This article was downloaded by: [Florida Atlantic University]On: 19 November 2014, At: 09:12Publisher: 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

Weight reduction of microfibre polyester fabric andthe effect on its physical and mechanical propertiesF. Mousazadegan a , S. Saharkhiz a & M. Maroufi aa Department of Textile Engineering , Amirkabir University of Technology , Tehran, IranPublished online: 22 Jul 2010.

To cite this article: F. Mousazadegan , S. Saharkhiz & M. Maroufi (2010) Weight reduction of microfibre polyester fabric andthe effect on its physical and mechanical properties, The Journal of The Textile Institute, 101:8, 716-728

To link to this article: http://dx.doi.org/10.1080/00405000902812685

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 Institute

Vol. 101, No. 8, August 2010, 716–728

ISSN 0040-5000 print/ISSN 1754-2340 onlineCopyright © 2010 The Textile InstituteDOI: 10.1080/00405000902812685http://www.informaworld.com

Weight reduction of microfibre polyester fabric and the effect on its physical andmechanical properties

F. Mousazadegan, S. Saharkhiz* and M. Maroufi

Department of Textile Engineering, Amirkabir University of Technology, Tehran, Iran

Taylor and Francis

(

Received 15 July 2008; final version received 9 February 2009

)

Journal of the Textile Institute

For the present work, a heat-set microfibre polyester woven fabric was treated with five different sodium hydroxideconcentrations in similar conditions. Their physical and mechanical properties were studied and discussed. Changesin eight properties due to the weight reduction, i.e. surface properties, tear strength, crimp, compression, pressurerecovery, crease recovery, abrasion and weave density which are reported in this work were not available for any typeof weight reduced polyester fabrics in the cited literature. Results show that the weight reduction decreases yarn andfabric strength, fabric abrasion resistance, fabric tear strength and bending stiffness. On the other hand, it increasesfabric thickness under low pressure, crease recovery angle, air permeability and drape of the fabric. The treatmentshowed no significant effect on the surface properties of the samples.

Keywords:

weight reduction; physical properties; mechanical properties; microfibre; polyester; comfort

Introduction and background

Polyester fabrics, because of their easy maintenance,fairly long life and low price are more under consider-ation than fabrics from other types of man-made fibres.However, apparel made from polyester fibres havesome disadvantages, such as undesirable handle, highstatic charge, hydrophobic properties, low moistureregain and tendency to pill. The weight reduction treat-ment improves a majority of the properties of thesetypes of fabrics as shown by numerous research sincethe early 1980s.

Based on microscopic images, Soon and Seon(1995) and Zeronian and Collins (1988) reported thatweight reduction treatment doesn’t change the shape ofthe fibre cross-section. Sanders and Zeronian (1982)and Haghighat Kish and Nouri (1999) worked on theeffect of weight reduction on change in fibre diameters.Sanders and Zeronian (1982) also measured the changesin yarn diameter in their research. Shet, Zeronian,Needles, and Siddiqui (1982) and Needles, Brook, andKeighley (1985) studied on fabric shrinkage property offabric after weight reduction treatment. Zeronian andCollins (1988) and Sanders and Zeronian (1982)worked on the effect of weight reduction on yarnbreaking load, tenacity and breaking elongation.

The reduction of fabric tenacity due to the weightreduction treatment was studied by Shet et al. (1982).

Sanders and Zeronian (1982) studied the fabric specificrupture energy.

Although all of them reported that this treatmentreduces the yarn and fabric strength in certain level,but since general performance of fabric such as handand drape properties of fabric improves dramatically,the advantage of the weight reduction treatment isgreater than its negative effects. In addition, thesereductions in fabric properties are not highly signifi-cant and have a limited effect on fabric strength.Among them, bending rigidity and drape are two prop-erties which improve considerably. Needles et al.(1985), Davies and Amirbayat (1994) and HaghighatKish and Nouri (1999) have studied on the effect ofweight reduction on fabric bending length, its stiffnessand fabric shear modulus. Drop property was specifi-cally studied by Davies and Amirbayat (1994). Theeffect of weight reduction treatment on fabric airpermeability was studied by Sanders and Zeronian(1982) and Needles et al. (1985). Two properties ofwater vapour transfer and liquid water transfer werestudied by Needles et al. (1985). Related to these prop-erties, contact angle and wicking were studied byNeedles et al. (1985) and Sanders and Zeronian (1982).This treatment improves the hand property of polyes-ter fabric after treatment which was studied by Soonand Seon (1995).

*Corresponding author. Email: natilus@aut.ac.ir

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

The Journal of The Textile Institute

717

A selected list of the researchers involved in thefield and the topics under their investigations are givenin Table 1.

A different attempt for improving the properties ofpolyester fabrics was found to be the production of finerfibres of approximately less than 1 denier, i.e. themicrofibres. During the recent years, consumption ofpolyester microfibre is increasing and because of theirbetter performance when compared with the ordinarypolyester filament yarns, it is found to be a goodreplacement for the latter in many applications.

Microfibre polyester fabrics are also being treatedby sodium hydroxide in weight reduction treatment inthe industry. Due to the fine structure, sensitivity andmore susceptibility to damage of such fibres, it is neces-sary to investigate the performance of these fabrics afterthe weight reduction treatments and level of the damageor improvement in such fabrics.

Experimental work

Material

The grey fabric used for the present work was a 100%polyester microfibre woven plain weave. Yarn count in

both warp and weft directions were 150d/144f texturedfilaments. Weave density were 56.5 ends and 30 picks/cm, and average fabric weight of 150 g/m

2

.

Sample preparation

There was a preparation prior to weight reduction treat-ment. Samples were soaked in a bath containing 1 g/lUltravon GP (a wetting agent from former Ciba) and1 g/l of laboratory grade of tri sodium phosphate for 20min at 60

°

C and rinsed with hot and later with coldwater prior to drying at 100

°

C. Finally, the fabrics wereheat-set at 150

°

C for 20 sec in dry condition. The treat-ment of the samples prior to weight reduction wasperformed for removing grease and any possible soiling.

Weight reduction treatment

The baths were prepared by using different concentra-tion of laboratory grade of sodium hydroxide with 4, 6,8, 10 and 12 g/l concentration. Two g/l quarternaryammonium compound named Tinegal PAC (from Ciba)was added to all baths working as an accelerator.Treatment started at room temperature and after adding

Table 1. A selected list of researchers and the properties investigated.

Shet et al.Sanders and

ZeronianNeedles

et al.Davies & Amirbayat

Soon and Seon

Zeronian and Collins

Haghighat Kish and Nouri

1982 1982 1985 1994 1885 1988 1999

Weight loss

✓ ✓ ✓ ✓

Fibre cross-section

✓ ✓

Yarn diameter

✓

Fibre diameter

✓ ✓

Yarn breaking load

✓

Yarn tenacity

✓ ✓ ✓

Fabric tenacity

✓

Initial modulus

✓

Shear modulus

✓

Specific rupture energy

✓

Bending length

✓

Bending stiffness

✓ ✓

Air permeability

✓ ✓

Drape

✓ ✓

Drop

✓

Contact angle

✓ ✓

Wicking

✓ ✓ ✓

Water vapour transport

✓

Liquid water transport

✓

Hand value

✓

Fibre density

✓ ✓

Scan electron microscopy

✓ ✓ ✓ ✓ ✓

Fabric shrinkage

✓ ✓

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

718

F. Mousazadegan

et al.

the fabric samples the bath was heated to boil within 20min and continued for 45 min at this temperature.Samples were then removed, rinsed with hot and coldwater and neutralised with acetic acid before drying.

Instrumentation and methods

The equipments and standard methods used for thiswork are shown in Table 2.

All sample preparation and testing procedure werecarried out in standard condition.

Results

This section represents the experimental results andnecessary information discussion. Numerical results ofthe experiments are represented in the Appendix.

Fabric weight

By plotting fabric weight reduction against the sodiumhydroxide concentration, it can be seen that there is ahigh non-linear correlation between sodium hydroxideconcentration and fabric weight (see Figure 1).

Figure 1. Fabric areal density after treatment with sodium hydroxide with different concentrations.

The percentage of fabric weight reduction aftertreatment with different concentration of sodiumhydroxide can be seen in Figure 2.

Figure 2. Fabric weight reduction per cent after treatment with sodium hydroxide with different concentrations.

Since the weight reduction, even if the material iscompletely dissolved can not be higher than 100%, thecurve has to be asymptotic to 100% line. For this reasonthe plots reported by Zeronian and Collins (1988) andHaghighat Kish and Nouri (1999), which shows a linearrelation, are not realistic.

Since the level of weight reduction of fabric in theprocess is the result of the level of sodium hydroxide

Figure 1. Fabric areal density after treatment with sodiumhydroxide with different concentrations.

Figure 2. Fabric weight reduction per cent after treatmentwith sodium hydroxide with different concentrations.

Table 2. List of testing equipment and testing methods.

Experiment Testing equipment Standard method

Stenter Wetner Mathis AG (Type LTF) –Weight reduction Ahiba Texomat (Type R6B/2) –Bending length Shirley Stiffness Tester ASTM D1388Crease recovery angle SDL Shirley Crease Recovery Tester & Loading Device BS 3086Air permeability SDL Air Permeability Tester BS 5636Yarn srength Instron 5566 ASTM D2256Fabric strength Instron 5566 BS 2576Fabric thickness Thickness Gauge SDL ASTM D1777Tear strength Elmendrof ASTM D1424Fabric drape Cusick Drape Tester BS 5058Fabric abrasion Abrasion Tester Model 174 ASTM D3884Fiber diameter Projectina ASTM D2130Fabric areal density – ASTM D3775Yarn crimp – BS2863Fabric roughness Kawabata Evaluation System for Fabrics (KES4) –

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

The Journal of The Textile Institute

719

concentration and time of staying of fabric in bath, theper cent of reduced fabric weight has been consideredas a base for analysing the changes in physical andmechanical properties.

Fibre diameter

As shown in Figure 3, by increase in weight reductionpercentage, there is a decrease in fibre diameter. In factsodium hydroxide works on the surface of polyesterfibres and reduces their diameters.

Figure 3. Effect of weight reduction treatment on fibre diameter.

It can be seen that there is a second-order correlationbetween fibre diameter and fabric weight reductionpercentage.

Weave set

As shown in Figure 4, the weight reduction treatmenthas no significant effect on warp and weft spacing of thefabric and as a result the weave count (number of warpthreads

×

number of weft threads per unit area) remains

unchanged. For this reason, variations of the coverfactor with weight reduction follows the variations ofthe fabric weight shown in Figure 1.

Figure 4. Effect of weight reduction on yarn spacing.

Yarn crimp

In all the samples treated with sodium hydroxide,changes in yarn crimp of fabrics were noticed (Figure5). Although there is a notable change of the crimp atthe first stage of the treatment, there are no considerablechanges between crimps of the samples upon furtherweight reduction. According to Shet et al. (1982), this isbecause of partial removing of the yarn twist during theinitial treatment which results in slight yarn extension inboth warp and weft directions.

Figure 5. Effect of weight reduction on yarn crimp.

Fabric thickness

As shown in Figure 6, the thickness of samples underlow pressure with higher levels of weight reductionare higher than the samples with lower weight

Figure 3. Effect of weight reduction treatment on fibrediameter.

Figure 4. Effect of weight reduction on yarn spacing.

Figure 5. Effect of weight reduction on yarn crimp.

Figure 6. Fabric thicknesses after treatment by differentweight reduction per cent.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

720

F. Mousazadegan

et al.

reduction percentages but there are opposite behav-iours under higher pressures. Figure 7 shows thechanges in thickness of treated samples under differentpressures.

Figure 6. Fabric thicknesses after treatment by different weight reduction per cent.Figure 7. Thicknesses of samples with different weight reduction levels under different pressure level.

Fabrics with higher weight reduction percentagesare firstly thicker than the samples with lower weightreduction rates. This increase is due to a partial removalof the compactness resulted from the heat setting. Thisincrease in the thickness and increasing the yarn crimp,as mentioned above, improves the tactile perception ofthe fabric.

Compressibility and pressure recovery

Compressibility

In order to study the compressibility behaviour of thetreated samples, the thickness of samples weremeasured during loading and unloading cycles undereight different pressures.

Pressure recovery

One of the good characteristics that produces in polyes-ter fabric after weight reduction treatment is the specialsoftness that creates a good feeling under hand. In order

Figure 7. Thicknesses of samples with different weightreduction levels under different pressure levels.

Figure 8. Thicknesses of samples after increment loading and unloading: (a) original sample, (b)–(f) after weight reductions.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

The Journal of The Textile Institute

721

to study the behaviour and recovery of the samples afterbeing subjected to compression, the thickness of eachsample was measured after an incremental load bythe order of 20, 50, 100, 200, 500, 1000, 1500 and 2000g/cm

2

and unloaded after the maximum pressure. Inorder to see the behaviour of the sample under pressureit was decided to use these wide ranges. The resultswhich represent the behaviour of the treated samples areshown in Figure 8.

Figure 8. Thicknesses of samples after increment loading and unloading: (a) original sample, (b) – (e) after weight reductions.

The pressure recovery of the samples was calculatedfrom thickness of the samples after loading and afterunloading cycles in per cent. As shown in Figure 9, thepressure recovery of all treated samples at every level ofpressure shows an improvement compared with theoriginal sample. At lower pressures the samples have abetter pressure recovery.

Figure 9. Percentage recovery of samples treated at different concentration of sodium hydroxide after applying and removing pressure at different levels (in each category charts are from left to right by the order of 13.1%, 15.6%, 19.2%, 21.8% and 25%).

Fabric crease recovery angle

As it is shown in Figure 10, weight reduction treatmentcauses an increase in fabric crease recovery angle andrecovery of fabric from crease. There is a linear positiverelation between weight reduction level and improve-ment in crease recovery angle.

Figure 10. Effect of weight reduction treatment on crease recovery angle.

Yarn strength

As shown in Figure 11, there is a non-linear (second-order) relation between yarn breaking load and increasein weight reduction rate.

Figure 11. Effect of weight reduction on yarn breaking load.

In order to identify whether this reduction is due tothe reduction in the strength of material (polyesterfibres) or due to the reduction of filament cross-sectionarea, it was decided to determine the stress applied tothe fibre cross-section. The fibre stress was calculated

by material strength approach which was the division offibre breaking load by total fibre area.

As it can be seen in Figure 12, the level of stress oncross-section of the fibres is nearly constant. Therefore,

Figure 9. Percentage recovery of samples treated at differ-ent concentration of sodium hydroxide after applying and re-moving pressure at different levels (in each category chartsare from left to right by the order of 13.1%, 15.6%, 19.2%,21.8% and 25%).

Figure 10. Effect of weight reduction treatment on creaserecovery angle.

Figure 11. Effect of weight reduction on yarn breaking load.

Figure 12. Stress on fibre cross-section of weight reducedsamples.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

722

F. Mousazadegan

et al.

it can be concluded that the strength of the polymer hasnot been affected by chemical process and the reductionof filament strength is only due to the reduction in thefibre cross-section.

Figure 12. Stress on fibre cross-section of weight reduced samples.

In addition, since yarn strength is from its fibrestrength, by drawing the fibre diameter against yarnstrength it can be seen that there is a strong non-linearrelation between fibre diameter and yarn strength(Figure 13).

Figure 13. Relation between fibre diameter and yarn breaking load.

Fabric tensile strength

As shown in Figure 14, there is a negative non-linearrelation between increase in sodium hydroxide concen-tration and decrease in fabric breaking strength (5 cmsample width) in both warp and weft directions. At 25%weight reduction, there is a 47.9% and 61.2% loss ofstrength in warp and weft direction of fabric.

Figure 14. Effect of weight reduction on fabric strength.

The major parameter involved in fabric strengthcomes from its yarn strength. By drawing the yarn

breaking load against fabric breaking load (Figure 15),it can be seen that there is a strong and direct relationbetween fabric and its yarn strength.

Figure 15. Relation between yarn and fabric breaking load.

Fabric tear strength

As shown in Figure 16, there is a negative linear rela-tion between weight reduction and tear strength in bothwarp and weft directions.

Figure 16. Effect of weight reduction on fabric tear strength.

Since the primary effect of weight reduction treat-ment on polyester filament yarns is reduction in fibrediameters, it is necessary to investigate the relationbetween filament yarn diameters and fabric tearstrength. As shown in Figure 17, there is a strong linearrelation between decrease in fibre diameter and fabrictear strength.

Figure 17. Relation between fibre diameter of treated samples and their tear strength.

Further study revealed that extensibility of yarns hasan effective role on the tear strength during that shortperiod of time. By studying the relation between fabricelongation at breaking point and fabric tear strength

Figure 13. Relation between fibre diameter and yarnbreaking load.

Figure 14. Effect of weight reduction on fabric strength.

Figure 15. Relation between yarn and fabric breaking load.

Figure 16. Effect of weight reduction on fabric tearstrength.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

The Journal of The Textile Institute

723

(Figure 18), it was found that there is a linear relationbetween the two mentioned parameters.

Figure 18. Effect of fabric extension at breaking point on fabric tear strength.

Abrasion resistance

Treated samples are tested on Taber abrasion testerunder 1000 g load at constant rate of 1 cycle/sec. Asshown in Figure 19, fabric abrasion resistance decreaseslinearly by increasing the fabric weight reduction rate.

Figure 19. Effect of weight reduction on fabric abrasion resistance.

Decrease in the thickness due to the weight reduc-tion as shown in the Fibre thickness section is the majorfactor in this behaviour. Slight increase in the thicknessunder low pressure is only due to increase in bulk anddoes not affect the abrasion resistance.

Bending length and bending stiffness

The results of experiment showed that there is a non-linear relation between the weight reduction and fabric

bending length (Figure 20). The results are in agree-ment with the pervious research (Davies & Amirbayat,1994).

Figure 20. Effect of weight reduction on fabric bending length.

By considering this matter that the fibre diameter isthe main parameter in fabric structure that changesbecause of weight reduction treatment and changes themechanical property of the fabric, the fibre diameterwas drawn against bending length. As it can be seenin Figure 21, there is good correlation between fibrediameter and bending length. The relation betweenfabric weight reduction and fabric bending stiffness isshown in Figure 22.

Figure 21. Effect of fibre diameter on fabric bending length.Figure 22. Effect of weight reduction on fabric bending stiffness.

The bending rigidity of fabric/fabric stiffness (

G

) isthe product of fabric modulus and second moment ofarea of each filaments (

EI

). By considering this matterthat the weight reduction process does not change themass density of the fibres, the main parameter thataffects the fabric stiffness is the moment of area of thefabric (

I

). Because of the filament yarns’ thicknesses

Figure 17. Relation between fibre diameter of treatedsamples and their tear strength.

Figure 18. Effect of fabric extension at breaking point onfabric tear strength.

Figure 19. Effect of weight reduction on fabric abrasionresistance.

Figure 20. Effect of weight reduction on fabric bendinglength.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

724

F. Mousazadegan

et al.

and their position in fabric structure, the total secondmoment of area of the fabric is the sum of each secondmoment of area of the filaments in respect to fabricneutral axis.

where

G

= fabric stiffness,

E

= fabric modulus,

I

fi

=second moment of area of each filaments,

I

fa

= secondmoment of area of each fabric,

A

fi

= area of the filamentcross-section, and

d

= distance of the filament fromneutral axis.

The second moment of area by assuming thecircular cross-section of the filaments is the related to

the power of four of diameter (

π

D

4

/16, where

D

is thefilament diameter).

The diameter of the filament after weight reductionis given by

where

D

0

= original diameter,

D

w

= diameter of filamentafter weight reduction, and

R

WR

= weight reduction ratein per cent.

As aforementioned,

I

fi

and

A

fi

are related to diameterof filament. Besides the diameter of the filament afterweight reduction is related weight reduction ratio (

R

WR

).By replacing the

D

W

in calculation of

I

fa

and

A

fi

, it canbe seen that the final equation for calculating the secondmoment of area of fabric (

I

fa

) will be the product of thesecond order of weight reduction rate in per cent (

R

WR

).The result achieved was according to the theoreticalpredictions.

Drape

Among different fabric properties, this property has animportant influence on form and shaping of the apparelon body. This matter creates a desirable feeling andcomfort for the consumer. In addition, this property ofpolyester fabric becomes closer to silk.

The relation between drape coefficient of fabricand weight reduction per cent at three diameters of 24,30 and 36 cm can be seen in Figure 23. As the level ofweight reduction increases, fabric drape improves.This is mainly related to the decrease in bendingstiffness. In addition, after weight reduction treatmentyarns have more space to move which causes morefreedom for the fabric to undergo easier in-planedeformation.Figure 23. Effect of weight reduction on fabric drape.

I I A dfa fi fi� � �� ( ) ( )2

G EI� fi ( )1

D D Rw WR= −01 21 100 3( / ) ( )/

Figure 21. Effect of fibre diameter on fabric bending length.

Figure 22. Effect of weight reduction on fabric bendingstiffness.

Figure 23. Effect of weight reduction on fabric drape.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

The Journal of The Textile Institute 725

Fabric air permeability

As shown in Figure 24, by increasing sodium hydroxideconcentration, fabric air permeability increases.Figure 24. Effect of weight reduction on fabric air permeability.When a heat-set fabric is treated with sodium hydrox-ide, the fibre diameters reduce and the structure of fabricbecomes more open. Figure 25 shows a good correlationbetween fibre diameter and fabric air permeability.Figure 25. Effect of fibre diameter on fabric air permeability.Since air passes through fabric, volume of the fibresin fabric structure is important. In this regards thevolume of fibre in fabric and the effect of weight reduc-tion on the volume of fibres in fabric structure wascalculated by considering the mass of the polyester inunit area, material density (ρ) and the fabric thickness.

As shown in Figure 26, there is a good linear corre-lation between volume of material in unit areas of fabricand fabric air permeability. It can be concluded thatreduction in fibre diameter and therefore its volume hasan important role in fabric air permeability.Figure 26. Relation between volume of polyester fibres and air permeability of fabrics.The flow rate passing a porous material can beexpressed by Kozeny–Carman equation as

where k = coefficient of permeability, C = constant, g =gravitational constant, µa = dynamic viscosity of air, ρa

= density of air, S = specific surface, DR = specificweight (DR = ρS/ρa), ρS = density of solid, e = void ratio(Va0/VT0), Va0 = volume of air in original sample, andVT0 = total volume of package.

In this equation for weight reduction case k, C,g, µa, ρa, DR, ρS are constant which in the continue willbe expressed as B. Equation (4) will be simplified as

After weight reduction, the thickness of the fila-ments will be reduced. Therefore, the volume andspecific surface of the filaments will change. By assum-ing the circular cross-section of the filaments, thevolume and surface of the filaments are given by

where Vf0 = volume of filaments in original sample,Vfw = volume of filaments after weight reduction, Sf0 =specific surface of filaments in original sample, andSfw = specific surface of filaments after weightreduction.

The relation between the void ratio of original fabricand the fabric after weight reduction is given by

k Cg e

S D e= ⋅ ⋅

+µ ρa a R

3

2 14

( )( )

k Be

S e= ⋅

+

3

2 15

( ). ( )

V V Rfw f WR= −0 1 100 6( / ) ( )

S S Rfw f WR= −01 21 100 7( / ) ( )/

Figure 24. Effect of weight reduction on fabric airpermeability.

Figure 25. Effect of fibre diameter on fabric air permeability.

Figure 26. Relation between volume of polyester fibres andair permeability of fabrics.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

726 F. Mousazadegan et al.

where ew = void ratio of package after weight reduction.By considering the weight reduction rate the

Kozeny–Carman equation will be as

After each weight reduction the thickness of thefibres will change, therefore the two parameters of totalvolume of fibres change, and hence the void ratio (ew)and the specific surface of the fibres (Sw) both will alsochange simultaneously but at a different rate. In addi-tion, both the parameters are related to the rate ofweight reduction (RWR).

Surface properties

In order to study the effect of the weight reduction onthe surface properties of the samples, they were testedby Kawabata KES4. As shown in Figure 27, weightreduction does not have a considerable effect on eitherthe roughness or the coefficient of friction of thesamples.Figure 27. Effect of weight reduction on: (a) roughness, and (b) the coefficient of friction.

Summary and conclusion

The weight reduction treatment has a considerableeffect on physical and mechanical properties of polyes-ter fabric. It can be said that almost all the fabric prop-erties are affected by this process.

Although nearly all the physical and mechanicalparameters of fabric change, yet the magnitude of thesechanges is not the same. Figure 28 shows (in %) thegraphical view of the normalised and the variations ofall measured values of physical and mechanical param-eters of the treated fabrics.Figure 28. Percentage of change in fabric properties due to weight reduction treatment (in each category, charts are from left to right by the order of 13.1%, 15.6%, 19.2%, 21.8% and 25%): a, fabric breaking load (warp); b, fabric breaking load (weft); c, yarn breaking load; d, tear strength(warp); e, tear strength (weft); f, fabric drape (24); g, fabric drape (30); h, fabric drape (36); i, bending length (warp); j, bending length (weft); k, fibre diameter; l, tear strength (warp); m, tear strength (weft); n, fabric density (warp); o, fabric density (weft); p, crease recovery (warp); q, creaserecovery (weft); r, thickness; s, crimp (warp); t, crimp (weft); and u, air permeability.

Although it can be seen that some changes are nega-tive, but not all the reduction is bad. This treatment hassome improvements and also some drawbacks on fabricproperties. Generally, these changes in fabric propertiescan be categorised in two groups: (1) related toimprovements in fabric performance and (2) related todrawbacks in fabric performance.

The improvements in fabric performance can bedivided into fabric mechanical behaviour and itscomfort characteristics as follows:

● There are reductions in two mechanical propertiesof fabric bending length and drape which is goodimprovement and important in shaping of fabricand its formability in clothing.

● Increase in fabric thickness and yarn crimpsincreases the volume of fabric, its handle and alsoits recovery from pressure. This improvementmakes the polyester soft and have a hand like silk.

● The weight reduction treatment reduces the diam-eter of the filaments. Therefore, there is a reduc-tion of packing density of fabric and increase inthe void factor of the package. In addition there isa reduction in surface of the fibres. These increasethe air permeability of the fabric and improve itscomfort in clothing applications.

● This treatment also improves the crease recoveryof fabric which is an important property inapplication.

Regarding drawbacks in fabric mechanicalperformance, three major mechanical properties – yarnbreaking load, fabric breaking load and fabric tearstrength – will be affected by this treatment. Studyshowed that the reduction in fabric strength is related toreduction in the area of yarns cross-section and is notrelated to reduction in material strength. Although thesereductions are not desirable but using these fabrics inclothing such as ladies blouse or night dress, whichfabric will not be subjected to severe tension or abrasionor frequent weaving (compared to other clothing like

eV

VRw

f

TWR= − −1 1 100 80 ( / ) ( )

k Be

e= ⋅

+w

w3

w

3

19

S ( ). ( )

Figure 27. Effect of weight reduction on: (a) roughness, and (b) the coefficient of friction.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

The Journal of The Textile Institute 727

jeans), the fabric performance is acceptable even withthese reductions. The tension and abrasion applied tothe fabric in wearing of garment is much lower than thestrength of the fabric even after the treatment.

Change in microfibre fabric properties are accordingto previous research. Specifically in regards to microfi-bre fabrics, it must be noticed that due to fineness offilament fibres and their sensitivity the weight reductiontreatment need to be done under more accurate andgood controlled condition.

The relation between concentration of sodiumhydroxide and weight reduction is not linear; even if thematerial is completely dissolved, it cannot be higher than100%. The curve has to be asymptotic to 100% line.

ReferencesDavies M., & Amirbayat, J. (1994). The effect of weight

reduction on the performance of a polyester fiber satin

bending, shear, drape and drop. Journal of the TextileInstitute, 85(3), 376–382.

Haghighat Kish, M., & Nouri, M. (1999). Effects of sodiumhydroxide and calcium hydroxide on polyester fabrics.Journal of Applied Polymer Science, 72, 631–637.

Needles, H.L., Brook, D.B., & Keighley, J.H. (1985).How alkali treatment affect selected properties ofpolyester, cotton and polyester/cotton fabrics. AATCC,17(9), 177–180.

Sanders, E.M., & Zeronian, S.H. (1982). An analysis of themoisture-related properties of hydrolyzed polyester.Journal of Applied Polymer Science, 27, 4477–4491.

Shet, R.T., Zeronian, S.H., Needles, H.L., & Siddiqui, S.A.(1982). Modification of polyester and polyester/cottonby alkali treatment. Textile Chemist and Colorist, 14,233–237.

Soon, L.J., & Seon, R.H. (1995). Alkaline softening ofpolyester fabrics treated with aqueous NaOH solutionscontaining CTAB & EDA. Proceedings of the 3rd AsianTextile Conference, 1, 256–261.

Zeronian, S.H., & Collins, M.J. (1988). Improving thecomfort of polyester fabrics. Textile Chemist andColorist, 20(4), 25–28.

Figure 28. Percentage of change in fabric properties due to weight reduction treatment (in each category, charts are from left toright by the order of 13.1%, 15.6%, 19.2%, 21.8% and 25%): a, fabric breaking load (warp); b, fabric breaking load (weft); c,yarn breaking load; d, tear strength (warp); e, tear strength (weft); f, fabric drape (24); g, fabric drape (30); h, fabric drape (36);i, bending length (warp); j, bending length (weft); k, fibre diameter; l, tear strength (warp); m, tear strength (weft); n, fabric density(warp); o, fabric density (weft); p, crease recovery (warp); q, crease recovery (weft); r, thickness; s, crimp (warp); t, crimp (weft);and u, air permeability.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14

728 F. Mousazadegan et al.

Appendix. Results of the physical and mechanical, and compression experiments(1) Results of the physical and mechanical experiments

(2) Results of fabric compression test

Sodium hydroxide concentration (g/l) 0 4 6 8 10 12

Weight reduction (%) 0 13.1 15.6 19.2 21.8 25

Fabric thickness (mm)

20 0.263 0.283 0.299 0.309 0.303 0.30150 0.231 0.234 0.242 0.254 0.231 0.236

100 0.219 0.218 0.228 0.233 0.21 0.214200 0.209 0.201 0.207 0.212 0.193 0.195500 0.193 0.179 0.185 0.187 0.171 0.174

1000 0.181 0.164 0.171 0.171 0.154 0.1551500 0.171 0.154 0.161 0.161 0.143 0.146

Pressure (g/cm2) 2000 0.164 0.148 0.154 0.151 0.135 0.1361500 0.167 0.152 0.156 0.158 0.138 0.1421000 0.174 0.156 0.162 0.161 0.143 0.146

500 0.183 0.167 0.173 0.175 0.155 0.158200 0.196 0.183 0.192 0.194 0.171 0.174100 0.203 0.196 0.206 0.204 0.187 0.187

50 0.211 0.208 0.216 0.219 0.200 0.20420 0.221 0.226 0.236 0.242 0.220 0.226

Sodium hydroxide concentration (g/l) 0 4 6 8 10 12

Fabric weight (g/m2) 149.9 130.2 126.5 121.2 117.3 112.5Weight reduction (%) 0 13.1 15.7 19.2 21.8 25Warp density (cm−1) 56.5 56.2 55.9 56.2 56.16 55.9Weft density (cm−1) 29.4 30 29.5 30.1 29.8 29.9Fibre diameter (Micron) 13.15 10.13 9.6 9.2 9.06 8.65Crimp–warp (%) 2.9 6.2 6.2 6.2 6.7 6.3Crimp–weft (%) 8.7 11 11.2 11 10.8 10.9Crease recovery–warp (deg.) 137.4 141.6 143.4 162.6 165.5 169.1Crease recovery–weft (deg.) 114.3 118.7 128.2 128.6 140.0 147.0Thickness (20 g/cm2) (mm) 0.263 0.283 0.299 0.301 0.303 0.309Tear strength–warp (cN) * 3360 3248 2988.8 2579.2 2458.4Tear strength–weft (cN) * 1459.2 1088 972.8 780.8 697.6Bending length–warp (cm) 3.28 2.23 2.22 2.07 2.04 1.98Bending length–weft (cm) 1.88 1.53 1.52 1.45 1.44 1.41Yarn strength–warp (cN) 6.33 3.82 3.55 3.27 3 2.96Fabric strength–warp (N) 1668.86 1150.28 1091.01 956.19 940.53 869.89Fabric strength–weft (N) 509.3 337.2 320.19 275.27 232.44 197.76Abrasion resistance (cycle) 1024 695 529 477 366 267Air permeability (ml/sec) 8.3 23.8 29.8 35.7 36.5 37.8Drape (24 cm) (%) 92.33 78.97 76.36 75.98 71.74 70.32Drape (30 cm) (%) 59.32 38.55 36.39 33.84 32.24 30.91Drape (36 cm) (%) 32.65 21.24 19.09 19.05 17.69 17.67

*The strength of the raw sample was above the capacity of the tester.

Dow

nloa

ded

by [

Flor

ida

Atla

ntic

Uni

vers

ity]

at 0

9:12

19

Nov

embe

r 20

14