Ind ian Journal of Fibre & Tex tile Research Vol. 3 1, September 2006, pp. 363-368

Ionic crosslinking of cellulosea

M Bilgen, P Hauser h & B Smith

Department of Tex til e Engineering, Chemi stry and Science, North Caro lina State Uni versity, Raleigh, North Carolina 27695, USA

Received 3 May 2005; accepted 13 l illie 2005

Cellulosic fab ric has been treated with anionic (chloroacetatic ac id) and cati onic (3-ehloro-2 hydroxypropyl trimethylammonium chloride) materi als followed by the application of a polyeation (cationi zed glycerin) and a po lyallioll (1,2,3,4-butanetetracarboxy li c ac id) to improve the fab ric durab le press performance. It is observed that the ionic crosslinks stabili ze the cellulose using ionic materials which do not release hazardous reactive chemi ca ls but at the same time provide improved wrinkle recovery angle as well as complete st rength retention in trea ted goods. The polyelectro lyte, the ionic content of the fab rics, and va ri ous fea tures of the application procedure have been va ri ed to optimi ze the results alld to deve lop all in-dep th funda mental physical and chemica l unders tand ing of the stabili zation mechani sm.

Keywords: Cellulose, Ioni c erosslin king, Wrin kle recovery

IPC Code: Int. CI8 00683/00

1 Introduction The tex til e market has shown an interes t in easy

care, wrinkle-res is tant cellulos ic fabrics over the years. Untreated cellulose has poor recovery, because cotton is stabilized by hydrogen bo nds within and between ce llulose chains. M oisture between the polymer chains can invade the cellulose s tructure and temporaril y re lease the s tabili z ing hydrogen bo nds which experience frequent breaking and reforming when extended . The newly formed hyd rogen bonds tend to ho ld cellulose chain segments in new positio ns when externa l stress is re leased . I Preventing w rinkle retentio n of cellulose can be accomplished by the cross linking of po lymer chains, thus making intermolecul ar bonds between chain s, so that wate r cannot re lease. In a typica l durabl e press (DP) treatment , some hyd rogen bo nds a re replaced with covalent bo nds be tween the fini shing agent and the fibre e lements . As the covalent bo nds are much stronger than the hydrogen bonds, they can res ist higher ex terna l s tress and di sruptio n by wate r. Hence, treated cellul ose has a hi gher initi a l modulus and better e las ti c recovery. After the ex te rn al force is released , the energy sto red in the stra ined covalent bonds prov ides the driving force to return chain segments back to the ir orig inal pos iti o ns.

a Prese nted at the 841h Texti le Institute World Confere nce, March 2005. Raleigh, North Carolina, USA . h To whom all the correspondence shou ld be add ressed. E-mai l: peter_hauser@nesu.edu

Formaldehyde-based ce llul ose cross linking was a very important textile chemical breakth ro ugh of the 1930s and it is still the basis fo r a vast array of modern f ini shed cellulose produc ts today. N-methylo l cross linkers have the bi gges t use in durabl e press fini shing . They g ive fabrics crease res is tance, shrinkage contro l, anti curl , and durabl e press , but they a lso impart strength loss and re lease fo rmaldehyde, a known human carc inogen. 2 Today ' s tex tile industry has, fo r a lo ng time, been searching fo r durable press f ini shes that can g ive same resul ts as fo rmaldehyde-based fi ni shes, but cause less strength loss and no fo rmaldehyde re lease. For example, po lycarboxy lic ac ids and c itric ac id have been used with varying degree o f success. 3.4 The perfo rmance of cross linkers can be measured by dry and wet wri nk le recovery ang le (WRA). Dry WR A is important ("or o ute rwear c lothing to he lp res ist dry w rinkling d uring wearing and wet WRA is more impo rtant for beddi ng which is a lmos t never iro ned and mu st resist w rinkling during laundering. [n our earli er work, the simultaneous enhancement of both wet and dry W RA has been studi ed.5.6 In add iti on, io nic cross links lTlay have other impo rtant ad vantages , such as an timi crobi a l activity and enhanced dyeab ility. The develo pment of multiple methods of fo rming ionic cross links to g ive non-wrinkl e e ffec ts to cellulosic fab ri c has a lready been repo rted .s These incl ude (i) treatme nt of cellul ose with an ani onic material fo ll owed by reacti on with a po lycat ion, (ii ) treatment

364 INDIAN 1. FII3RE TEXT. RES. , SEPTEMBER 2006

of cellulose with a cationic material followed by application of a polyanion, and (iii) treatment of cellulose with a precondensate of an ionic reactive material and a polyelectrolyte of the opposite charge. Methods (i) and (ii), which have been used in this study, involve a pretreatment step for the cellu losic fabric, but the third method is very simi lar to commercial DP applications. Cellulose can react with several material s which impart an anionic character to it, for example chloroacetic acid (CAA), chlorosulfonic acid 5 and sodium 4-(4,6-dichloro-1,3,5-triazinylamino)-benzenesulfonate7 or a cationic character, for example 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHT AC)6, 1,1-dimethyl-3-hydroxy-azetidinium chloride and 1,1-diethyl-3-hydroxy-azetidiniull1 chloride. s Our work is based on Methods (i) and (ii) , the first method consisting of the reaction of cellulose with CAA, which produces partially carboxy methylated cellulose followed by a treatment with a polycation , for instance cationized chitosan , cationized glycerin, cationized ethylene glycol, cationized dextrose,

cationized D-cellobiose, and cationized ~cyclodextrjn.~ WRA improvements with divalent cations such as Ca++ and Mg++ have been observed. Method (i i) consists of the reaction of cotton with CHT AC to produce cationic cellulose followed by the application of a polyanion, namely polycarboxylic acids, 1,2,3,4-butanetetracarboxylic acid (BTCA), ethylenediamine tetraacetic acid, nitrilotriacetic acid, trisodium salt, monohydrate, ethylenediamine d i(o-hydroxyphenylacetic acid, oxalic acid, citric acid and mal ic acid. In this work, the treatment of cellulosic fabric with cati onic (CHTAC) and anionic (CAA) materials followed by the application of polyanion (BTCA) and polycation (cationized glycerin) has been studied. Both the methods show promising results with excellent washing durability. Polyelectrolytes are strongly bound and thus do not desorb durin o

. 5 b wash Ing.

2 Materials and Methods

2.1 Materials Scoured, desized, and bleached plain weaved

cellulosic fabric, procured from Testfabrics, Inc. and having the specifications style # 400; weight 102 g/m2 ; width 44- 45 inches; 78 ends x 76 picks ; ISO 105/F02, was used for the study. Aqueous sodium hydroxide (20% weight) solution and glycerin were obtained from Fisher Chemicals; CAA (99%) was

purchased from Aldrich Chemical Company Inc.; and sodium salt of CAA was prepared with sodiull1 carbonate.

2.2 Ionic Cellulosic Fabric Production The fabric was treated with anion ic and cationic

materials to produce ionic cellulose, giving the opportunity of forming ionic crosslinks, following the Methods (i) and (ii) , as described above. 5.s

2.2.1 Reaction of Cellulose with CAA

The optimull1 conditions for carboxymethylation of cellulose using CAA and the determination of carboxyl content were extracted from the previous work.s Cellulosic fabric samples were soaked in 20% NaOH aqueous solution for 10 min at room temperature (RT) and then squeezed to a wet pick-up (wpu) of approximately 100%. The samples were

dried at 60°C for 10 min. The alkali-treated samples were steeped in aqueous solutions of sodium salt of CAA with different concentrations (0, 0 .5, I, 1.5,2.5 M) for 5 min and then squeezed to approximately 100% wpu. After the samples were packed in

polyethylene bags and kept at 70°C for I h, they were washed several times with water (ho t and cold), acidified with 0 .2 M acetic acid and again washed with distilled water to adjust the pH at 7. Finally, the samples were dried at room temperature for 24 h.

The carboxylic acid group contents of the partially carboxy methylated fabrics were determined as per the following procedure. The fabrics were cut into small pieces and then steeped in 100 mL of 0 .5 % aqueous HCl fo r 16 h. The samples were then filtered off and washed several times with distilled water ulltil free from HCI, maintaining a pH of -7. Silver nitrate drop test was performed which showed no presence of chloride. The samples were dried at 105°C for 3 h. Accura te weight of samples (exactly 0.2 g each) was soaked in 25 mL of 0.05 N aqueous NaOH solutions at RT for 4 h. First, a blank solution (solution without any sample) was titrated with 0.05N aqueous HCI solution using phenolphthalein pH indicator. The volume of HCl solution (mL) spent was recorded fo r the blank. Each of the solutions with different carboxymethylated samples was titrated similarly . The carboxyl contents of samples were calculated using the following relationship:

Carboxymethyl contents (mmols)1l00 g=

100 X [(Vblank - Vsample) HCI X NHC1 /0 .2]

BILGEN el al.: IONIC CROSSLINKING OF CELLULOSE 365

where Vblan k is the vo lume o f HCI used for the titration of blank soluti on; V sample, the vo lume of HCI used for the titration of sample solution; and NHCJ, the normality of HCI titrant. Finally, fi ve different carboxymethyl ations, name ly 6.2, 30.2, 60.7 , 87.1 and 114 .5 mmol carboxy methyl groupsllOO g of fabric , were obtained.

Figure ] shows the production of anionic cellulose in two steps. The cross links are found to be bonded to cellulose through a very stable ether linkage.

2.2.2 Reactioll a/Cellulose with CHTAC

Cationic cellul os ic fab ric was produced by cold pad-batch treatment of fabrics with mixtures of di fferent mole ratios of CHT AC, cationizati on reagent and NaOH .6 Four di ffe rent mole ratios, such as 0.23/0.475 , 0.4610.95, 1.28/1.5 3 and 1.8312.2 respecti vely were used. Aqueous solutions of each reactant were prepared separate ly as per the fo llowing procedure. A known amount of NaOH was charged into alL glass beaker and fill ed with di stilled water to 500 mL and cooled to room te mperature. In the same way, a known amount of CHTAC solution was charged into ~lIloth er beaker and filled with distilled water to 500 mL. These two so lutions were mixed in a 1000 mL beaker, cooled to RT in ice and immediately applied onto cellulos ic fabri c us ing the fo llowing procedure. Fabrics were padded through the CHT AC/NaOH solutions, squeezed to a wpu of approximately 100% and ro lled on to a beam. The fabrics were then covered with pl as tic to prevent air interaction and kept overni ght at RT. Finally, the fabri cs were washed with a nonionic wetting agent at bo iling temperature for 10 min, centrifuged and dried at RT for 24 h. Appli cati on with the las t mole ratio ( 1. 8312.2) was repeated multiple times in order to accompli sh hi gher degree o f cationi zati on. The level of nitrogen fixed (%N) for each treatment was determined by nitrogen analys is using a Leuco CHN analyzer. Cellulos ic fabrics hav ing 4 different levels of fixed %N, such as O%(untreated) 0.1 9%, 0 .28%, 0 .46%, and 0.57% respecti ve ly were produced. The poss ible reac ti on mechani sm is shown in Fig. 2 . The cross links are found to be bonded to ce llulose through a very stable ether linkage as stated prev iously .

2.3 Reaction of CHTAC with Glycerin

The optimum condition fo r quaterni zati on o f g lycerin was ex tracted fro m the study by Hashe m et al.s CHT AC ( 11 56 g) was charged into a 2L beaker and 228 mL of 50% NaOH solution was added

Fig. I- Reactions of ce llulose with CAA, imparting an ani onic charac ter

C~ 8 Cel lJose-09 Na$ + CH2CHC H2~l~ CH3 _ CeJloose-0- CH,CHCH2N(CH3b

" 0 / CH3 6H

Fi g. 2-Reactions of cellulose with CHTAC, illlparting a cationic character

dropwise to adjust the pH of CHT AC at 10-11 fo ll owed by the addition of 46 .05 g g lycerin . T he g lycerin to CHT AC mole ratio was kept at I : 10. T he mi xture was stirred fo r 10 min at RT, transferred in to

a preheated water bath and stilTed at 60°C for another 20 h. A viscous and ye llowish mi xture was collected at the end. The resulting reac tion product was cooled off to room temperature, filtered and pH adjusted to 7 with aceti c ac id. The resulting reaction mi xture was recovered by drying; the product had a high degree of cationi zation and was eas ily redi ssolved in water at room temperature .

2.4 Traditional Durable Press Application

To compare the WRA performance of ioni c cross linked fabrics and traditional N-methylol treated cellulos ic fa bric, a res in treated sampl e was also produced. The chemi cals used in the reacti on mi xture and their concentrations were as follows: Freerez® 900 Reactant (modi fied ethylene urea res in), 250 giL; Freecat® 9 Accelerator (MgC I2 and AICI) catalyst), 62. 5g/L ; Renex® 36 (wetting agent), I giL; and Mykon® HD (po lyethylene softener), 3% on the weight of bath . The applicati on process was pad-dry-cure. The fa bric was first padded through the mi xtu re with approx imately 100% wet pick-up and then dried at 105°C for 5 min fo llowed by curing at 177°C for 2 min . Finall y, the fabri c was washed with a noni onic wetting agent at bo iling temperature for 10 min and dried at room temperature for 24 h.

2.5 Treatment of Anionic Cellulose with Cationized Glycerin

Carboxy methy lated cellul os ic fabrics were treated separately with cati oni zed chitosan, cationi zed g lycerin , calcium chl oride, magnesium chloride, cati oni zed ethylene g lycol, cati onized dex trose,

366 INDIAN J. FIBRE T EXT. RES., SEPTEMBER 2006

cationized D-cellobiose and cationized B-cyclodextrin. All of these cationic crosslinkers gave promising resull s, but in this paper only the cat ionic glycerin treatment is reported , as it enhanced the WRA of the fabrics the best. Crosslinking with cationic g lycerin was studied using pad-dry-cure, cold pad-batch and exhaustion application procedures. Treatment with exhaustion and cold pad-batch methods produced a high wet WRA but o nly average dry WRA . On the other hand, a hi gher dry and wet WRA was observed with the pad-dry-cure method . Therefore the results obtained by pad-dry-cure application were recorded. The treatment procedure used was as follows: blank and carboxy methy lated (hav ing 5 differen t carboxyl contents) fabrics were cut

into 15 cm x 15 cm pieces and warp and weft directi ons were marked. The fabrics were soaked in different concentrations of aqueous cationizecl glycerin so lu tions. A blank (0%) and three different concentrations of crosslinker [I , 3, and 6% with weight (w/w)] solutions were prepared. The cationic glycerin was di ssolved in de ionized water at a pH of 7. The sa mples were squeezed to a wet pick-u p of approximately 100% using a laboratory padding machine. The sampl es were then dri ed in a laboratory

tente r frame oven at 85°C for 5 mi n and cured at 140"C for 1.5 min. Then , the fabri cs were washed

with a non ionic wett ing agent (2 giL) at I OO°C for 10 min with a liquor rati o of I :50. Fina lly, the fabri cs were rinsed with cold water, centrifuged and dried at RT for 24 h.

2.6 Treatment of Cationic Cellulosic Fabrics with BTCA Thi s app licatio n is for Method (ii ) which is the

second part of o ur work . The approach is to fo rm io ni c cross links between cellul ose chains by treating cat io nic cellulosic fabric with a po lyanio n. Different polyani ons, namely STCA, po lycarboxy li c acids, ethylenediaminetetraacetic acid , nitril o tri acetic acid tri sodium salt monohydrate, ethyl enediamine d i(o-hyd roxyphenylacetic acid, oxalic ac id , citric acid, and malic acid, were used as crosslinkers. All of these cross linkers improved crease recovery ang le o f the fab ric w ith varying degree of success, but the higher WRA was achieved with STCA treatments. STCA acts as a polyelectrolyte and form s ionic crossli nks with cationic cellu lose, not as an ether-form ing material. Therefore, for Method (ii ) only the results of treatments with STCA was recorded. Untreated and cati oni zed cellulosic fabrics with vary ing level of

fixed nitrogen were used . Aqueous solutions o f BTCA with concentrations of I, 3 , and 6% (w/w) were prepared. The pH of the solutions was adju sted to 6-7 with 50% NaOH solution, as the pH o f crosslinker solutions were initially < 2, which may reduce the strength of cellulose. The applicati on procedure for treatments was the same as previous ly desc ri bed for cationic g lycerin treatment.

3 Results and Discussion

3.1 WRA of Treated Fabrics

Crease recovery angles were measured acco rd ing to AATCC Standard Test Method 66 Option 2. WRA was recorded as the added total of warp and weft averages. The WRA of resin-treated, untreated, carboxy methylated and polycati on-treated samples are shown in Table I . Standard dev iati on o f WR A

measurements was between 3° and 12°. A corre lation between wet WRA and carboxyl content for cationic g lycerin treatment was a lso observed . The wet and dry WRA enhanced with an increase in carboxy l content of the treated fabric. Wet WRA was found to be hi gher than dry WRA due to the formation of crosslinks in the wet s tage of the app licati on. The cationized cellu los ic fabrics were al so trea ted with a po lyanion, STCA . This applicati o n is for Method (ii ). The results are shown in Tabl e 2. The STCA treatment shows an increase in both dry and wet WRA , the wet WRA being higher than dry. A corre latio n be tween wet WRA and %N fi xed was also obtained for BTCA treatment. Hi gher %N fi xed onto cellulose produces a hi gher WRA .

The WRA of anionic cellu los ic fab ric treated with a polyanion seems to improve the crease recovery angle better than that of cationic cellulose trea ted wi th a polyanion . Treatment of anionic ce llul ose with

T able I- Dry and wet WRA for ca tionizeci g lycerin treated fabri cs

[Cat ioni zed g lycerin treatment (pad batch 11l'~lh od) ; Co nt rol (u ntreated)- 1381125 , and Resintreatmcl1 t --2721266J

COO- Wrinkle recover~ angle, d~ (d r~/wet) content 0' 1 " 3 " 6"

Illllloll100 g (13 Iank)

6.2 1381125 1881185 17411 83 1851192 30.2 1601149 2 16/250 2061256 2071257 60.7 1631145 20 1/256 2081262 212/265 87.1 1621153 215/259 2 15/258 204/265 11 4.5 1661159 2 14/269 227/266 2241273

" Cat ion ized g lycerin concent ration in per cent.

I3ILGEN el 01. : ION IC CROSS LIN KING OF CELLULOSE 367

Tablc 2- Dry and wct WRA for !3TCA trca tcd f:Jbri cs IBTCA treatmc nt (pad batch method); Con tro l (untrca ted)-

1381125, and Rcsin trcatment - 272/266]

Catio ni zati on Wrin kle recovcrl anglc. dcg (dr}'/wctl contcnt 0" I " ~ ;1 6" .)

'7o N fi xed (I3lank )

0 1381125 170/138 1621150 156/138 0. 19 1551158 1621180 1741193 185/180 0.28 1571145 1841178 1841186 18 1/178 0.46 1501154 172/201 160/209 158/194 0 .57 153/152 186/204 158/208 1681233

" I3TCA concentrat ion in per ccnt.

cat io nic g lyce rin shows we t WRA between 240° and

280° and dry WRA between 180° and 230°. The ave rage difference of wet WRA between blanks and

treated fabrics is 120°, which is a ve ry s ig nifi cant

increase, while that of dry WRA is 55°. The BTCA

treatment produces wet WRA between 180° and 240°

and dry WR A between 160° and 190°.

3.2 Whiteness Index of Untreated and Treated Samples

C IE whiteness index of the cellulos ic fabrics was determined by a OataColor Spectraflash SF600X spectrophotometer, Four measurements were do ne for each sample and the average va lue was calculated and reported. The data for each treatment is shown in Figs 3 and 4. The whiteness index of treated fabrics seems to decrease as the concent rati o n of cross linker increases. It is a lso observed that the decrease in wh iteness index is higher fo r BTCA treatment. The change is more signi ficant for the treatments of fabrics having higher levels of cati o ni c or ani onic con tent. The whiteness index of untreated fab ri c dropped from 62.58 to as low as 51.77 for catio ni c glyce rin trea tments and 3 1.82 for BTCA trea tments. The whiteness index of resin treatment fabri c was measured as 5 1.04.

3.3 Breaking Strength of Treated Samples T he breaking streng th of the fabr ics was

determined with a Syntech Tensile Strength Tester according 10 ASTM Test Method 05035. The breaking loads for untrea ted and trea ted fabri cs in warp directi on are show n in Figs 5 and 6. Strength testing for ISO treated samples reveals up to 58% increase in tensile strength . Only one sampl e shows strength loss of 7%. The standard deviation of strength tests for treated samples is found to be between 2 Ib and 5 lb. On average, cationized g lycerin

70 ,-----------------------------------,

o '" w~."" &3%0 G,~."" o· "W"",,," I 0 0% (blank) ~ 60 - g

I I ! ° ::l •• Ii I c: •

~ 50+------------------------·~ ~

~ w 40 +---~~----------------------~ U

30+---~--~---~---_r----~-,_-------4

o 30 60 90 120 Carboxyl content of the fabrics (mmolsl100g)

Fi g. 3--White ncss index o f catio nic g lyce rin trea ted fabr ics versus crosslinkcr concen tl 'a tio n

)( 70 r-'-- 0 0% (blank) ,,1 % STCA . 3% STCA . 6% STCA i ~ 60 ---'°"--------,:0,...----------- ---J E III III .. ~ 50 +----- - .. c -- ~

o

• ~ .. w 40 • -------. • .---u

o 0.1 0.2 0.3 0.4 0.5 %Nitrogen content of the fa brlcs

0.6

Fig. 4- Whitc ncss index o f I3TCA treated fa bri cs ve rsus cross linker conccn trati o n

70 - .------------------------ -,

Carboxyl content of the rabrlcs (mmoI8l100g)

Fig. 5--l3rca king streng th of cati onic g lyce rin treated fabri cs ve rsus crossl inkcr concc ntrat ion

70 --~

0 0% (blank) ,,1 % STCA . 3%BTCA . 6% BTCA

g 60 " D ~ '" . : 0 ~ 50 · .~ c: :i • ~ • --. • III 40 j ..

° 0 0 30

0 0.1 0.2 0.3 0.4 0.5 0.6

%Nltrogen content orthe fabrics

Fig. (r--Break ing strcng th of I3TCA trea ted fabri cs vc rsus c ross lin ker conccntra ti on

368 INDIAN 1. FIl3R E T EXT. RES., SEPT EM BER 2006

2eo

2eo

i 240 - 220

~ 200 ~ 160

160 . 140

45 50 55 eo e5 70 75

Br .. klng load (I b)

Fig. 7---Correlation between wet WR A of ca tioni c g lycerin treatment and tensile strength

250 ........... _ ............... ..... .... .

230 .

i 210+-------------------T-----=--=T-~-------: :!!. • ;!5 190

~ ·70 }-----------___ ~----------------------~ • I: 50 •

• • 130 }---~---___,----._---~--___,------; 30 35 ~O 45 50 55 60

Br .. klng load (Ib)

Fig. 8----Correla tio n between wet WR A of BTCA (rea tment ano tensi Ie strength

treatment produces a higher strength gain (>24%) than BTCA treatment. The breaking strength of res in treated fa bric was 14.53 lb.

3.3. 1 Breaking Strength and WRA

Ionic cross links between cellulose chains stabili ze the structure and therefore, fabrics res ist wrinkli ng . The WRA and strength data for treated fabrics prove that increasing the density of cross links in the polymer provides a higher WR A, especially we t W RA and strength gai n. Both the improvements are significant. Figures 7 and 8 show that the wet WRA of treated samples versus strength data have corre lations with the coeffi cients of determination (R2) of 0.71 fo r cati onic g lycerin and 0.42 for BTCA treatments respectively.

4 Conclusions Ionic crosslinking of cellulose fo r DP finish can be

a potenti al solution for today's tex tile industry, which is searching fo r DP fi ni shes th at can give the same advantages as formaldehyde-based fini shes without causi ng strength loss and formaldehyde release. There are many alternati ves to form ionic cross links, fo r example making cellulose anioni c with CAA and

reacting wi th a polycation or producing cati oni c cellulose with CHTAC and then reacting with a polyani on. In both procedures, the po lymer chains are bound a t as many sites as poss ible wi th hav ing an excellent washing durabili ty. These treatme nts produce improvements in both dry and wet WR A with significant increase in tensil e strength . Up to

140° increase in WRA is obtained in wet state and up

to 100° in dry state, including as high as 58% strength gain . In addition to the increase in crease recovery angle, the ionic cross links may have other importan t advantages, such as antimicrobi al ac ti Vity and enhanced dyeability . The chemicals used are common and inex pensive industri al reactants. Processes use ex isting equipment and do not need a high temperature curing. S imil ar processes arc already wide ly used in the text ile industry . The process appears to be economically feas ibl e, the cost estimated to be less than fo rmaldehyde-based fin ishes and there are no unusual safety or environmental Issues.

References 1 We i C, Gary C L & Charles Q Y, Mo lecli lar modeling of

cellulose in amorphous sta te Part II: Effects of ri gid and fl ex ibl e crosslin ks on cellulose, Polymer. 45 (2004) 7357· 7365.

2 Day M P & Coll ier B 1, Pred ic tion of fo rmn ldehyde re lease fro m durable press trea ted fabr ics, Text Chem C%r, 29 ( 1997) 33-36,.

3 Xu W & Li Y, Colton fab ri c strength los·; from treatment with polycarboxy lic ac ids fo r durable press perfo rmance, Text Res J, 70 (2000) 957-96 1.

4 Kittin aovaru t S, Acrylic and citric ac id in non fo rma ldehyde d urab le press finis hing o n colton fab ric, AA TCC Rev, 3 (2003) 62-64.

5 Hashem M, Hauser P & Smi th B, Wrin kle recovery fo r ce llul osic fab ri c by means of ionic crosslin kin g, Text Res J, 73 (2003) 762-766.

6 Hashem M, Hauser P & Smith 13, Reaction e ffi ciency for cellulose cat io ni za ti on using 3·chloro-2·hydroxypropy l trime thyl ammon ium chloride, Text Res J, 73 (2003) 10 17-1023 .

7 Ky ullg K T, Han Y S & SOil Y A, Effec t 0 1' reac ti ve an ionic agent 0 11 dyei ng of cellulosic fi bres wi th a Berberine colorant, Dyes Pigm, 60 (2004) 12 1- 127.

8 Kamel M M, Yousse f G M & Sho kry G M, Dyeing of cati oni zed colton Part II : Direct dyes, AIIl Dyest Rep , 88 ( 1999) 28-3 1.

9 Smith 13 , IOllic Crosslill killg - A Novel Me/hod oj Fabric Stabilizatiol1, 2005 . http://www.ntcresearc h.org/projectapp/ index.c fm ?project=C04-NSO I & topi c=l ate t results (8 June 2006).