**4. Liquid transport system**

Water transport in yarns is only slightly influenced by the wetting properties of the individual fibre materials and depends mainly on the wetting behaviour of the whole yarn. The rate of water transport decreases as the roughness of the yarn increases due to the random arrangement of its fibres [7]. This is thought to be dependent on two factors that are directly related to capillary water transfer. (a) As the yarn roughness increases, so does the effective advancing contact angle of water on the yarn. (b) As the fibre arrangement gets more random, the capillary continuity generated by the yarn fibres appears to decrease. Most elements of water transport behaviour are accounted for by the penetration of capillaries created by the fibres in the yarns. Both the amount of water carried by the fabric and the distance that it travels in unit time are influenced considerably by the randomness of the arrangement of fibres in the yarns [8].

Perwuelz et al., on the other hand, worked on liquid organisation during capillary rise in yarns. It was found that capillary rise was dependent on the capillary diffusion coefficient of the yarn, and twist increase reduced the average value of the diffusion coefficients [9]. Twist retraction can cause fibres around the yarn centre to buckle when a high twist is applied into the yarn. This can damage the pore structures between fibres and influence the wicking behaviour [10]. Moreover, another study showed that wicking velocity increased with the increase in cross-sectional area of yarn and decrease in liquid viscosity [11]. In accordance with the literature, packing density of the yarns also influences wicking property. Compact yarns have higher packing density than conventional ring spun yarns, as a result of that they show lower wickability [12].

### **4.1 Wicking in yarn**

Researcher investigated the wicking property of the yarns and found that the wicking behaviour of the yarns improved with the increase in the cross-sectional area due to a larger number of capillaries in yarns [13]. In the case of plied yarns, it is been found that the difference of wicking height of 2-ply and other higher plied yarns is more in finer yarn (40<sup>s</sup> ) as compared with coarser yarn (20s ) [14]. The difference of wicking height between 2-ply yarn and a higher number of yarns gradually decreases from finer yarn to coarser yarn [15].

#### *4.1.1 Effect of yarn modification on water absorbency*


decrease in yarn structure compactness [20] and an increase in yarn bulkiness, which increases the availability of air spaces in the yarn structure, resulting in an increase in water absorbency [21, 22].

3. It has been discovered that when the sheath content of the yarn increases, fabric's water absorbency also increases. The explanation for this could be due to an increase in fabric openness [23] and yarn bulkiness when the sheath is removed, resulting in more air gaps in the yarn structure, which leads to an increase in water absorbency [20].
