hygroscopic.
For example: after cotton is mercerized, the moisture absorption increases due to the decrease in crystallinity; cotton and viscose belong to cellulose fibers, and each glucose residue contains 3 -OH, but the crystallinity of cotton fiber is about 70%. And viscose fiber is only about 30%, W viscose>W cotton.
The more pores in the fiber amorphous region, the stronger the moisture absorption capacity of the fiber.
For example: the structure of viscose fiber is looser than cotton fiber, and there are many gaps and holes, which is one of the reasons why its moisture absorption capacity is much higher than that of cotton; the structure of synthetic fiber is generally dense, while there are microscopic gaps in natural fiber tissue, which is also the moisture absorption of natural fiber. One of the reasons why the capacity is much greater than synthetic fibers.
The larger the specific surface area of the fiber, the greater the surface energy, the stronger the surface adsorption capacity, the more water molecules are adsorbed, and the better the hygroscopicity. Thin fibers have larger specific surface area and higher moisture regain than thick fibers.
a. Cotton
b. Wool
c. flax
d. silk
E. Oil agent on the surface of chemical fiber
In general, as the temperature of the air and fiber material increases, the equilibrium moisture regain of the fiber will decrease.
Under certain temperature conditions, the higher the relative humidity, the greater the pressure of water vapor in the air, that is, the greater the number of water molecules in a unit volume of air, the more opportunities for water molecules to reach the surface of the fiber, and the greater the moisture absorption of the fiber. many.
These two factors in temperature and humidity:
For hydrophilic fibers, the influence of relative humidity on moisture regain is the main one, and for hydrophobic synthetic fibers, the influence of temperature on moisture regain is obvious.
From the hysteresis of hygroscopicity, we can know that when the fiber material is placed in a new atmospheric condition, its moisture regain from dehumidification to equilibrium is higher than that from moisture absorption. Therefore, the original moisture regain of the fiber also has a certain influence.