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This article was downloaded by: [University of Boras] On: 06 October 2014, At: 22:41 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK The Journal of The Textile Institute Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tjti20 The effect of fabric structure and yarn-to-yarn liquid migration on liquid transport in fabrics S. Mhetre a & R. Parachuru a a Department of Polymer Textile & Fiber Engineering , Georgia Institute of Technology , Atlanta, USA Published online: 17 Jun 2010. To cite this article: S. Mhetre & R. Parachuru (2010) The effect of fabric structure and yarn-to-yarn liquid migration on liquid transport in fabrics, The Journal of The Textile Institute, 101:7, 621-626, DOI: 10.1080/00405000802696469 To link to this article: http://dx.doi.org/10.1080/00405000802696469 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions

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This article was downloaded by: [University of Boras]On: 06 October 2014, At: 22:41Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

The Journal of The Textile InstitutePublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/tjti20

The effect of fabric structure and yarn-to-yarn liquidmigration on liquid transport in fabricsS. Mhetre a & R. Parachuru aa Department of Polymer Textile & Fiber Engineering , Georgia Institute of Technology ,Atlanta, USAPublished online: 17 Jun 2010.

To cite this article: S. Mhetre & R. Parachuru (2010) The effect of fabric structure and yarn-to-yarn liquid migration on liquidtransport in fabrics, The Journal of The Textile Institute, 101:7, 621-626, DOI: 10.1080/00405000802696469

To link to this article: http://dx.doi.org/10.1080/00405000802696469

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use ofthe Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

The Journal of The Textile InstituteVol. 101, No. 7, July 2010, 621–626

The effect of fabric structure and yarn-to-yarn liquid migration on liquid transport in fabrics

S. Mhetre and R. Parachuru∗

Department of Polymer Textile & Fiber Engineering, Georgia Institute of Technology, Atlanta, USA

(Received 31 August 2008; final version received 15 December 2008)

Wicking experiments were carried out on a range of cotton and polyester fabrics, which exhibited differences in terms of yarnsize, thread spacing, and yarn type. Wicking coefficients in the warp and weft direction as well as for the constituent warpand weft yarns were determined using image analysis technique in which height of liquid front was measured as a functiontime. Results showed that the wicking in fabrics is determined by the wicking behavior of the yarns, the thread spacing, and,more importantly, the rate at which liquid migrates from longitudinal to transverse threads and again from transverse threadsback to longitudinal threads. This yarn migration phenomenon, which has not received significant attention in the past, wasstudied by measuring the gain in wicking coefficient and the equilibrium wicking height and by actual visualization of thewicking process. Fabric wicking rates were found to be directly associated with yarn wicking behavior. Inter-yarn spaceswere found to exert a major influence on fabric wicking behavior.

Keywords: wicking; liquid transport; liquid migration; fabric structure

Introduction

Wicking in fabrics has long been the subject of interest ofboth academia and industry because of the important roleit plays in many end applications, including apparel andnonapparel end uses, and manufacturing processes such asdyeing, finishing, and coating. Different techniques suchas direct observation (Danino & Marmur, 1994; Kawase,Sekoguchi, Fujii, & Minagawa, 1986a, 1986b), use of cam-era and image analysis techniques (Arora, Deshpande, &Chakravarthy, 2006; Kumar & Deshpande, 2006; Perwuelz,Mondon, & Caze, 2000), use of liquid-sensitive sensors(Hollies, Kaessinger, & Watson, 1957; Ito & Muraoka,1993), and use of force balance (Hsieh, 1995; Hsieh &Yu, 1992; Hsieh, Yu, & Hartzell, 1992; Pezron, Bourgain,& Quere, 1995) have been employed to quantitatively an-alyze liquid flow through yarns and fabrics. In essenceliquid absorption in textile structures is typically studiedin one of two ways – by measuring the height of liq-uid front or by measuring the weight of liquid absorbedas a function of time. Both methods are useful, and theyhave their own special significance. For example, in ap-plications such as coating, spraying, and resin impregna-tion of composite materials, measurement of the heightof liquid front is more relevant than measurement of theweight of the resin. However, in many other applicationsin which knowledge of the amount of liquid absorbedis more critical, gravimetric method is the appropriatemethod.

∗Corresponding author. Email: [email protected]

The application of multiple techniques to analyze liq-uid flow has helped to understand the influence of mate-rial (Hollies et al., 1957; Hsieh & Yu, 1992; Liu, Choi,& Li, 2008; Yoon & Buckley, 1984) and liquid prop-erties (Hamdaoui, Fayala, & Nasrallah, 2007; Kamath,Hornby, Weigmann, & Wilde, 1994) on the wicking phe-nomenon. The wicking process has also been used toobtain structural information such as porosity, size, andsize distribution of pores (Hsieh, 1995; Marmur & Cohen,1997).

Capillary forces are governed by the properties of theliquid, the contact angle established by the liquid, and thegeometric configurations of the pore structures. For an idealcapillary, capillary pressure (P ), because of which trans-port of liquid occurs inside capillaries, has been shown tobe a function of surface tension of liquid (γ ), contact angle(θ ), and radius of pore (ri), and its magnitude is gener-ally given by the Laplace equation (Equation (1); Kissa,1996))

P = 2 × γ × cos θ

ri

. (1)

Liquid moves upward in the capillary due to a net pos-itive force if the capillary pressure (P ) is greater than thepressure of the liquid column inside the capillary. The pres-sure of the liquid column inside the capillary is ρLgh, where

ISSN 0040-5000 print / ISSN 1754-2340 onlineCopyright C© 2010 The Textile InstituteDOI: 10.1080/00405000802696469http://www.informaworld.com

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ρL is density of the liquid; g is the acceleration due to grav-ity; and h is the height of the liquid inside the capillary.Liquid rises until both pressures become equal after whichthe net force driving the liquid becomes zero. Height ofthe liquid column at this position is designated equilibriumwicking height (Leq) and can be expressed by the followingequation (Hsieh, 1995)

Leq = 2 × γ × cos θ

ri × g × ρL. (2)

Kinetics of wicking in textile fabrics is more criticalin many applications and is often investigated by fitting theexperimental data to the famous Lucas–Washburn equation.When the effect of gravity is neglected, at low values of t ,and when the height of liquid rise (L) is much smaller thanLeq, the Lucas–Washburn equation is given by (Kamathet al., 1994; Kissa, 1996)

L =√

ri × γ × cos θ

2 × η× t0.5 = K × t0.5, (3)

where η is the viscosity of the liquid. Parameter K is oftenreferred to as wicking coefficient, and it is determined byfitting the experimental data to Equation (3).

The above expressions and many wicking studies asso-ciated with them consider textile assemblies as single cap-illaries, even though textile structures consist of capillariesthat vary in diameter and length and are interconnected ina complex manner. The extent to which the actual wickingbehavior agrees with that of the above expressions underthe range of structural variations that exist in commercialfabrics needs to be verified, and if necessary, the equationsneed to be expanded/modified to account for structural vari-ations. When fabric is immersed in a liquid, the liquid firststarts to wick through the longitudinal threads. When thetraveling liquid front encounters transverse threads, someof the liquid in longitudinal threads may move into trans-verse threads. The rate at which liquid transfers dependsupon the nature of capillaries and pores, solid–liquid phys-iochemical parameters of the two yarns, and the nature ofliquid–solid contact. Transferred liquid remains in the seg-ments of transverse threads, and it may act as new reservoirfor the wicking process in longitudinal threads. Due to theseadditional reservoirs, the rate of wicking of liquid in longi-tudinal threads can go up. Liquid may also get stored in theinter-yarn spaces, which can also act as additional reser-voirs. This migration process from liquid reservoirs and itsmoderation by structural variations has rarely been studied(Hollies et al., 1957; Minor, Schwartz, Buckles, & Wulkow,1960). Full understanding of this process could enable thedevelopment of fabrics with superior wicking properties.

In this research, we have studied the wicking of pigmentink in different fabrics by measuring height of liquid front

with time, using image analysis method. We also inves-tigated the migration process through direct visualizationand also by the determination of the gain in wicking co-efficient and the equilibrium wicking height of yarns, asa result of the yarns remaining an integrated part of thefabric. We investigated the influence of fabric structuralparameters on the migration phenomenon and the wickingbehavior.

Experimental

Water-based black pigment ink (Fabric Fast Ultra) devel-oped by the Trident company (Brookfield, CT, USA) wasused for the wicking experiments. Pigment ink renders avery clear and sharp flow front as liquid wicks into fab-ric. We did not use simple dye solutions, as they wereshown to give a fuzzy flow front in fabrics, which is dif-ficult to detect, and the flow appeared to change with thetype and intensity of the surrounding light source. The vis-cosity and surface tension of the pigment ink used in thestudy were 3 cp and 36 dynes/cm, respectively. Contactangle of the ink on polyester film was found to be 54 de-grees. This indicates that the ink can wet both polyesterand de-sized cotton fabrics. Experiments were done on arange of fabrics, which varied in terms of fiber composi-tion and structure. Description of the fabrics is provided inTable 1.

To measure the height of the flow front, actual wickingof liquid in the fabric was recorded by a Canon camcorder.The recorded videos were converted into picture frames(1 frame per second), using video-editing software. Eachpicture image was converted into a greyscale image, andwicking height (h) as a function of time (t) was measuredby analyzing the images using codes written in MATLAB.Wicking tests were performed on all the fabrics by dippingthe 3-cm long and 1.5-cm wide fabric strips into a fixedvolume of ink kept in a glass beaker. Short strips of the fab-rics were used to minimize the effects of evaporation andgravity. At shorter times and during early absorption whenwicking height is much smaller than equilibrium wickingheight, effects of gravity and evaporation are minuscule.Fabric strips were dipped in the liquid to a 2-mm depth.Wicking experiments were done on constituent yarns, us-ing the same procedure as that described above, and 3-cmlong yarn segments were used. As yarns were removed di-rectly from fabrics, they retained most of their structuralcrimp. Thus, the yarns were immersed under a load of10 gm. Ten samples for each fabric and yarn were tested,and the average and standard deviation values were deter-mined. Experiments were done warp way and weft wayfor each fabric. We analyzed the data for the first 60 sec-onds for all the fabrics, and the wicking coefficient (K)for that period was determined for all the yarns and fab-rics by fitting the data to the Lucas–Washburn equation(Equation (3)).

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Table 1. Description of fabric samples.

Fabric Warp yarn Weft yarn EPI PPI

Cotton 3508 280 denier (19 Ne), ring yarn, twisted (20 TPI),diameter ∼ 270 µm

660 denier (8 Ne), ring yarn, twisted (10 TPI),diameter ∼ 500 µm

80 35

Cotton 4508 280 denier (19 Ne), ring yarn, twisted (20 TPI),diameter ∼ 270 µm

660 denier (8 Ne), ring yarn, twisted (10 TPI),diameter ∼ 500 µm

80 45

Cotton 6018 280 denier (19 Ne), ring yarn, twisted (20 TPI),diameter ∼ 270 µm

296 denier (18 Ne), ring yarn, twisted (13 TPI),diameter ∼ 300 µm

80 60

Cotton 7018 280 denier (19 Ne), ring yarn, twisted (20 TPI),diameter ∼ 270 µm

296 denier (18 Ne), ring yarn, twisted (13 TPI),diameter ∼ 300 µm

80 70

PET 490 denier (11 Ne), rotor yarn, twisted,diameter ∼ 340 µm

350 denier (15 Ne), filament yarn, twistless,width ∼ 350 µm

52 42

PET tape 280 denier, filament yarn, twistless, width ∼410 µm

310 denier, filament yarn, twistless, width ∼ 510µm

60 40

Sized PET 530 denier, rotor yarn, twisted, diameter ∼ 300µm

530 denier, rotor yarn, twisted, diameter ∼ 300µm

56 44

Note: EPI, threads per inch in the warp direction of fabric; PPI, threads per inch in the weft direction; TPI, twists per inch of yarn.

The gain in wicking coefficient �K was determinedusing the following equation:

�K = (Kf − Ky)

Ky× 100, (4)

where Kf is the wicking coefficient of fabric and Ky is thewicking coefficient of yarn.

The equilibrium wicking heights (Leq) for yarns andfabrics were determined by dipping one end of the samplein a fixed but copious quantity of liquid for 12 hours. Thepercentage gain in equilibrium wicking height (�Leq) wascalculated in a manner similar to that of �K:

�Leq = (Leqf− Leqy

)

Leqy

× 100. (5)

Results and discussion

The average wicking rates of the warp and weft yarns of thedifferent fabrics and the gain in wicking rates are shown in

Table 2. As the warp yarns used in all cotton fabrics were thesame, they had the same wicking rates. Weft yarns of differ-ent counts were used in the cotton fabrics. Thicker cottonyarns (coarse denier yarns) showed higher wicking rates, asthey had lower twist levels. Low twist levels keep the yarnsmore open, and hence the effective capillary radius is morein case of open yarns. The highest wicking coefficient wasobserved in polyethylene terephthalate (PET) weft filamentyarn. Wicking coefficient was very high in these yarns be-cause these were twistless (open) filament yarns. Althoughyarns in the PET tape fabrics were also twistless filamentyarns, low wicking rates were observed in these yarns, asthe filaments in these yarns were closely packed. Closepacking reduced the capillary radius and hence the wickingcoefficient, which is in accordance with Washburn’s law.The sized warp yarns in the sized PET fabric showed thelowest wicking coefficient, and equilibrium wicking heightfor these yarns was just 2 mm. As most of the capillaries insized yarns are filled by size-coating formulation, wickingin these yarns is negligible and occurs very slowly.

As can be seen in Table 2, most of the fabrics showedwicking rates higher than their constituent yarns. Higher

Table 2. Yarn and fabric wicking coefficients.

Wicking coefficients K (cm/s0.5) Gain in wicking coefficient (%)

Sample Yarn – warp Yarn – weft Fabric – warp Fabric – weft Warp Weft

Cotton 3508 0.18 0.34 0.36 0.38 100 12Cotton 4508 0.18 0.34 0.31 0.34 72 0Cotton 6018 0.18 0.20 0.30 0.30 67 50Cotton 7018 0.18 0.20 0.28 0.27 56 35PET 0.18 0.42 0.38 0.30 111 −32PET tape 0.15 0.19 0.11 0.11 −27 −42Sized PET 0.03 0.19 0.09 0.12 200 −37

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Figure 1. Typical patterns of the liquid front exhibited by different samples.

fabric-wicking rates were observed in cotton 3508, cotton4508, and PET fabrics whose constituent yarns showedhigher wicking rates. Also, as the thread density of thefabrics went up, wicking rates went down. The percentagegain in wicking rates of the corresponding yarns in fabricsis shown in the last two columns of Table 2. The highest gainwas observed in the warp direction of the sized PET fabricfollowed by the warp directions of the PET and the cotton3508 fabrics. Lowest wicking rates and negative gains wereobserved in the case of PET tape and sized PET fabrics andin the weft direction of the PET fabric. Cotton fabrics with18-Ne weft yarn showed lower wicking rates compared tocotton fabrics with 8-Ne weft yarn, and this agreed with thedifference in wicking behavior exhibited by the two yarns.

Further, while the liquid was wicking through fab-rics, we continuously observed the liquid front under amicroscope. We noticed that the liquid front propagatesin one of the three ways or patterns as shown in Figure1. Fabric samples that exhibited the particular pattern arelisted below that pattern. In the first case, before liquidfront could pass any transverse thread, all previous trans-verse thread segments were completely filled. This indi-cates very quick transfer of liquid from longitudinal threadsto transverse threads. Liquid stored in those transversethreads is thus readily available for transfer from trans-verse threads back to longitudinal threads. Hence, sampleswhich exhibited this pattern showed highest gains in wick-ing coefficient. In the second type of liquid front pattern,few transverse threads (typically two) remained unfilled

probably because the rate of wicking in longitudinal threadsis quite high. This indicates somewhat less intensive migra-tion process. The samples that exhibited this pattern showedvery low wicking-coefficient gains. In the third type, dueto very poor migration of the liquid between threads,many transverse thread segments (typically more than four)remained unfilled. Longitudinal threads lost liquid to trans-verse threads, and they could not gain any liquid fromtransverse threads, thus explaining the negative gain inwicking coefficient observed specially in the case of PETtape fabric.

Trends similar to those seen in wicking rates were ob-served for equilibrium heights of the yarns and fabrics(Table 3). Higher equilibrium lengths were observed in thecase of cotton and PET fabrics. Contrary to the gain inwicking rates, the percentage gain values were positive forall fabrics, except for the sized PET fabric. This probablyimplies that at a short time duration, the migration of liquidfrom longitudinal yarns to transverse yarns is not complete,and hence in some cases the transverse threads may not actas reservoirs, thus producing a negative gain in wickingcoefficient. However, at longer time periods, migration iscomplete, and transverse threads act as reservoirs to givepositive gains in equilibrium wicking heights in most of thecases. Higher gains were observed once again in the warpdirection of sized PET fabric followed by the warp direc-tion of PET and cotton 3508 fabrics. Equilibrium wickingheights as well as gains decreased with increasing threaddensity.

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Table 3. Equilibrium wicking heights of yarns and fabrics.

Equilibrium wicking height (cm) Gain in wicking height (%)

Sample Yarn – warp Yarn – weft Fabric – warp Fabric – weft Warp Weft

Cotton 3508 2.0 4.2 6.6 7.6 230 81Cotton 4508 2.0 4.2 5.4 6.6 170 57Cotton 6018 2.0 2.4 4.4 5.0 120 108Cotton 7018 2.0 2.4 4.2 4.7 110 96PET 1.9 3.8 6.4 5.8 237 53PET tape 1.3 1.0 1.6 1.5 23 50Sized PET 0.2 2.0 0.7 1.4 250 −30

From the data it is thus clear that the wicking in fabricsis determined by the wicking rates of the yarns, the threadspacing, and more importantly the speed at which liquidmigrates from longitudinal to transverse threads and againback to longitudinal threads. We found that the migrationprocess is affected by the wicking rates and nature of lon-gitudinal and transverse threads. It is also affected by thenature of contact and the thread spacing.

If the wicking rate of the longitudinal threads is veryhigh, these threads may end up only giving the liquid totransverse threads but may not gain the benefit of migrationof the liquid from transverse threads back to them. This willlower the gain in wicking coefficient as well as the wickingcoefficient. This phenomenon was observed in case of weftdirection wicking of the PET fabrics.

Further, migration from longitudinal yarns to transverseyarns occurs only when longitudinal yarns become suffi-ciently saturated, meaning that it occurs only when there isenough liquid available on the surface of the longitudinalyarns. We found that migration from longitudinal yarns totransverse yarns occurs more easily if the longitudinal yarnsare twisted than when they are twistless filament yarns. Thesurface profile of the twisted yarns is rougher than that ofthe twistless yarns, which leaves more liquid on the surfaceof these yarns compared to filament yarns. Hence, liquidmigration from longitudinal yarns to transverse yarns ispoor when filament yarns are present in the longitudinal di-rection. This is why negative wicking-coefficient gain andvery low gains in equilibrium heights were observed in thecase of PET and PET tape fabrics.

Migration from transverse yarn segments back to lon-gitudinal threads depends upon the relative size of the cap-illaries present in those yarns. For a given liquid, yarnswith higher wicking rate normally suggest higher capillaryradius. Capillary pressure is higher for lower radius capil-laries and vice versa (Equation (1)). Thus, finer capillariescan easily pull the liquid from larger capillaries. There-fore longitudinal yarns with finer capillaries can easily pullthe liquid from transverse threads that have bigger capil-laries. This boosts the wicking rate and the wicking heightin longitudinal direction. Cotton 3508 and PET therefore

exhibited the highest gains in warp direction, as the warpyarns had finer capillaries, and the weft yarns had largercapillaries.

Further, capillary pressure is less in the case of fil-ament yarns than in the twisted yarns. Therefore, moregain in warp direction was observed in the case of PETfabric (111% in wicking coefficient and 237% in equilib-rium wicking height) compared to that in the cotton 3008fabric (100% in wicking coefficient and 230% in equilib-rium wicking height). This indicates that the presence oftwisted yarn in longitudinal direction and filament yarn inthe transverse direction can establish the best contact andrender superior wicking properties.

Wicking coefficient, equilibrium wicking height, andgain in wicking coefficient and height were all affectedby the thread spacing. Values of all these parameters de-creased when thread density was increased. This meansthat the liquid stored in inter-yarn spaces also plays a majorrole. Liquid fills these inter-yarn spaces after all the sur-rounding yarns are saturated and enough liquid is availableto fill up the inter-yarn space. Inter-yarn spaces are gener-ally larger than interfiber spaces in the yarn. Hence, liquidstored in inter-yarn spaces is more readily available, as cap-illary pressure for it is less. Thus, inter-yarn spaces are themore efficient reservoirs to boost up the wicking rate andwicking height. Better wicking properties can be achievedby decreasing thread spacing. However, if thread densityis decreased too much, inter-yarn spaces may remain un-filled, and improvement in wicking properties may not beachieved.

We observed that equilibrium wicking height values ofthe yarns and fabrics were not in accordance with thosepredicted by Equations (2) and (3). Equation (3) suggeststhat wicking coefficient is proportional to the square root ofcapillary radius. Thus, capillaries with larger radius shouldgive higher wicking rates. But these capillaries with higherradius should show lower equilibrium heights, as equilib-rium height is inversely proportional to capillary radiusas described by Equation (2). Therefore, there should bean inverse relationship between the wicking coefficientand equilibrium wicking height. However, we observed

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Figure 2. Wicking coefficient versus equilibrium wicking height.

mostly a direct relationship between these two parameters(Figure 2). This clearly indicates that the classical capillarytheories may not be applicable to the textile assemblies. Theanomaly in this case results from various factors. Twistedyarns for example show low wicking rates as well as lowequilibrium wicking height due to the presence of discon-tinuous capillaries and tortuous paths the liquid has to take.As discussed before, storage of liquid in transverse yarnsegments can boost up both wicking rate and equilibriumwicking height. Decrease in thread density or increase ininter-yarn space results in storage of more liquid, whichalso boosts up both wicking rate and equilibrium wickingheight. Migration process is thus a very important part ofthe wicking process in fabrics and requires further in-depthinvestigation. Determination of the gain in wicking coeffi-cient and wicking height is the best way to quantitativelydescribe the migration process.

Conclusions

Results of the wicking experiments on textile fabrics hav-ing different structures showed that the wicking in fabricsis determined by the wicking rates of the yarns, the threadspacing, and more importantly the rate at which liquid mi-grates from longitudinal to transverse threads and againfrom transverse threads back to longitudinal threads. Thismigration process can be effectively quantified by measur-ing the gain in wicking coefficient and equilibrium wick-ing height. The gain in wicking coefficient describes themigration process at shorter times, and the gain in equi-librium wicking height describes the migration process atlonger times; hence the two are totally different. Yarn type,effective capillary size of the yarns, and thread spacingaffect the migration process and hence also the wickingproperties of fabrics. We found that twisted yarns in thelongitudinal direction and filament yarns in the transversedirection of the fabric can maximize the migration processand hence can render superior wicking properties. Fabricswith lower thread densities show better wicking properties

provided that inter-yarn spaces are completely filled. Largerinter-yarn spaces can trap more liquid, which could becomeavailable for migration.

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22:

41 0

6 O

ctob

er 2

014