Investigation On Moisture Permeability Of Fiber Assembly Based On Simulation Of Fiber-location Mode In Yarn

Functional modification of chemical fibers is an important developing direction for chemical fiber industry. In past few years, a series of fibers with high moisture permeability modified from traditional chemical fibers have become the focus in the textile market because of its excellent moisture permeability and comfort character. More and more researchers dedicate the investigation on moisture permeability of fiber assembly. However, the existing fundamental theory and mathematics models are limited, so the development of high moisture permeability fibers is devoid of theoretic support.Moisture transmission in fabrics contains several processes, such as wetting, wicking and evaporation. Wetting is the basis of excellent moisture permeability. The wetting ability of Polytrimethylene Terephthalate(PTT) fiber has been improved by treatment with "X-22-8645" hydrophilic finishing agent with the contact angle of fiber decreasing from 90°to 50°. Meanwhile, the moisture permeability of yarns is improved. From the continuous images of moisture transmission in fabric, it is shown that wicking behavior is the mainly mode of moisture transmission in fiber assembly, and the capillary space inside yarns are channels for wicking. Weave structure has little effect in the moisture permeability of fabrics weaved by same yarns.Based on the comprehension of the mechanism of moisture permeability in fiber assembly, a vertical wicking mathematics model named Model of Fiber Bundle(MFB) has been established, by which the maximal wicking height, the maximal wicking volume and initiatory wicking velocity can be calculated quantitatively. Such parameters were applied to characterize the moisture permeability of fiber assembly. In addition, in order to compute the moisture permeability of given fibers and liquid, the number and geometrical character of the capillary space in fiber assembly are required. Therefore, an original simulator named ShapeGanerator (SG) has been compiled by "Visual C++", by which the emulated location mode of fibers in yarn has been achieved. And the parameters for moisture permeability have been obtained quantitatively.A series of PTT yarns have been simulated by SG and the moisture permeability has been computed by MFB. It is indicated that the maximal wicking height and the maximal wicking volume of yarns increased with fining of fibers till a certain size of 0.36dtex. Fibers with concave cross section, such as "+" or "H" shape, have better moisture permeability than fibers with convex cross section. Compared with the circular fiber assembly, the maximal wicking height of "+" shaped fiber assembly increased by 10%, the maximal wicking volume and initiatory wicking velocity increased over 40%. Therefore, cross section modification is an effective method to improve the moisture permeability of fiber assembly, and the "+" shape is optimal. The maximal wicking height and the maximal wicking volume of yarns increased linearly with increasing of profile degree of fibers. When the profile degree of fibers increased from 30% to 70%, the maximal wicking height of yarns increased by 15%, and the maximal wicking volume of yarns increased by 66%. Compared with the pure "+" shaped yarn, the maximal wicking volume of the yarn blended by "+" shaped fibers and "－" shaped fibers increased by 30%. Therefore, blended yarn with different shape has better moisture permeability.