Pore and Crosslinking Structures of Cotton CelluloseCrosslinked with DMDHEU-Maleic Acid

Chang Wang,1 Jui-Chin Chen,2 Wei-Hua Yao,2 Cheng-Chi Chen3

1Department of Civil Engineering, Nanya Institute of Technology, Jhongli, Taoyuan, Taiwan, R. O. C.2Department of Materials and Textiles, Oriental Institute of Technology, Pan-Chiao, Taiwan, R. O. C.3Department of Chemical Engineering, Nanya Institute of Technology, Jhongli, Taoyuan, Taiwan, R. O. C.

Received 31 March 2004; accepted 6 July 2004DOI 10.1002/app.21169Published online in Wiley InterScience (www.interscience.wiley.com).

ABSTRACT: Two dicarboxylic acids (maleic acid and tar-taric acid) were used in conjunction with DMDHEU as thecrosslinking agents to treat cotton fabric samples. Thetreated fabrics then were dyed with direct red 81. The resultsshow that the values of the dye absorption, equilibriumabsorption, rate constants, and the pore index of structuraldiffusion resistance constant for the various crosslinkingagents are ranked as DMDHEU-tartaric acid � DMDHEU-maleic acid � DMDHEU alone at the same dyeing temper-ature. The activation energies for the three crosslinked fab-rics are in the rank of DMDHEU � DMDHEU-maleic acid

� DMDHEU-tartaric acid. The CL length values for thevarious crosslinking agent systems are in the series of DM-DHEU-tartaric acid � DMDHEU-maleic acid � DMDHEUalone for a given number of CL/AGU. The values of thepore index of structural diffusion resistance constant anddyeing rate constant are increased with the increase of CLlength. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 143–148,2005

Key words: crosslinking; activation energy; catalysts; UV-vis spectroscopy

INTRODUCTION

Some previous studies have shown that the carboxylicacid group of a polycarboxylic acid1–3 or acrylic acid4

can react with cellulose to improve the crease recoveryproperty of the finished fabrics. Our recent study5,6

showed that the carboxylic acid of the �-amino acidsused as coreactants of crosslinking reagents can reactwith the hydroxyl group of the N-methylol crosslink-ing agent (DMDHEU) to affect the physical propertiesof the treated fabrics. Such an additional reactionshould affect the crosslinking structures and porestructures of the treated fabrics.

In this study, we are interested in the effects of thevinyl group of the dicarboxylic acid that was joinedwith the N-methylol compound together to treat thecotton fabric samples on the crosslinking structuresand pore structures of the treated fabrics. Dimethyl-oldihydroxyethyleneurea (DMDHEU) and two dicar-boxylic acid compounds (one is vinyl group containedmaleic acid, and the other is nonvinyl group containedtartaric acid) were used as the crosslinking agent andcoreactants, respectively. Here, we expect the reactionbetween the vinyl group of dicarboxylic acid and thecellulose and/or DMDHEU under a pad-dry-cure

process to change the pore structures and thecrosslinking structures of those finished cotton fabrics.

Also, C I Direct Red 81 having a molecular weight of767 g/mol will be used to study the pore structures ofthe DMDHEU-dicarboxylic acids treated fabrics. Westudied the pore structure by using the following dif-fusion equation7,8:

a � ae �1 � exp(�kC0t�]n (1)

� ae�1 � exp(�k�t�]n,

where a is the absorption of the dye on cotton in timet, ae is the equilibrium absorption at t 3 �, k is thespecific rate constant, k’ is the rate constant, C0 is theconcentration of cotton in a finite bath, and n is thestructural diffusion resistance constant. The higher thevalue of n, the larger the pore size of the treated fabric.

EXPERIMENTAL

In this study, we used desized, scoured, and bleachedcotton fabric 32s � 32s end (60) and picks (60).

The crosslinking agent used was DMDHEU (dim-ethyloldihydroxyethyleneurea).

Correspondence to: C.-C. Chen (c1133@nanya.edu.tw).

Journal of Applied Polymer Science, Vol. 97, 143–148 (2005)© 2005 Wiley Periodicals, Inc.

Di-carboxylic acids were maleic acid and tartaric acid.

Ammonium sulfate was reagent grade, as were theother chemicals.

The cotton fabric samples were padded twice to about90% wet pickup with freshly prepared (2, 4, 6, and 8w/w) aqueous solutions of the mixtures of DMDHEU/dicarboxylic acids (weight ratio of 3 : 1) and the ammo-nium sulfate catalyst. The catalyst concentration was 0.10times the crosslinking agent solid concentration. Paddedfabrics were dried at 80°C for 5 min, cured at 160°C for3 min, soaped, washed, and dried.

Formaldehyde and nitrogen determinations of thetreated fabrics were made using the chromotropic ac-id9 and Kjeldahl methods, respectively.

The crosslinked cotton fabrics (4% w/w) were cutinto pieces approximately 0.5 cm2 and dyed with C. I.Direct Red 81 (dye: 0.05 g/L, NaCl: 10g/L) at a 60 : 1liquor ratio. Dyeing temperatures were 50, 60, and70°C and were kept constant in a water bath. The dyesolution and cotton fabric were stirred slowly using amagnetic stirrer. After selected time intervals, the dyeconcentration in the dye solution was measured di-rectly on a Hitachi U-3010 (Hitachi Ltd., Tokyo, Japan)spectrophotometer.

RESULTS AND DISCUSSION

Pore structures

Figures 1(a), (b), and (c) show the rates of dye absorp-tion that were dyed with C I Direct Red 81 under 50

� 70°C for the crosslinked cotton with DMDHEU,DMDHEU-maleic acid, and DMDHEU-tartaric acid,respectively. From those figures, we can find that thetype of the dye absorptions for DMDHEU alone andDMDHEU-dicarboxylic acids are the same. However,from the overall dyeing time duration, we can findthat the values of the dye absorption for the variouscrosslinking agents are in the rank of DMDHEU-tar-taric acid � DMDHEU-maleic acid � DMDHEU aloneat a same dyeing temperature. The higher dye absorp-tion values for DMDHEU-dicarboxylic acids may becaused by the different pore structures of thecrosslinked fabrics. Our previous study suggested thatthe crosslinking reaction for DMDHEU-dicarboxylicacids is different from that for DMDHEU.10 This dif-ference may cause the pore structures of the treatedfabrics to be different from each other.

Figures 2(a), (b), and (c), respectively, for the rates ofdye absorption of the crosslinked cotton with DMDHEUalone, DMDHEU-maleic acid, and DMDHEU-tartaricacid show the linear relationships between the logarith-mic values of the dye (C I Direct Red 81) absorption (loga) under the different temperatures and the logarithmicvalues of the time intervals of dyeing (log t) over theinitial dyeing time duration. From those results of linearrelationships, we believe that the use of the diffusionkinetic equation reported by Chrastil et al.7,8 to study theequilibrium absorption (ae), rate constant (k’), and struc-tural diffusion resistance constant (n, the index of thepore structure) of the various treated cotton fabrics issuitable. Several data obtained from the dyeing kineticsof eq. (1) are all listed in Table I.

Table I shows that the equilibrium absorption val-ues of the direct red dye for the DMDHEU-dicarboxy-lic acids crosslinked fabrics are higher than those for

Figure 1 The rates of dye (C I Direct Red 81) adsorption for (a) DMDHEU, (b) DMDHEU-maleic acid, and (c) DMDHEU-tartaric acid crosslinked fabrics (▫ - 70°C, ‚ - 60°C , E - 50°C).

144 WANG ET AL.

DMDHEU at a given temperature. This phenomenonmay be caused by the condensation reaction betweenDMDHEU and dicarboxylic acids being significantlyhigher than that between DMDHEU and DMDHEU toform a loose crosslink. Our previous study10 revealedthe reaction between DMDHEU and dicarboxylic ac-ids. Additionally, the equilibrium absorption value forDMDHEU-tartaric acid crosslinked cellulose is higherthan that for DMDHEU-maleic acid. This result maybe caused by: (1) the bonding between the two dicar-boxylic acids and direct dye, and (2) the crosslinkingstructures of the treated fabrics for the two dicarboxy-lic acids are different from each other.

For all cases, the rate constants are increased withthe rise of dyeing temperature. Rate constants for thethree crosslinked fabrics that were dyed with the samedirect dye and at the same dyeing temperature showthe rank of DMDHEU-tartaric acid � DMDHEU-ma-leic acid � DMDHEU. Those results may be caused bythe pore structure and/or bonding dependence of thedye absorption.11,12

Structural diffusion resistance constants are onlyslightly changed with increasing the dyeing tempera-ture (Table I). Table I also shows that the structuraldiffusion resistance constants for the three crosslinkedfabrics reveal the following rank: DMDHEU-tartaricacid � DMDHEU-maleic acid � DMDHEU. Severalreports13–15 revealed that the crosslinks decrease thestructural diffusion resistance constant. Those resultsagree with the results of the expansion patterns ofSEM in another report,10 and indicate that the porestructure of the crosslinked cotton is changed with theaddition of different dicarboxylic acids to DMDHEUand the functional groups of dicarboxylic acids. Wereported that the coreactant dicarboxylic acids will

react with crosslinking agent (DMDHEU)10 to create aloose crosslink that is a larger pore structure.

Arrhenius plots (three crosslinked fabrics) for the CI Direct Red 81 are shown in Figure 3. The activationenergies (‚E*) from the figures are also listed in TableI. The activation energies for the three crosslinkedfabrics are ranked as follows: DMDHEU � DMD-HEU-maleic acid � DMDHEU-tartaric acid. Thisranking also agrees with the pore structure of thecrosslinked fabrics that is the structural diffusion re-sistance constant. Crosslinking length is a powerfulfactor for the estimation of pore size.

Degree of crosslinking

The nitrogen and formaldehyde contents and numberand length of crosslinks for the cotton fabric cross-linked with varying resin concentrations for DMD-HEU alone, DMDHEU-maleic acid, and DMDHEU-tartaric acid are presented in Table II. As expected, thevalues of nitrogen and formaldehyde contents andmole/AGU of nitrogen and formaldehyde show agradual increase with increasing resin content in thebath in all cases. The nitrogen and formaldehyde con-tents of the finished samples for DMDHEU-dicarboxy-lic acids are significantly lower than those for DMD-HEU alone for a given resin concentration in pad bathand are shown in Figures 4(a) and (b), respectively.Those results are mainly caused by the use of dicar-boxylic acid crosslinking agents, which have no nitro-gen and formaldehyde contained in molecules. On theother hand, the nitrogen and formaldehyde contentsof the finished samples for DMDHEU-maleic acid areslightly lower than those for DMDHEU-tartaric acid ata given resin concentration. Clearly, the difference

Figure 2 Plots of log a versus log t for (a) DMDHEU, (b) DMDHEU-maleic acid, and (c) DMDHEU-tartaric acid crosslinkedfabrics (dyed with C I Direct Red 81) (▫ - 70°C, ‚ - 60°C , E - 50°C).

COTTON CELLULOSE CROSSLINKED WITH DMDHEU-MALEIC ACID 145

between maleic acid and tartaric acid would be causedby the slightly higher reactivity of tartaric acid. Ourprevious study10 suggested that maleic acid could behydrolyzed to react with DMDHEU as follows.

The tartaric acid molecule that has two hydroxylgroups may have higher reactivity than the hydroxy-succinic acid that has a single hydroxyl group. At thesame time, this additional hydroxyl group for tartaricacid may also increase the affinity to have highervalues of direct dye equilibrium absorption (ae) andrate constant (k’) shown in Table I.

The number of crosslinks per anhydroglucose (CL/AGU) and length of crosslinks (CL length) of thefinished fabrics listed in Table II, obtained using themethods of Frick et al.,16,17 indicate that both increaseas the concentration of the resin in the bath increasesfor all crosslinking agents. The curvilinear relationshipbetween the length of crosslinks and CL/AGU of thetreated fabric samples for all the crosslinking agents

TA

BL

EI

Th

eV

alu

esof

Eq

uil

ibri

um

Ad

sorp

tion

,Rat

eC

onst

ant

(th

ed

ata

wer

eob

tain

edfr

oma

dye

ing

tim

ein

terv

alof

10m

inu

tes)

,Str

uct

ura

lD

iffu

sion

Res

ista

nce

Con

stan

t,an

dA

ctiv

atio

nE

ner

gyof

the

Var

iou

sFa

bri

csT

reat

edw

ith

DM

DH

EU

,DM

DH

EU

-Mal

eic

Aci

d,a

nd

DM

DH

EU

-Tar

atri

cA

cid

,Res

pec

tive

ly

Dir

ect

dye

CI

no.

Mol

ecul

arw

eigh

t(g

/m

ol)

Dye

ing

tem

p.(°

C)

DM

DH

EU

DM

DH

EU

-mal

eic

acid

DM

DH

EU

-tar

tari

cac

id

a e�

10�

3

Mn

k��

10�

3

min

�1

E

*(K

cal/

mol

)a e

�10

�3

Mn

k��

10�

3

min

�1

E

*(K

cal/

mol

)a e

�10

�3

Mn

k��

10�

3

min

�1

E

*(K

cal/

mol

)

502.

942

0.27

63.

157

3.72

40.

356

5.00

23.

890

0.36

85.

623

8167

660

2.86

70.

285

5.47

413

.405

3.70

00.

672

8.62

111

.004

3.82

90.

376

8.98

210

.012

702.

819

0.30

010

.691

3.62

30.

376

13.6

063.

786

0.38

513

.983

Figure 3 Arrenhius plots of the E DMDHEU, ‚ DMD-HEU-maleic acid, and ▫ DMDHEU-tartaric acid crosslinkedfabrics dyed with C I Direct Red 81.

146 WANG ET AL.

(Fig. 5) is similar to that reported in our previousstudy.18 For a given number of CL/AGU, the CLlength values for the various crosslinking agent sys-tems are in the rank of DMDHEU-tartaric acid � DM-DHEU-maleic acid � DMDHEU alone. The longer CLlength for DMDHEU-dicarboxylic acids may becaused by the higher aggregation of the crosslinkingagents in pad bath by Scheme 4 to enlarge the poresize.

Figure 6 reveals the relationships between the val-ues of n (structural diffusion resistance constant) andk’ (rate constant) and the CL length of the varioustreated fabrics, which shows that the values of n and k’are increased with the increase of CL length. Thoseresults clearly show that the pore sizes are dependenton the length of crosslink.

CONCLUSION

In this study, we used two dicarboxylic acids (maleicacid and tartaric acid) to join with DMDHEU as the

TABLE IIStructural Characteristics of Cotton Cellulose Fabrics Treated with DMDHEU Alone, DMDHEU-Maleic Acid, and

DMDHEU-Tartaric Acid

Di-carboxylicacids

Di-carboxylic acidsconc., (%)

DMDHEUconc., (%)

Nitrogen(%)

Formaldehyde(%)

Moles/AGU CL/AGU(�102)

CLlengthNitrogen Formaldehyde

2 0.180 0.326 0.0210 0.0177 0.724 1.4484 0.360 0.635 0.0422 0.0348 1.365 1.547

- 6 0.513 0.890 0.0605 0.0490 1.875 1.6148 0.706 1.118 0.0839 0.0620 2.006 2.091

Maleic acid 1.5/3 4.5/3 0.152 0.267 0.0177 0.0145 0.567 1.5633.0/3 9.0/3 0.275 0.466 0.0323 0.0255 0.938 1.7194.5/3 13.5/3 0.403 0.643 0.0476 0.0354 1.164 2.0446.0/3 18.0/3 0.535 0.818 0.0636 0.0454 1.357 2.341

Tartaric acid 1.5/3 4.5/3 0.148 0.257 0.0173 0.0140 0.536 1.6113.0/3 9.0/3 0.259 0.437 0.0304 0.0239 0.873 1.7394.5/3 13.5/3 0.398 0.634 0.0470 0.0349 1.143 2.0546.0/3 18.0/3 0.527 0.803 0.0626 0.0445 1.321 2.368

Figure 4 The nitrogen and formaldehyde contents of thecrosslinked fabrics for the different resin concentrations.DMDHEU: nitrogen content (E), formaldehyde (F); DMD-HEU-maleic acid: nitrogen content (‚), formaldehyde (Œ);and DMDHEU-tartaric acid: nitrogen content (▫), formalde-hyde (f).

Figure 5 Plots of CL length versus CL/AGU for DMDHEU(E), DMDHEU-maleic acid (‚), and DMDHEU-tartaric acid(▫) crosslinked fabrics, respectively.

COTTON CELLULOSE CROSSLINKED WITH DMDHEU-MALEIC ACID 147

crosslinking agents to treat cotton fabric samples. Thetreated fabrics then were dyed with C I Direct Red 81to study the crosslinking structures and pore struc-tures. The values of the dye absorption, equilibriumabsorption, rate constants, and structural diffusion re-sistance constant for the various crosslinking agentsare in the rank of DMDHEU-tartaric acid � DMD-HEU-maleic acid � DMDHEU alone at the same dye-ing temperature. The activation energies for the threecrosslinked fabrics are ranked as follows: DMDHEU� DMDHEU-maleic acid � DMDHEU-tartaric acid.For a given number of CL/AGU, the CL length values

for the various crosslinking agent systems are in therank of DMDHEU-tartaric acid � DMDHEU-maleicacid � DMDHEU alone. The relationships betweenthe values of n (structural diffusion resistance con-stant) and k’ (rate constant) and the CL length of thevarious treated fabrics show that the values of n and k’are increased with the increase of CL length.

References

1. Lewis, D. M.; Voncina, B. J Appl Polym Sci 1997, 66, 171.2. Kotte, B. A. Textile Chem Color 1990, 22, 63.3. Voncina, B. Fibres & Textiles in Eastern Europe 1996, January/

March, 69.4. Chen, J. C.; Yao, W. H.; Chen, C. H.; Chen, C. C. J Appl Polym

Sci 2001, 82, 1580.5. Wang, T. J.; Chen, J. C.; Chen, C. C. Textile Res J 2003, 73, 797.6. Shih, M. K.; Chen, J. C.; Yao, W. H.; Wang, C.; Chen, C. C.

Textile Res J, to appear.7. Chrastil, J. Textile Res J 1990, 60, 413.8. Chrastil, J.; Reinhardt, R. M.; Blanchard, E. J. Textile Res J 1990,

60, 441.9. Meyer, U.; Muller, K.; Zollinger, H. Textile Res J 1976, 46, 756.

10. Hsiung, H. H.; Huang, H. Y.; Wang, Y. H.; Wang, C.;. Chen, J. C;Chen, C. C. J Appl Polym Sci, to appear.

11. Bertoniere, N. R.; King, W. D.; Rowland, S. P. Textile Res J 1981,51, 242.

12. Roland, S. P.; Bertoniere, N. R.; King, W. D. Textile Res J 1984,54, 318.

13. Chen, W. Y.; Liaw, M. Y.; Lan, G. W.; Chen, C. C. Textile Res J1993, 63, 535.

14. Hsiung, H. H.; Chen, C. C. Textile Res J 1997, 67, 77.15. Liang, T. Y.; Hwang, J. Y.; Ju, D. S.; Chen, C. C. Textile Res J

1992, 62, 547.16. Frick, J. G.; Kottes Andrew, B. A.; Reid, J. D. Textile Res J 1959,

29, 314.17. Frick, J. G.; Kottes Andrew, B. A.; Reid, J. D. Textile Res J 1960,

30, 495.18. Chen, C. C. Textile Res J 1989, 59, 464.

Figure 6 The relationships between CL length and the rateconstant (k’, ‚) and structural diffusion resistance constant(n, E) for the various crosslinked fabrics.

148 WANG ET AL.