dyeing of jute fibre with direct dyes and their...

Indian Journal of Fibre & Textile ResearchVol. 15, June 1990, Pp 65-72

Dyeing of jute fibre with direct dyes and their fastness characteristics

Faisul Islam Farouqui & Md Ibrahim HossainDepartment of Applied Chemistry and Chemical Technology, Rajshahi University. Rajshahi, Bangladesh

Recei ved 5 January 1990; accepted 2 February 1990

The effect of dye conc., electrolyte (common salt) conc., dyeing time and dyeing temperature on the dyeingof jute fibres with direct dyes, viz. Congo Red, Titan YelIow, Fast Orange PRS, Durazol Red and DirectYeIlow 29, has been studied. The dye absorption increases with increase in electrolyte conc., dyeing time ordyeing temperature and decreases with increase in dye cone. In some cases, higher temperature decreases thedye absorption. The colour of dyed and modified jute fibres fades on exposure to sunlight, washing with soapsolution and acid and alkali spottings. A mixture of2% potassium bichromate, 2.5% blue vitriol and 3% of30% acetic acid has been found to be effective in preventing the colour of Titan Yellow on the dyed fibres, but itdoes not prevent the strength loss of direct dyed jute fibres.

Keywords: Direct dyes, Dyeing, Jute fibre

1 IntroductionJute being a lignified fibre differs somewhat from

cotton in dyeing properties. Due to its structural pee-uliarities,jute has an affinity for a wide range of dyesincluding basic, acid, direct and vat dyes. Some inves-tigators·-4 have studied the dyeing of jute with acidand basic dyes but no effort seems to has been made tostudy the dyeing nature and the fastness character ofjute fibre dyed with the direct dyes. In the presentwork, the effect of dye conc., electrolyte conc., dyeingtime and dyeing temperature on the dyeing of jutefibres with direct dyes, viz. Congo Red, Titan Yellow,Fast Orange PRS, Durazol Red and Direct Yellow29, has been studied. The colour fastness of dyed jutefibres on exposure to sunlight in air, washing withsoap solution, and spottings with acids and alkalieshas also been studied. To obtain fast colour, the dyedfibres were treated with a mixture of metal salts, usedas a modifier.

2 Materials and Methods

Corchorus olitorius (Toss a) variety of jute fibre, co-llected from the local market (Durgapur, Rajshahi),was used. The portion between 75 and 100 em fromthe bottom was taken and cut into two equal pieces of12.5 em, blended and washed with a solution of soda(6.5 g/l) and soap flake (3.5 g/l) at 75"C for 30 min>.The jute fibre was then bleached with sodium chlor-ite solution (0.5%) atpH 4 and at 85-90°C for 90 min".The bleached fibre was dried at 85T and used as theexperimental material.

2.1 Methods of Dyeing and Selection of Optimum DyeingConditions

Five direct dyes, viz. Congo Red (C.I. 22120), TitanYellow (C.I. 19540), Fast Orange PRS (C.I. 23655),Durazol Red (C.I. 28160) and Direct Yellow 29 (C.I.19556), were used for dyeing jute fibre. Structures ofthe dyes are given below:

WNH2N=N0'V-N=NWNH2" ~. / /1

I .,/ .

SO]No SOJNO

To obtain optimum conditions for dying jute withdirect dyes, dye conc., electrolyte cone., dyeing timeand dyeing temperature were. selected as follows:

65

INDIAN J. FIBRE TEXT. RES., JUNE 1990

2.1.1 Dye ConcentrationSeven dye-baths were prepared with 0.5, 1.0, 1.5,

2.0,2.5,3.0 and 3.5% dye (owf) and the dyeing wascarried out with 20% common salt at IOO'C for 60min 1.2.7. After dyeing, the concentration of the exha-usted dye-bath was determined". Using Grey scale?(for assessing the change in colour), the percentage ofdye which gave the fibre even and maximum shadewas selected.

2.1.2 .Electrolyte ConcentrationJute fibre was dyed using the selected dye concen-

tration in presence ofO, 5, 10, 15,20,25,30 and 35%common salt (electrolyte) at IOO'C for 60 min. Theelectrolyte cone. at which the fibre attained maximumshade was selected by using the Grey scale.

2.1.3 Dyeing TimeThe fibre was dyed with the selected dye and electr-

olyte concentrations at IOO'Cfor 10,20, 30,40, 50, 60and 70 min. The time at which the fibre absorbed max-imum dye was selected.

2.1.4 Dyeing TemperatureThe fibre was dyed with the selected dye and electr-

olyte concentrations at 60, 70, 80,90 and lOO'Cfor theselected time. The temperature at which the fibre abs-orbed maximum dye was selected.

The selected dye cone., electrolyte conc., dyeingtime and dyeing temperature were taken as the opti-mum dyeing conditions for dyeing of jute fibre.

The quantity of dye or dye assistant (common salt)required was calculated using the following formul-a".

WxpStock solution required (ml) =

cwhere Wis the weight (in grams) of sample required;P, the concentration (%) of dye or dye assistant to beused (expressed on the weight of fibre); and C, theconcentration (%) of stock solution.

2.2 Aftertreatment of Dyed Fibre with Metal SaltsDyed fibres were treated with a mixture of2% pota-

ssium bichromate, 2.5% blue vitriol (cupric sulphate)and 3% of 30% acetic acid (owf) using the fibre-liquor ratio I:50 at 85-90'C for 45 min!".

2.3 Fastness TestsThe colour fastness of dyed and modified fibres was

measured using the Grey scale", the fastness grade 5being the control.

2.3.1 Light FastnessThe dyed and modified fibres were exposed to sun

on a flat board for 250 h at the rate of8 h/dayll. After

66

every 50 h, the change in colour of the fibres withrespect to control was assessed by the Grey scale.

2.3.2 Wash FastnessThe dyed and modified fibres were treated with a

solution of soap flake (5 gjl) at 40± 2"C for 30 min 12.

After the treatment, the change in the colour of thewashed fibre was assessed. Similarly, the wash fast-ness was measured at 70' and IOO·C.

2.3.3 Fastness to SpottingsDyed and modified fibres were combed and compr-

essed to form a sheet of 10em x 4 em. The specimenwas spotted with four drops of water at room temper-ature. The change in the colour of the spotted area wasassessed after dryingl3. In the same way, the change incolour on acid 14 and alkali 15 spottings was assessedby using the following solutions.

Sulphuric acid solution (relative density, 1.84) (50g1l).

Acetic acid solution containing glacial acetic acid(300 gjl).

Tartaric acid solution containing crystalline tarta-ric acid (l00 gjl).

Sodium carbonate solution containing anhydroussodium carbonate (l00 g/\).

Sodium hydroxide solution (50 g/l).Ammonia solution (10%).

2.4 Measurement of Breaking StrengthBreaking strength of dyed and modified fibres was

measured by using the tensile strength tester (TorseesSchopper type-OS- 100). The length of each speci-men (total length, 25 em; and weight, 0.5 g) betweenthe jaws was kept at 10em and 1 twistj2 em was givenalong the length of the fibre. In each experiment, thebreaking strength of lOspecimens was measured andthe mean of these values was taken as breakingstrength 16.

3 Results and Discussion

3.1 Effect of Dye ConcentrationDye absorption by jute fibre decreases with incre-

ase in dye cone. in the dye-bath (Fig. I).This may bedue to the high concentration of dye ions which hin-der the absorption of dye by the fibres whereas the lowconcentration of dye ions favours it!", With the incre-ase in dye conc., the absolute quantity of the absorbeddye also increases while the relative quantity diminis-hes!". Thus, the fibre absorbs a relatively greater am-ount of dye from a dilute solution. Fig.l also showsthat in some cases the absorption of dye by the fibre isvery high. It seems that all water-soluble dyes areelectrolytes and in aqueous solution they dissociate

FAROUQUI & HOSSAIN: DYEING OF JUTE FIBRE WITH DIRECT DYES

into ions. In direct dyes, the coloured ion is negativelycharged and the colourless compensating ion is posit-ively charged. When the jute fibre is immersed in dyesolution, the negatively charged ions of direct dye arerepelled by the surface potential of cellulose. Thispotential barrier overcomes by the presence of electr-olyte. In some cases, the effect is so pronounced thatthe exhaustion is very high 18. Another explanation isthat the dyes are absorbed and retained by cellulosefor the reason that the free partial valencies on thesurface of the cellulose macromolecules get saturatedby the strong partial valencies of the dye. This mutualsaturation is possible only if the dye has a long stretc-hed molecule similar to that of cellulose!".

It was observed from experiments that even andacceptable colour produced onjute fibre when it wasdyed with 2.0-3.0% dye (2.0% Congo Red, 3.0% Ti-tan Yellow, 2.5% Fast Orange PRS, 2.5% DurazolRed and 3.0% Direct Yellow 29). Above or belowthese dye concentrations, dull and uneven shadeswere obtained.

3.2 ElI"ed of Electrolyte CODCeIItrationFig.2 shows that some dye absorption takes place

when the jute fibre is dyed with 2.0-3.0% dye (2.0%Congo Red, 3.0% Titan Yellow, 2.5% Fast OrangePRS, 2.5% Durazol Red and 3.0% Direct Yellow 29)in the absence of common salt as electrolyte in thedye-bath. The chemistry of jute and direct dye (boththe fibre and the dye give similar charges of ions) reve-als that no dye particle would attach to the fibre with-out electrolyte but in practice it happens. This is beca-use commercial dyes are not pure and usually containinorganic salts, dextrin, and possibly wetting or disp-ersing agents. These are added to achieve the stand-ard tinctorial strength and to increaseabsorption'v-!". Electrolyte may also be present inthe water used in dyeing, either as water hardness or assoluble salts produced by water-softeningtreatments'". These electrolytes also effect the dyeabsorption.

Dye uptake by the fibre increases with the increasein electrolyte conc. in the dye-bath and reaches tosaturation when jute is dyed in presence of 10-30%common salt. The electrolyte, in this case, lowers therepulsion due to the similar charges on the chargedfibre surface and coloured dye anions by impartingoppositely charged ion with the charged dye anionand thus, by overcoming the potential barrier, impro-ves dyeability'Y'". Another explanation is that thepresence of an electrolyte in the dye-bath decreasesthe membrane potential of cellulose, reduces the rep-ellency of cellulose and dye particles with the samecharges and also improves dyeability!".

90

~~ eo.c~~070

60

50L-~------~----~------~o 0'5 1-5 70S l'S~ conl.,.I, .,.

Fig. I-Effect of dye concentration on dyeing of jute fibre withdirect dyes: (0) ~ IUd, (0) TItan Yellow, (e) Fast ~ PRS,

(6) Durazol Red, and (A) Direct Yellow 29

O~O--~5------~IS~----~2S~----~lS~EI~clrolyt~ cone.,·'.

Fig. 2-Effect of electrolyte (common salt) concentration on dy-eing ofjute fibre with direct dyes: (0) Congo Red, «(») Titan Yellow,(.) Fast Orange PRS, (6) Durazol Red, and (A) Direct Yellow 29

It was observed from the experiments that even andbright shades produced when thejute fibre was dyedwith Congo Red, Titan Yellow, Fast Orange PRS,Durazol Red and Direct Yellow 29 in presence of 10,30,25,30 and 25% common salt respectively. Shadeswere not uniform and acceptable above or belowthese concentrations.

3.3 Effect of Dyeing TimeFig.3 shows that with increase in dyeing time the

dye absorption by the fibre in the dye-bath increasesand reaches to maximum during 30-50 min of dyeing.The maximum dye absorption occurs in 50, 50, 30, 50and 30 min for Congo Red, Titan Yellow, Fast Ora-

67


nge PRS, Durazol Red and Direct Yellow 29 respecti-vely. The dye absorption remains nearly constantwith further increase in dyeing time. The reason forsuch a behaviour is that the cellulosic fibre immersedin a dye solution absorbs dye until equilibrium is reac-hed. Under any given condition of temperature andelectrolyte conc., the true equilibrium is reachedwhen each fibre has been evenly dyed throughout itscross-section and when no change in the concentrat-ion of dye in the fibre and in the solution takes placewith further increase indyeing time. With any partic-ular dye-fibre system, this equilibrium may reach in acomparatively short or long time!". The equilibriumdyeing time of all the direct dyes is not same becausethe speed of dye diffusion inside the fibre depends onthe size of the dye particles and on the state of the fibre,i.e. the smaller the dye particle and greater the fibreswelling, the higher is the mobility of the dye particlesand the quicker they penetrate inside the fibre and,conversely, the greater the dye particles and lesser theswelling capacity of the fibre, the slower is their diffus-ion!".

Experiment showed that the dyeing time was short,but it required a long time to obtain level dyeing. Thedye was rapidly taken up by the fibre and fixed to theone part of the fibre while another part was left und-yed or only slightly coloured. Most dyes possess twoproperties depending upon dyeing time. The first pro-perty is their migration or levelling power. This is thetendency of particular dye molecules,attached to thesurface of the fibre, to detach themselves, re-enter thesolution and again attach themselves to another reg-ion of the fibre. The second property is the effect oftemperature or addition of other compound to thedye solution. These factors can effect the absorptionof the dye from the solution by the fibre!".

3.4 Effect of Dyeing TemperatureFigA shows that the absorption of Titan Yellow,

Fast Orange PRS and Direct Yellow 29 by jute fibreincreases with the increase in dyeing temperature andbecomes maximum at IOO'C. It seems that dyes existin solution as aggregates of various sizes and at hightemperature, large dye aggregates are broken downto smaller units, causing easy penetration of smallerdye particles into the fibre1o,19. Another explanationis that at high temperature the size of the fibre poresincreases and dye particles easily penetrate into thefibre. When the dye-bath cools down, the fibre porescontract and the dye particles remain in the fibre!".Hence, at higher temperature, dye absorption is high-er. It is also observed from the figure that dye absorpt-ion decreases linearly with the increase in temperat-ure above 60°C for Durazol Red and above 90°C forCongo Red. This may be mentioned here that the

68

100,----:::o:=u===!:r==u==cr=C/"'I

-c.~-;;;:>~ 1.0..•.s

20

o~~-----~---~------~10 30 50Dyeing time,min

70

Fig. 3-Effect of dyeing time on dyeing of jute fibre with directdyes: (0) Congo Red, «) Titan Yellow, (.) Fast Orange PRS, (f',)

Durazol Red, and (A) Direct Yellow 29

100r------------:::::c)=::::;'"

80

c~~ 60

~•...>-c 40

20 40 60. 80Temperature, C

100

Fig. 4-Effect of dyeing temperature on dyeing of jute fibre withdirect dyes: (0) Congo Red, «)) Titan Yellow, (.) Fast Orange PRS,

(f',) Durazol Red, and (&) Direct Yellow 29

amount of dye absorbed by the fibre in the equilibr-ium condition is reduced with an increase in tempera-ture. The exhaustion of dyes which do not activelyinteract with the fibre is reduced more considerablythan that of dyes which interact more intensively withthe fibre. The temperature at which the maximumamount of dye is practically exhausted should be ado-pted for dyeing with the dyes, which, in solution, app-roach the molecular condition and, therefore, poss-ess the required diffusion speed. The dyes whose solu-tions are colloidal in a considerable degree diffuseslowly!".

The optimum dyeing conditions of direct dyes aregiven in Table 1.


3.5 Light FastnessTable 2 shows that the colour of dyed fibre fades on

exposure to sunlight in air and the light fastness dep-ends on the exposure period. All the dyes, except Co-ngo Red, exhibit good colour fastness on exposure.The light fastness of different dyes on jute fibre dep-ends upon one or more factors. One factor which cert-ainly has an important bearing on the light fastness ofvarious dyestuffs on jute is the change in colour ofundyed jute on exposure to light. Another factor isthat the different assistants used in dyeing with thevarious classes of dyestuffs have a marked effect onthe colour of the fibre and may tend to minimize oraccentuate the apparent fading of the dyestuff". Atthe short exposure period, the change in colour occ-urs rapidly and then no or slight change occurs onfurther increase in exposure period. This is possiblydue to the mechanism of the light action produced bythe dye on the fibre. An intensive oxidation of the fibreis due to the capacity of the dye molecule, excited bythe absorption of the short wave or UV light, to bereduced because of the hydrogen contained in cellul-ose. As a result of further oxidation of the reduced dyeby the oxygen of the air, dye hydroperoxide may beformed which is also capable of oxidizing the fibre! o.This oxidation reaction rapidly occurs at short periodof light exposure and hence the colour of the dyed

Table I-Optimum dyeing conditions for direct dyes

Dye Dye Electrolyte Dyeing Dyeingcone. (common salt) time temp.

0/0 cone. 0/0 min °C

Congo Red 2.0 10 50 90Titan Yellow 3.0 30 50 100Fast Orange PRS 2.5 25 30 100Durazo 1 Red 2.5 30 50 60Direct Yellow 29 3.0 25 30 100

fibre abruptly changes. When the reaction is complet-ed, the change in colour or fading does not occur. It isalso seen from Table 2 that Fast Orange PRS, TitanYellow, Durazol Red and Direct Yellow 29 exhibitbetter light fastness on modified fibre. Durazol Red,Fast Orange PRS and Direct Yellow 29 have conside-rably better light fastness even in absence of modifier.Only the colour of Titan Yellow on jute fibre wasprevented by the modifier, and this colour did notundergo any appreciable change during modification(Table 2). So, the modifier can be used in dyeingjutewith Titan Yellow to obtain light fast colour. Thelight fastnesses of the dyed and modified fibre were 3,4-5,4-5,4 and 3-4 for Congo Red, Titan Yellow, FastOrange PRS, Durazol Red and Direct Yellow 29 res-pectively.

3.6 Wash FastnessAmong the direct dyes, Titan Yellow, Fast Orange

PRS, Direct Yellow 29 and Congo Red withstandtheir colour, to a great extent, on jute fibre on washingwith soap solution. The colour of the dyed fibres fadeson washing and the wash fastness decreases with theincrease in washing temperature (Table 3). This maybe mentioned here that all the dyes used in our experi-ments are water soluble. The dye is more easily dissol-ved in the fibre mass than in water. If the dyed fibre isplaced in a medium which dissolves the dye betterthan the fibre, the dye will be easily washed off thefibre!". The solubility of the dye increases with theincrease in washing temperature. Hence, at highertemperatures, more dye will be easily washed off thefibre.

A comparison of the dyed and modified fibresshows that improved wash fastness is achieved by themodifier in the case of Congo Red, Titan Yellow andFast Orange PRS. But Fast Orange PRS shows better

Fibre

Table 2-Light fastness of dyed and modified fibres on exposure to sunlight in air

Exposure Fastnessperiod

h CongoRed

DirectYellow 29

Dyed

o50

100150200250

o50

100150200250

53

2-32-32-32-3

52-322

1-21-2

Modified

TitanYellow

Fast OrangePRS

54-54444

54-54-54-54-54-5

55

4-54

3-43-4

54

3-43-43-43-4

DurazolRed

544

3-43-43

54-54-54-544

55

4-54-54-54-5

54-54444

69


Table 3-Wash fastness of dyed and modified fibres on washing with soap solution

Fibre Washing Fastnesstemp.T Congo Titan Fast Orange Durazol Direct

Red Yellow PRS Red Yellow 29

Unwashed 5 5 5 5 540 4-5 5 5 4 4-5

Dyed 70 3-4 4-5 4-5 3 4100 3-4 4 4 3 4

Unwashed 5 5 5 5 540 5 5 5 4-5 4-5

Modified 70 5 5 5 4 4100 4-5 4-5 4-5 3-4 3-4

Table 4--Fastness of dyed and modified fibres to spotting with acid

Fibre Acid Fastness

Congo Titan Fast Orange Durazol DirectRed Yellow PRS Red Yellow 29

Unspotted 5 5 5 5 5Sulphuric acid Blue black 4 5 5 Black

(Shade increased)Dyed Acetic acid Light black 5 5 5 5

Tartaric acid Light black 4-5 5 5 5(Shade increased)

Unspotted 5 5 5 5 5Sulphuric acid Light bluish 4-5 5 5 Blackish

black (Shade increased) yellowModified Acetic acid Light black 5 5 5 5

Tartaric acid Light bluish 4-5 5 5 5black (Shade increased)

wash fastness in the absence of modifier and Congo - modified fibres to spottings with sodium carbonate,Red fades at the time of modification. So, the colour sodium hydroxide and ammonia solution is satisfact-of Titan Yellow dyed fibre is better protected by the ory and nearly same in most of the cases. The abovemodifier. results show that the modifier has no positive impact

on the colour fastness of dyed jute fibre to spottingswith acid and alkali. So, it is not necessary to modifythe dyed fibre with metal salts to achieve fast colour inthese cases.

Considering the effects of sunlight in air, washingwith soap solution. and water, acid and alkali spott-ings on dyed and modified fibres, it can be concludedthat the modifier is, comparatively, more effective inpreventing the colour of jute fibre dyed with TitanYellow.

3.7 Fastness to Spottings with Water, Acid and AlkaliThe colour fastness of dyed and modified fibres to

spotting with water was tested. In all cases, no colourchange was found, i.e. fastness grade 5 (according toGrey scale).

Table 4 shows that the colour fastness of both thedyed and modified fibres to spottings with sulphuricacid, acetic acid and tartaric acid is satisfactory with afew exceptions. Congo Red dyed and modified fibresshow poor colour fastness by changing their colour tospottings, Titan Yellow increases its shade to spott-ings with sulphuric acid and tartaric acid, and DirectYellow 29 changes its colour to spotting with sulphu-ric acid. The changes in colour of dyed and modifiedfibres to spotting are not the same because the acidhydrolyzes the fibre and the dye, and the hydrolysischanges its mode in presence of metal saIts. Table 5shows that the colour fastness of both the dyed and

70

3.8 Effect of Sunlight on Breaking StrengthOn exposure to sunlight in air for 250 h, the break-

ing strength of dyed and modified fibres decreases(Table 6). It seems that on exposure, dyes have a sensi-tising action on photo-oxidation process, which incr-eases the loss in resistance. The intensive oxidation offibre is due to the capacity of the dye molecule, whichis excited by the absorption ofUV light. This excitat-


Table 5-Fastness of dyed and modified fibres to spotting with alkali

Fibre Alkali Fastness

Congo Titan Fast Orange Durazol DirectRed Yellow PRS Red Yellow 29

Unspotted 5 5 5 5 5Sodium carbonate 4 5 5 4 5

Dyed Sodium hydroxide 5 5 5 4 5Ammonia solution 5 5 5 5 5

Unspotted 5 5 5 5 5Sodium carbonate 5 5 5 4-5 5

Modified Sodium hydroxide 5 5 5 4-5 5Ammonia solution 5 5 5 5 5

Table 6--Loss in breaking strength of dyed and modified fibres on exposure to sunlight in air

Fibre Exposure Breaking strength, 'kg/yarnperiod

h Congo Titan Fast Orange Durazol DirectRed Yellow PRS Red Yellow 29

Dyed 0 23.628 19.800 21.600 24.400 23.867250 19.375 18.675 19.900 17.840 20.086

Modified 0 21.125 19.361 21.013 23.743 23.267250 15.533 17.714 18.640 16.080 18.556

Loss in breaking strength, %

Dyed 250 17.999 5.682 7.870 26.885 15.842Modified 250 26.471 8.507 11.293 32.275 20.247

Breaking strength retained by the modifier (metal salts), %250 -8.472 ~2.825 - 3.423 - 5.390 -4.405

ion energy is transmitted by the dye to the oxygen ofthe air, causing its activation. Activated oxygen oxid-izes water vapour to hydrogen peroxide, which, inturn, causes the activation of the fibre1o.2o. The % lossin breaking strength after exposure to sunlight is hig-her in modified fibre than dyed fibre. This means thatdirect dyes are very much sensitized by the light inpresence of modifier and cause degradation of themodified fibre in all possible manners. Hence, the mo-difier, in this case, is not only unable to prevent thestrength loss of dyed fibre but also enhances the degr-adation of fibre.

4 Conclusions

4.1 Dye uptake by jute fibre is higher at low concent-ration of dye and it decreases with the increase in dyeconcentration in the dye-bath for all the direct dyes.Even and bright shades are obtained on dyeing jutefibre with 2-3% dyes.

4.2 The absorption of dye becomes minimum whenthe jute fibre is dyed with direct dyes in absence ofcommon salt as electrolyte. The dye absorption incre-ases with the increase in electrolyte cone, and reachessaturation absorption at 10-30% common salt whenuniform and acceptable shades are obtained.

4.3 Higher dye absorption is obtained by increasingthe dyeing time up to equilibrium absorption. Thedyeing time for saturation absorption of direct dyes is20-60 min. In most cases, dye absorption occurs wit-hin a few minutes, but it requires long time to obtainlevel or uniform dyeing.

4.4 Dye absorption increases with increase in dye-ing temperature and reaches maximum at lOOT in thecase of Titan Yellow, Fast Orange PRS and DirectYellow 29 and at 90°C and 60°C in the cases of CongoRed and Durazol Red respectively.

4.5 The colour of dyed and modified fibres fades onexposure to sunlight. The fading is rapid at the shortexposure period and then no or slight change occurson further increase in exposure period. The modifierprotects the colour of Titan Yellow dyed fibre fromthe sunlight effect.

4.6 Washing of dyed and modified fibres with soapsolution removes the attached dye molecules from thefibre and hence the fibre fades. Removal of the attac-hed dye molecules from the fibre increases with theincrease in washing temperature. To obtain fast col-our from washing treatment, the modifier should beused for jute fibre dyed with Titan Yellow and FastOrange PRS.

71


4.7 The effects of acid and alkali spottings on thecolour fastness of both the dyed and modified fibresare nearly the same. So, the modifier is not required inthese cases.

4.8 On exposure to sunlight in air, the loss in break-ing strength (%) of modified fibre is higher than thatof dyed jutefibre.So, the modifier should not be usedin this case.

ReferencesI Patro P S. Text Dyer Printer, 4(8) (\971) 57.2 Carter D. J Text Inst, 30 (1939) T328.3 Douglas A E, Text Color. 59 (\ 937) 229.4 Holden F G. Am Dyest Rep, 19(5) (1930) 169.5 Farouqui F I & Hossain M I, Rajshahi University Studies (in

press).6 Sarkar P B & Chatterjee H, J Text Inst, 39 (\948) T274.7 Giles C H. A laboratory course in dyeing, 3rd edn (The Society

of Dyers and Colourists, England) 1974,54, 79.

72

8 Farouqui F I, Rahman S M, Bakr M A, Alam M S & Faruq M0, Rajshahi University Studies, (Part-B)-XIII (1985) l.

9 International Standard ISO: 105-A02-1978(E).10 Sadov F, Korchagin M & Matetsky A. A chemical technology

offibrous materials (Mir Publishers, Moscow) 1973,315,454.II International Standard ISO: 105-803-1 978(E).12 International Standard ISO:105-COI-I982(E).13 International Standard ISO: 105-E07-1978(E).

14 International Standard ISO:105-E05-I978(E).15 International Standard ISO:I05-E06-1978(E).16 International Standard ISO:508I-1977(E).17 Farouqui F I, Ali M M, Rahman S M, 8akr M A & Faruq M 0,

J Bangladesh Acad sa. 2(2) (1987) 233.

18 VickerstaffT, The physical chemistry of dyeing (Imperial Che-mical Industries Ltd, London) 1954,234.

19 Cockett S R & Hilton K A, Dyeing of cellulosic fibres and rela-tedprocesses [Leonard Hill (Books) Ltd, LondonJI96I, 21 I,238.

20 Egerton G S, J Soc Dyers Colour, 65 (1949) 764.

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