Indian Journal of Fibre & Textile Research Vol. 21, March 1996, pp. 69-78

Surface modification of fibre and polymeric materials by discharge treatment and its application to textile processing

Tomiji Wakida

Gifu Women's University, Taromaru, Gifu, 501-25 Japan

and

Seiji Tokino

Kyoto Institute of Technology, Matsugasaki, Kyoto, 606 Japan

The effect of discharge treatments such as low-temperanire plasma treatment, atmospheric low­temperature plasma treatment and sputter-etching on the surface characteristics of different textile fi­bres and polymeric materials has been investigated. The plasma treatment causes mainly chemical mod­ification and increases wetting and adhesion, whereas sputter-etching produces a number of protrusions on the surface and leads to increase in adhesion and decrease in light reflection, thereby increasing the depth of shade considerably.

Keywords: Low-temperature plasma treatment, Polymeric materials, Sputter-etching, Surface modification

1 Introduction It is well known that the surface characteristics

such as wetting,water and oil repellency, soil re­lease, adhesion, light reflection, colour, handling, friction coefficient, and antistatic property play an important role in textile processing. Surface modi­fication is effective for improvement in functional­ity without changing the bulk characteristics of fi­bres. Especially, the surface modification by dis­charge treatments, such as low-temperature plas­ma, sputtering and corona discharge, is of great interest because these treatments could be carried out without using large amount of water and sur­factant and are effective for energy saving because of dry system. Many studies have been carried out on the surface modification of polymeric ma­terials by discharge treatments in relation to an improvement in functional properties of the tex­tile fibres.

In the present paper, surface modification of fi­bres and films by low-temperature plasma and sputter-etching treatments has been investigated. on the basis of surface tension, ESCA (electron spectroscopy for chemical analysis) and colour measurement.

2 Effect of Surface Modification on Functional Properties of Fibre and Polymeric Materials The effects of surface modification on the func­

tional properties of fibre and polymeric materials

are shown in Fig. 1. There are many techniques to control surface characteristics of fibres with re­gard to textile processing. Formerly, liquid sys­tems were mainly applied but at present dry sys­tems such as plasma, sputtering, and ion beam are of much interest. Therefore, it is necessary to se­lect the best technique complying with the pur­pose. Typical techniques for surface modification and their effects on surface are shown in Table 1.

Low-temperature plasma treatment causes mainly chemical implantation, etching, polymeri­zation, free radical formation, crystallization and crosslinking, and improves the hydrophilic/hydro­phobic and adhesive properties, whereas sputter­etching brings about cbiefly physical changes such as surface roughness and leads to increase in adhesion and decrease in light reflection.

2.1 Low-temperature Plasma Treatment Low-temperature plasma is an useful technique

to improve the surface characteristics of the fibre and polymeric materials by utilizing the ingre­dients such as electron, ion, radical, and excited molecule produced by electrical discharge. The current frequency generally used is 13.56 MHz. Glow discharge is available as a plasma source for processing under a pressure of 1 Torr (133 Pa). AS the glow discharge is not reached a thermal eqUilibrium between gases and electrons, it is called non-equilibrium plasma. Although, electron

70 INDIAN 1. FIBRE TEXT. RES., MARCH 1996

Surface I • Activated Surface-modified .... Improvement of

1 surface polymer functionality

+ + + Surface modification Change in surface Surface characteristics Printing Chemical Functional group Wetting Adhesion Physical Cross-linking Adhesion Coating Additive Crystallization Refractance Magnetical Clearance Free radical Reflectance Electrical

Implantation Rubricity Transmittance Etching Surface tension Medical suitability Grafting Surface roughness Anticlouding

Porosity ... ... ... ... Wear resistance ...... . .. . . . ...... .. ..... ....... 0 •••••

Fig. I-Effect of surface modification of polymer on functionality

Table I-Typical techniques for surface modification and their effects on activated layer

Modification Activated layer technique

Functional Molecular Crosslinking Free radical Surface Surface group layer

Chemical 0 Coupling

agent 0 Grafting 0 UV Irradia-

tion 0 Low-

temperature 0 0 plasma

Sputter-

etching

Plasma 0 polymeriza-

tion

Ion beam 0 0 0

temperature rises over several tens thousand K, gas temperature remains at 100 K. Therefore, it is generally called low-temperature plasma and used for modification of polymer .surface.

To investigate the surface characteristics of the plasma-treated polymer, Zisman's plot, cos () VS

YL' of the films irradiated with low-temperature plasma was recorded using several wetting liquids which are different in nonpolar dispersion force

energy roughness

0 0

0 0

0

0 0

0 0 0

0 0

yt, dipole force rE , and hydrogen bonding force yE,: Surface tension (Ys) of the film could also be divided into nonpolar dispersion force Ys, dipole force y~ l , and hydrogen bonding force Ys accord­ing to the following extended Forkes equation:

yd 1 + cos 6) = 2 (J y~y; + J YtY~ + JY~y~j

where () and YL are the contact angle and surface tension of the liquid respectivelyl . The lowest sur-

WAKIDA & TOKINO: SURFACE MODIFICATION OF FIBRE 71

face tension Yc(Zisman), . the highest surface tension Yc(max ), and each component of surface tension of the PET films treated with various plasmas are given in Table 2 [ref. 2]. It is obvious that thc sur­face tension of the PET film depends on the gas type employed in plasma treatment. Wettability and adhesion of polymer are related to the chemi­cal composition in polymer surface. Thus the sur­face of plasma-treated PET film is characterized by ESCA. This technique was used for the char­acterization of relative chemical components C I "

Ols> N i s ' Fh , and S2p in surface of the films~ (Table 3). The O 2, N 2, He and Ar plasma treat­ments led to increase in 0 h intensity and de­crease in C I , intensity, while CF4 and CHF) plas­ma treatments increased F I , intensity and de­creased C Is intensity.

2.1.1 Application of Low-temperature Plasma Treatment to Textile Processing

Various applications of low-temperature plasma treatment to textile processing have already been reported, e.g. shrink-resistant finish of wool fa­bric3-8 and improvement in dyeing properties of wooI9

•1O

• O 2 and CF4 plasma-treated wool in­creased significantly the rate of dyeing with levell­ing type acid dye, whereas milling type acid dye increased not only the rate of dyeing but also sat­uration dye exhaustion 10 (Table 4).

Low-temperature plasma scouring of gray cot­ton fabric has also been studied II. For dewaxing of gray cotton fabric, O 2 low-temperature plasma scouring was used instead of conventional wet

Table 2-Surface tension of poly(ethylene terephthalate ) films treated with low-temperature plasma

Plasma Surface tension, mN/ m treatment

Zisman plot Extended Fowkes equation

YC(Zi,man) YC(max ) Y~ y~ Y§ Ys

Untreated 43 46 37.6 · 1.2 4.2 43.0

O 2 56 56 16.6 0.1 40.1 57.4

N2 ~7 ' 57 17.6 1.0 38.4 57.0

H2 39 50 33.6 0.6 14.4 48 .7

He 56 56 16.8 1.1 37.2 55.1

Ar 56 56 17.6 1.2 37.2 56.0 CF4 20 20 19.7 1.8 3.2 24.7 CHF3 19 20 22.6 2.1 0.8 25.5

CCIFJ 36 . 44 41.8 4.0 2.4 48.2

(CHJ )4Si 34 35 42.5 0.4 1.1 44.0

02- CF4 20 20 21.2 1.3 4.0 26.5 CF4 -02 58 58 17.0 1.4 37.5 55.9

scouring processes (Table 5). Residual wax and size contents after both the scouring processes were compared under the same condition (Table 6). The quantities of both wax and size on the fabrics were a lmost same after the treatment.

Table 3-ESCA relative intensity of surface atoms of poly(ethylene terephthalate ) films treated with low-tempera-

ture plasma

Plasma Chemical composition of surface, % treatment

C I , 0 1, N I , FI , Si 2p CI2P

Untreated 73 .1 26 .9 0 0 0 0

0 ) 64 .3 34.3 1.4 0 0 0 N) 67.9 29.7 . 2.4 0 0 0

H2 77.7 22.3 0 0 0 0 He 69.3 29.7 1.0 0 0 0 Ar 68.4 31.6 0 0 0 0

CF4 41.8 6.5 0 51.6 . 0 0

CHFJ 45.4 1.2 0 53.3 0 0

CCIFJ 53.4 13.5 0 8.4 0 24.6

(CH 3)4Si 68 .6 10.2 0 0 21.2 0

0 2- CF4 39.6 6.6 0 53.8 0 0

Table 4-Saturation dye uptake of wool treated with low-temperature plasma

Dye Saturation dye uptake x 105 ,

mol /g fibre

Untreated Gases in plasma treatment

O 2 CF4

C.I. Acid Orange 7 26.95 27.02 29.87

c.1. Acid Blue 40 20.20 20.79 20.83

c.1. Acid Blue 83 3.61 7.62 7.27

c.1. Acid Blue 113 11.67 13.50 13.45

Table 5-Dyeing process with 0 ) plasma scouring

Conventional scouring

Singing - Desizing - Scouring - Washing­Bleaching - Drying - Mercerizing - Dyeing - Finishing

Low-temperature Plasma treatment - Singing - Washing -plasma scouring Bleaching - Drying - Mercerizing - Dyeing

- Finishing

Table 6-Comparison of scouring effect between conven­tional and plasma processes

Residual wax

Residual size

Control Conventional (Gray fabric) process

0.73

13.30

0.23

0.66

Residual wax and size were measured by JIS L-1096.

Plasma process

0.15

0.47

72 INDIAN 1. FIBRE TEXT. RES., MAREH 1996

2.2 Atmospheric Low-temperature Plasma Treatment

Low-temperature plasma is an useful technique for the modification of fibre or polymeric materi­als in a dry system, i.e. without water. There have been some problems 'with productivity and equip­ment costs because of the treatment at low pres­sure (below 1 Torr ). Therefore, practical applica­tion to textile finishing has been limited as the vacuum evacuation system and maintenance of vacuum pipeline are necessary.

Recently, Okazaki et a/. 12- 15 found that low-tem­perature plasma can be generated under atmos­pheric pressure in the presence of helium. T hey pointed out that to stabilize the glow discharge, the use of helium as a dilution gas, insertion of dielectric layer between electric plates, and the use of high frequency electric source are necessary.

Discharge conditions of atmospheric low-tem­perature plasma are similar to that of corona dis­charge. The apparatus for the treatment is shown in Fig. 2.

Although helium could be used to generate the atmospheric low-temperature plasma, it is expen­sive to use industrially. We found that helium/ ar­gon and acetone/ argon mixture are effective in generating atmospheric low-temperature plasma. For the helium/argon plasma, each gas was intro-

Fig. 2-Apparatus for atmospheric low-temperature plasma treatment: (1) power supply, (2) glass jar, (3) brass electrode, (4) cock, (5) dielectric layer (polyimide), (6) specimen for

treatment, (7,S;9) gas Wet, (10) acetone, and (11) gas outlet

duced from inlets (7 and 8) controlling the gas flow. For the acetone/ argon treatment, argon flowed from a gas inlet (9) through acetone va­pour (10) without bubbling in acetone solution. Acetone contained in argon was estimated to be about 5 ppm. The current frequency was 3 kHz, whereas for low-temperature plasma by glow dis­charge it was 13.56 MHz. Discharge power was kept at 80 W, discharge voltage at 4000-4200 V and discharge current at 30-35 rnA.

2.2.1 Application of Atmospheric Low-temperature Plasma Treatment to Textile Processing

The wettability values of wool and PET fabrics treated with atmospheric low-temperature plas­mas (Table 7) show that the wcttability of both the fabrics increased remarkably with the increase

Table 7 - Effects of atmospheric low-temperature plasma treatment on wat:er penetration of polyester and wool fabrics

Treatment Time of water penetration

s

Polyester

Untreated >3600

Acetone/ Ar plasma

lOs 1167

30 s 285

60s 173

180 s 24

He/ Ar plasma

10 s 240

30 s 94

60 s 60

180 s 20

Wool

Untreated > 3600

Acetone/ Ar plasma

lOs >2400

30 s 2000

60 s 900

180 s 60

He/ Arplasma

lOs > 1800

30 s 150

60s 10

180 s <I

I

I I

WAKIDA & TOKINO: SURFACE MODIFICATION OF FIBRE 73

in treatment time I". The critical surface tensions of the PET films treated with the two plasmas un­der atmospheric pressure (Table 8 ) show that the critical surface tension of 43 dyn/ cm for untreat­ed PET film increased to about 52 dynkm, inde­pendent of the plasma gas and treatment time 1t\ .

To investigate the surface chemical composition of the treated wool and PET fabrics, ESCA was done l

". Relative intensities of C b , 0 1" NJ, and S 2p are shown in Table 9. The 0 J, intensity in­creased considerably, independent of fibre type and treatment time. The increased surface tension is apparently due to oxygen incorporation.

Five textile fabrics (polypropylene, polyeste r, nylon 0, wool, and m-aramid ) were treated with atmospheric low-temperature helium/ argon and acetone/ argon plasmas. Adhesion of the plasma­treated fabrics with adhesive tape by 1800 peeling test ge nerally increased I ? (Table 10). Adhesion st rength increased significantly by atmospheric plasma pretreatment.

2.3 Sputter-etching

Sputtering is a technique involving the coating of a substrate by thin metallic and ceramic layers. Argon ions produced by the application of high vo ltage direct current under a pressure of 0.1 Torr ill the presence of argon attack the surface o f cathode. Metals placed on cathode are sput­te red with argon ions and deposited onto the corresponding anode. Sputter-etching is also a method whereby the surface of polymeric materi­als on a cathode can be etched with argon ions, which leads to physical and chemical changes in the polymer surface itself. Sputter-etching was done under a pressure of 0.1 Torr in the presence

Table /l-Critical surface tension of PET films treated with atmospheric low-temperature plasmas

Treatment

Untreated Acetone! Ar plasma

10 s

30 s

00 s

180 s He! Ar plasma

10 s

:10 ~

00 ~

I XI),

Critical surface tension dyn/cm

43

52

52

51

51

50

5 1

52

52

---------------------------------------

of argon. The equipment for sputter-etching IS

shown in Fig. 3.

I Anode I

~( ~ 0~~ Ar (0 POIYm~ material e· T

Fig. 3-Apparatus for sputter-etching

Table 9-Relative intensities of C I" 0 1" N I, and S2p in ES­CA spectra of polyester and wool fabrics treated with atmos­

pheric low-temperature plasmas

Treatment

Untreated Acetone! Ar plasma

30 s

180 s

He/ Ar plasma

30 s

180 s

Untreated Acetone/ Ar plasma

30 s

180 s

He/ Ar plasma

30 s

180 s

Relative intensity, %

C I , 0 1, N I , S2p

Polyester

74.5 25.5

68.6 31.4

68 .0 32.0

67.9 32.1

67.7 32.3

Wool

69.9 14.3 • 9.1 6.7

62.1 33.1 2.4 2.4

59.8 33.8 4.4 2.0

56.3 26.8 12.3 4.6

53.2 30.4 11 .5 4.9

Table 10-Adhesive property of fabrics treated with atmos-pheric low-temperature plasmas

Fabric Peeling strength, glcm

Untreated He! Ar Acetone/ Ar

60 s i80 s 60 s 130 s

Polypropylene 174 289 295 295 295

Polyester 453 468 500 568 542

Nylon 6 289 379 358 363 384 m-A ramid 358 411 432 353 411

Wool R4 237 232 237 284

74 INDIAN J. FIBRE TEXT. RES., MARCH 1996

SEM micrographs of uniaxially- and biaxially­stretched, and subsequently sputter-etched PET films are shown in Figs 4 and 5 respectively' H. Grain structures on untreated polymer surface are crystallites. The biaxially-stretched films formed many protrusions by sputter-etching. On the other hand, uniaxially-stretched films formed wavy cre­vice, and then their surface morphology changed with the increase in sputtering time. As is evident from Figs 4 and 5, a number of the protrusions

decrcased with increase in the treatment time, whereas the height increased considerably with sputtering time.

2.3. 1 Application of Sputter-etching to Textile Processing

The effects of sputter-etching on adhesion of various synthetic polymer films are shown in Table 11 [ref. 19]. Surface mCldification by sputter­etching and . plasma treatments is effective to im­provc the ad hesive property, especially by sput-

Fig. 4-SEM micrographs of uniaxially-stretched and sputter-etched PET films ( x 40000) [Duration of sputter-etchIng: (1 ) 30 min, (2) 60 min, and (3) after ultrasonication of (2)J. Arrow indicates direction of stretching

Fig. 5-SEM micrographs of biaxially-stretched and sputter-etched PET films (x 40000) [Duration of sputter-etching: ( I ) 0 min, (2) 10 min , (3) 20 min, (4) 30 min, (5) 60 min , and (6) after ultrasonication of (5)J

WAKIDA & TOKINO: SURFACE MODIFICATION OF FmRE 75

Table 11-Changes in peeling strength of various polymeric films treated with sputter-etching and low-temperature argon plasma

Sample Peeling strength, g/cm

Untreated Sputter-etching Argon plasma

0.5 min I min 5 min 10 min 0.5 min 1 min 5 min 10 min

PET 447 526 530 584 700 516 500 526 605 Nylon 6 421 600 1037 1337 1368 526 547 632 674 p-Aramid 653 863 932 921 958 532 526 495 758 Polyamide 668 763 926 937 1416 563 563 547 511 'Polycarbonate 511 605 621 826 826 626 621 579 611

PPS 558 579 605 684 789 489 432 479 574

Adhesive test was carried out with polyester tape coated with acrylic pressure sensitive adhesive.

Fig. 6-Technora (po1y-p-phenylene!3,4'-oxydiphenylene-terephthalamide)

Fig. 7 -SEM photographs of Technora treated with sputter-etching and argon low-temperature plasma for 3 min: (J ) untreated, (2) sputter-etched, and (3) argon plasma treated

ter-etching. It is obvious that physical and chemi­cal changes in the polymer surface contribute to the increase in adhesion as a results of the in­crease in surface tension and anchor effect by the protrusions.

It is well known that the lustre and colour of the textile fabric are significantly influenced by the surface structure of the fibres. Black dyed Jr aramid (Technora, polY-Jrphenylene/ 3,4' -oxydiphenylene-terephthalarnide, Teijin Ltd., Fig. 6) fabric was sputter-etched and the changes in the surface characteristics were observed by

SEM, ESCA, light reflectance and colour mea­surement20. The SEM photographs of sputter­etched Technora are shown in Fig. 7 [ref. 20]. In­numerable fine microcraters of the size 0.1-0.3 .urn were produced by sputter-etching on the sur­face normal to the fibre axis, while fewer micro­craters were produced by low-temperature plas­ma.

The reflectance spectra of black dyed Technora fabric treated by sputter-etching are shown in Fig. 8 [ref. 20]. Even with a treatment time of 30s a marked decrease in reflectance was noticed.

76 INDIAN J. FIBRE TEXT. RES., MARCH 1996

-!! • ... QJ (.)

20

C 010 .... (.)

QJ

Technora --- Untreated

- - - - Treated for 5 min

...... QJ

a:: //--------~----_/

----" O~----------~-----------L------__ ~

400 500 600

Wavelength, nm

Fig. 8-Reflectance spectra of black dyed Technora treated by sputter-etching

Table 12-Ch3JIge in colour depth of black-dyed Technora treated with sputter-etching and low-temperature argon plasma

Treatment Sputter-etching Argon plasma time

s L* !J.E* L* !J.E*

0 33.2 33.2 30 29.8 4.6 32.7 0.5 60 27.7 6.5 32.4 0.8

180 25.7 9.0 30.5 3.4 300 24.7 9.9 29.7 4.2

Table 13-Relative intensities in narrow-scanning ESCA spectra of Technora treated with sputter-etching and argon

low-temperature plasma

Chemical Chemical composition -of surface, % component

Untreated Sputter- Argon etching plasma

0 1, 33.8 34.3 40.7

Nis 3.8 2.8 4.1

C I , 62.5 62.9 55.2

Table 12 shows the metric lightness L* and co­lour difference I1E* of Technora treated by sput­ter-etching after dyeing20. The L* values of Tech­nora decreased with increasing time of sputter­etching. The relative amounts of the chemical composition of CIs> 01. and N ls at the surface of sputter-etched Technora are shown in Table 13 [ref. 20]. Little change in surface composition was observed with Technora after sputter-etching, de­spite the large increase in colour depth, whereas argon low-temperature plasma treatment substan­tially increased the ° Is intensity, but with only a <;mall increase in colour depth.

Technora

20

10

o 2

o Sputter etching • Argon plasma

4

Treatment time, m in

Fig. 9- KlS values of Technora fabric treated by sputter-etch­ing and argon low-temperature plasma aft,er dyeing with c.1.

Disperse Blue 56

2.3.2 Change in Colour of Dyed Aramid Fabric by Sputter­etching

Technora fabrics dyed in yelJow, red and blue shades with Disperse Yellow 54, Disperse Red 60 and Disperse Blue 56 respectively at 190°C were sputter-etched and the change in colour was in­vestigated on the basis of CIELAB colour space in terms of L*, C*and h, and IJ.E* [ref. 21]. Fig. 9 shows the change in KlS values of Technora fabrics treated by sputter-etching and argon low­temperature plasma after dyeing with Disperse Blue 56 [ref. 21]. The surface irregularity caused by sputter-etching decreases the amount of light reflected, thereby increasing the depth of shade considerably.

The changes in L *, C *, I1H* and I1E*, . in­duced by sputter-etching, are shown in Table 14 [ref. 21]. To investigate the colour differences in detail, the relationship between L * and C* of dy­ed Technora sputter-etched for different durations are shown in Fig. 10 [ref. 21]. The change in co­lour of the sputter-etched yellow dyeing was. chiefly related to the change in C*, whereas with the blue and red dyeings differences in I1E* were caused by the change in both L * and C*. While the value of L * of each dyed fabric decreased considerably with increasing dye concentration, C* showed hardly any change. When the Techno­rafabrics dyed at the lowest initial dye concentra­tion were sputter-etched for different durations, a decrease in L * and an increase in C* were ob­served for blue and red dyeings whereas for yel­low dyeing no decrease in L * was observed.

WAKIDA & TOKINO: SURFACE MODIFICATION OF FIBRE 77

Table 14-Change in colour of aramid fabric treated by sputter-etching and argon low-temperature plasma after dyeing with three disperse dyes

Treatment C.I. Disperse Yellow 54 c.1. Disperse Blue 56 c.1. Disperse Red 60 time, s

L* C* l1H* l1E* L* C* l1H* l1E* L* C* l1H* l1E*

Sputter-etching

0 68.9 57.4 37.2 21.7 45 .6 43 .1

30 68.2 65 .3 0.6 7.9 32.8 23.8 0.9 5.0 42.9 47.8 1.9 6.0

60 67.7 67.2 0.0 9.9 32.1 23.9 1.1 5.6 42 .7 48.0 2.0 6.2

180 67.7 69.8 0.0 12.4 30.8 24.7 1.4 7.2 41.7 49.7 2.5 8.3

300 67.8 70.3 0.6 13.0 30.9 25.2 1.1 7.4 41.6 50.3 2.5 8.8

Argon plasma

0 68.9 57.4 37.2 2 1.7 45 .9 43.1

30 69.1 57.9 0.0 0.5 37.2 21.9 0.1 0.2 46 .3 43.2 0.1 0.4

60 68.8 59.6 0.2 2.3 36.9 21.8 0.1 0.4 46.2 43 .5 0.0 0.5

180 68.6 63 .2 0.5 5.8 35 .5 22. 1 0.3 1.8 44.6 45 .5 1.1 2.9

300 68.0 65.6 0.0 8.2 33.9 22.8 0.9 3.6 43.5 47.2 1.8 5.2

70 CI Disperse Yellow 54 CI Disperse Red 60 38 CI Disperse Blue 56

68 • 46

36

66 Dyeconcn Sputter

44 (o.w.f.) etching

:... t3 4% time

0 8% & 10 s 34

64 012% • 309 42 6.16% • 60s 020% .120s 32

62 \124% .180s 40

55 60 65 70 40 45 50 15 20 25 C·

Fig. 10-Relationship between L * and C * of dyed Technora treated by sputter-etching for different durations

3 Conclusion In order to improve functionality, surface modi­

fication is an important technique for materials. The plasma treatment mainly causes chemical modification and increases wetting and adhesion, whereas sputter-etching produces a number of protrusions on the surface and leads to increase in adhesion and decrease in light reflection, there­by increasing the depth of shade considerably.

References 1 Kitazaki Y & Hata T, Nippon Settyaku-kyokaishi, 8

(1972) 131. 2 Wakida T, Kawamura H, Song J, Goto T & Takagishi T,

Sen'i Gakkaishi, 43 (1987) 384.

3 Pavlath A E & Slater R F, Appl Polym Symp, ·18 (1971 ) 1317.

4 Millard M M, Lee K S & Pavlath A E, Text Res ], 42 (1972) 307.

5 Lee KS & PavlathAE, Text Res ], 45 (1975 )625. 6 Pavlath A E & Lee K S, Text Res], 4j(1975 ) 742. 7 Giegorski K S & Pavlath A E, Text Res], 50 (1980) 42 . 8 Ryu J, Wakida T, Kawamura H, Goto T & Takagishi T,

Sen'i Gakkaishi, 43 (1987 ) 257. 9 Lee M & Wakida T, Sen'i Gakkaishi, 48 (1992) 699.

10 Ryu J, Kawamura H, Wakida T & Lee M, Sen'i Gak­kaishi, 48 (1992 ) 213.

II Goto T, Wakida T, Nakanishi T & Ohta Y, Sen'i Gak­kaishi, 48 (1992) 133.

12 Okazaki S & Kogoma M, Kogyo Kanetsu, 27 (1992 ) 5. 13 Yokoyama T, Kogoma M, Moriwaki T & Okazaki S, ]

Phys D: Appl Phys, 23 (1990) 11 25.

78 INDIAN 1. FIBRE TEXT. RES., MARCH 1996

14 Kanazawa S, Kogoma M, Moriwaki T & Okazaki S, J Phys D: App/ Phys, 21 (1988 ) 838.

15 Yokoyama T, Kogoma M, Kanazawa S, Moriwaki T & Okazaki S, J Phys D: App/ Phys, 23 (1990) 374.

16 Wakida T, Tokino S, Niu S, Kawamura H, Sato Y, Lee M, Uchiyama H & Inagaki H, Text Res J, 63 ( 1993 ) 433.

17 Wakida T, TolOno S, Niu S, Lee M, Uchiyama H & Kane­ko M, Text Res J, 63 (1993 ) 438.

18 Koo K, Wakida T, Kawamura H & Ueda M, Sen' i Gak­kaishi, 48 (1992) 372.

19 Koo K, Wakida T, Sato Y, Paku P & Kimura T, Sen'i Gakkaishi,49(1993 ) 137.

20 Kobayashi S, Wakida T, Niu S, Hazama S, Ito T & Sasaki Y, J Soc Dyers Colour, III (1995 ) 72.

21 Kobayashi S, Wakida T, Niu S, Hazama S, Doi C & Sasa­ki Y, J Soc Dyers Colour, III (1995 ) Ill.