Indian Journal of Fibre & Textile ResearchVol. 19, December 1994, pp. 260-268

Behaviour of crosslinking on cotton fabric dyed with direct andreactive dyes"

N Bhattacharyya, B A Doshi & A VenkataramanThe Bombay Textile Research Association, L B S Marg, Ghatkopar (West), Bombay 400 086, India

Received 5 October 1993; revised received 10 February 1994; accepted 1 March 1994

Mercerized-bleached cotton has been dyed with direct and reactive dyes and subsequentlycured with dimethyloldihydroxyethylene urea (DMDHEU) along with mixed catalyst containing mag-nesium chloride hexahydrate and ammonium chloride in presence of polyethylene emulsion soften-er. The differential behaviour of direct-dyed and reactive-dyed crosslinked cotton with respect tofastness properties, formaldehyde release, moisture regain, etc. has been discussed. Infrared, opticalmicroscopic and X-ray diffraction studies show more crosslinking in the reactive-dyed samples ascompared to that in the direct-dyed ones.

Keywords: Cotton fabric, Crosslinking, Cuprammonium dissolution, Direct dye, Formaldehyderelease, Reactive dye, Wickability

1 IntroductionFinishing of cotton fabrics with resin is a com-

mon practice for improving easy care propertyand wrinkle resistance. The most commonly usedresin dimethyloldihydroxyethylene urea(DMDHEU) reacts with two ceUulose moleculesto form a covalent link between them'. Crosslink-ing reactions depend on the reaction of functionalgroups of the resin with the hydroxyl groups pres-ent in the amorphous region as well as their spa-tial availability in different structural units of thecellulose. The environment in which the crosslink-ing reactions occur in fabric finishing. is governedby the presence of foreign substances, viz. addi-tives, contaminants, and dyes/colorants, as well asby the amount of moisture present in the fibre atthe time of reaction-, Braun and Rieker' observedthat a variation in the resin treatment parameterssignificantly affects the degree of fixation and theshade of the dyed fabric. Extensive studiest-' werecarried out on the relationship between selectedfabric residues and formaldehyde release. In thepresent investigation, chemical modification bycrosslinking reactions were carried out on direct-and reactive-dyed cotton fabrics using DMDHEUresm. An attempt has been made to correlate theeffect of cross linking on the fastness propertiesand formaldehyde release of the finished fabric as

"Paper presented at the 42nd Southeast/46th Southwest Com-bined Regional Meeting of the American Chemical Societyheld. SRRC, New Orleans, during 5-7 December 1990.

well as to study the structural changes broughtabout by the different dyes present on the modifi-ed crosslinked fabric.

2 Materials and Methods2.1 Fabric

Mill mercerized-bleached poplin having the fol-lowing specifications was used: count, 39s x 36s;reeds/in, 50; picks/in, 24; and weight, 117 g/m",

2.2 DyesFour direct dyes and three reactive dyes were

used. The structure and other details of directdyes are given in Table 1 and the structures ofreactive dyes are given in Fig. 1.

2.3 Dyeing ProcedureDyeing with direct dyes was carried out in an

automatic laboratory jigger by exhaust method.The dyeing recipe and dyeing conditions used fordirect dyes are as follows:

Dye,X%owfSodium sulphate, 10 g!lDyeing temperature, 60-95°CMaterial-to-liquor ratio, 1:10Duration of dyeing, 2 hThe dyeing techniques, recipes and other condi-

tions for reactive dyes are given in Table 2.

2.4 FinIshingResin finishing was carried out after padding in

BHATIACHARYYA et al.: BEHAVIOUR OF CROSSUNKING ON COTION FABRIC 261

Table I-Structures and other details of direct dyes

Commercial ColourName Index

Constitution MolecularNo. Weight

Atul Direct C.I. Dilllct 22311Brown MR Brown 2

Chlorantin C. I. Direct 28160Fast Red Red 815 B

ChlorantinFast OrangeTGll

C.I. birectOrange 34

40215

Diazol Blue6 B

C.I. DirectBlue 1

24410

Structure Solubilising MaximumGroup Aflinity

at

627NaOOC OH

<9>-N:N@@-N:N$orNH2OH Na03~

60 ·80·C

675 so·C

1004 4

992

C.!. Reactive Orange I.

C.l. Reactive Violet I

C. I. Reactlw Blue 11.0

Fig. l+-Structures of reactive dyes

4 60 -8{J°c

a Benz verticallhorizontal padding mangle. Thefollowing finishing formulations were used:- 60 g!1 Resin + 5 g!1 MgCI2. 6H20+0.33 g/l

NH4CI +20 g!1Aqualine N + 1 g!1Lissapol N- 90 g!1 Resin + 10 g!1 MgC12' 6H20+0_66 g/l

NH4Cl + 20 g!1Aqualine N + 1 g!1Lissapol N- 120 g!1 Resin + 15 g!1 MgC12. 6H20+ 1 g!1

NH4CI + 20 g!1Aqualine N + 1 g!1Lissapol Nwhere Aqualine N is a cationic softener; and Lis-sapol N, a wetting agent.

2.5 Fastness TestsWash fastness of the samples was assessed by

ISO 2 test for direct dyes and by ISO 4 test forreactive dyes. Light fastness was assessed by aXenotest 150.

2.6 Determination of Formaldehyde ReleaseFormaldehyde release of the finished fabric was

evaluated by AATCC-112 (1984) sealed jarmethod.

2.7 Cuprammonium Dissolution for Detection of CrosslinkDyed-finished and crosslinked sample (0.1 g)

was kept in a stoppered conical flask containing30 ml cuprammonium hydroxide solution for 20h at 29 ± 1°C. The content of the flask was fil-tered through a G-l crucible and subsequentlythe residue was treated with HCI (O.IN) for dis-solving cuprammonium in the residue and then

262 INDIAN J. FIBRE TEXT. RES., DECEMBER 1994

Dyeing technique

Table 2-Dyeing techniques and conditions for reactive dyes

Dye bath

Sodiumchloride

g/IC.I. Reactive Blue 140Exhaust technique

M:L ratio, 1:5Total dyeing time, 2 hExhaustion at 40-50°C

followed by fixation at 85-90°Cfor I h

C." Reactive Orange 4Pad-batch techniaue

Batching time, 20 h at 30 ± 1°C

C.I. Reactive Violet 1Pad-dry-cure technique

Drying at 85-90°C for 5 minCuring at 165°C for 3 min

50

Sodiumcarbonate

g/I

Sodiumbicarbonate

g/I

Resistsaltg/I

Urea

g/I

10

5 15

16 150 10

rinsed thoroughly with water and dried at 100°Cfor 4 h.

2.8 Infrared StudiesInfrared (IR) studies on crosslinked fabric were

carried out on a Hitachi Model 270-30 IR Spec-trophotometer using KBr pellet technique.

2.9 X-ray StudiesX-ray diffraction (XRD) scans of DMDHEU

crosslinked fabric samples were obtained using aPhilips X-ray Generator (Model PW-1720) withmicroprocessor-based PW-1710 Textured Goni-ometer Control.

2.10 Wickability TestWicking tests on direct- and reactive-dyed

crosslinked fabrics were carried out as per themethod reported by Ravichandran et al':

2.11 Moisture RegainMoisture regain and water imbibition of cross-

linked cotton fabrics were determined by thestandard methods reporied earlier".

2.12 Optical Microscopic StudiesMicroscopic studies on crosslinked residue of

direct- and reactive-dyed fabrics were carried outusing the Ernst Leitz Compound Microscope atx 100 magnification. Samples of Direct Red 81and Reactive Blue 140 dyed finished residueswere treated in cuprammonium solution for 5.5min and exposed for 2 s to obtain the micro-graphs.

Table 3-Conditioned WRA of dyed cotton fabrics at variouslevels of DMDHEU finishing

Sample Condo WRA (W + F), deg

DMDHEU, g/I 60

265

120

299

90

285UndyedDyed with

Direct Brown 2Direct Red 81Direct Orange 34Direct Blue 1Reactive Blue 140Reactive Orange 4Reactive Violet 1

258258251258257252252

280270280277279257267

292293296293295267269

WRA of unfinished white control, 198°

3 Results and DiscussionCrosslinking reactions with resin as well as

other agents on 'cellulose not only improve easycare property but also enhance wet fastness pro-perties. Figs 2 and 3 show the improvement inthe wash fastness properties of direct- andreactive-dyed samples respectively. With the in-crease in the concentration of resin, crosslinkingincreases and the fastness properties are en-hanced from a rating of 1 to 3-4 in the case of di-rect-dyed fabrics. In the case of reactive-dyedsamples, only the Blue 140 dyed and finishedsample shows some increase in the fastness rating(2-3 to 4).

Conditioned WRA of cotton dyed with four di-rect dyes and three reactive dyes and subsequent-ly finished with various concentrations of

BHATTACHARYYA eta!.: BEHAVIOUR OF CROSSLINKING ON COTTON FABRIC 263

o 4zI--c(

3a:I/)I/)liJ

0-<> BROWN 2zl-I/) .-. RED 81~ ~ORANGE34:c 0-0 BLUE 1I/)-c( 0~ 0 30 60 90 120 150

DMDHEU CONC-,gl1

Fig. 2-Correlation of wash fastness of direct-dyed cottonwith concentration of crosslinking agent

5~----------------------~Co!)z 4I-

<a:III 3IIIUJZI-

2 -<>- BLUE 14O~u, -.- ORANGE":x: -Ir VIOLET 1III<~

°O~--~30~--~60~--9~O~~12~O~~1~~DMDHEU CONC.,9 I 1

Fig. 3-Correlation of wash fastness of reactive-dyed cottonwith concentration of cross linking agent

DMDHEU resin (60, 90 and 120 gIl) are shownin Table 3. It is observed that the conditionedWRA increases progressively for both types ofdye with increase in resin concentration. It is fur-ther observed that all the direct-dyed samplesshow more or less same values at a particular res-in concentration while among the reactive-dyedsamples, Blue 140 dyed sample shows higherWRA as compared to the other two samples.

Formaldehyde release from the crosslinked fa-bric increases with the increase in resin concen-tration. As the fabric acidity or alkalinity influ-ences the formaldehyde release from the finishedfabric, the same is tested and adjusted if neces-sary to make it neutral before finishing with sodi-um bicarbonate and dil. acetic acid respectively.Figs 4 and 5 show the data on formaldehyde re-lease from direct- and reactive-dyed andDMDHEU-finished fabrics respectively. It is ob-served that at the same level of resin concentra-tion and catalyst, formaldehyde release variesfrom dye to dye as well as with the type of dye

500 '"0 z ~'" ~z w w>

~ - 0 a:: 0 -1-0 ~ z CD z ww :;) < :;)w i w :;) CD ~ ...J> 0 ...J CD0 Z CD 0Z w:;) < a::~ CD s -0wa::

r-

o60 90

DMDHEU CONC.,g/1

Fig. 4-Effect <.,f resin finishing on formaldehyde release ofdirect-dyed cotton

700 ..,w -0 Cl •...- ! z w.., 0< ...J•...

W s 0w w ::l s~ e ...J ...JZ 0 III - ,-0< sw s -::l ,-

aj - a,- w>-aa zw ::l>- r-az::l1-.-

600

~ 500

~~...JW 400a:

~>-x~ 300...J-e2

~ 200

100

oo 80 90

DMDHEU CONe., g/'Fig. 5-Effect of resin finishing on formaldehyde release of

reactive-dyed cotton

(Fig. 6). It has been reported ' that the varying for-maldehyde levels are obtained in presence of dif-ferent dyes and possibly there exists a correlationbetween formaldehyde release and dye. In thepresent investigation, among the direct-dyed fa-brics, Brown 2 dyed fabric shows the highest va-lue and Red 81 dyed fabric, the lowest. Amongthe reactive-dyed fabrics, Violet 1 dyed fabricshows the maximum formaldehyde release andBlue 140 dyed fabric, the lowest. This indicatesthat the formaldehyde release is, to some extent,dye specific.

264 INDIAN J. FIBRE TEXT. RES., DECEMBER 1994

700DMDHEU Cone. ~

~~- ~1209/1 w~ ~ ~...J

N CD~ "/z ,..

0 ; ~ ~ ~~

w - ~ ~> w w ~ "/0 e~z Iii g ~

~ ~~ iiI0 ~ ~ ~~ ~

Ii:"/ "/ %

x )( ::;: ~ ~~ ~ ~

~ ~ ~~ ~E:: ~ ~~ ~ tI

)c ~ ~ ~~ ~ ~

)( ~ ~~ ~)c '/ ~

')c ~ ~ ~

100

oDIRECT REACTIVE

Fig. 6-Comparative values of formaldehyde release fromdirect- and reactive-dyed cotton

Table 4-Comparative data on nitrogen content and condi-tioned WRA of dyed samples finished with 120 g/l

DMDHEU

Sample Nitrogen Nitrogen Condocontent % (owf) WRA

for (W+F)unfinished deg

%

0.04 1980.81 299

0.07 0.84 2920.10 0.84 2930.16 1.02 2960.03 0.78 2930.09 0.97 2950.14 0.65 267O.H 0.68 269

Untreated undyed controlUntreated undyedDyed with

Direct Brown 2Direct Red 81Direct Orange 34

Direct Blue IReactive Blue 140Reactive Orange 4Reactive Violet 1

Table 4 shows the nitrogen content and condi-tioned WRA of direct- and reactive-dyed finishedfabrics. Data on nitrogen content reveal that fixa-tion of nitrogen is more in direct-dyed samplethan in reactive-dyed samples except in Blue 140dyed sample which shows higher WRA also.However, the higher value of nitrogen content on

direct-dyed finished fabric may not indicate morecross linking.

Direct dyes are held inside the fibre by van derWaals' forces or hydrogen bonding. After reactionwith DMDHEU, the free amino or hydroxylgroup of the direct dye may react with one end ofthe bifunctional resin while the other end formsether linkage with cellulose. The direct-dyed sam-ples when soaped under mild condition showedno bleeding. It may be noted that although DirectOrange 34 does not possess any OR or NR2group, due to its planer and linear structure thisdye tends to form dimer or higher aggregates,thus becoming insolubilized inside the fibre struc-ture and improving wash fastness properties. Thisshows that the dye which has reacted with theresin is anchored or entangled mechanically insidethe cellulose network, 'thereby improving washfastness and the wrinkle recovery angles also. Fur-ther studies on the extraction with 25% aqueouspyridine of the direct-dyed and dyed-finishedsamples showed that significant reduction inbleeding could be achieved after resin finishing.The optical densities of the extracts for DirectBrown 2, Red 81, Orange 34 and Blue 1 at theunfinished stage were 3.81, 3.81, 3.74 and 2.04respectively whereas the values for finished sam-ples were 1.38,2.42,0.07 and 1.04 respectively.

Table 5 shows the data on detection of cross-links in direct- and reactive-dyed cotton. The dy-ed fabrics were crosslinked with DMDHEU (120g/I) alongwith the mixed catalyst and the dissolu-tion of the finished samples in cuprammonium so-lution was studied. Considerably higher flow timefor reactive-dyed samples before finishing sug-gests that the covalent bond formed between thetriazinyl group and cellulose imparts marginalcrosslinking. Reactive-dyed samples after resinfinishing become completely insoluble. The flowtime for direct-dyed samples also increases andBrown 2 dyed samples became insoluble. As thefluidity could not be measured, the crosslinkedsamples were treated with cuprammonium hy-droxide solution for 20 h and then filteredthrough a G 1 crucible. The details are given inthe experimental methods.

Taking undyed finished control fabric as 100%,it is observed from Table 5 that the reactive-dyedfinished fabrics have more residue as comparedto the direct-dyed finished samples, possibly dueto more crosslinking in the former as comparedto the latter. However, moisture regain and waterimbibition values are higher for reactive-dyedcrosslinked samples as compared to that for the

BHATTACHARYYA et al.: BEHAVIOUR OF CROSSLINKING ON COTTON FABRIC 265

Table 5-Detection of crosslinks in direct-dyed and reactive-dyed cotton by dissolution in cuprarnrnonium solution

Sample Nitrogen fixed Condo WRA Flow time, s Fluidity, s Residue ofdue to resin of fmished crosslinked

only samples Unfinished Finished Unfinished Finished samples% deg sample sample sample sample %

White Control 0.56 299 436 Insoluble 3.66 Insoluble 100Dyed with

Direct Brown 2 0.66 290 358 Insoluble 4.10 Insoluble 78Direct Red 81 0.55 277 389 659 2.71 2.51 88Direct Orange 34 0.61 270 554 565 2.65 2.68 85Direct Blue 1 0.90 290 512 1800 2.98 Insoluble 84Reactive Blue 140 0.95 295 Insoluble Insoluble Insoluble Insoluble 95Reactive Orange 4 0.59 267 719 Insoluble 2.12 Insoluble 91Reactive Violet 1 0.60 269 Insoluble Insoluble Insoluble Insoluble 95

direct-dyed crosslinked samples (Table 6). Thewater imbibition values in Table 6 are ofDMDHEU-finished samples. Therefore, these va-lues are much lower than that of unfinished con-trol", It is interesting to note that although there ismore crosslinking in the reactive-dyed samples,the moisture content and water imbibition are stillhigher as compared to those of direct-dyed fin-ished samples. The hydroxyl groups of cellulosewhich did not react with reactive dye or resin arestill available for H-bonding with the water mole-cule. Further, the spatial arrangement of the reac-tive dyes inside the amorphous region of cellulosepossibly forms a network structure having moreaccessible regions. On the other hand, direct dyesare absorbed inside the fibre structure at the ac-cessible regions and due to the penetration of res-in, the crosslinked structure is modified in such away that the structure becomes more compact.The hydroxyl groups of cellulose responsible forH-bonding with water molecules are now weaklybonded with the direct dyes, thus making thedirect-dyed finished fabric less hydrophilic,

3.1 Microscopic Studies on Crosslinked SamplesThe crosslinked residues were examined under

microscope after treating with cuprammonium so-lution and the treated cellulose structures ofdirect- and reactive-dyed cotton are shown in themicrographs (Fig. 7).

Direct Red 81 dyed-finished residue on treat-ment with cuprammonium hydroxide solutionswelled into a balloon shaped structure (Fig. 7A),indicating very less amount of crosslinking in thisstructure". On the other hand, the structure ofreactive Blue 140 dyed-finished residue was notmuch affected on' cuprammonium treatment due

Table 6-Moisture regain and water imbibition of poplin dyedwith direct and reactive dyes and finished with 120 g/l

DMDHEU

Sample Moisture regain Water imbibition% %

Undyed finished 5.60 7.89

Dyed withDirect Brown 2 5.30 7.10Direct Red 81 5.30 7.80Direct Orange 34 5.40 7.30

Direct Blue I 5.40 7.00Reactive Blue 140 6.00 11.00

Reactive Orange 4 6.00 11.40

Reactive Violet 1 6.00 9.50

Table 7-X-ray diffraction data on varioustreated cotton samples

Sample Ratio of lOIand 002 peaks

untreated and

Half width of002 peak, deg

UndyedControl 0.11 1.7

Control alkali-treated 0.50 3.3

Finished 0.12 1.8

Finished, alkali-treated 0.36 2.5

Direct Red 81 DyedControl 0.12 1.7

Control alkali-treated 0.49 3.5

Finished 0.11 1.7

Finished, alkali-treated 0.45 3.1

Reactive Blue 140 Dyed

Control 0.10 1.5

Control alkali-treated 0.42 3.1

Finished 0.12 1.5

Finished, alkali-treated 0.37 2.5

266 INDIAN J. FIBRE TEXT. RES., DECEMBER 1994

Fig. 7-0ptical micrographs of dyed finished cotton treated with 0.5% cuprammonium hydroxide solution: A-Direct Red 81dyed sample showing enormous swelling with constructions in between them, and B-Reactive Blue 140 dyed sample showing

very little swelling, indicating moderate crosslinking

to the higher crosslinks already present (Fig. 7B).Studies on the wickability of the dyed-finished fa-bric showed that the reactive-dyed samples havemore accessible regions (Fig. 8). These observ-ations are in conformity with the results on mois-ture regain and water imbibition.

3.2 IR StudiesThe IR spectra of the control and finished sam-

ples are shown in Fig. 9. In the case of undyedresin-finished and reactive-dyed finished samples,an additional band at 1720 ern - I indicates thecrosslinking of resin with cellulose!", In the caseof direct-dyed finished samples, a weak band indi-cates only very less crosslinks which goes hand inhand with the microscopic investigations.

3.3 XRD StudiesWhen the cotton cellulose is swollen in alkali

the lattice undergoes transformation from cellu-lose I to II. The fraction of cellulose II in thesample is indicated by the relative intensities of101 and 002 peaks of cellulose II and also broad-ening of 002 peak in XRD scan II. When somerestrictions are imposed upon the structure in anyform, and in this case by covalent lateral linkages,the transformation will be incomplete. Therefore,

Ev

r-

REACTIVE DYE

~Wp g,3Wt 7/'/I

"'\ / 'Iv 'I [:x

'TDIRECT DYE Vro; 11\

~II IK/1)<

v V /[> iX

~Kv v /1\

<~X D< I I~~K [)( )( V /v)X v IDe Xv X 1\ ~ De I 11\ IDe

X K V vl\ vx II Iv ~K v vx D< v / v}( /

~I\ )( [)( v vK I ~)(v VI VI)( v I

2

oN

I w:>-'OJ

Fig. 8-Wicking distance of direct- and reactive-dyed sam-ples finished with DMDHEU (120 g/l)

in the present study, the restriction imposed uponlattice conversion was assessed by taking X-raydiffraction scans of various samples treated with20% alkali for 10 min at 200e and subsequently

BHATTACHARYYA et al.: BEHAVIOUR OF CROSSUNKING ON COTTON FABRIC 267

tfl~ If)Z ~::l Z> ::>ex: >« ex:ex: «~ ex:~a:l CDex: ex:« «">~

tfl If)

Z ZW W~ ~Z Z

-Undyed Control

- Reactive Blue IloODyed Finiahed

_ DlrKt Red IIDyed Fi nillled

WAVE NUlo4BER., cm-\

Fig. 9-Infrared spectra of control and finished cottonsamples

c.r. Direct Red 61

25 20 15 10DIFFRACTOMETER ANGLE,2e

Fig. IO-XRD scan of cotton dyed with Direct Red 81 andfinished with DMDHEU resin

measuring the relative intensities of 101 and 002peaks as well as the half width of the 002 peak inthe cellulose diagram. The XRD scans of varioussamples are shown in Figs 10 and 11 and theXRD data are given in Table 7.

In the case of undyed control sample, sincethere is no restriction due to covalent bonds re-sulting from crosslinks, conversion of cellulose Ito II is maximum on swelling, as indicated by therelative intensities of 101 and 002 peaks and alsothe maximum broadening of the peaks. Undyedfinished and reactive-dyed finished samples, how-ever, show much less conversion of the cellulose Ito II as well as the less broadening of 002 peak ascompared to the control, due to the restrictionsimposed by covalent crosslinking.

On the other hand, for the direct-dyed finishedsample, on swelling, cellulose I to II conversionand the half width of 002 peak are more. Thisimplies that in the case of direct-dyed finishedsamples only a limited restriction due to covalentlinkages is present, probably most of the covalentbonds are formed by resin with direct dye andnot with cellulose hydroxyl groups. Hence, onswelling, cellulose I and II conversion is more in

C.\ Reactive Blut> 140

25 20 15 10DIFFRACTOMETER ANGLE,2 e

Fig. Il-XRD scan of cotton dyed with Reactive Blue 140and finished with DMDHEU resin

268 INDIAN J. FIBRE TEXT. RES., DECEMBER 1994

the case of direct-dyed finished samples as com-pared to that in reactive-dyed finished samples.XRD studies also show that the cross linking be-haviour in direct-dyed and reactive-dyed samplesare different.

4 ConclusionsChemical modification of cotton through cross-

linking reaction with DMDHEU resin improvesthe wash fastness properties of direct-dyed cottonsignificantly as compared to that of the reactive-dyed finished fabrics. Presence of different classesof dye as well as their structures play importantrole during crosslinking reactions.

The values of WRA are more or less same fordirect- and reactive-dyed samples at the finishedstage. More crosslinking takes place in thereactive-dyed samples as compared to that in thedirect-dyed ones.

Formaldehyde release from the finished fabricis lower in the case of direct-dyed cotton as com-pared to that in reactive-dyed cotton.

Crosslinked lamellae seem to be different forcotton samples dyed with direct and reactivedyes. The resin probably reacts preferentially withthe functional groups present in the direct dyesstudied rather than with the hydroxyl groups ofcellulose.

AcknowledgementThe study was undertaken as a part of the US-

DA-funded project IN-ARS-270 (Grant No. FG-In-698). The authors are thankful to Dr S M Be-

trabet, Director of BTRA, and to Prof. E H Dar-uwalla, Research Advisor, BTRA, for their keeninterest and encouragement during the presentwork. They are also thankful to Dr Robert M.Reinhardt, Co-Scientist, for presenting the paperat the ACS Meeting and to Mrs A S Sahastra-budhe and Mr P R Mistry for the experimentalwork.

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