Indian Journal of Fibre & Textile Research VoL 2~ , March 1999, pp. 49-57

A new insight into the rheological properties of alginates and carboxymethyl starches for printing of reactive colours

B N Bandyopadhyay, A K Mukhopadhyay, A V Afini, N R Salaskar & S B Acharekar

The Bombay Textile Research Association, Lal Bahadur Shastri Marg, Ghatkopar (West), Mumbai 400 086, India

/(eceived 22 Jalluary 1998: revised received alld accepted 24 March 1998

Alginate (Manutex Rs-2JO) and different carboxymethyl starch (CMS) samples with different degrees of substitution have been compared from rheological point of view to establish whether Alginate could be substituted with CMS. It is ob­se rved th at one C' MS paste (9 .5% MT-:\) closely matches with 3.5% Alginate in rheological properties as well as printing performance. Technique of prediCIJon of printlllg behaviour from rheological angle is also discussed.

Ke~words : Alginate, Ca rbox ymeth yl starch, Colt on, Printlllg, Reacti\'e co lours, Rheology, Thixotropicity

I Introduction High s pe ~'d and surl~lce printing on textiles are

gaining importance day hy day lor CLi stolllcr demand to obtai n lower colour coat in g on the fabric ror making less colour In ci'lluent. II igh speed printing requires sufficientl y \'ISCIHIS print paste to minimise the quantum of colour In \\ C\:-; hing liquur ti:Jr combatll1g pollution. The stnke tl lrough of the print in the fabric may not be gll\nncd by the vi scosity alone . Rheology plays the lllost illlpllrtant role In pnnt ing . ThiS r0ll11S the bas is oj' our present study \~ hcre thixotropicity and recon:r) hl.' k l\lour and their reiJ tionships \\llth the elast ic Clllllp(1lll'nts and I() s~ bctor ha\'C been ~ tudied in detail so th:l t the pnnting behaviour can he preui t: teu lore hand Ihl' prediction IS a complex exerci se or dynam ic hl' h ~l\t()lIr of print pastes on whi ch Ilori acher (' / ill .1 ulllkrllllCd the Importance .

I'he rheoillg ical studlesC ~ contemporarily had mainl y rocused un the change of vi scosity at different shear r:1 te s. shcar thinning indi ces and change of shear <,(re ,, ~ at eli lfcrcnt ~ hea r rates, etc. These studies could not s uec,~ed tll predict the printing behaViour earlier and lert many fundamcntal questions on rheology unanswered. Therci'ore, it v,:a s considered worthwhile to study some Important thickeners of different concentra ti ons from the rhccilogical point of view with speCIal cmphasis on uynamlc experiments so that the Il1ter-relationship amongst variOUS rheological properties clluld he rightly ascertained. In the present work. rheologICal properties of carboxymethy l starch of different dl'grees of substitution and concentration

have been stud ied both in the parent state as well as after addition of dye and auxiliaries and correlated \'ii th the result of Alginate (Manutex RS-230) , An attempt has al so been made to predict the printing performance II'OIn the rheological point of view.

2 Rheology In order to appreciate the importance of the

rheological eh3racteristics of thickeners it would be appropriate to understand the effec t or shear rate on deformationlllow of various types or polymeric material s.

The now curve of an ideal liquid follows Newton's !a\\' \vhere shear viscosity (11) = shear stTess (T)/shear ratc ( y ). This means that the viscosity is not a Ifected

by the changes in shear rate (y ). Typica l print pastes

arc described as non-newtonian, since their viscosity changes as the shear rate is changed, Most print pastes show shear thinning properties, with a sigmllcant reduction in apparent vi scosity as the shear rate is increased. Another kind of tluid is <-(died thixotropic . They are shear thinning but the \ .,cosity recovery takes place after some interval of time. A thixotropic tluid is defined by its potential to have its gel structure reformed whenever the sub~tance is allowed to rest for an extended perind of time.

The non-newtonian tluid is def'!ned by the 'Ostwald­de- Waelc' or ' Power-law' equation as:

T = K . j"

wher~~ ,= Shear stress K'= {'oll si:;te Il C\' as:1 vl<; L'o ;:. it y related constant

50 INDIAN J.FIBRE TEXT. RES., MARCH! 1999

y = Shear rate

a= Exponent - slope of the log-log flow curve of log t vs log y

The exponent a= 1 for newtonian liquids and it decreases the more the sample becomes non­newtonian. This is a very important tool to find out the characteristic flow behaviour.

Fig. I shows that at lower shear rates5, viscosity is

constant (I-First Newtonian Range). The pseudoplastic component (II) complies with the initial range, viscosity decreasing as shear rate increases as a result of molecular or particle orientation. Flow behaviour in thi s region is already defined by Power­law equation. At very high shear rates, viscosity is agam independent of shear rate (IIJ--Second Newtonian Range).

2.1 Thixotropicity and Recovery of Gel Structure of a Sheared Thixotropic Liquid

A system is called thixotropic6 only when the decrease in viscosity occurs with a distinct time dependence under the action of constant shear rate and temperature. Upon removal of the shear, the viscosity recovers with time near up to its initial value. In the pres~nt study, time dependence of viscosity and recovery have been given importance. The viscosity­time curve marks the two phases of transformation. In the first phase, a gel turns rapidly to a sol when subjected to a constant shear rate and in the second phase, the sol is converted back to a gel. Measuring the rate of recovery is often scientifically important since it is thi s rate of recovery which acts as yardstick in judging the performance of thickener. The recovery required, in principle, is that the thickener in its sol­state rebuilds the structure at rest.

2.2 Storage Modulus, Loss Modulus and Loss Factor

The th ickeners employed are viscoelastic compounds. Viscoelastic substances are capable of storing energy, depending on their elastic proportions. Elastic and viscous proportions can be determined with the aid of dynamic experiment. The viscoelastic subs lances are subjected to an oscillation deformation process and their reaction to the deformation is measured as :

y = Yo sin wt "( = yos in (wt +8)

where y is the strain ; Yo, the maximum strain; and 8, the phase angle.

viscosity curve

-

----I~f- III

log shear rote(v) Fig. I-Shear rate dependence of pseudoplastic liquids [I--First Newtonian range; II-Pseudoplastic component; and III-Second Newtonian range]

Purely viscous compounds have phase displacement of 90°, while there is no phase displacement with purely elastic substances. Viscoelastic compounds fall between these two limits. G*=G'+iG" where G' is the elastic or storage modulus; Gil, thl;: viscous or loss modulus ; G*, the complex modulus ; and i. the complex number.

The loss factor is given by the following relationship:

Loss factor (tan 8) = G"/G'

3 Materials and Methods 3.1 Fabric

100% cotton poplin bleached fabric having the following specifications was chosen for the laboratory printing trial : Warp count, 32s; Weft count, 31 s; Endslin, 75 ; Pickslin, 66; and Weight, 108 gim2

•

3.2 Dyes and Chemicals Reactive Red 31 (Procion Red H8B), sodium

bicarbonate (LR Grade), urea (extra pure grade) and water having hardness of 50 mg/litre were used.

3.3 Stock Paste Preparation

ManutexlCMS powders were added slowly in cold water, stirred and kept in water bath at 90°-95°C for 30 min . Different concentrations of carboxymethyl starches (6.0% MT-2, 4.0% MT-2, 6.5% MT-I , 9.5% MT-3) and 3.5% Alginate (Manutex RS-230) were prepared. MT-l /MT-2/MT-3 were the different CMS samples with 0.27, 0.23 and 0.30 degrees of substitution respectively. The pastes were prepared keeping in mind the viscosity requiremen t for printing:

BANDYOPADHYAY et at.: RHEOLOGICAL PROPERTIES OF ALGINATE & CARBOXYMETHYL STARCHES 51

3.4 Print Paste Preparation

The print pastes were prepared as per the following reCIpe :

4 parts dyestuff 2 parts sodium bicarbonate 5 parts urea 17 parts water 72 parts thickener

100 parts

The studies of rheological properties, viz. shear viscosity at different shear rates, a-values, thixotropicity (hysteresis loop and viscosity-time curve), and dynamic properties were carried out on both stock paste and print paste using HAAKE cone and plate viscometer (RS-I 00) with a cone of angle 2° at 24°C.

3.5 Laboratory Printing Trial

Printing studies were carried out in Zimmer Flat Bed and Rotary Screen Printing Machine with two different speed settings with equivalent magnetic setting for the rod pressure. At the same time, screen printing was carried out with stripes so that the area swelling could be ascertained apart from finding out the stiffness of the fabric. The printed samples were dried at 80°C for 5 'min followed by steaming at 105°C for 15 min in a cottage steamer. The samples were then suhjected to cold and hot wash (60°-80°C) followed by soaping at boil for IS min. Finally, the fabric samples were washed with cold water and dried .

.1.6 [yaluation of Prin(('d Samples

.l.ti.1 Colour Measurements

The colour values were measured using Macbeth Spectrophotometer (7000 A) in a reflectance mode. The colour diffe rence, colour value, chroma value and the related details were found out.

3.6.2 Fastness Tests

Fastness to light, washing and rubbing was assessed in accordance with rS:2454-1985, IS: 765-1979 and IS :766-1956 respecti vely. The changes in colour of the specimen and staining of the adjacent fabri cs were assessed . As regards fastness to washing, ISO grey scale ratings ISO-105-A02 and ISO-105-A03 were followed for change in shade and staining respectively.

3.6.3 Measurement of Stiffness

It was measured in terms of ben9ing length using Shirley stiffness tester in accordance with IS:6490-1971. Test specimens (25 mm x 200 mm), cut from screen printed samples in warp direction, were used.

The prediction of printing performance from the view point of rheology will be discussed later in this paper.

4 Results and Discussion 4.1 Flow Curves

The shear rate in the range of 0.3-100s-1 was chosen. The dependence of viscosity with respect to the shear rate and power-law index (a-value) for parent and print pastes are shown in Figs 2 and 3 respectively_ Table 1

shows the viscosity at different shear rates (10, 50 and 100 S-I), viscosity drop and a-values.

It is observed from Table 1 that the viscosity drop for all the parent p"astes is 75% except in case of 6.5% MT-l and 6.0% MT-2 where the drop is 72.7% and 78.5% respectively. The viscosity drop after addition of colours and auxiliaries is restricted to 60% and 61.5% for 9.5% MT-3 and 3.5% Manutex. All other CMS thickeners show 74-75% viscosity drop. The shear viscosity values at different shear rates for 3.5% Manutex and 9.5% MT-3 are closely matching. The a­values for the parent pastes are in the range of 0.33-0.43, but after the addition of dye and auxiliaries, remarkable change is observed in the a-values for

Sr

4

'" 0 Cl.

E 3

-.J' 9 )(

c'

o 10 40 60 -{IS

Fi g. 2- Variati on in viscos ity of p3rent pastes [( -t.-) 4.0% MT-2, a = 040; (-x -) 6.0% MT-2 , a =O.41 ; (-0 -) 9.5% MT-3, a = 043;

(-0-) 6. 5% MT-I , u = 0.33; and (-0-) 3.5% Manutcx, a = 0.37)

52 INDIAN HIBRE TEXT. RES, MARCH 1999

- - --- _ . . _ - - --_._---------- ---------'I able I- -- Apparent viscosity at different shear rates, viscosity drop and a-values of different thickeners

Thickener Apparent viscosity (m Pas) Vi scosity a-Values

\1\ o

a.. E

)(

c:'

2 0

., .5% Manutex Parent paste I'rint Paste

') .5'Yo MT- .' Parent paste Print paste

4 .iI"" MT-2 Parent paste i-'nnt paste

(l.S '!" MT-I P ~lr('nt paste Print paste

(J,() '!i, MT-2 Parcnt paste Pnnt paste

;lIs

at different shear 10s i 50s l

14,000 6,500 5,200 3,000

12,000 5,000 5,000 2,500

4,800 2,()OO 3,200 1,200

11 ,000 4,000 4,000 2,500

14,000 4,000 7,800 3,000

Fi g 3- V'lriati on in viscosil Y of print pastes [(-X- ) 6 .0% MT-2 , (1 = (1.30; (-t'\ -) 4.0% MT-2, u = 041. (-0 -) ( .. 5% MT-I, u = OAO;

(- . -) I) .S% MT-.\ , u = 0.02; and (-0- ) .' .5% Manlltex , (J. = 0.(9)

3S % Manutex and <} .5'% MT-3. The shear vi scosity va lues at different shear rates for 3. 5% Manutex and (d)'~'O MT-2 are al so closely matching, However, the printing performance of the two samples is entire ly J ilferenl. Therefore , the pnntlllg perf0n11anCe is not ,l!m'erned on ly by the shear vi SCOSity alone but by the complex Iflteraction e,f other propel1ies which wtll he dealt subsequentl y.

·U Thixotropicity 4.2. t lI ystl'resis Loop

The shear rate for these stucites was increased ti'om (U s I to 100 S· I within 2 mlll 'and then programmed

rates drop (Power-law 100s·1 0/.) Index)

3,500 75 0.37 2,000 Ii is 0.69

3,000 75 OA3 2,000 GO 0.G2

1,200 75 OAO SOt) 75 OA I

3,0(10 72.7 0:\ :' 1,000 75 OAO

3,000 78. 5 0.41 2,000 74.3 0.3 .

TJb le 2- Thi xo!ropy of different thi ~keners

ThicKl' ll er Area A (hysteresis) Pals

.1 .5'::, M.lIl llt c'\ P~IIT llt p ~ l s t e

Prill t paste ').-' ''" MT-3

1' ~ Irt: nt paste Prillt PdStC'

.J.() " " 1\,tT-2 Parellt PdSlC 1'1'1111 paste'

(, . 5 ~ " 1'\'IT· 1 P~ II-C llt Pdstc 1'1 il1t paste

(1.! )";, I\1T- 2 1\ 1I,(, l1t pastl' 1\1111 paste

23 17 188

454 23 7

21D 4 ()

3(10 360

328 480

back to 0.3 S· I ti'om 100 S- I within the identical time span. Table 2 shows the magnitude of thixotropy of parent and print pastes. It is observed that there is a reduction in the hysteresis area after the addition of dye ~md aux i I iaries except in cases of 6.5% MT - I and 6.0% MT-2. Maxim um reduction in area is observed in 3.5% Manutex . Surprisingly, there is an increase in area (after the addition of" dye and auxil iaries) for 6.5% MT-l and 6.0'% MT-2 . lIowever, dilutmg MT-2 to 4.0(% results in a drastic reduction in area and improves the pr:nting perfOnllance.

-t.2 .2 \, i scosi t ~ '-Time C ur\'c, Ratl' of Recovery and RccoYl'ry Pcrcentage

Figs 4 and 5 show the viscosity-time c rves where

~ -

BANDYOPADHY A Y et al.: RHEOLOOICAL PROPERTIES OF ALGINATE & CARBOXYMETIlYL STARCHES 53

6

"II 4 .. n. E

~

51 ,. C' 2

7 t, min

Fig. 4-Recovery behaviour of parent pastes [(-0-) 3.5% Manutex, (-6-) 4.0% MT-2, (-X-) 6.0% MT-2, (-0-) 6.5% MT-I, and (-0-) 9.5% MT-3]

3-0

4 5 6 7 t,min

Fig. 5--Recovery behaviour of print pastes [(-0-) 3.5% Manutex, (-6-) 4.0% MT-2, (-X-) 6.0% MT-2, (-0-) 6.5% MT- I, and (-0-) 9.5% MT-3]

the thickener was subjected to a shear rate of 0.3 S· I for 2 min in order to ascertain the initial viscosity. In the second phase, a constant shear rate of 100 S·I was kept for 2 min to have the complete breakdown of thixotropic structure. In the third phase, a very low constant shear rate of 0.3 S· I was kept for 2 min to allow the thickener to recover. Recovery behaviour of 3.5% Manutex, 9.5% MT-3, 4.0% MT-2, 6.5% MT-l and 6.U% MT-2 (parent and print pastes) is shown in Table 3.

The rate of recovery of parent and print pastes is

2 It

• .. I .. .. 2 >< C'

O~4----~~----~~----~----~~----~

Fig. 6-Rate of recovery of parent pastes [(-0-) 3.5% Manutex, (-6-) 4.0% MT-2, (-X-) 6.0% MT-2, (-D·) 6.5% MT-I, and (-0-) 9.5% MT-3]

Table 3-% Recovery and rate of recovery of different pastes

Thickener % Recovery Rate of recovery Slope (deg)

3.5% Manutex Paren t paste 71.4 72.6 Print paste 88.8 57.1

9.5% MT-3 Parent paste 86.0 56.4 Print paste 85 .2 49.7

4.0% MT-2 Parent paste 90.2 39.3 Print pdste 94.1 40.1

6.5% MT- \ Parent paste 87.0 61.0 Print paste 84.2 61.4

6.0% MT-2 Parent paste 89.5 71.2 Print paste 77.2 74.2

shown in Figs 6 and 7 (magnitying the recovery zone). The rate of recovery drastically goes down in case of 3.5% Manutex (after the addition of dye and auxiliaries ) and a marginal drop is observed in case of 9:5% MT-3. No significant change in the rate of recovery is observed for 4.0% MT-2 and 6.5% MT-I and an increase in the rate of recovery is observed for 6.0% MT-2. It is clear from Table 3 that the higher recovery (ultimate) does not necessarily mean the higher rate of recovery. In fact, the rate of recovery for 6.0% MT-2 is highest but the ultimate recovery (%) is lowest. The printing perfonnance of this printing paste was extremely poor.

54 INDIAN J.FIBRE TEXT. RES., MARCH 1999

• • &.

• .~

2 If e-

4.2 4.4 4.6 4 .1 ~·O

t ,111111

Fig. 7--Rate of recovery of print pasteS' [(-0-) 3.5% Manutex, (-.1-) 4.0% MT-2. (-X-) 6.0% MT-.2, (-0-) 6.5% MT-I, and (-0-) 9.5% MT-3]

102

G IL

-0

10'

o~ __________________ ~ ________________ ~~ ________________ ~~ 10 -1 0 1 2

10 10 10 .0 ·w,rad/l

Fig. 8--Yariat ion In storage modulus for parent pastes [(-0-) 3.5% Manutcx, (-.1-) 4.0% MT-2 , (-X-) 6.0% MT-2, (-0-) 9.5% MT-J, and (-0-) 0.5% MT-I ]

The recovery behaviour is governed by the elastic components (storage modulus). Figs 8 and 9 show the trend of storage modulus (G') of parent and print pastes respectively. It is observed that 6.0% MT-2 shows the highest value of G', which signifies the highest contribution by elastic components. The highest value of storage modulus in 6.0% MT-2 is reflected in the highest rate of recovery. 6.5% MT-I and 6.0% MT-2 (as such and after addition of dye) show similar trends in the sense that the higher rate of recovery in both the cases is accompanied by the higher values of G.

.02

G .0' IL

'" -G

.00

-1 10 -1

100 10

W, ra.l,

Fig. ~Variation in storage modulus for print pastes [(-0-) 3.5% Manutex, (-X-) 6.0% MT-2, (-.1-) 4.0% MT-2, (-0-) 9.5% MT-3, and (-0-) 0.5% MT-I)]

'" ~ .00

w,rad/l

Fig. ·1 O--Yariation in loss factor for parent pastes [(-0 -) 3.5% Manutex, (-.1-) 4.0% MT-2, (-X-) 6.0% MT-2, (-0-) 9.5% MT-3, and (-tJ-) 6.5% MT-I]

Among all the thickeners, the Manutex behaves in an entirely different manner. After the addition of dye and auxiliaries, the storage modulus drops at the lower frequency and then increases steeply.

The combined trend of loss factor (tan 8) (Figs 10 and II) shows the lowest value for 6.0% MT-2, The loss factor is defined by the ratio of loss modulus (Gil) to the storage modulus (G). Therefore., the samples with higher contribution of G' will automatically lead to tht: lower values of tan 8. The trend of Manutex and

BANDYOPADHY A Yet 01.: RHEOLOGICAL PROPERTIES OF ALGINATE & CARBOXYMErnYL STARCHES 55

• !

-t~ __________ ~ ______ ~~ ________ ~

to to-1 10 0 101 102

w,r •• '.

Fig. II-Variation in loss factor for print pastes [(-0-) 3.5% Manutex , (-X-) 6.0% MT-2, (-6-) 4.0% MT-2, (-0-) 9.5% MT-3, and (-D-) 6.5% MT- I]

Table 4--Combined trend of G' and G" for different thickeners

Thickener G' and G" Cross-over point

3.5% Manutex Parent paste 30 radls Print paste 100 radls

9.5%MT-3 Parent paste 30 radls Print paste 60 radls

4.0% MT-2 Parent paste 15 radls Print paste 30 radls

6.5%MT-1 P'lrent paste 7 radls Print paste 20 radls

6.0% MT-2 Parent paste 4.5 radls Print paste 9 radls

MT-3 got reversed after the addition of dye and auxiliaries.

The implication of G" and G cross-over at an early and later stage is of great importance for predicting printability. Table 4 shows that the cross-over point of G" and G' shifts to the higher level of frequency after the addition of dye and auxiliaries. The crossing of G" and G' at an early stage is observed in 6.5% MT-I and 6.0% MT-2. Therefore, G will be dominating in the earlier stage. While on diluting 6.0% MT-2 to 4.0%, the G" and G' cross-over point is shifted to the higher level of frequency for both the parent and print pastes.

The cross-over point at the highest level of frequency is observed only in case of 3.5% Manutex. Therefore, G' will be dominating over a longer duration of frequency, facilitating transfer of the paste.

4.3 Prediction of Printing Performance from Rheological View PoiDt At an equivalent magnetic pressure and at a lower

speed setting, 3.5% Manutex resulted in more penetration and sharp outline. This could be attributed to the fact that G' and G cross-over point (after addition of dye) shifted to the highest frequency level, resulting in Gil dominating over a longer duration of shear rate, facilitating penetration. 6.0% MT-2 gave a very poor printing performance. It is interesting to note that 3.5% Manutex and 6.0% MT-2 each resulted in an entirely different printing behaviour. The early cross­over point signifies the predominance of G at lower shear rate (domination of the elastic component), resulting in poor transfer. However, fixation and strike through depend not only on transfer but also on dielectric properties of the substrates. For example, the prediction of the paste for transfer onto the substrate will be governed by the cross-over phenomenon but if the substrate is not properly prepared, strike. through and the colour fixation cannot be predicted. There are other reasons behind this poor transfer. The thixotropic hysteresis area for 6.0% MT-2 after addition of dye was increased by 46% and the a-value decreased. The poor flow coupled with the presence of highest elastic component was the responsible factor. However, diluted paste of 4.0% MT-2 resulted in least penetration. The reason could be the later cross-over of G" and G and no significant change in the a-value even after the addition of dye and auxiliaries. 6.5% MT-I also showed a poor printing performance. The reason is same as for 6.0% MT-2. Out of all the eMS samples, 9.5% MT-3 closely matched with Manutex.

A similar trend was observed at an equivalent magnetic pressure and at higher speed setting.

4.4 Evaluation of Printed Samples 4.4.1 Colour Value

The colour values of the printed samples were assessed in terms of tone (total colour difference, hue/chrome, etc.) as well as depth (K/S value at wavelength of maximum absorption) under 065 illuminant and 10° standard observer. The results are shown in Table 5. It is observed that there is a significant improvement in KIS values. 9.5% MT-3

56 INDIAN 1. FIBRE TEXT. RES., MARCH 1999

Table 5--Colour data on printed samples

Sample dE dH de dL L a b c h K/S Strength %

Magnetic pressure, 10 ; Speed setting, 2

3.5% Manutex 40.03 51.18 -5 .96 5 \.53 353.6 12.21 100 4% MT-2 3.285 2.123 0.977 -2.30 37.72 52.36 -3.94 52.50 355 .69 15.51 127 6.5% MT-I 4.812 3.310 1. 165 -3 .29 36.74 52.62 -2.76 52.69 355.99 16.87 '138 9.5% MT-3 5.508 3.767 0.698' -3.95 36.08 52.18 -2.26 52.23 357.52 17.32 141

Magnetic pressure, 10 ; Speed setting, 10

3.5% Manutex 40.68 51.18 - 6.4-6 51.59 352.S- 11.52 100 9.5% MT-3 6.564 4.44 1.078 -4.70 35.98 52.63 -2.12 52.67 357.69 18.09 157

Table 6--Fastness data Fastness to

Sample Washing' Rubbing" Lighth

Change in Staining Dry Wet shade

3.5% Manutex (10/2) 4 3.5% Manutex ( 10/ 10) 3-4 4.0% MT-2 ( 10/2) 4 4.0% MT"2 (10/ 10) () .5% MT-I ( 10/2) 4-5 9.5% MT-3 (10/2) 4-5 9.5% MT-3 (10/ 10) 4-5

• [1-5 scale rating] b [1-8 scale rating]

Table 7-Bending length of samples

Sample

Untreated 3.5% Manutex 9.5% MT-3 4.0% MT-2 6.5% MT-I 6.0% MT-2

Bending length, em

1.64 1.69 1.71 1.63 1.7 1 1.73

shows the highest KIS values. The eMS samples show a sigflificant colour difference (dE values) as compared to Manutex RS-230 . These samples are darker and yellower as compared to the Manutex. There is a significant tonal and depth difference also. The change in hue angle and chroma is not that significant as in case of Manutex. The results for 3.5% Manutex and 9.5% MT-3 at high speed setting show similar trenus as observed at low speed setting.

4.4.2 Fastness Properties

It is observed from Table 6 that the fastness to washing in case of 9.5% MT-3 is better than that in case of 3.5% Manutex . However, staining is similar in

4-5 4-5 4-5

4-5 4·5 4-5

4-5 4 3-4 4-5 4 3-4 4-5 3 3

4-5 3 3 4-5 3 3-4 4-5 3-4 3-4

all the cases. Dry rubbing fastness is similar in all the cases. Wet rubbing fastness in case of 9.5% MT-3 is half/one unit lower than that in case of 3.5% Manutex. Light fastness of 3.5% Manutex and 9.5% MT-3 is comparable . 4.011'0 MT-2 and 6.5% MT-l result 111

slight ly lower rating as compared to Manutex

-tA.3 Stiffness

The stiffness of all the samples is shown in Table 7. It is observed that the stiffness of all the samples is comparable .

5 Conclusions 5.1 Amongst all the eMS pastes, 9.5% MT-3 has

been found to be the best and it matches closely with 3.5% Alginate as far as its rheological properties and printing performance are concerned.

5.2 Apparent shear viscosity values for 3.5% Manutex and 6.01)10 MT-2 almost match . However, their printing perfom1ance is different. The poor perfo rmance of 6.0% MT-2 could be due to the decrease in a-value and early cross-over point of G' and Gil .

BANDYO PADHYAY et al. : RHEOLOGICAL PROPERTIES OF ALGINATES & CARBOXYMETHYL STARCHES 57

5.3 Higher rate of recovery never lead to the higher ultimate recovery. 6.0% MT-2 shows a poor performance, although it has the highest rate of recovery . Rate of recovery has been found to be nicely agreeing with the storage modulus (G').

5.4 9.5% MT-3 gives a brilliant print and higher KIS value.

5.5 The sti rtiless of all the samples is comparable. 5.6 Fastness to washing in case of 9.5% MT-3 is

better than that in case of 3.5% Manutex. However, staining is similar in all the cases. Light fastness of 9.5% MT-3 and 3.5% Manutex is same. Wet rubbing fastness in case of 9.5% MT-3 is slightly lower than that in case of 3.5% Manutex.

5.7 The loss factor and the cross-over points of storage modulus and loss modulus are the most important phenomenon which should be considered for printing. Only a measure of viscosity alone cannot

predict the printability although it is an important element.

Acknowledgement The authors are indebted to the Ministry of Textiles,

Govt. of India, for sponsoring the project "Development of Eco-friendly Polymers for Textile Application" . They are also thankful to the various BTRA member units for supporting the work with various inputs.

References I Horlacher P & Roth A, Melliand Textilber. 76 (1995) 142. 2 Teli M D & Ramani V Y, Alii Dyest Rep. 82 (1993) 26. 3 Hebeish A, EI-Kashouti M A, EI-Zairy M R & Haggeg K,

Alii Dyest Rep. 84 (1995) 28. . 4 Bide M & O'Hara DC, Text Chem Color. 26 (1994) 6. 5 Schramm G, A practical approach to rheology and rheome­

try (HAAKE, Germany), 1994, 16. 6 Lin 0 C C, J Appl Polym Sci. 19 (1975) 199.