rheological studies of mixed printing pastes from sodium alginate and modified xanthan and their...

Rheological studies of mixed printing pastesfrom sodium alginate and modified xanthanand their application in the reactive printingof cottonLili Wang, Baojiang Liu, Qun Yang and Danian Lu*Key Laboratory of Science and Technology of Eco-Textiles, Ministry of Education, DonghuaUniversity, Shanghai, 201620, ChinaEmail: [email protected]

Received: 2 June 2013; Accepted: 17 February 2014

The rheology of printing pastes using sodium alginate and modified xanthan as mixed thickeners has beenmeasured by steady shear tests and dynamic strain sweep tests. The rheological results showed that, with asmall addition of modified xanthan to sodium alginate, the flowability of the mixed printing pastes was betterthan that with sodium alginate alone. Subsequently, as the addition of modified xanthan increased, theapparent viscosity at low shear rates increased gradually, and the mixed printing pastes gained increasinglypronounced shear-thinning features. In addition, the mixed printing pastes with more sodium alginateexhibited mainly viscous behaviour under strain, and the liquid-like features became increasingly weak withthe addition of modified xanthan. On the other hand, the mixed printing pastes with more modified xanthanexhibited mainly elastic behaviour within the linear viscoelastic region, and the solid-like features becameincreasingly marked with the addition of modified xanthan. Mixtures of sodium alginate and modified xanthancan be used as thickeners in the reactive printing of cotton, producing a good colour yield, levelness, andoutline sharpness. In particular, for large patterns, the mixed printing paste performed best when the ratio ofsodium alginate to modified xanthan was 80:20; for fine patterns, it performed best when the ratio of sodiumalginate to modified xanthan was 20:80.

ColorationTechnology

Society of Dyers and Colourists

IntroductionTextile printing is an important method for producing adecorative pattern on textile fabrics. The thickener is anindispensible part of the printing paste. Printing qualities,such as colour yield, levelness, outline sharpness, andhandle, depend heavily on the type of thickener used andthe resulting printing paste rheology.

The thickeners impart sufficient rheological properties tothe printing paste under the different flow conditionsencountered in the printing process. The rheological prop-erties ensure the homogeneous distribution of the printingpaste on the screen, its uniform flow through the screenopenings, and its possible instant recovery after application.During the first step of the printing process, high-shear-rateconditions are present, and the paste, having been forcedthrough the screen openings and deposited on the fabric,will continue to flow at very low shear rates [1]. Theproperties conducive to easy application and good perfor-mance of the printing paste are generally low viscosityvalues at high shear rates and high viscosities at low shearrates respectively [2]. Moreover, elasticity has a greatinfluence on the flow behaviour of the printing pastethrough the screen opening onto the fabrics and then intothe fibres. Alginates, guar gum and its derivatives, methyl-and carboxymethylcellulose, some exudate gums, andxanthan are excellent thickeners for the application, asthey can possess high viscosity at low concentrations andadequate rheological behaviour [3,4].

In the textile industry, cotton is one of the major fibres,and more than 70% of all printed substrates are cellulosicfabrics [5]. Moreover, reactive dye printing is the mostcommonly used method after pigment printing. Sodiumalginate (SA), a derivative of seaweed, is widely used for

reactive dye printing owing to the good screenability, highcolour yield, bright colour, and soft handle. However, itsrelatively high cost, unstable quality, and limited supplyhas spurred efforts to find alternatives [6]. Recently, therehas been increasing research on the use of mixed thickenersto achieve excellent printing properties in reactive printing.Kumbasar and Bide [7] studied the rheology and printabilityof binary mixtures with three anionic thickeners, alginate,carboxymethyl starch, and modified polyacrylic acid.�Sostar-Turk and Schneider [8] investigated the printingproperties of mixed thickeners from highly substituted guargum and sodium alginate. Rekaby et al. [9] preparedcarboxymethyl sesbania galactomannan gum, and dis-cussed the printing performance of it and of its mixturewith SA. The use of mixed pastes in reactive printing isadvantageous.

The natural polysaccharide xanthan, which is producedby the bacterium Xanthomonas campestris, has foundincreasing utility in food and industrial applications [10].In order to improve the rheology and printablility ofxanthan, Wang et al. [11] modified xanthan by deacetyla-tion under alkaline conditions at 90 °C. When used asthickener, the xanthan modified by full deacetylation(MXG) could perform as excellently as SA in the printingof large patterns, and even had an advantage over SA infine-pattern printing. Consequently, using SA and MXG asmixed thickeners should be considered to integrate theexcellent rheology of these thickeners for a better printingperformance. So far, there has been little research on suchmixed printing pastes.

In the present research, the rheological properties ofprinting pastes with binary mixtures of SA and MXG havebeen extensively investigated by steady shear and dynamicstrain sweep tests, and their printing performances have

© 2014 The Authors. Coloration Technology © 2014 Society of Dyers and Colourists, Color. Technol., 130, 273–279 273

doi: 10.1111/cote.12089

been compared and tentatively analysed in relation to therheology. Moreover, the best ratios for large-pattern andfine-pattern printing have been explored to examinewhether such mixing could exploit the advantages of thetwo thickeners while overcoming their disadvantages.

ExperimentalMaterialsSA was produced by Jie Crystal Chemical (China) with anintrinsic viscosity of 11.9 dL/g. Keltrol-RD xanthan wasprovided by CP Kelco (USA) with an intrinsic viscosity of18.4 dL/g. MXG was prepared by full deacetylation underalkaline conditions at 90 °C with an intrinsic viscosity of12.2 dL/g.

The dye used was the monochlorotriazine dye CI Reac-tive Red 245. Other printing paste additives, namely ureaand sodium bicarbonate, were supplied by ShanghaiEnterprise Group Chemical Reagent (China). Reservehao S(sodium-m-nitrobenzene sulphonate) was supplied byShangyu Kangte Chemical (China).

All printing experiments were performed on 100% cottonfabric (warp: 13 threads/cm; weft: 7 threads/cm; threaddensity tex: 14.575 mg/m), which was already desized,scoured, bleached, and mercerised.

Chemical modification of xanthanXG powder was dried to constant weight in a vacuum oven.A three-necked flask (1000 ml) containing 0.933% XGsolution was incubated in an orbital shaker at 600 rpm at90 °C. A standard sodium hydroxide (NaOH) solution(0.914 mol/mol repeated pentasaccharide units) was addedto the XG solution. After reaction for 4 h, the modifiedsample was precipitated repeatedly using acetone, thendried and crushed into powder.

Preparation of the mixed printing pastes and the screenprinting processStock pastes with 3 wt% SA and 3 wt% MXG weredetermined to be suitable. The thickener and demineralisedwater were mixed in a magnetic stirrer and placed in arefrigerator overnight to attain full swelling. The blendswere prepared by mixing the stock pastes according toTable 1. Printing pastes were prepared from the stockpastes according to the formulas given in Table 2.

A 10 9 10 cm2 square pattern, a thick line (800 lmwidth), a thin line (200 lm width), and a wedge design

(100 mm length, 2 mm height) were printed on cottonfabrics with a laboratory printing machine (Mini MDF R286;Klagenfurt, Austria). The printing process was conductedusing a flat-screen 180 mesh with a magnetic rod diameterof 8 mm at a printing speed of 6 m/min and a magneticforce of grade 3. The square-pattern samples were dried for2 min at 80 °C and steamed in a high-temperature steamoven (DHE; Mathis, Switzerland) for 10 min at 102 °C, andthen washed with cold and warm water and soaped inboiling water with a bath ratio of 1:50 for 10 min to removethe thickener and unfixed dyes. However, the line andwedge samples were only dried for 2 min at 80 °C.

Rheology measurementThe rheological properties of all printing pastes weremeasured using a senior rotating rheometer (ARES-RFS,USA) with a cone-and-plate geometry (diameter 50 mm,cone angle 0.04 rad, gap 0.0489 mm) at 25 � 0.01 °C. Theprinting paste was loaded into the rheometer andequilibrated at the test temperature for 120 s beforemeasurement.

Steady shear testsSteady flow tests were implemented in a wide shear raterange (0.1–1000 per second) to obtain flow curves of theprinting pastes.

Dynamic strain sweep testsDynamic strain sweep tests were carried out in the strainrange 0.1–1000% with a fixed frequency of 1 Hz. Therelevant viscoelastic parameters could be obtained as afunction of strain.

Quality-determining parametersPrinting paste add-on was determined gravimetrically fromthe differences in the mass of cotton fabric samplesdetermined before printing and immediately after theapplication of the printing paste. The tests were repeatedthree times.

The surface colour yield (K/S) was measured on aDatacolor 650 colour measurement spectrophometer (Data-color, USA). According to the Kubelka–Munk principle, K/Swas calculated as:

K=S ¼ ð1� RÞ22R

ð1Þ

where K is the absorption coefficient, S is the scatteringcoefficient, and R is the emissivity at the maximumabsorption wavelength without light projection.

Table 1 Ratio of thickeners in the 3 wt% stock pastes

Thickener Ratio,% Abbreviation

Sodium alginate 100 SAModified xanthan 100 MXGSA:MXG 90:10 SAMXG9SA:MXG 80:20 SAMXG8SA:MXG 70:30 SAMXG7SA:MXG 60:40 SAMXG6SA:MXG 50:50 SAMXG5SA:MXG 40:60 SAMXG4SA:MXG 30:70 SAMXG3SA:MXG 20:80 SAMXG2SA:MXG 10:90 SAMXG1

Table 2 Printing paste recipes

Ingredients Amount, g

Reactive dye 10Urea 50Reservehao S 10Sodium bicarbonate 10Stock paste 700Water 220Total 1000

Wang et al. Rheological studies and application of mixed printing pastes

274 © 2014 The Authors. Coloration Technology © 2014 Society of Dyers and Colourists, Color. Technol., 130, 273–279

The penetration of samples was determined as follows[12]:

Penetration ð%Þ ¼ ðK=SÞb0:5½ðK=SÞf þ ðK=SÞb�

� 100 ð2Þ

where (K/S)f and (K/S)b are the K/S values of the face andback of the printed square samples respectively.

The colour unevenness for 13 K/S values of the face wascalculated as follows [13]:

Colour unevenness ð%Þ ¼

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi112

P13i¼1

K=Si � �K=�S� �2s

�K=�S� 100 ð3Þ

where K/Si represents the K/S values of the face of theprinted square samples and �K=�S is the average K/S value.

The width of the line and the height of the wedge designwere measured by electron microscope (Nikon, Japan). Theaverage width and line unevenness for 30 widths of theprinting lines were obtained as follows [13]:

Line unevenness ð%Þ ¼

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi129

P30i¼1

Di � �Dð Þ2s

�D� 100 ð4Þ

where Di is the line width and �D is the average width of theline.

The sharpness of the wedge design was the ratio of thelength after printing to the actual length, and the fineness ofthe wedge design was calculated by:

Fineness ð%Þ ¼ 100�hl � 0:020:02

� 100 ð5Þ

where l and h are the length and height of the wedge designafter printing respectively.

Results and DiscussionRheological properties of printing pastes using mixedthickenersThe rheological properties of printing pastes were investi-gated under steady shear and dynamic oscillatory condi-tions. The abbreviations of the mixed stock pastes in theprinting pastes are listed in Table 1, and these were alsoused to distinguish the different printing pastes.

Steady shear propertiesThe results in Figure 1 indicate that the printing pastesusing SA and MXG as mixed thickeners exhibit non-Newtonian pseudoplastic behaviour. Flow-curve experi-mental data correlate well with the power-law model in theshear-thinning region (shear rates 10–1000 per second).Table 3 presents the flow parameters for fitting Eqn (6) tothe experimental data:

0.1

App

aren

t vis

cosi

ty, P

a s

0.1 1 10

Shear rate, s–1

100 1000

1

10

100

1000SASAMXG9SAMXG8SAMXG7SAMXG6SAMXG5SAMXG4SAMXG3SAMXG2SAMXG1MXG

Figure 1 Flow curves of printing pastes using sodium alginate and modified xanthan as mixed thickeners at 25 °C

Table 3 Flow parameters of printing pastes using sodium alginateand modified xanthan as mixed thickeners at 25 °C

Printing pastes g0.1a, Pa s K, Pa sn n R2 REb

SA 17.098 27.532 0.448 0.99179 0.167SAMXG9 10.872 14.876 0.480 0.99183 0.0973SAMXG8 14.582 14.860 0.457 0.99404 0.0800SAMXG7 22.915 15.420 0.427 0.99581 0.0650SAMXG6 36.279 16.779 0.385 0.99790 0.0456SAMXG5 58.748 19.287 0.335 0.99906 0.0313SAMXG4 90.709 22.888 0.286 0.99971 0.0185SAMXG3 159.205 24.827 0.241 0.99994 0.00850SAMXG2 201.702 28.180 0.195 1.00000 0.00118SAMXG1 240.719 33.676 0.149 0.99999 0.00336MXG 248.263 34.284 0.117 0.99997 0.00600

a g0.1 is the apparent viscosity at a shear rate of 0.1 s�1.

b RE: relative deviation error =Pni¼1

xexp;i � xcalc;i� �

=xexp;i��

=n



1

G',

Pa

0.1 1 10

γ100 1000

10

100

SASAMXG9SAMXG8SAMXG7SAMXG6SAMXG5SAMXG4SAMXG3SAMXG2SAMXG1MXG

, %

Figure 2 Storage modulus, G0, as a function of strain, c, for printing pastes using sodium alginate and modified xanthan as mixed thickenersat 25 °C.

1

G",

Pa

0.1 1 10

γ

100 1000

10

100


, %

Figure 3 Loss modulus, G″, as a function of strain, c, for printing pastes using sodium alginate and modified xanthan as mixed thickeners at25 °C.

g ¼ K _cn�1 ð6Þ

where K is the consistency coefficient (Pa sn) and n is theflow index.

The flow properties of the mixed printing pastes areconnected with the addition of MXG to SA, as shown inTable 3. With a small addition of MXG to SA, the mixedprinting pastes SAMXG9 and SAMXG8 show a lowerapparent viscosity at low shear rate (g0.1) and a larger flowindex (n) in comparison with SA printing paste, implyingtheir better flowability. As the proportion of MXG risescontinually, g0.1 of the mixed printing pastes increases over

that of the SA printing paste, and n decreases near to 0.1.This illustrates that the mixed printing pastes exhibit agreater apparent viscosity at low shear rate and a morepronouced shear sensitivity with an increase in MXG.

Viscoelastic propertiesThe shear-thinning feature of the printing paste is insuffi-cient to demonstrate the excellent printing performance itachieves. However, the viscoelasticity of the printing pasteshould also be considered. The elasticity of the printingpaste has an effect on its ability to pass through the screenopenings onto the fabric and its penetrability into the fibres.



Figures 2–4 show the relationships between the visco-elastic parameters and the strain. The viscoelastic param-eters within the linear viscoelastic region are displayed inTable 4. The results show that the viscoelasticity of themixed printing pastes is influenced by the proportions ofSA and MXG. As can be seen in Figure 2 and from the dataon the storage modulus (G0) in Table 4, with a smalladdition of MXG to SA, the mixed printing pastes SAMXG9and SAMXG8 have a lower G0 in comparison with SAprinting paste, indicating a decrease in elastic behaviour. Asthe proportion of MXG rises continually, G0 of the mixedprinting pastes surpasses that of the SA printing paste,implying enhancement of elasticity with a large addition ofMXG.

Table 4 Viscoelastic parameters of printing pastes using sodiumalginate and modified xanthan as mixed thickeners

Printing pastes G0, Pa G″, Pa d, deg

SA 20.03 38.66 62.77SAMXG9 16.72 31.02 61.54SAMXG8 18.90 29.73 57.72SAMXG7 22.88 29.82 52.13SAMXG6 27.41 28.63 46.04SAMXG5 37.20 29.75 39.16SAMXG4 48.33 29.86 31.78SAMXG3 59.52 29.01 25.91SAMXG2 72.69 28.88 21.98SAMXG1 87.58 29.93 18.82MXG 80.94 26.39 18.09

00.1 1 10

γ

100 1000 10 000

15

30

45

60

75

90


, %

δ , d

eg

Figure 4 Loss angle, d, as a function of strain, c, for printing pastes using sodium alginate and modified xanthan as mixed thickenersat 25 °C.

60

65

70

75

80

85

90

SA

SAMXG9

SAMXG8

SAMXG7

SAMXG6

SAMXG5

SAMXG4

SAMXG3

SAMXG2

SAMXG1MXG

Pas

te a

dd-o

n, g

/m2

Figure 5 Screenability of printing pastes using sodium alginate and modified xanthan as mixed thickeners



The loss angle d (tan d = G″/G0) is used to characterise therelative elasticity and viscosity values of the printing paste.The greater the value of d, the greater is the viscousbehaviour exhibited by the printing paste. Loss angled = 45° is the critical point of viscoelasticity: whend > 45°, the paste mainly exhibits liquid-like viscousbehaviour; when d < 45°, the paste exhibits clear solid-likeelastic behaviour. From Figure 4 and the data for d inTable 4 it can be seen that d of SA printing paste is greaterthan 45° under strains of 0.1–1000%, with pronouncedliquid-like viscous behaviour. MXG printing paste experi-ences a transition from elasticity to viscosity and exhibitsviscous behaviour only under higher strains. Mixed print-ing pastes with SA and MXG ratios greater than 60:40primarily exhibit viscous behaviour in the whole strainrange, like SA printing paste, and the liquid-like featuresbecome increasingly weak with the addition of MXG. Onthe other hand, mixed printing pastes with SA and MXGratios less than 60:40 exhibit viscoelastic behaviour, like

MXG printing paste, and the solid-like features becomeincreasingly marked with the addition of MXG.

Printing performance of printing pastes usingSA and MXG as mixed thickenersPrinting performance for large patternsThe printing paste is forced through the screen openingsunder high shear rates. Simultaneously, elasticity alsoaffects the flow behaviour of the printing paste, hinderingpassage of the paste through the screen openings underforce. The printing paste add-on, colour yield (K/S), andcolour unevenness were used to evaluate the screenability,colour depth, and levelness for the printing pastes.Figures 5 and 6 show that MXG printing paste exhibitspoorer screenability, colour yield, and penetration than SAprinting paste and the mixed printing paste, which may beattributed to the more pronounced shear-thinning featuresproducing a lower apparent viscosity under high shear andeasier flow through the screen openings.

0

2

4

6

8

10

0

20

40

60

80

100

SA

SAMXG9

SAMXG8

SAMXG7

SAMXG6

SAMXG5

SAMXG4

SAMXG3

SAMXG2

SAMXG1MXG

K/S

Penetration, colour unevenness, %

K/S

Penetration

Colour unevenness

Figure 6 Colour yield, penetration, and colour unevenness of printing pastes using sodium alginate and modified xanthan as mixedthickeners.

Table 5 Fine-pattern printing performance of printing pastes using sodium alginate and modified xanthan as mixed thickeners

Printing pastes

Thick line Thin line Wedge design

Width, lm Unevenness, % Width, lm Unevenness, % Sharpness, % Fineness, %

SA 1058 2.61 322 14.40 96 70.64SAMXG9 1112 4.19 375 17.40 96 71.04SAMXG8 1074 4.90 377 14.32 96 74.17SAMXG7 1072 3.53 354 17.27 96 71.88SAMXG6 1049 5.85 372 16.16 96 73.70SAMXG5 1032 3.48 344 14.01 96 72.86SAMXG4 1037 4.39 333 13.21 96 76.09SAMXG3 969 8.01 324 11.31 96 74.95SAMXG2 946 7.72 302 16.42 96 75.16SAMXG1 960 8.28 301 17.19 96 76.51MXG 1025 7.19 376 7.38 96 71.35



Moreover, compared with SA printing paste, the mixedprinting pastes with SA and MXG ratios greater than 60:40have a larger paste add-on and K/S, while the mixed pasteswith SA and MXG ratios less than 60:40 have lower values.According to the results of dynamic strain sweep tests, themixed printing pastes with more SA had greater viscousbehaviour, and the mixed printing pastes with more MXGhad greater elastic behaviour. This implies that greaterelasticity might adversely affect the ability of the paste to beforced through the screen openings and deposited on thefabric.

In particular, mixed printing paste SAMXG8 performedbest in the printing of large patterns when the ratio of SA toMXG was 80:20.

Printing performance for fine patternsThe paste should have higher apparent viscosity at lowshear rates. In addition, elasticity dominates the possiblerecovery of the paste immediately after its application [14].Line width, line unevenness, wedge sharpness, and fine-ness were used together to assess the outline sharpness ofthe printing paste. A line width nearer to the original linewidth on the screen is desirable. The values of thick-lineunevenness and thin-line unevenness should be within 10and 15%. If not, the phenomena of warp-lacking, weft-lacking, and thin stem will appear. Moreover, higher valuesof wedge sharpness and fineness are expected.

As shown in Table 5, mixed printing pastes with SA andMXG ratios less than 40:60 are more desirable for fine-pattern printing. This may be attributed to the elasticity ofthe printing paste, which is beneficial for the recovery of thepaste to ensure favourable outline sharpness. In particular,mixed printing paste SAMXG2 performed best in theprinting of fine patterns when the ratio of SA to MXG was20:80.

ConclusionsPrinting pastes using SA and MXG as mixed thickenersexhibit different rheological properties. Steady shear resultssuggest that, with a small addition of MXG to SA, theflowability of the mixed printing pastes is better than withSA alone. Subsequently, with the continual addition ofMXG to SA, the apparent viscosity at low shear ratesincreases gradually, and the mixed printing pastes show

increasingly pronounced shear-thinning features. More-over, the results of dynamic strain sweep tests show thatmixed printing pastes with more sodium alginate mainlyshow viscous behaviour under strain, and the liquid-likefeatures become increasingly weak with the addition ofMXG. On the other hand, mixed printing pastes with moremodified xanthan mainly exhibit elastic behaviourwithin the linear viscoelastic region, and the solid-likefeatures become increasingly marked with the addition ofMXG.

Mixtures of SA and MXG can be used as thickeners in thereactive printing of cotton, affording prints of excellentcolour yield, levelness, and outline sharpness. In particular,mixed printing paste performs best for large patterns whenthe ratio of SA to MXG is 80:20, and best for fine patternswhen the ratio is 20:80.

AcknowledgementsThe authors gratefully acknowledge support from the KeyLaboratory of Science and Technology of Eco-Textiles,Ministry of Education, Donghua University, and financialsupport from the Innovation Foundation for PhD Candi-dates of Donghua University (CUSF-DH-D-2013046).

References1. R Fijin, M Basile, S �Sostar-Turk, E �Zagar, M �Zigon and R

Lapasin, Carbohydr. Polym., 76 (2009) 8.2. R Lapasin, S Pricl, M Graziosi and G Molteni, Ind. Eng. Chem.

Res., 27 (1988) 1802.3. A V Baranov, N S Dymnikova and A V ll’in, Fiber Chem., 34

(2002) 38.4. R Fijan, S �Sostar-Turk and R Lapasin, Carbohydr. Polym., 68

(2007) 708.5. N S E Ahmed, Y A Youssef, R M El-Shishtawy and A AMousa,

Color. Technol., 122 (2006) 324.6. E S Abdel-Halim, H E Emam and M H El-Rafie, Carbohydr.

Polym., 74 (2008) 938.7. E P A Kumbasar and M Bide, Dyes Pigm., 47 (2000) 189.8. S �Sostar-Turk and R Schneider, Dyes Pigm., 47 (2000) 269.9. M M Rekaby, I A El-Thalouth, A A H Rahman and S A E

El-Khabery, BioResour., 5 (2010) 1517.10. E E Fitzgerald, AATCC Meet. New Orleans, LA (1983).11. L L Wang, F R Zhu, Q Yang and D N Lu, Cellulose, 20 (2013)

2125.12. M Bide and D C O’Hara, Text. Chem. Color., 26 (1994) 13.13. L L Wang, F R Zhu and D N Lu, Text. Res. J., 83 (2013) 1873.14. R Fijan, M Basile, R Lapasin and S �Sostar-Turk, Carbohydr.

Polym., 78 (2009) 25.



rheological studies of mixed printing pastes from sodium alginate and modified xanthan and their...

Documents