Absorbency and Wicking Behaviour of Natural Fibre-Based Yarn and Fabric

Abstract

In textiles of natural fibres, absorbency and wicking are considered as most indigenous liquid transmission properties, which play significant role in assessing the comfort of textile garments as well as in functioning of technical textiles. To explain the general principles of absorbency and wicking and their related parameters, a review of different theories is illustrated. Various structural aspects of textile intermediates such as yarn and fabric on wicking are discussed. An experimental analysis is also described to understand the wicking phenomena on fabrics in multiple directions such as warp-way, weft-way and diagonally for varying weave forms. A critical evaluation is presented for establish the wicking behaviour between these fabrics and their constituted yarns having preferred twisted forms such as single and ply. A unique representation of correlation matrices is shown to interrelate the yarn and fabric wicking.

1. Introduction

In terms of comfort and exuberant use, cotton fibre is considered the most classical fibre in garment technology. Versatility of cotton fibres ranging from very finer to very courser and structure of cotton yarns such as single to ply are considered as decisive factors of selection regarding their use in apparel production. On the other hand, the comfort property, being one of the prime features of woven fabric used as a garment, is greatly influenced by the structure of constituent yarns in that particular fabric. Comfort evaluation includes mainly vapour and liquid transmission properties of yarn and fabric at constant atmospheric conditions and constraints. Liquid transmission includes water absorbency and wicking [1, 2].

Absorbency is used to describe the ability of a fabric to take in moisture—an important feature that influences a variety of other factors such as skin comfort, static build-up, shrinkage, water repellency and wrinkle recovery. One of the most common occurrences in the manufacturing and usage of textile materials is liquid flow. Wicking is the spontaneous transfer of a liquid into a porous structure caused by capillary forces. Therefore, study of capillary flow in textile media is very important. When the free energy of the solid-gas interface surpasses that of the solid-liquid interface, capillary phenomena occur. A liquid that does not wet fibres cannot wick into a fabric, and wicking can only take place when fibres are assembled with capillary spaces. But the objective of this is to present an overview only in wicking property of textiles.

Study of wicking in textile material is of great interest for two main reasons. Firstly, it allows a better understanding of liquid-fibre contact in order to characterise any liquid flow of spin finishes, dyeing or coating of either fabrics or yarns. Secondly, it enables the characterisation of textile structures, their porosity resulting from the capillaries formed by the inter-filament spaces in which the liquid flows [3]. Moisture absorption is intimately linked to the comfort of garments made from cellulosic fibres. The term wetting is usually used to describe the displacement of solid-air interface with solid liquid interface. Wetting behaviour is commonly characterised by the value of the contact angle within the liquid [4]. The wetting and wicking behaviour of the fibrous structure is a critical aspect of performance of products such as sports clothes, hygiene disposable materials and medical products. Clothing comfort is influenced by the wetting and wicking processes that occur during wear.

Therefore, a thorough understanding of liquid transmission behaviour inside various intermediate forms of textiles is obviously needed through absorbency and wicking phenomena of yarns and fabrics. As the yarns are composed of fibres with a structured arrangement, any change of this arrangement by twisting and plying creates different sort of wicking behaviour on them and in turn, the fabrics made out of these yarns along with its varying weave forms and directions must exhibit different nature of wicking effects. The findings that are interlinking between fabric wicking and corresponding yarn wicking are always a matter of interest to study the nature of absorbency specially for textiles made out of natural fibres and hence, are elaborated progressively in this chapter.

2. Lucas-Washburn theory

The so-called wicking (or absorbency) rate is of great importance for both scientific and practical uses. The Lucas-Washburn idea provides a more scientific definition of the wicking rate. This theory deals with the rate of a liquid drawn into a circular tube via capillary action. A capillary like this is a severely simplified representation of a pore in a true fibrous media with a complex structure. For laminar viscous flows, theory is a specific form of the Hagen-Poiseuille law state Landau and Lifshitz. According to this law, the volume dV of a Newtonian liquid with viscosity μ that wets through a tube of radius r and length h during dt is given by the relation:

$$\mathrm{dV}/\mathrm{dt}=\text{πr4}\left(\text{p1}–\mathrm{p}2\right)/\text{8hμ}$$E1

where p1 – p2 is the pressure difference between the tube ends. The capillary force and gravitation both contribute to the pressure difference here. The angle between the tube axis and the vertical direction is denoted by β, while the contact angle of the liquid against the tube wall is denoted by θ. The value of the capillary pressure p1 is:

$$\text{p1}=\text{2γ}cos\mathrm{\theta }/\mathrm{r}$$E2

While hydrostatic pressure p2 is:

$$\text{p2}=\mathrm{h}\mathrm{\zeta }\mathrm{g}cos\mathrm{\beta },$$E3

where γ denotes the liquid surface tension, ζ is liquid density, g is the gravitational acceleration, and h, in this case, is the distance travelled by the liquid measured from the reservoir along the tube axis. This distance obviously is the function of time, h = h (t), for a given system. The Lucas-Washburn equation is obtained by substituting the values p1, p2 and h(t) into Eq. (1), expressing the liquid volume in the capillary V as πr²h:

$$\mathrm{dV}/\mathrm{dt}=\mathrm{r}\mathrm{\gamma }cos\mathrm{\theta }/\text{4μh}–\mathrm{r}2\mathrm{\zeta }\mathrm{g}cos\mathrm{\beta }/\text{8μ}$$E4

For a given system, parameters such as r, γ, θ, ζ, g and β remain constant. We can then reduce the Lucas-Washburn equation (4) by introducing two constants,

$$\mathrm{K}\prime =\mathrm{r}\mathrm{\gamma }cos\mathrm{\theta }/4\mathrm{\mu }\text{and}\mathrm{L}\prime =\mathrm{r}\mathrm{\zeta }\mathrm{g}cos\mathrm{\beta }/\text{8μ}$$E5

into a simplified version,

$$\mathrm{dh}/\mathrm{dt}=\mathrm{K}\prime /\mathrm{h}–\mathrm{L}\prime$$E6

The above relation is a non-linear ordinary differential equation that is solvable only after ignoring the parameter L′; this has a physical interpretation when either the liquid penetration is horizontal (β = 900 C) or r is small or the rising liquid height h is low that K′/h > > L′ or L′ → 0, and the effects of the gravitational field are negligible and the acceleration g vanishes. The Lucas-Washburn equation (6) could thus be solved with ease:

$$\mathrm{h}=\surd \text{2K}\prime \mathrm{t}.$$E7

The result satisfies the initial condition h = 0 for t = 0.

Despite the intricate, noncircular, non-uniform and nonparallel nature of the pore spaces, the Lucas-Washburn technique provides an approximation tool for investigating the wicking and wetting behaviour of textiles. In the field of liquid sorption in a porous area, Washburn (1921) has expressed the following equation:

$$\mathrm{H}={\mathrm{Ct}}^{0.5}$$E8

where H is the wicking height (m); C, the capillary liquid transport constant. The capillary force causes liquid to flow through a capillary channel, as shown in the equation above. The radius of the capillary channel, the contact angle between the liquid and the capillary channel and the rheological qualities of the liquid all influence the capillary force [5].

3. Wetting

The displacement of a solid-air interface with a solid-liquid contact is commonly referred to as ‘wetting’. Two separate equilibrium regimes may be identified when a small liquid droplet comes into contact with a flat solid surface. Complete wetting with a zero-contact angle or partial wetness with a finite contact angle is shown in Figure 1. The equilibrium at a solid-liquid boundary is commonly described by the Young’s equation:

Figure 1.

A small liquid droplet in equilibrium over a horizontal surface: (a) partial wetting, mostly non-wetting; (b) partial wetting, mostly wetting; (c) complete wetting.

$${\mathrm{\gamma }}_{\mathrm{SV}}–{\mathrm{\gamma }}_{\mathrm{SL}}–{\mathrm{\gamma }}_{\mathrm{LV}}cos\mathrm{\theta }=0$$E9

where, γ_SV, γ_SL and γ_LV denote interfacial tensions between solid/vapour, solid/liquid and liquid/vapour, respectively, and θ is the equilibrium contact angle.

The parameter that distinguishes partial wetting and complete wetting is the so-called spreading parameter S, which measures the difference between the surface energy (per unit area) of the substrate when dry and wet:

$$S={\left[E_{\mathit{\text{substrate}}}\right]}_{\mathit{dry}}–{\left[E_{\mathit{\text{substrate}}}\right]}_{\mathit{wet}}$$E10

Or,

$$S={\mathrm{\gamma }}_{\mathrm{SV}}–\left({\mathrm{\gamma }}_{\mathrm{SL}}+{\mathrm{\gamma }}_{\mathrm{LV}}\right)$$E11

The liquid spreads entirely to lower its surface energy (θ = 0) if the parameter S is positive. The end result is a layer with a nano-scopic thickness that results from molecular and capillary forces competing. If S is negative, the drop does not spread out and instead forms an equilibrium spherical cap resting on the substrate with a contact angle of. When θ ≤ π/2, a liquid is said to be ‘mainly wetting’, while when θ > π/2, it is said to be ‘primarily non-wetting’. When a surface is connected with water, it is referred to as ‘hydrophilic’ when it is θ ≤ π/2 and ‘hydrophobic’ when it is θ > π/2 [6].

3.1 Wicking

Wicking is the capillary-driven spontaneous flow of a liquid in a porous medium. Wetting causes capillary forces; hence, wicking is the result of spontaneous wetting in a capillary system. A meniscus is created in the simplest case of wicking in a single capillary tube as shown in Figure 2. A pressure difference across the curved liquid/vapour contact is caused by the surface tension of the liquid. The value for the pressure difference of a spherical surface was deduced in 1805 independently by Thomas Young and Pierre Simon de Laplace and is represented with the so-called Young-Laplace equation [6]:

Figure 2.

Wicking in a capillary.

$$\text{∆P}={\mathrm{\gamma }}_{\mathrm{LV}}\left(\frac{1}{R1}-\frac{1}{R2}\right)$$E12

For a capillary with a circular cross section, the radii of the curved interface R1 and.

R2 are equal. Thus:

$$\text{∆P}={\text{2γ}}_{\mathrm{LV}}/\mathrm{R}$$E13

where,

$$R=r/cosӨ$$E14

and r is the capillary radius. Since the capillary spaces in a fibrous assembly are not uniform, the effective capillary radius re is utilised instead, which is usually an indirectly determined parameter.

3.2 Capillary theory

Capillary action is governed by the properties of the liquid, the fibre surface wetting characteristics and the geometric configurations of the porous medium. In a capillary, liquid rises due to the net positive force (ΔP) across the liquid-solid interface.

$$\mathrm{\Delta P}=\mathrm{P}–\mathrm{\delta gh},$$E15

where δ = liquid density in g/cc, g = gravitational acceleration of 980.7 cm/s2, height of liquid rise in cm = h, the capillary pressure (p) is described by the initial wetting force (Fwi) in the capillary area (πri²):

$$\mathrm{P}=\mathrm{Fwi}/{\mathrm{\pi ri}}^2=2\mathrm{\pi }\text{riγcos}\mathrm{\theta }/{\mathrm{\pi ri}}^2=2\mathrm{\gamma }cos\mathrm{\theta }$$E16

where, γ = liquid surface tension in dyne/cm.

ri = radius inside the capillary in cm and.

θ = liquid-solid contact angle.

Where capillary pressure (P) is greater than the weight of the liquid (δgh), the positive forces drive the liquid upward. Upon reaching equilibrium where P – δgh, the net driving force ΔP becomes zero. The liquid stops rising at the equilibrium height (h).

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^s) as compared with coarser yarn (20^s) [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

1. It is evident that as the fibres become coarser, the water absorbency increases. The explanation for this could be due to coarser fibres’ higher bending rigidity [16, 17] and a decrease in the number of fibres in the yarn cross section. As a result, the bulkiness of the yarn increases [18, 19]. Increased water absorbency is also linked to the availability of more pore volume in yarn structures [19].

2. It has been noticed that when yarn coarseness increases, cloth water absorbency increases at first, then declines. The explanation for this could be due to a 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].

4.1.2 Effect of yarn modification on wicking characteristics

1. It is evident that as the fibre gets coarser, the fabric wicks more. The explanation for this could be due to coarser fibres’ higher bending rigidity [18] and a decrease in the number of fibres in the yarn cross section. As a result, the bulkiness of the yarn increases [19, 23]. Increased wicking is caused by the availability of increased pore space within the yarn structure [24].

2. It has been noticed that when yarn coarseness increases, fabric wicking increases at first, then decreases. Because of the decrease in compactness of yarn structure [20] and rise in bulkiness of yarn, the size of the pores initially increases as the yarn becomes coarser, increasing the availability of air spaces in the yarn structure. Wicking increases as a result of this [25]. However, beyond a certain degree, the pore structure opens up, slowing the flow of water through the pores.

3. Fabric wicking is observed to increase when the proportion of sheath fibres rises. The explanation for this could be due to an increase in fabric openness [21] and yarn bulkiness when the sheath is removed, resulting in more air gaps in the yarn structure [23]. Furthermore, parallel fibre arrangement creates correct channelling within the yarn, resulting in increased wicking [26, 27].

4.2 Wicking in fabric

Fabric with a high and consistent absorbency is desirable in almost every wet finishing procedure and many finished fabrics. The wicking property of materials affects their absorbency. When a fabric is entirely or partially submerged in a liquid, or in touch with a small amount of liquid, such as a drop placed on the fabric, wicking occurs. As a result, capillary penetration of a liquid can occur from either an infinite (unlimited) or a finite (limited) reservoir. Immersion, transplanar wicking and longitudinal wicking are the wicking processes that occur from an infinite reservoir. A drop placed on the cloth surface demonstrates wicking from a restricted reservoir [28]. The places of interlacement between warps and wefts were constantly formed in horizontal and vertical directions as fluid flow split. The horizontal yarns (either warp or weft, depending on the test direction) served as fluid reservoirs to wick further along the vertical yarns [29].

4.2.1 Effect of fabric parameters on wicking and its application as technical textiles

Researchers have discovered that fabrics with equally distributed float wick slower and horizontally striped fabrics wick quicker. Because the floats of threads in horizontally striped fabrics are positioned on the edge of the horizontal stripes and spread throughout the entire fabric surface, this happens. This uneven structure could explain why horizontally striped materials have a higher wicking rate. The pace of warp and weft way wicking differs slightly, and in some situations, the rate of weft way wicking is larger than the rate of warp way wicking. This could be caused due to tension differences between warp and weft threads. The rate of wicking for uniformly dispersed floats increases as weave factor P1 increases, which is due to the increase in floats in the fabrics [30]. Fabrics made of ring yarn wick faster than fabrics made of compact yarn [31]. Moisture management behaviour of knitted fabric has been studied from structurally modified ring and vortex spun yarn where the air permeability, water vapour permeability and total absorbency of the knitted fabric made from changed yarn all improved significantly, whereas the wicking characteristic decreased [32]. Fabrics composed of coarser yarns (40s Ne) wick more quickly than fabrics made of finer yarns (50s Ne). Fabrics behave in the same way that yarns do when it comes to wicking. The difference in wickability between plain weave and twill weave fabrics grows as the constituent yarn fineness increases. This variation is substantially more noticeable in diagonal wicking than in warp- and weft-way wicking [33]. The Lucas-Washburn equation was found to be suitable for analysing the wicking behaviour of woven cotton fabrics, and the wicking height square had a positive and good correlation with time in both the warp and weft directions, according to Zhu et al. [34]. Wicking height decreases with increasing weft yarn density as it leads to a decrease in porosity due to increased warp yarn crimp [35].

Using a sink time technique, the wettability of various terry towel fabrics was tested, and it was discovered that fabrics with higher loop density (repeat with 3-pick) sink faster than those with lower pick density (4, 5 and 6-pick weaves). Vertical wicking studies reveal that materials with a 3-pick density wick the fastest, followed by fabrics with 4, 5 and 6-pick density [36]. Moisture management is used in applications such as active athletics, exercise garments, work clothing, intimate apparel and footwear to avoid or limit liquid collection on the wearer’s skin owing to perspiration. This is accomplished by rapidly wicking or diffusing the liquid through an inner hydrophobic fibre layer to an outside hydrophilic layer, then evaporating it into the atmosphere. Sportwool is a two-layer sportswear with good moisture management qualities that is utilised in a variety of sports apparel. The inner layer, which is closest to the skin, is made up of chemically treated ultrafine Merino wool fibres (˂20 μm). The exterior layer is completely constructed of polyester filament yarn. Wool fibres have a high-water vapour permeability, which allows heat and moisture to be transferred from the skin to the outside surface, where it can escape due to wind speed and body movement [37]. A multi-layer construction is appropriate for sportswear [38, 39]. According to D’Silva and Anand [38], in a two-layer construction, the wicking layer is made up of synthetic fibres, such as micro-denier polyester, while the absorbent and evaporating layer is commonly cotton or rayon.

Many healthcare and personal hygiene items require liquid flow management in terms of liquid volume and flow rate elements that are acceptable for the end use. The incorporation of effective capillary systems into the final product allows for controlled liquid flow. Hygiene goods are made up of different layers of materials with different properties that allow liquid or moisture to drain swiftly away from the inner surface of the material in contact with the wearer’s body. Wicking and wetting principles are applied to multilayer protective clothing. The outer layer of protective clothing consists of permeable fabric or a liner or a layer made of carbon-loaded foam. To reduce the wetting due to body fluid, the outer layer is treated with a fluoro-chemical, and this reduces the surface energy, and thereby, the wetting is reduced [40]. Geotextiles are permeable fabrics that can hold solid items in place while allowing water to pass through. Due to their low cost, consistent qualities and convenience of placement, they have been widely used as drainage, separation and filter materials in geotechnical and geo-environmental activities for about 30 years. The primary goal of geotextiles is to allow water to flow through the filter into the drain over the course of the project while keeping soil particles in place and avoiding migration through the filter [40]. Natural geotextiles are now being used such as jute geotextiles (JGT) where biodegradability of JGT is an advantage when control of surficial soil erosion is considered. It acts as mulch, attenuates extremes of temperature, adds micronutrients to the soil, leaves fibrous residues that improve hydraulic conductivity of soil and thus eases dissipation of pore water pressure [41].

5. Experimental

The study focused on 100% cotton fabrics and their constituent cotton yarns, which included plied yarn for the warp and single yarn for the weft. During the preparation of the yarns, three (3) different counts, namely 20s, 30s and 40s Ne, were prepared from 0.9 s Ne cotton roving using a TRYTEX Miniature Ring Spinning machine for specific TM values of 4 (in indirect cotton count system), ensuring that the helix angle of fibres remained constant in all yarn structures. For all of the yarns, machine parameters such as the ring frame machine’s spindle speed were set to 10,000 rpm.

Second, after necessary assembly winding and a portable laboratory winder, the yarns in the 20s, 30s and 40s were made 2-ply each using a TRYTEX Miniature TFO machine. Then, using 2-ply of each count as warp and single yarn of each count as weft, 1/1 plain and 2/1 twill weave fabric samples were produced, with their respective sample codes provided in Table 1.

Sample No.	Fabric construction	Sample code
		Plain weave	Twill weave
1	2/20 as warp and 20s as weft	FP1	FT1
2	2/30 as warp and 30s as weft	FP2	FT2
3	2/40 as warp and 40s as weft	FP3	FT3

Table 1.

Fabric sample and used codes.

Thus, a total of six yarn samples and six fabric samples were prepared for this study. All the yarn (single and plied) and fabric (plain and twill) samples had undergone a scouring process with the standard recipe as wicking is highly correlated to wetting so it is a prerequisite that the sample should be as hydrophilic as much as possible. All the scoured samples (yarns and fabrics) were subsequently used for testing of wicking phenomena after conditioning the fabric in standard atmospheric conditions for 48 h. The basic parameters of fabrics are determined in Table 2.

Sample No.	Sample codes	Thread density		Cloth cover factor
		Ends/inch	Picks/inch
1	FP1	53	60	22.17
2	FP2	58	60	20.07
3	FP3	62	60	18.64
4	FT1	54	63	22.57
5	FT2	58	63	20.33
6	FT3	59	63	18.46

Table 2.

Thread density and cloth cover factor of respective fabric samples.

After setting up the experimental set-up in the testing centre, all of the yarn and fabric samples were evaluated for wicking parameters. Different yarn and fabric samples are initially built up in accordance with DIN 53924. Fabric pieces of 200 mm × 25 mm were used in the experiment. A beaker was placed beneath the yarn and fabric strip such that the yarn and fabric strip’s end was dipped into the water. Figures 3 and 4 demonstrate how yarns and fabric samples were hung in a stand by a clip. The laboratory travelling microscope was placed at the water level, and readings of the water level were taken at regular intervals.

Figure 3.

Wicking set-up for yarn.

Figure 4.

Wicking set-up for fabric.

6. Wicking behaviour of woven fabrics and its interrelation with their constituent yarns

As reviewed, wicking behaviour has been evaluated classically in terms of wicking height of the respective fabrics and its constituent yarns. Wicking height of fabrics has been shown in three different directions, and ultimately, related results have been used to establish the relationship between fabric wicking and its constituent yarn wicking phenomena.

6.1 Effect on wicking height (with respect to time) in various directions (warp-way, weft-way and diagonal-way) of fabrics as well as their constituent yarns

Tables 3–5 indicate the values of wicking height as a function of time as recorded in the trials for different orientations of fabrics and their constituent yarns in the 20s, 30s and 40s, respectively. Figure 5 depicts the liquid flow for a specific set of warp and weft threads in the warp, weft and diagonal directions of fabric samples.

Time (min)	Wicking height of yarn (cm)		Wicking height of FP1 (cm)			Wicking height of FT1 (cm)
	2ply	Single	Warp	Weft	Diagonal	Warp	Weft	Diagonal
0.5	3.2	2.2	0.3	0.3	0.2	0.5	0.2	0.3
1	4.4	3.0	0.6	0.4	0.4	1.0	0.5	0.6
2	5.9	3.7	1.4	0.9	0.7	1.7	1.1	1.3
3	6.9	4.5	2.0	1.4	1.0	2.3	1.5	1.6
4	7.6	5.2	2.6	2.1	1.4	2.6	2.0	1.9
5	8.1	5.7	3.0	2.4	1.8	3.0	2.4	2.5
10	10.2	7.3	3.5	2.7	2.3	3.6	2.7	2.9
20	12.3	8.1	4.1	3.0	2.5	4.0	2.9	3.1
30	13.7	8.2	4.4	3.2	2.7	4.2	3.1	3.3
60	13.7	8.2	4.9	3.4	3.0	4.5	3.2	3.4
120	13.7	8.2	4.9	3.4	3.1	4.5	3.2	3.4

Table 3.

Wicking height of fabric samples (with codes) in different directions along with its constituent 2/20s Ne plied yarns (used as warp) and 20s Ne single yarns (used as weft).

Time (min)	Wicking height of yarn (cm)		Wicking height of FP1 (cm)			Wicking height of FT1 (cm)
	2ply	Single	Warp	Weft	Diagonal	Warp	Weft	Diagonal
0.5	3.2	2.2	0.3	0.3	0.2	0.5	0.2	0.3
1	4.4	3.0	0.6	0.4	0.4	1.0	0.5	0.6
2	5.9	3.7	1.4	0.9	0.7	1.7	1.1	1.3
3	6.9	4.5	2.0	1.4	1.0	2.3	1.5	1.6
4	7.6	5.2	2.6	2.1	1.4	2.6	2.0	1.9
5	8.1	5.7	3.0	2.4	1.8	3.0	2.4	2.5
10	10.2	7.3	3.5	2.7	2.3	3.6	2.7	2.9
20	12.3	8.1	4.1	3.0	2.5	4.0	2.9	3.1
30	13.7	8.2	4.4	3.2	2.7	4.2	3.1	3.3
60	13.7	8.2	4.9	3.4	3.0	4.5	3.2	3.4
120	13.7	8.2	4.9	3.4	3.1	4.5	3.2	3.4

Table 4.

Wicking height of fabric samples (with codes) in different directions along with its constituent 2/30s Ne plied yarns (used as warp) and 30s Ne single yarns (used as weft).

Time (min)	Wicking height of yarn (cm)		Wicking height of FP1 (cm)			Wicking height of FT1 (cm)
	2ply	Single	Warp	Weft	Diagonal	Warp	Weft	Diagonal
0.5	3.2	2.2	0.3	0.3	0.2	0.5	0.2	0.3
1	4.4	3.0	0.6	0.4	0.4	1.0	0.5	0.6
2	5.9	3.7	1.4	0.9	0.7	1.7	1.1	1.3
3	6.9	4.5	2.0	1.4	1.0	2.3	1.5	1.6
4	7.6	5.2	2.6	2.1	1.4	2.6	2.0	1.9
5	8.1	5.7	3.0	2.4	1.8	3.0	2.4	2.5
10	10.2	7.3	3.5	2.7	2.3	3.6	2.7	2.9
20	12.3	8.1	4.1	3.0	2.5	4.0	2.9	3.1
30	13.7	8.2	4.4	3.2	2.7	4.2	3.1	3.3
60	13.7	8.2	4.9	3.4	3.0	4.5	3.2	3.4
120	13.7	8.2	4.9	3.4	3.1	4.5	3.2	3.4

Table 5.

Wicking height of fabric samples (with codes) in different directions along with its constituent 2/40s Ne plied yarns (used as warp) and 40s Ne single yarns (used as weft).

Figure 5.

Wicking phenomena in fabric for various directions such as (a) warp way, (b) weft way and (c) diagonal way.

The tabulated findings show a few generalised observations about the behaviour of yarn wicking in comparison to fabric wicking. First and foremost, it is well established that ply yarns usually provide superior wicking than single yarns of the same fineness due to the presence of densely populated fibres in the plied structure versus a single form of yarn. It is also discovered that the wicking height of constituent yarns, whether plied (used as a warp) or single (used as a weft), of any fineness (expressed by counts), is higher than that of their respective fabrics, regardless of the direction of testing for plain weave samples. This usual phenomenon can be understood specifically for plain weave due to the compact fibrous structure of yarns in comparison to the porous-interlaced structure of fabrics made out of this constituent yarn resulting in much better capillary action facilitating higher liquid transmission inside the structure. An exception to this trend has been observed for twill fabrics produced from medium and finer count yarns when viewed with respect to wicking of single yarn structure. Lesser number of interlacements may predominate for the attainment of higher wicking height in a twill weave in comparison to that of a single yarn.

However, a thorough explanation of the relative wicking phenomena is needed to set up a relationship between fabric wicking in various directions with respect to their constituent yarns of different counts. In this direction, a precise observation from Table 3 reveals that 20s 2-ply yarn shows maximum wicking than single yarn of the same count when tested individually as well as than the fabrics made out of these yarns as warp and weft respectively irrespective of warp, weft and diagonal way-wicking test. In the case of 20s 2-ply yarn, wicking height reaches up to 13.7 cm, whereas in warp-way fabric, wicking height reaches only up to 4.9 cm, the single yarn is in the intermediate height of 8.2 cm. Fabric wicking is reduced in comparison to yarn wicking for three reasons: yarn deformation in the fabric due to crimped condition, the number of interlacement in a unit length of a fabric sample and finally, the disruption of vertical wicking due to the occurrence of horizontal wicking at every point of interlacement. These characteristics can also be seen in twill weave fabrics. However, the effect is more or less the same as plain weave fabric considering the use of constituent coarser yarn in the fabric structure.

The maximum wicking height in 2 h for 30s 2-ply yarn is 10.7 cm, as indicated in Table 4, but when this yarn is present in fabric, the maximum warp-way wicking height is 5.7 cm in plain and 8.2 cm in a twill structure. The reason is the same as discussed before, but if we compare between plain weave fabric and twill weave fabric, the wicking height of twill weave fabric generates a higher value than that of the plain weave fabric. The explanation for this could be due to their fundamental design, as twill weave fabrics have less interlacements than plain weave fabrics. Another aspect we noticed from Table 4 is that twill weave fabric’s warp-way wicking reaches the height of 30s single yarn, which is not visible in plain weave fabric. The comparatively finer yarn composition could be the predominant factor for this behaviour.

The wicking behaviour of plain weave fabric is low when compared with both ply yarn and single yarn, as shown in Table 5, but when considering the twill weave, the wicking height in diagonal-way direction crosses the wicking height of warp-way direction, crosses the wicking height of single yarn and approaches the wicking height of ply yarn. This phenomenon might be caused by the angle of ply yarn and single yarn orientation in diagonal-way fabrics. The yarns are at a 45° angle in this orientation, which facilitates the wicking process rather than creating obstructions in the point of interlacement as observed in warp or weft-way fabrics. Moreover, it is observed that the fabric made of 40s 2-ply warp and 40s weft twill weave fabric has higher wicking height, which is may be due to the reason of higher porosity of the fabric woven from the finer yarns. As the cover factor is low in the finer fabric, which may be responsible for higher porosity, which confirms the same reported by Erdumlu and Saricam [42]. According to the capillary principle, smaller pores are filled first and influence the movement of the liquid. As the smaller pores are completely filled, the liquid moves to the larger pores [43].

6.2 The relationship between yarn wicking and fabric wicking in reference to different constituent yarns for various directions of plain and twill fabrics

The accompanying graphical figures (Figures 6–17) show the relationship between fabric wicking in various directions (warp, weft and diagonal) and its constituent yarn wicking (warp or weft) for plain and twill weave structures, from coarser to finer count. The first six graphical figures (Figures 6–11) are for plain weave fabrics only, while the remaining (Figures 12–17) are for twill weave fabrics. For all of these representations, a linear relationship is found to be the best fit, and the associated regression equation is also derived to establish the relationship.

Figure 6.

Relationship of wicking height between plain weave fabric (FP1) and constituent plied warp yarn (2/20^s).

Figure 7.

Relationship of wicking height between plain weave fabric (FP1) and constituent single weft yarn (20^s).

Figure 8.

Relationship of wicking height between plain weave fabric (FP2) and constituent plied warp yarn (2/30^s).

Figure 9.

Relationship of wicking height between plain weave fabric (FP2) and constituent single weft yarn (30^s).

Figure 10.

Relationship of wicking height between plain weave fabric (FP3) and constituent plied warp yarn (2/40^s).

Figure 11.

Relationship of wicking height between plain weave fabric (FP3) and constituent single weft yarn (40^s).

Figure 12.

Relationship of wicking height between twill weave fabric (FT1) and constituent plied warp yarn (2/20^s).

Figure 13.

Relationship of wicking height between twill weave fabric (FT1) and constituent single weft yarn (20^s).

Figure 14.

Relationship of wicking height between twill weave fabric (FT2) and constituent plied warp yarn (2/30^s).

Figure 15.

Relationship of wicking height between twill weave fabric (FT2) and constituent single weft yarn (30^s).

Figure 16.

Relationship of wicking height between twill weave fabric (FT3) and constituent plied warp yarn (2/40^s).

Figure 17.

Relationship of wicking height between twill weave fabric (FT3) and constituent single weft yarn (40^s).

Table 6 has a relationship matrix containing all of the regression equations (18 numbers) from Figures 4 to 9, expressing substantial evidence of a highly positive relationship between fabric wicking (y) and yarn wicking (x) for plain weave samples. The coefficient of determination (R2) is found to be in the range of 0.836–0.991, which means the coefficient of correlation values are almost closer to 1, which indicates that the proportion of variation is very low in the dependent variable that can be attributed to the independent variable within the range of experiments. The R2 values of the diagonal-way samples are between the R2 values of warp-way and weft-way samples composed of coarser to medium fineness yarns (20s and 30s), most likely due to the resultant effect of both the constituent plied warp and single weft yarns because the yarns are not in the direction in which the wicking has been measured. Regardless of warp or weft yarns, the relationship in a diagonal direction is found to be inferior for finer count (40s) fabric samples. As seen in Table 2, this result might be attributable to the lower fabric cover.

Parameters		Wicking height of plain weave fabric (cm)
		Warp-way	Weft-way	Diagonal-way
Wicking height of 20^s yarn (cm)	2-ply warp	y = 0.420x – 0.925 (R^2 = 0.972)	y = 0.294x – 0.562 (R^2 = 0.937)	y = 0.268x – 0.696 (R^2 = 0.969)
	Single weft	y = 0.713x – 1.289 (R^2 = 0.973)	y = 0.508x – 0.864 (R^2 = 0.968)	y = 0.457x – 0.938 (R^2 = 0.976)
Wicking height of 30^s yarn (cm)	2-ply warp	y = 0.709x – 2.478 (R^2 = 0.966)	y = 0.390x – 1.147 (R^2 = 0.990)	y = 0.393x – 1.403 (R^2 = 0.981)
	Single weft	y = 1.125x – 2.665 (R^2 = 0.836)	y = 0.645x – 1.384 (R^2 = 0.932)	y = 0.635x – 1.567 (R^2 = 0.881)
Wicking height of 40^s yarn (cm)	2-ply warp	y = 0.335x – 0.847 (R^2 = 0.941)	y = 0.219x – 0.520 (R^2 = 0.958)	y = 0.144x – 0.315 (R^2 = 0.895)
	Single weft	y = 0.695x – 1.082 (R^2 = 0.985)	y = 0.452x – 0.664 (R^2 = 0.991)	y = 0.335x – 0.847 (R^2 = 0.941)

Table 6.

Matrices of regression equations and R² values between fabric wicking and yarn wicking for plain weave fabric samples.

The correlation of wicking behaviour between fabrics of different directions (warp-way, weft-way and diagonal way) with respect to their constituent warp and weft yarns for twill weave samples is shown in a single representation using a similar relationship matrix derived from Figures 10–15 and arranged as Table 7. This table also aids in the identification of differences in relationship with plain weave samples of similar types as displayed in Table 6.

Parameters		Wicking height of twill fabric (cm)
		Warp-way	Weft-way	Diagonal-way
Wicking height of 20^s yarn (cm)	2-ply warp	y = 0.356x – 0.335 (R^2 = 0.967)	y = 0.273x – 0.404 (R^2 = 0.931)	y = 0.285x – 0.376 (R^2 = 0.946)
	Single weft	y = 0.610x – 0.671 (R^2 = 0.982)	y = 0.473x – 0.696 (R^2 = 0.970)	y = 0.492x – 0.671 (R^2 = 0.979)
Wicking height of 30^s yarn (cm)	2-ply warp	y = 0.877x – 2.085 (R^2 = 0.974)	y = 0.687x – 1.466 (R^2 = 0.987)	y = 0.685x – 1.691 R^2 = 0.991
	Single weft	y = 1.446x – 2.600 (R^2 = 0.912)	y = 1.159x – 1.997 (R^2 = 0.966)	y = 1.140x – 2.139 (R^2 = 0.943)
Wicking height of 40^s yarn (cm)	2-ply warp	y = 0.769x – 0.84 (R^2 = 0.981)	y = 0.659x – 1.206 (R^2 = 0.991)	y = 0.771x + 0.272 (R^2 = 0.985)
	Single weft	y = 1.526x – 1.114 (R^2 = 0.939)	y = 1.331x – 1.528 (R^2 = 0.982)	y = 1.539x – 0.036 (R^2 = 0.954)

Table 7.

Matrices of regression equations and R² values between fabric wicking and yarn wicking for twill weave fabric samples.

From the tabulated data of twill weave fabrics, the relationship of wicking between fabric and yarns is found to be much stronger (as the range of R2 lies within 0.912–0.991) compared with that of the plain weave in the fabric axis of the twill weave creating less amount of disturbance on capillary action due to the lower number of interlacements of twill design. As a result, the smooth movement of liquid within the yarn structure helps in a more effective wicking effect than plain weave structures, strengthening the relation between yarn and fabric wicking. As a result, regardless of the different directions of experimental fabric samples used in this investigation, changes in yarn fineness have a comparatively smaller impact on the connection [44].

7. Conclusion

The cotton fabrics presented in this chapter are only small fractions, which are produced globally for several applications. Absorbency and wicking are the key factors while producing or engineering a fabric for particular end uses such as sports, medical and other technical applications. Therefore, wickability of yarn and fabric has been studied critically as it is completely governed by their structure primarily. Therefore, even minor differences in structure can affect wicking height in both yarn and fabric. Increased fineness diminishes wickability in both ply and single yarn structures separately, but when employed in fabric structures, increased yarn fineness improves wicking [44]. Based on scientific experiments, uniquely presented correlation matrices have expressed the interrelation between cotton fabric and its constituent yarns showing strong correlation but varying nature due to differences in structure, direction of measurement, etc. Hence, these correlations can be used as a quick predictor of cotton fabric wicking based on the measured wicking of their constituent yarns for future research. Further research includes the study of absorbency and wicking with various solvents, temperature, and humidity for wide range of textile materials using these correlations with some modified equations.

Acknowledgments

The authors gratefully acknowledge the assistance provided by Prof. Sumanta Bhattacharya, Former Principal, and Prof. Biswapati Chatterjee, Former Head of the Department in Textile Technology, Government College of Engineering and Textile Technology, Serampore, West Bengal, India.