Indian Journal of Fibre & Textile ResearchVol. 18, September 1993,pp.139-144

Action of weak alkali on jute

B Sikdar. A K Mukhopadhyay & B C Mitra

Indian .lute Industries' Research Association. 17 Taratola Road, Calcutta 70n OHR, India

Received 18 January 1993: accepted 3 May 1993

The effect of various weak alkalies at very low concentration (0.25%) on jute fibre has be~n studied.It is observed'that sodium carbonate in very dilute solution cleans the fibre surface more WIthout anydamage. Also, the treated fibres become more regular to cause reduced spinning end breakage rate,leading to higher yam productivity.

Keywords: Fibre morphology, Jute fibre, Spinning end breakage rate

1 IntroductionThe inherent drawhack of jute yarn is its poor

quality and higher irregularity which is due to themulticellular nature of the fihre. The numher ofindividual cells varies widely from fihre to fihreand also along the length of the fihre. These indi-vidual cells are cemented with lignin and hemicel-lulose and form a composite fihre. When the jutefihres are treated with alkali, non-cellulosic materi-als (mostly hemicellulose) dissolve, making the fi-hres regular which give rise to a better qualityyarn for use in diversified product. Macmillan etal:' gave a detailed account of the action of var-ious alkalies on jute fibre and the extent of weightloss in the process. However, their study dealt on-ly with the effect of different alkalies (at variousconcentrations with a minimum of 0.5% on theweight of jute) and it was found that the more thedissolution of the non-cellulosic materials, themore was the strength loss in jute yarn. The effectof weak alkalies on yarn properties was not stud-ied. In the present study, the effect of weak alka-lies of very low concentration (0.25%) on yarnproperties has heen studied considering that theweight loss will he low with weak alkali and thestrength of yarn will not he affected much hut theinter-fibre friction or the regularity of the fihremay increase, which would result in hetter spinn-ing of jute yarn.

2 Materials and Methods2.1 Preparation of Sample

Raw jure fibres (TD4 and W4 quality) weretreated with 0.25% sodium carbonate, calcium hy-droxide, liquor ammonia and sodium sulphite se-parately, keeping the material-to-liquor ratio at

1: 10, for different durations at room temperatureI 25-27°C).

2.2 Chemical Analvsis

The alkali-t~eated fihres were extracted withwater and the comhined alkali and water extractwas analyzed for the estimation of pectin andother carhohydrates such as hemicellulose usingthe colorimetric method. The pectin was estimatedquantitatively by Carbozole reaction:' while thehemicellulose by the method of Sarkar et al.' andRov". The holocellulose, obtained from the singletreatment of sodium chlorite on jute fihre, wastreated with sodium hydroxide solution (9.3%w/w) at room temperature. To the filtrate, abso-lute alcohol was added and the hemicellulose wasprecipitated, washed with alcohol, dried and final-ly determined gravimetrically.

2.3 SEM Studies

For SEM studies, the fihre samples were firstcoated with a thin layer of gold-palladium alloyusing a sputter coater and then observed in thesecondary mode at a beam voltage of around 5 kV{ref. 2).

2.4 Tensile Properties

The tensile strength of the untreated and alkali-treated jute fibres was measured using an Instrontensile tester at a test length of 2 em, keeping thetime of hreak at 20 ± 5 s.

Jute fibres (TD4) were treated with 0.25%Na,CO, (on the weight of the fibre). The chemicalwas applied on jute along with 3°/c, oil in wateremulsion at the batching stage. The processed sliv-

14() INDIAN 1. FIBRE TEXT. RES., SEPTEMBER 1993

cr was spun with 4 t in. slip-draft flyer spinning frameto make jute yarn of 8 1b (276 tex) linear density.

3 Results and Discussion1. I S['\1 Studies

The scanning electron photomicrographs of un-treated and treated jute fihres (Figs 1-6) show thechangcx in the morphology of the fihre and hence!:!ive an idea of how the fihre surface is affectedwith dilute alkalies. The photomicrograph of a rawjute Iibrc in untreated condition (Fig. I) does not.",i\e any clear idea about the fibre surface. The in-eli\ idual cells of the multicellular fibre are notck~lr and some untreated material :mostly pecti-'lllllS is deposited on the fibre surface. The xcann-ill.". electron photomicrographs of the jute fibreu e.ucd with (1.25'\) sodium carbonate tor I hand,.;1 the fibres treated with ().2:'i", calcium hvdrox-Ilk. liquor ammonia ami sodium SUlphite for i()min :Fig. :2) show that liquor ammonia and sodi-Llill sulphite have hardly any effect on the fibre<urface whereas sodium carbonate and calciumhydroxide result into the cleaner surface of the fi-hrcx. The unretted material is removed more andmore by sodium carbonate and calcium hydroxideas the duration of treatment is increased. Fig. 3shows the scanning electron photomicrographs ofthe fibres treated with NacCO, and calcium hy-droxide for 240 min and 20 min respectively. It isobserved that the surface of the sodium carbonate-treated fibre is clean and that the polygonal natureof the fibre is prominent. The cleaning by calciumhydroxide is stronger than that by sodium carbo-

Fig. I-Scanning electron photomicrograph of untreated rawjute fibre

nate but sometimes the individual cells are sepa-rated and also get damaged. Moreover. there is achance of calcium hydroxide deposition on the fi-bre surface as is evident from Fig. 4 which showsthe surface features of the fibre treated with cal-cium hydroxide for 50 min. and of that treatedwith sodium carbonate for Sh. The calcium hv-droxide-trcnted fibre shows clear deposition ofcalcium sa!l\ whereas the sodium carbonate-treat-ed fibre shows more clear surface than that in Fig.~. The structural features i some fibrils) are visiblebecause \)1 hetter cleaning operation. Liquor am-monia and sodium sulphite have negligible effectas compared to sodium carbonate and calcium hy-droxide. Also, these IWO alkalies are hazardousand \\ ere, therefore, not used in longer durationtreatments.

The important feature that the above photomic-rographs reveal is that calcium hydroxide treat-ment causes some decernenting action on the fi-bre. leading to separation of individual cells anddamage t(1 the fibre. whereas the sodium carbo-nate treatment cleans the fibre surface only andthere is no decementing as done by calcium hy-droxide (Fig. 3) or by strong alkali like 17.5°/r)NaOH solution (Fig. 5 This is also revealed fromthe photomicrograph of the fibre treated withNa2C01 for longer period (Fig. 6). Since there isno decernenting in the multicellular structure bythe weak alkali like O.25'1r) sodium carbonate, thefineness of the fibre may not be affected but thecleaning process may make the fibre more regular.As a result, the spinnability of the fibre may im-prove.

3.2 Chemical Analysi»

The chemical analysis of only Na~C01-treatedfibre was done. From the water extract of thetreated fibre, pectin, hemicellulose and lignin wereestimated. The presence of hemicellulose or ligninwas not detected. Pectin was estimated from the fi-bre treated for different periods. Fig. 7 shows theremoval of pectineus matter from the treated fihrewith respect to untreated fibre. It is evident thatthe dissolution of pectineus matter gets saturatedin l6-24h. Therefore, for the best cleaning, 24h oftreatment with the weak alkali was considered.

3.3 Effect of Treatment on Fibre Tenacity

The fibre samples (both untreated and treatedwith 0.25% Na2CO) for 24 h) were subjected forthe measurement of fineness, strength and elonga-tion at break. The results (Table 1) show that

SIKDAR et al.: ACTION OF WEAK ALKALI ON JUTE 141

1_==-10,om 5·1KV 02 010 5

Fig. 2-Scanning electron photomicrograph of raw jute fibres treated with (a) 0.25% Na2CO] for lh, (b) 0.25% Ca(OHh for 10min, (c) 0.25% liquor NH3 for 10 min, and (d) 0.25% NazS03 for 10 min

Fig. 3-Scanning electron photomicrograph of raw jute fibres treated with (a) 0.25% Na2C03 for 4h, and (b) 0.25% Ca(OHh for20 min

142 INDIANI FIHRFTFXT RES .. SEPTEMBER 1'1'13

-- 20.ftJm 55·2KV 04 001~----------------------------------------~

Fig. 4~Scanning electron photomicrograph of raw jute fibres treated with (a, 0.25% Ca(OH), for 50 min. and (h! U.25% Na,CO,

for 8h

20JU m

Fig. 5~Scanning electron photomicrograph of raw jute fibretreated with 17.5% NaOH solution

60 .- Treo t eo withNo2C03(02S",)

a-u nt r eo teo

'"',9 36

c

u 24"a.

12

Ir eot rnen t nrne , h

Fig. 7~Pectin liberated from treated and untreated jute fibresat different durations of treatment

Fig. 6~Scanning electron photomicrograph of raw jute fibret.eated with 0.25'10 Na,CO, for 24 h

Table I =Effect of alkali treatment on tensile properties

(Na,CO, conc., 0.25%; Treatment period, 4h)

Sample Linear Breaking Breaking Breakingdensity load tenacity elongation

tex g g/tex %

Control fibre 3.10 106.30 34.40 1.76Sodium carbonate 3.28 116.94 35.60 1.82treated fihre

------------------_._------

there is no change in fineness. It is also evidentthat though there is some dissolution of non-cellu-losic matter from the fibre surface (as revealed bySEM photographs), the fibre tenacity is not affect-

SIKDAR et al: ACTION OF WEAK ALKALI ON JUTE 143

Parameter

Table 2-0bserved end breaks and properties of yams spun from untreated and treated jute fibresMill-I

Normal Experimental

Set-l Set-2 Set-3

77.0 83.0 72.0 84.0 •19.8 18.2 25.0 16.6149.0 101.0 57.0 68.07.8 S.5 S.I 7.613.5 10.0 12.0 18.021.0 21.5 22.0 22.0

Mill-2

Normal Experimental

Set-I Set-2 With chemical Without chemical(0.25% Na2C03) (only oil in water emulsion)

Set-I Set-2 Set-I Set-2

80.0 78.0 85.0 78.0 81.0 83.024.0 24.0 22.0 23.5 21.0 22.01.32.0 170.0 65.0 93.0 168.0 120.07.7 8.0 8.3 S.I 7.8 S.218.0 12.0 18.0 12.0 13.0 17.022.5 24.0 21.0 22.0

Quality ratio (yam tenacity)Strength CV'/o

Ends down/ 100 spindle-hourGrist at 16%moisture regain, IbYarn moisture, %Irregularity, U%

Quality ratio (yarn tenacity)Strength CV'/o

Ends down! 100 spindle-hourGrist at 16% moisture regain, lbYarn moisture, %Irregularity, U%

Set-2 and Set-3 in MiIl-1 and Set-2 in Mill-2 are the repeat experiments of Set-L The machine parameters for Set-I and normalwere same except that chemicals were added in the emulsion for experimental.

ed at all. Thus, the weak alkali solution does notdeteriorate the fibre quality.

3.4 Spinning PerformanceHessian warp yarn with nominal grist of H lb

(276 tex) were spun in two member mills using0.25% Na2C03 (on the weight of the fibre) in jutebatching oil emulsion. The spinning was carriedout in the member mills by using more or less thesame product mix. In each mill, one spinningframe with average mechanical condition was se-lected for study of end breakage rate. The ob-served spinning end breakage and yarn propertiesare given in Table 2. The results show that thequality ratio (yarn tenacity) of both untreated andtreated yarns remains unchanged. However, thereis a considerable decrease in the spinning endbreaks/IOO spindle-hour in the case of treatedyarn in the both mills.

4 ConclusionsIt was expected that the dilute alkali may dis-

solve some non-cellulosic matter giving rise to bet-

ter fibre fineness which may lead to higher qualityratio of the yarn. But the above studies reveal thatthere is no change in fibre fineness or tenacity.However, the fibre surface is cleaned more with-out any damage because of the dissolution of pee-tinous matter by the dilute solution of sodium car-bonate. The yarn spun from alkali-treated fibredoes not show any improvement in quality ratiobut considerable reduction in the spinning endbreakage rate gives rise to higher production.There may be two possible reasons for this. Eitherthe inter-fibre resistance is increased due to clean-ing operation, leading to less yarn breakage, or thefibre itself becomes more regular due to treatment.The second one is more plausible because the di-ameter CV'/o of the treated fibre is much less (8-20%) than that of the untreated fibre (28-48%)and the more the fibre is regular the less is theyarn breakage.

AcknowledgementThe authors are grateful to Dr A. K. Mukher-

jee, Director, IJIRA, for useful discussion.

144 INDIAN J. FIBRE TEXT. RES., SEPTEMBER 1993

References

Macmillan W G, Sengupta A B & Mazumdar S K, J TextInst, 45( 1954) T703.

2 Mukhopadhyay A K, Bandyopadhyay S K & Mukttopadhy-ay U, Text ResJ, 55 (1985) 733.

3 Colowick Sidney P & Kaplan Nathan 0, Methods in enzy-mology, Vol 3 (Academic Press), 1957,93.

4 Sarkar P B, Mazumdar A K & Pal K B. J Text lnst; 39(l948)T53.

5 Roy A, Studies on the isolation and chemical nature of thenoncellulosic constituents of jute, D Phil thesis, CalcuttaUniversity, Calcutta, 1958.