Indian Journal of Fibre & Textile ResearchVol. 22, September 1997, pp. 154-162

A study on some physical properties of modified cotton yamS Rajendran & S S Ramasamy

The South India Textile Research Association, Coimbatore 641014, Indiaand

S P MishraDepartment of Industrial Chemistry, Alagappa University, Karaikudi 623 003, India

Received 5 August 1996; revised received 8 November 1996; accepted 31 December 1996.

The structural and morphological features of cotton yam pretreated with trichloroacetic acid-methylene chloride (TCAMC) reagent under slack condition at room temperature have been studied andthe stress-strain behaviour of the treated yam analysed. Modification of cotton due to TCAMC treatmentresults in significant increase in tensile strength and noticeable increase in elongation. The extent ofmodification depends on the concentration of the reagent and the treatment time. The probable reasonsfor improvement in tensile properties are discussed. It has been found that the changes effected by theTCAMC treatment enhance the abrasion resistance of yam. SEM examination reveals that the treatedyam possesses some characteristic features.

Keywords: Abrasion resistance, Cotton yam, Crystallinity index, Fibre friction, FTIR spectra,Methylene chloride, Tensile properties, Trichloroacetic acid, Work of rupture

1IntroductionCotton fibre still occupies its position as premier

textile fibre despite its poor qualities likeinadequate strength, shrinkage, wrinkling, etc. Thetensile properties of cotton fibre depend mainly onmolecular structure and arrangement of molecularchains in the fibre. At yam stage, the twist and thefibre cohesion also contribute to the strength-elongation property. The strength of the cottonmay be improved either by changing its geneticcharacter or by suitable chemical modification toreorganize fibre structure. Since changing thehereditary character of a fibre is a time consuminglong-term process, more attention is paid by theresearchers on the chemical modification processof cotton fibres. Several attemptsl'? have beenmade' in the past for a permanent structuralmodification of cotton cellulose; of these, causticsoda and liquid ammonia13

-16 treatments proved to

be useful in improving the tensile strength, lusture,dye uptake, etc. of cotton. However, the maximumtensile strength achieved by alkali treatment isabout 25% which is still inadequate for subsequentprocessing of cotton. The change in strength ofmodified-cotton due to cross linking agents has also

been studied by many workers'":". In this paper,the effects of trichloroacetic acid - methylenechloride (TCAMC) reagent on the structure andmorphology of cotton yam are reported.

2 Materials and Methods2. t Materials

100% cotton yams having the followingspecifications were used: Ne 2011, Combed, TPI16; Ne 4011, Combed, TPI 21; and Ne 8011,Combed, TPI 33.

2.2 ChemicalsTrichloroacetic acid (CCI3.COOH), methylene

chloride (CH2CI2) and acetone (CH3COCH3), all oflaboratory grade, were used.

2.3 Pretreatment

Desired concentration of TCAMC was preparedfor pretreatment of yam samples made in the formof skein. The treatment was performed fordifferent durations in slack condition at ambienttemperature of about 30°C in a specially madetrough, keeping the material-to-liquor ratio at1:100. The treated samples were first rinsed with

RAJENDRAN et al.: PHYSICAL PROPERTIES OF MODIFIED COTION YARN

methylene chloride and then with acetone toremove any adhering reagent. The rinsed sampleswere pressed with filter paper for partial removalof acetone. Since the evaporation of acetone ishigh even at room temperature because of its lowerboiling point, the treated yam samples were driedat ambient temperature without oven drying. Theyams were conditioned and the tensile, fibrefriction, and abrasion testings were carried out inan atmosphere of 65±2% RH and 27±2°C.

2.4 Tensile TestAn Instron tensile tester (Model No.6021) was

used for determining the stress-stain behaviour ofyam samples. A gauge length of 100 mm was usedand the extension rate was kept at 50 mm/min. Thetenacity and extension-at-break were determinedfrom the average value of 30 tests for yam samplesand 75 tests for fibre as well as roving samples.For each sample, 10 stress-stain curves whosebreaking load was close to the mean value wereselected and superimposed to get a characteristiccurve. The work of rupture was calculated from thestress-strain curves. A gauge length of 100 mmwith an extension rate of 50 mm/min wasemployed for roving sample.

2.5 Abrasion TestA Zweigle G-550 yam abrasion tester was used

to test the abrasion resistance of yams. An emerypaper (No.800), as abradant, and a pretensionweight of 20 g were used and the results wererecorded as the number of strokes required tobreak the specimen. For each sample, 19 tests wereconducted.

2.6 Fibre Friction TestAn apparatus suitable for measuring fibre-to-

fibre friction was fabricated and used. The frictiondevice consists of a long platform (40 ern length)with a small frictionless pulley (2 em diam.)mounted at one end and a sample holder at theother end. The device was attached to the lowerstatic jaw of the Instron tester (Model No.6021). Anon-elastic thread from the sample under test waspassed over the pulley and fixed to the uppermovable jaw of the Instron. An angle of 90° waskept between the sample pulley and the upper jaw.

The sample fringe was made by cementing oneend of the combed cotton fibres with adhesive

155

between a pad of thick paper cards. Aftercementing, the fibres were combed several timeswith the help of fibrograph comber to make themparallel and to remove loose fibres. The fringe wasmade about 2.5 em wide and its density was keptconstant as far as possible. Two fringes wereplaced one over the other on the friction deviceplatform, of which the lower fringe was fixedstationery in the platform and the upper movableone was fixed to the upper jaw of Instron through anon-elastic thread. A normal load of about I kgwas applied on the fringes and the upper fringewas set in motion. The maximum force required totravel the fringe for a distance of 20 mm wasrecorded. A cross-head speed of 5 mm/min wasselected after some preliminary trials. Theexperiment was repeated 5 times for each pair offringe. Five pairs of fringes were tested from eachsample and an average of 25 readings wasreported. Greater care was taken to comb the fibresafter every test to ensure that the fibres in thefringe were fairly straight and parallel. Theuntreated control as well as treated fibre sampleswere tested under identical experimental condition.

2.7 X-Ray Diffraction

A 'Philips' x-ray diffraction unit (Model PW-1710) fitted with a texture goniometer attachmentand a microprocessor recorder was used. Thepowdered sample was scanned in reflection modebetween 28 angle of 8° and 28°. The x-rayradiations used were nickel filtered Cu, K (alpha)having wavelength ()..) of 1.5418A. Crystallinityindex of cotton sample was calculated using aformula given by Segal et at". For determining theorientation of fibres, the yam sample wasuntwisted and individual fibres were separated andmade into a parallel bundle. The fibre bundleswere azimuthally scanned by rotating themthrough 360°, keeping the 28 angle at 22.58° on atexture goniometer.

2.8 FTIR Analysis

A 'Bio-Rad' FTS-165 spectrometer equippedwith a standard DTGS detector was used forsurface analysis of sample. A horizontal attenuatedtotal reflectance (ATR) accessory with a zincselenide (ZnSe) crystal as internal reflectionelement (IRE) was used for collecting the spectra.

156 INDIAN 1. FIBRE TEXT. RES., SEPTEMBER 1997

A pressure plate was employed to ensure adequatecontact between the crystal and the sample. Otherconditions for data acquisition were: resolution, 4cm'; and Number of scans, 256.

2.9 SEM Study.SEM observation was carried out on the samples

after mounting them on specimen stubs and coatedwith Au-Pd in a vacuum fine coat ion sputter (JFC-1100). The thickness of coating and time wereoptimized before examining the samples in a'JEOL SEM' (T 330 A-368).

3 Results and Discussion3.1 Effect of TCAMC on Tensile Properties

The tensile characteristics of treated cottonyams (Table 1) clearly indicate that the TCAMCtreatment enhances the tensile strength of cottonyam. The extent of increase varies from high tovery high and depends on the TCAMCconcentration and treatment time, irrespective of

the yam count. It is interesting to note that there isa sudden increase in strength at 2 min treatmentand thereafter the magnitude of increase instrength is not appreciably high. The highestimprovement of about 140% is observed for 20syam treated with 5% TCAMC for 10 or 20 min.The increase in strength decreases after 5%TCAMC and 20 min treatment. A similar increasein strength is also noticed for 40s and 80s treatedyams. Table 1 also shows that the elongation of thetreated yams increases noticeably. The increase ismore pronounced at 5% TCAMC and 2 mintreatment time and thereafter the effect ismaintained. On close statistical scrutiny it may beobserved that the CV% of all the treated yams islower than that for the' corresponding control,justifying the greater uniformity of the treatment.

The changes in tensile properties of TCAMC-treated yams are due to the changes in morphologyand fine structure of cotton cellulose. Themorphological structure of cotton is more complex

TCAMC Work of

conc., %

(w/v)

Untreated

5

5

5

5

5

5

10

10

Untreated

5

Untreated

5

Untreated

5

Table I-Tensile properties and work of rupture of TCAMC-treated cotton yarns

Treatment Breaking strength Breaking elongation

time

min

2

10

20

30

60

90

60

90

5

5

10

Value CV% % increase Value

gf %

20s Yarn

213.3 21.2 5.5

425.0 12.4 99.3 6.7

515.3 11.0 141.6 6.8

514.3 12.1 141.\ 6.8

440.6 11.7 106.6 6.0

417.2 12.4 95.6 6.5

403.6 17.3 89.2 6.3

439.5 11.1 106.1 6.2

437.2 12.0 105.0 6.3

40s Yarn

196.9 9.9 5.9

262.3 12.0 33.2 5.7

80s Yarn

123.8 15.2 6.4

173.5 '0.9 40.2 6.6

Roving

209.5 28.8 2.5

2174.7 12.3 938.0 6.9

CV%

10.0

10.5

8.3

9.8

6.6

11.9

8.5

9.4

7.3

12.2

9.1

9.5

6.8

12.1

10.1

% increase

21.8

23.6

23.6

9.1

18.2

14.6

12.7

14.6

-3.4

3.1

176.0

rupture

g.cm

58.3

106.4

140.4

142.2

97.9

118.8

97.9

102.2

120.8

32.7

36.5

19.2

24.9

RAJENDRAN et al.: PHYSICAL PROPERTIES OF MODIFIED COTTON YARN

and is described in detail elsewhere". Similarly,the changes in structure due to various chemical,physical and thermal agencies are also reviewed",In addition, the mechanical properties of cottoncan also be affected by convolutions, spiral angles,structural reversals, strength of inter- fibrillar bondsand inherent strains. The presence of weak links incotton fibre, which depends on the growth ofcotton, also affects the tensile characteristics. Atyam stage, the presence of weak point is more thanat fibre stage. It is known" that increase inmoisture content of cellulosic fibres increases thetensile strength and elongation. Moisture allowsthe residual stresses present in cotton to relax, andhence increase in tensile property with moisturecontent. However, this assumption has not beenconfirmed with experiment". Since staple yamcomposes of large number of fibres and most ofthe cotton yams are twisted in nature, the fibreassemblies are assumed to be in helical path. Thefibre molecules arranged in a helical path mayhave reasonable mechanical properties. Thestrength of staple yam is maximum at helix angleof about 20° (ref.26). It has been observed" thatthe fibre strength of mercerised roving is higherthan that of mercerised fabric, indicating theassociation of fibre assembly in imparting strength.The fibre cohesion also plays an important role incontributing to the strength of yam. The naturalconvolutions in cotton fibre impart some cohesionto the fibre. The higher the coefficient of friction,the better is the tensile strength. Besides, themigration of fibres and twist are also contributingfeatures to generate strength in yarn".

The foregoing discussion elaborates the variouscontributing factors responsible for change inmechanical properties, especially strength, ofcotton. The probable reasons for improvement instrength of cotton yam after TCAMC treatment arediscussed, keeping in mind the aforementionedfeatures, in the following sections.

3.1.1 General Characteristics of Stress-Strain Curve

The stress-strain (S-S) curves of 20s yam treatedwith 5% TCAMC for lower and higher treatmenttime are depicted in Fig.I. The S-S curves reaffirmthe increase in tensile strength after the TCAMCtreatment. It is interesting to note from the originalInstron S-S graph (Fig.2) that the strength at break

157

is very sharp and does not contain creeps at thefinal fracture, indicating the contribution of morenumber of fibres in opposing the distribution oftensile load. The S-S curve of the untreated cottonyam (Fig.3) shows more creeps at the final break.The mechanism of creep at very high load in thecase of nylon 6 is explained by Morton andHearle" in terms of statistical behaviour of randomfluctuation, giving to certain probability that a

2018

16

14 r-iI

12 l-I

Control

-+ 5~u:2Il1in

tJ) "* 5~0: ~() min--fr 5°·U: 30 min

8 10

Fig.I-Stress-strain curves of cotton yam (20s)

I-I

I

-coo-'

,/ /;'~-.II 1////11/! Ifj/,/ /~(/I·/!f !

! .;,./;1l," .,I _i' '/

Ex I ens!on

Fig.2-Instron plot of treated yam (5% TCAMC; 2 min)

158 INDIAN J. FIBRE TEXT. RES., SEPTEMBER 1997

cross link will break in a given time. In theabsence of an applied stress or with a low stress,the probability that a crosslink will break in agiven time is infinitesimal and even when a linkdoes break, the neighbouring links hold thestructure in place and prevent any extension of thefibre. As the stress increases, the most strainedcrosslinks become less stable and thus more easilybroken by thermal fluctuation, causing the yieldstress to be rate dependent. Since the structure ofcotton is more or less similar to that of nylon 6 interms of crosslinks like hydrogen bonding, thisexplanation may hold good for cotton.

Besides, the high cohesion imparted to cottonyarn by TCAMC treatment has been taken asanother key factor for increase in tensile strengthsince friction holds staple fibre yarn together andhigh friction provides effective transfer of strengthto yarn. In order to examine the frictionalbehaviour of cotton fibres, the roving sample afterbeing treated with 5% TCAMC for 10 min wasSUbjected to Instron strength-elongation test. It isobserved that the treatment imparts high inter-fibrefriction. The tensile strength of roving increases by938% (Table 1) after TCAMC treatment. Althoughit is not an usual practice to subject the rovingsample for tensile measurement, the test reflects anidea about the frictional behaviour of fibres in yarnassembly. The combed sliver samples treated with5% TCAMC for different durations were tested fortheir frictional behaviour using friction device andInstron. The force required by the movable fringeto travel a known distance over the same fibrefringe gives an indication of frictional behaviour of

,-----------------------------------,

II

I"01~I

I

Extension

Fig.3-lnstron plot of untreated yarn

fibres. It is found that there is a significant increasein fibre cohesion of treated samples over thecontrol. The maximum force recorded foruntreated one is 271 g whereas it is 399, 360 and388 g respectively for 2, 10 and 60 min treatedsamples. Fibres in a staple yarn transmit stressfrom fibre to fibre via frictional forces and as thefibre friction in the yarn increases the chances offalling the tensile load at fibre ends decrease andas a result, the stress in the neighbouring fibresdoes not increase and hence improvement intensile strength.

3.1.2 Influence of TCAMC Treatment on Work of Rupture

The work of rupture calculated from the areaunder the load-extension curve is given in Table 1.It shows that cotton yarns treated with TCAMCpossess higher work of rupture than the untreatedcontrol ones. The toughness increases withincrease in treatment time. The extent of increasevaries from 68% to 144% and the highest isobserved in the case of 20s yarn treated with 5%TCAMC for 10 and 20 min durations.

3.2 X-Ray Crystallinity

The crystallinity index, calculated using Segal'sformula, and the orientation of the treated as wellas untreated yams are given in Table 2. It isobserved that there is no large variation in thecrystallinity index of all the treated yams.Similarly, variation in the orientation angle of thetreated yarns is not much. Generally, the structuralchanges occurred in cotton can be estimated byvarious methods, of which x-ray diffractiontechnique is the most commonly used one.However, there are some drawbacks associatedwith the x-ray measurement. The imperfection andcrystalline size in cotton pose some problems ingetting the sharp x-ray diffraction pattern". Someresearchers have reported" very high crystallinityvalue of cotton (> 84%), calculated making use ofx-ray diffraction technique. It emphasizes thatcotton is highly crystalline in nature. However, insome cases such as sodium hydroxide treatment, x-ray diffraction technique proved to be a powerfultool in assessing the structural changes of cotton.The x-ray crystallinity index shows that theTCAMC does not change the crystalline structureof cotton cellulose. It also indirectly indicates that

KAJhNURAN et al.: PHYSICAL PROPERTIES OF MODIFIED COTTON YARN

Table 2-X-ray diffraction data of treated cotton yams

TCAMC Treatment Crystallinity Half Orientationcone, % time index width of angle at

(w/v) min 1m•• peak 29 = 22.5°002 em

205 Yarn

Untreated 87.7 2.1 25.5

5 2 90.6 2.1 25.5

5 10 88.0 2.1 25.5

5 20 88.7 2.2 24.0

5 30 91.6 2.0 26.5

5 60 86.6 2.1 25.5

Untreated 405 Yarn 2.2 28.5

5 5 90.4 2.1 28.1

80s Yarn

Untreated 86.9 2.0 26.6

5 5 9\.5 2.0 27.8

the reagent enters the accessible regions ratherthan the crystalline region. Moreover, it is thegeneral opinion that crystallinity of any polymerdirectly relates with its strength. However, thereverse is true in the case of cotton", Thecrystallinity of cotton decreases from 70% to 50%after mercerization with sodium hydroxide".

Most of the reactions of solvent on cottoncellulose act as a two-phase process, viz. reactionwith polar solvents and also non-polar solvents.Interaction of cellulose with polar or highly polarsolvents is accompanied by large-scale swellingand ultimately changes in fibre structure. It is thegeneral observation that the solvent first enters intothe less ordered regions on the surface followed byinterlinking regions between the crystallites in thefibrils. The highly interacting solvent enters thewell-ordered crystalline regions. It isunderstandable that as long as the reaction islimited to the accessible surface of the fibrils andthe interlinking regions, there is no visible effect inthe crystalline structure of the fibre. Since there isno appreciable change in the crystallinity of theTCAMC-treated yams, it is assumed that thereagent attacks the less ordered amorphous and theinterlinking regions rather than crystalline regions.It may be mentioned that the experiments on fibrebundles did not result in significantly higherstrength value. However, an increase of about 5%in tensile strength of fibre sample is observed in

159

the case of sample treated with 5% TCAMC for 5mm.

3.3 Effect of TCAMC Treatment on the Morphology ofYam

The scanning electron photomicrogrsphs ofuntreated and treated yams are depicted in Fig.4.The photomicrographs of treated yams (Figs 4b &4c) show that the change in morphology, besidesthe fine structure and other factors, also contributesto the tensile characteristics of cotton. The changesin morphology and, of course, structure of cottoncan also be brought out by swelling treatment withchemicals and solvents. The effects of swellingagents on the tensile strength and other mechanicalproperties of cotton have been reviewed by manyinvestigators'S":":", The reactivity of the cellulosecan be greatly increased by swelling treatment",Swelling in water or other polar solvents is themost frequently applied activation treatment forcotton.

Optical microscopic examination reveals thatthe swelling of cotton treated with TCAMC iseither nil or negligible. This observation isreaffirmed by SEM examination. In addition, it isobvious from SEM investigation that the treatedyam possesses some characteristic surface features(Fig.4b). Treatment of cotton with TCAMCproduces marked changes in the fibre surface. Theconvolutions of the fibres do not disappear unlikein sodium hydroxide treatment and instead moreconvolutions are observed. The surface of thefibres becomes more smooth although moreconvoluted. This may perhaps be due to theremoval of non-cellulosic constituents from thesurface of the fibre. Besides, it has been observedthat the treatment does not influence fibreshrinkage both in width and length as evidenced byscanning electron photomicrographs and shrinkagemeasurement. Similarly, negligible weight loss hasbeen observed on samples treated with variousconcentrations of TCAMC at ambient temperaturefor different durations. Since there is noappreciable swelling with TCAMC treatment, thepossibility of breaking some of the hydrogen bondspresent in the cotton cellulose is ruled out. It maybe borne in mind that the interaction of cellulosewith polar solvents is accompanied by increasedswelling due to breaking of hydrogen bonds.

160 INDIAN 1. FIBRE TEXT. RES., SEPTEMBER 1997

Fig.4--Scanning electron pnotormcrograpns ot cotton yams:(a) untreated, (b) treated with 5% TCAMC for 30 min, and (c)treated with 10% TCAMC for 30 min

3.4 FTIR Study

To assess any change on the surface of cottoncellulose and creation of any new functional groupor the alteration of existing groups, the 20s countyarn sample was subjected to FTIR analysis afterbeing treated with 5% TCAMC for 2, 10 and 90min. The spectra are shown in Fig.5. The surfacemodification of cotton yarns effected by theTCAMC treatment is evidenced by FTIR spectra.

1)-11..:-I

. !t:

/.11'-IIi If \".1( """~ ~".•

l rc.nmcm ilnl.:!ml!lI'>1k \.II~I! ,

:it I

0-08t

O'06r

I ?O{)Ll

I Ct ",0.02[01 '.e'("~!~~ • ..,..

)500 )000 1500 2000 1508 IUJ J

wove-oc m ber • c.m • 1

Fig.5-FTIR spectra of cotton yam

11{ .pcctra ,01 couon 'iampk~

\\1 -pccrra an: phutcd \\1111the same ordmntc scale

'108'-.,,-

-','

\ \006 '

\ 800'(- 'c

002(' ,-,----

Io[ cr-t r eote d

1800 1600

.-'_" ./ .....r ...•......... _ ,

/ rA ' i\f (V \."/-' r- , Ie \\1l c,,,,,""',, ,~

.\ i Ir..:atnll'IlI11m<'illll!l)l.HI(.\, •

.. ';f. II~BI .~tl I .

1000 8001l,00 1200

WQ~numbE"r ,em-1

Fig.6-Ex panded fingerprint region of cotton yam

The prominent bands in 1100-1000 cm' region aredue to cellulose, Although the spectra of treatedsamples appear similar to that of the untreatedcontrol, the peaks at 1740, 2916 and 2850 cm'seem to be the main difference. The peak at 1740em'! is the characteristic of carbonyl (C = 0) groupand the absorption band at 2850 em'! refers to theC-H region. The expanded fingerprint regionbetween 1800 em'! and 800 em'! is shown in Fig.6.It may be seen that the main difference betweenthe spectra of control and the treated ones is theband at around 1740 ern". The intensity of thispeak is high for the sample treated for longerduration .. For closer examination of the differencesbetween the spectra, the spectrum of untreatedsample was subtracted from the spectra of othertreated samples. The resulted spectra are shown inFig.7. From spectral subtraction once again thebands in the C-H region and C = 0 region appearprominent, thus demonstrating that they representthe main differences between the samples. Thecellulose bands between 1100 em'! and 1000 em'!

RAJENDRAN et al.: PHYSICAL PROPERTIES OF MODIFIED corrox YARN

wcvcnumber ,·e m-'

Fig.7-Subtracted FTIR spectra of cotton yam

Table 3-Effect of TCAMC reagent on abrasion resistance ofcotton yam (20s count)

Abrasion resistanceTCAMC Treatment

timeMean CV%, % increasevaluecycles

cone, %(w/v), min,

Untreated 63, 61.9,

5 2 163 19.5 158.7

5 \0 182 16.0 188.9

5 20 188 16.9 198.4

5 30 147 14.4 133.3

5 60 156 18.7 147.6

5 90 179 16.2 184.1

10 60 158 13.6 150.8

10 90 158 14.2 150.8

do not cancel out perfectly, probably the treatedcellulose undergoes some structural changealthough the change is not reflected in x-rayanalysis. The changes in absorption bands indicatethat the TCAMC treatment induces the structuralmodification in cotton fibre in terms of (i)breakage of strained hydrogen bonds, and (ii)enhancement of free c=o and C-H groups. Thisenhances more flexibility as well as moreextensibility to the chain molecules. As a result,when the fibre is extended, higher deformation andorientation of chain molecules take place and thusenhance their resistance capabilities to the loadapplied, at higher loads.

3.5 Effect of TCAMC Treatment on Abrasion Resistance

The resistance of treated cotton yarn againstabrasion is shown in Table 3. The results show thatthe TCAMC treatment influences the abrasion

161

resistance of yarn. The resistance of treated yarn towithstand the action of rubbing and pulling IS morein case of sample treated with 5% TCAMC for 20min. The higher work of rupture, high cohesion

• and rigid structure observed after the treatment aresome . of the probable reasons for improvedresistance against abrasion. It has been observed"that the work of rupture influences the abrasionresistance. Because of high cohesion, the fibresfrom the surface of the spun yarn cannot easily bepulled out or cut through during severe abrasion.

4 ConclusionsTCAMC reagent activates the cotton cellulose

by opening the fibrillar interstices and entering theinterlinking regions between crystallites andchanges its surface characteristics, The increase intenacity of cotton 'yarn following TCAMCtreatment has been attributed to the surfacemodification, release of internal stresses,strengthening of weak links, improvement incohesion and improvement in the uniformity ofdistribution of loads along the fibres in the yarn.The extent of penetration of TCAMC into the finestructure of cotton fibres and its effect ofmodification depend on the concentration ofTCAMC and duration of treatment. At highertreatment duration, it appears that the reagentalters the structure of cellulose, as evidenced bydecrease in improvement rate of tensile strength,although the effect is not reflected in x-rayanalysis. Another interesting feature observed inthe treated yarns is the higher improvement inwork of rupture; the work of rupture observed for20s yarn treated with 5% TCAMC for 20 min isabout 2.5 times of that for the control. Theimprovement in abrasion resistance of yarns is alsoan additional noteworthy feature effected by theTCAMC treatment; the abrasion resistance of 20syarn treated with 5% TCAMC for 20 min is about25% more than that of the control. In addition, thefibre surface smoothness is obtained due to thetreatment.

AcknowledgementThe authors are thankful to Ms. Indra

Doraiswamy, Director, SITRA, for encouragementand keen interest during this study. One of theauthors (SR) is grateful to her for providingSITRA's research fellowship.

162 INDIAN J.FIBRE TEXT. RES., SEPTEMBER 1997

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