Indian Journal of Fibre & Textile Research Vol. 25, December 2000, pp. 315-329

Review Article

Some innovations in UV protective clothing

P Baja/" V K Kothari & S B Ghosh

Department of Textile Technology, Indian Insti tute of Technology, New Delhi 110016, India

Received 6 December 1999; revised received alld accepted 15 May 2000

With the increasing awareness of dangers posed to human health by overexposure to solar radiation and , in particul ar, ultravio let components of radiati on, due to the depletion of the ozone layer, efforts have been made to provide su n protec­tive clothing while permitting outdoor activi ti es. The degree of protection offered by such clothing depends on a number of factors. III thi s paper, an attempt has been made to coalesce the ideas of the various researchers who have developed ultra­violet protective clothing, and to understand the influence of UV rays on the structure and morphology of fibres , fabrics and fabric assemb li es. The effects of humidity, chemical processing. dyeing with reacti ve/direct/vat dyes on cellulosics and their blends, and lini shing chemicals on sun protection factor have also been hi ghlighted .

Keywords: Co ver factor, Porosity, Protective clothing, Sun protecti on factor , UV abso rber, UV protection factor, UV radiation

1 Introduction Sunlight is the source of a ll life on earth. Its spec­

trum extends up to about 3000 nm at sea level. Small doses of ultraviolet solar radiation are beneficial to humans. But large doses of UV radiation have detri ­mental effects such as sunburn, skin cancer, photo­keratiti s, cataract, e tc .

Increasing incidence of skin cancer is a major

concern throughout the world. The most common type of sk in cancers are squamous cell and basa l cell cancers . However, malignant melanoma is pos ing a more serious problem, due to excessive sun ex po­sure. Approximately 90% of non-melanoma and 65 % of melanoma skin cancers have been attributed to ultraviolet exposure. Incidence of skin cancer in Australia and USA are shown in Fig. I .The rate of skin cancer in New Zealand and Norway also seems to be very high. Even in Great Britain , the number of persons affected with skin cancer appears to be ri s ing. In Scotland, there was a rise of 82% in me la­noma cases over that during 1979-1992. Recogniz­ing these facts , it is important to protect skin from excess ive exposure of UV radiation. Using s imula­tion of spectrum of so lar radiation , Hilfike r et al. ' have studied the function of various parameters , viz .

"To whom all the correspondence should be addressed . Phone: 6591403 ; Fax: 009 1-0 11 -6526 154 E. mail: pbajaj @textile.iitd.ernet.in

time of the day , latitude and ozone layer thickness, on critical exposure time for skin reddening for sen­s itive persons. They have observed that the critical

time for sun burn is less than 30 min at 40° latitude even in autumn at ten 0 ' clock in the morning. It has also been shown that for brown skin, the critical dose at 290-300 nm for skin reddening is much less for white skin which always burns easily (Table I).

M adronich and Gruiji 2 have shown the increase in sk in cancer incidence due to ozone layer depletion (Fig. 2), using Total Ozone M apping Spectrometer (TOMS) aboard the Nimbu s 7 satellite. Thi s clearly shows that the ozone layer depletion reduces to minimum, i.e . at 5N and 5S latitudes, the ozone de­pletion is only 0.6 and 1. 1 respectively. However, the relation between skin cancer incidence and ul­traviolet dose is generally non-linea r and is repre­sented by an exponential model ) .

~ 1000 USA

12:1 7000 Australia

Fig. I-Death in Australia and United States due to skin cancer (refs 1, 4 & 5)

316 IND IAN 1. FIBRE TEXT. RES., DECEM BER 2000

Tablc I-Class ili cati on oJ'dilTcrcn t ski n typcs by scnsiti vity to UV radiation (Southern Europc; mid-day sun in summcr)")

Skin typc

II

III

IV

V

VI

80

~ 70 ><? ~ 60

C1J u 50 c

C1J '0

40 'u .S

30 iii u 20 c ro u 10 c

:;< 0 (jJ

Appcarancc Critical (u ncx- dosc poscd) to sk in

rcddcning mJ/c m2 at 290-300

nm

Whitc IS-3~

Whitc 2S-3S

Browni sh 30-S0

Brown 4S-60

Brown 60- 100

Dark 100-200 brolVn-black

SclJ'-pro-

tccti on ti mc min

5-10

8- 12

10- IS

IS-20

20-3S

3S-70

Sunburn ;lIld rc-sponsc to radia-ti on

Burns casil y, ncvcrt ans Burns casi ly, thcn tans Burns modcratc ly, always tans Burns sli ghtl y, always tans Burns rarcly. hcavy pigmcnta­tion Nevcr burns. heavy pigmcnta­tion

8.8 9.0 7.4 1.' 6.6 4.8 2.7 1.5 0.6 1.1 1.9 2.6 4.0 5.6 9.015.019.5 2U

Ozone deptetion ('!oJ

Fi£. 2-EITcct or latitudc and ozonc dcp lction 0 11 sk in canccr incidcncc (rer. 2)

Incidence-constant x (D ) OAF

where BAF is the so called biological amplifi cati on factor and is a function of cancer type and the ac ti on spectrum used to compute the ultraviolet dose. For fair-skin people, the epidemi ologica l determinati ons of BAF of the va lues of 1.4±0.4 for basal ce ll carc i­noma and 2.5±0.7 for squamous ce ll carcinoma have been repo rted.

2 UV P.-otection Factor/Sun Protection Factor UV radiat ion have been classified on the basis of

energy levels: • Very hi gh energy UV-C rays (IL < 280 nm): ]t is

highly damaging to human sk in , but it is filtered by ozone layer and can not reach the earth 's surface.

UPF range

Tab lc 2-UPF classi/l c;](iOIl systcmJ,5

UVR protcction catcgory

Effcctive UVR

transmi 'sion %

UPF ratings

IS-24 Good protection 6.7-4.2 IS , 20

2S-39 Vcry good protcction 4.1 - 2.6 2S, 30, 3S

40-S0, SO+ Excellent protcction ~2. S 40,4S, SO, SO+

• High energy UV-B rays (IL = 280-320 nm): It penetrates to a depth of few mm into the skin and forms stable pigment in the epidermis of the sk in. Melanoma or skin cancer is increased considerab ly due to the prolonged exposure of UV -B rays.

• Low energy UV-A rays (IL = 320-400 nm) : It penetrates into the skin, leading to premature age­ing. But its effect is onl y nominal and of short du­ration. Before understandin g the influence of various tex­

ti Ie parameters on UV protec ti on, it is necessary to defin e the protection fact or fi rst. The ultraviolet pro­tection facto r (UPF) or the sun protection factor (S PF) is the factor by which the period of ex posure to sun can be extended without redden ing the skin4

.5.

The UV protection factor is ca lcu lated by using the fo ll owing equat ion:

400 11111

2. EASAD.A UP F = ED = _ 2R_'O_"_I11 ___ _

ED 400,""

III 2. EASATAD.A

... ( I )

28011111

where SA.=Spectral irradiation of the sk in in UV re­gion or so lar spectra l i. radiance in Wm-2+

nm' t (to be obtained from AS/NZ Standard 26 or solar spectra such as CrE 85)

ED = Erythemal dose EDIIl = Minimum erythemal dose

EA = Relative erythemal spectral effecti veness TA = Spectral transmittanc of the item LlA = Increment re lating to wavelength

A = Wavelength in nm For the purpose of labelling, : un protective cloth­

ing shall be categori zed according to its rated UPF as given in Table 2.

3 Parameters which lnfluence the UV Protection Factor

3.1 Chemical Nature of Fihres

BAJAJ elol : SOME INNOVATIONS IN UV PROTECTIVE CLOTHI NG 317

The ultraviol et protection factor is strongly de­pendent on the che mica l nature of the fibres. Grey cotton ex hibits moderate absorpti on in the UV region, may be due to the presence of pigments, pectin s and waxes6

-8

. Grey jute also shows strong absorption in the UV region, but no comparative study is available between grey cotton and grey jute. The strong ab­sorption of jute may be due to the presence of lignin which acts as a natural UV absorber7. Wool in con­trast absorbs strongly, i.e. lower transmittance over 280-400 nm and even far beyond 400 nm. Silk occu­pies an intermediate position; it has been found to be more absorbent than cotton but less than wool as shown in Fig. 3a.

Dull viscose (TiOrtreated) shows strong absorp­tion as compared to lustrous viscose. Thus, a dull vis­cose fabric ( I 05g/m2) with 22 weft threads/cm showed a UPF of 13 while the lustrous viscose fabric ( 107 g/m2) with the same number of weft threads/cm showed a UPF rat ing of 9. Presence of Ti02 reduces the UV transmission and provides higher UPF due to

. 8 scattering.

Polyester fibre absorbs more (less transmittance) in the UV-A and UV-B region than acrylic and pol y­amide fibres (Fig . 3b). However, a liphatic polyamides are relatively permeable to UV rays and are less ef­fective in UV protection than aromatic polyamides. The presence of aromatic groups enhances the UV absorpt ion property as is the case with polyester. Low SPF of acry li c fibre may be attributed to the dipolar interaction of the nitrile groups. Hilfiker et al.' have reported that thin , untreated fabrics made from cot­ton, silk , polyamide and polyacrylonitrile offer SPF onl y in the range of 3-5.

3.2 Humidity

The re lati ve humidity and/or moisture content af­fects the UPF or SPF of a fabric in two ways. The more moisture the fibre absorbs , the larger will be the

fibre cross-section due to swelling. This reduces the space between the ends and picks by which the fabric density is increased, consequentl y dimini shing the UV transmittance. On the other hand, the presence of water reduces scatteri ng effects as the refractive in­dex of water is closer to that of textile polymers as compared to air, and hence a greater UV transmission vis-a-vis a lower UPF. Actual UPF thus depends on the interaction of swelling of fibre and scattering of light.

60 (0)

50-

1.0 Cotton

30

~ 0 20 ~ u c a ----.§ VI c: 0 ( b) c:.. I-

~ 50 ~ :t: Cl

30

~o - 400 Wavelength (nm)

Fi g. 3-Diffuse transmittance spectra of (a) natural libres and their blends in UV region, and (b) synthetic libres and their bl ends in UV region (ref. I)

Relotive Humidity

u..

160

120

~ 80

40

025 % ~ 45 % ~ 65 'Yo o 65 %

O~~~~~~~~~~~~~ ENKA Sun ViScose

Polyester Silk Cotton

Fi g. 4-EfTect of humidity on UV protec ti on factor of different fibres (ref. 8)

318 I DIAN J. FIBRE TEXT. RES. , DECEM BER 2000

can't be related to humidity.

3.3 Fabric Construction

3.3.1 Fabric Thickness/Weight

Dependence of humidity is most pronounced in silk and vi scose fabric (Fig. 4). Viscose has a hi gh water absorption and swelling capacity whil e silk has poor swelling properti es. But silk fibres are very fine ensuring a hi gh number of ends and picks, which means that even mild swelling wou ld lead to substantial reduction of the open surface (poros ity) and consequently a decrease in UV transmittance. For cotton , although an effect similar to viscose was expected, th e fini shing treatment might prevent the fabric from swel ling? Polyester has a low absorp­ti on and swel ling capacity and th at is why the UPF

With the increase in fabri c thickness, the fabri c UPF/SPF increases with the same fabric constructi on (Fig. 5). For the same fabric construction , SPF in­creases with increase in the fabric weight a lso. As the weight of a cotton fabric increases from I 10 g/m2 to 165 g/m2 and thickness from 0.18 mm to 0.52 mm, SPF increases from 3.2 to 5 (Tab le 3). Beyer and Cox 9 have also studied the effect of fabri c cover,

Fabric (undyed)

Colton

Wool

70

60

so / I

40 I u.. I Cl. 30 I Vl 20 I

I

./

----------/~--

--.~ . ----' .-'

,/

./

,/

./ ./

/" -'-Pure c.otton ./ - Co lIon +0.5 'l, UVA- 2

_ . / --"'Cotton +2.0'/, UVA-2

Fabric Thickness Imm I

Fi g. 5-lnll ucnce of fabric thickness on Slln protection factor (ref. I)

Tab le 3-EfTect of fabric construction and UV absorbers on UPFI. 11I.

1Y

Weight Thick-g/m2 ness, mm

110 0.18

165 0.52

87 0.32

125 0.29

Porosity %

0.6

0.2 1

4.07

0.63

UV abso rber concentration (owl)

Nil

2.3 % hydroxytri azole derivative

Nil

2% oxalanilide derivative (Cibatex UPF)

Nil

2% monosulphonated benzotriazole derivative (Cibafast W) Nil

2% Cibarast W

Method of application

Ex haust or pad batch

Exhaust or pad batch

Padding or fi xing (pH 4.5-5 .5)

Padding or fixing (pH 4.5-5 .5)

PF

3.2

20

5

>50

6

2 1

15

46

(Conld)

BAJAJ el a/: SOME INNOV ATIONS IN UV PROTECTIVE CLOTHI NG 319

Table 3-EfTect of fabric construction and UV absorbers on UPF1.1tI. 1~ -Col/ld

Fabric (undyed)

Weight Thick-g/m2 ness, mm

Porosity %

UV absorber concentrat ion (owl)

Method of app li cat ion UPF

Silk 4 1 0.10 0.6 1

84 0.20 0.43

Polyester 70 0.18 0. 13

Nil

2% Cibafast W

Ni l

2% Cibafas t W

Nil

Padd ing or fixing (p H 4.5-5.5)

Padding or t1 xing (p H 4.5-5.5)

6

24

14

48

42

2% di spersion of benzotriazole derivative (Cibatcx APS)

Exhaustion with disperse dyes

»50

165 0.28 3.80 Ni l 15

2% Cibatex APS Ex hausti on with di sperse dyes

24

Polyamide 67 0. II

140 0.29

2.7

2.3

Nil

2% Cibafast W il

2% Cibafas t W

thread count and thickness on UPF. For woven cotton fabrics, the thickness is the best predictor of UPF. On the other hand , both thread count and cloth cover are good pred ic tors of UPF on fabrics of ave rage thick­ness. However, thread count and c loth cover have been found to be the poor predictors of UPF for thin woven cotton fabrics.

3.3.2 Fabric Weave

Des ign of the fabric also affects the UV transmi s­sion . Obviously, the ti ghter the weave, the greater will be the UV protecti on. Loosely structured fabrics will afford very little protection. For the woven fab­rics of same wei ght , the plain weave designs give the highest protection.

3.3.3 Fabric Cover Factor/Porosity

Cover facto r is essenti a ll y concerned wi th the por­ti on of the fabric surface that is covered by yarn . Cover factor is re lated to UPF as follows :

UPF = 100 100 Poros ity 100 - cover factor

.. . (2)

Thu s, to obtain a hi gher UPF, the cover factor must

be high. Substantial improvement in UPF has been shown when the cover factor exceeds to 95 % (Fig. 6).

The importance of cover factor is realized while considering the e ffect of st retching and mechani ca l

Exhaust or pad batch

Exhaust or pad batch

3.8

37 10

29

finishing. Stretch reduces the UPF rat ing of a fabri c during wear as the effective cover factor is reduced . For example, in nylon/lyc ra type garment the UPF is s ignificantly reduced due to stretching in compari son to the UPF measured in a re laxed state. Any mechani ­cal finishing that increases the cover factor will a lso increase the fabric UPF. Thus , the overfeed on the stenter allows the fabric to shrink, which increases the cover factor and as a consequence, the fabric UPF increases. Underfeed on the ste nter, with the same argument, reduces the fabric UPF. Compressive shrinkage such as 'compac ting' and 'sanfori zing' in­creases the cover fac tor vis-a-vis the fabric UPF.

Laundering/washing during wear a lso has a sig­nificant effect on the cover factor. It was observed that for a 100% cotton long sleeve T-shirt (with a UPF rating of 15), the UPF rating increased to 35 af­te r first washing, primarily due to the consolidat ion shrinkage, i.e. due to an increase in the cover factor8

Poros ity, i.e. the number of pores per unit of fabric surface, has an in verse re lat ion with cover factor. Therefore, with a decrease in porosity the sun protec­tion fac tor (SP F) increases (Fig. 6) .

3.4 Chemical Processing

3.4.1 Bleaching

320 INDIAN J. FIBRE TEXT. RES ., DECEMBER 2000

White fabrics made of bleached cotton and viscose provide relatively low SPF in comparison to the grey fabrics with the same construction. This is because the natural pigments, pectins, waxes, etc . in raw cot­ton, which ac t as UV absorbers, are removed during bl eachingl D.

3.4.2 Dyeing

For all dyes, the absorpti on band extends to UV radiati on spectrum (280-400 nm) and all the dyes, therefore, can act as UV absorbers . . The extinction coeffi cients of these dyes determine their ability to increase the UPF of fabric.

UV absorbing capac ity of each dye is unique to that dyes tuff, and hence it is very difficult to gene-

'- 200 -t; o "-

is 150 ~ u

.2!

!l. 100 c :>

Vl

x 50 o 1:

10 -------____ _

ralise. However, from the study of Reinert et al. lion the influence of dyeing on various fibres, it was re­vealed that the sun protection properties were im­proved on dyeing, irrespective of the chemical nature of the fibres. In their experiment , two cotton fabrics differing in porosity and thickness were dyed to pale and deep shades with Cibacrori reactive dyes. The sun protection properties of both the fabrics were im­proved (Table 4). However, Reinert et al. II and Pailt­horpe and Cruiskis 7 have demonstrated that the darker the shade of any colour, the higher wou ld be the pro­tection , indicating that the dark coloured fabrics transmit less UV rays th an lighter shade fabrics. However, no correlation between the chemical struc­ture of the dyes and UPF has been establi shed as the

Fig. 6-Sun protection factor as a function of cover factor and porosity (ref. 26)

Table 4-EITcct of dyes on UV protection factorJII-12.24

Fabric Thick ness Porosity Sample Dyes appli ed Method of UPF mm % appli cation

Cotton 0.20 3.05 Cont ro l 3

Dyed (Pale yel- Reactive dye III OSD Exhaust or pad 7 low) (Cibacron batch

Yellow F4G) III SO 23

Dyed (B lue) Reactive dye 1I10SD Exhaust or pad 6 (Cibacron batch Blue F-GFN) III SO 22

0.20 0.21 Control 3

Dyed (2.4%) Vat dye (S tructure III) Ex haust or pad 54 batch or pri nti ng

0.20 0.64 Contro l 4

Dyed (2%) Direct dye (Structure I) Exhaust or pad 11 0- 11 34 batch (CIE 0 ( 5)

(Contd)

BAJAJ el Cl f : SOM E INNOVATIONS IN UV PROTECTI VE CLOTHI NG 321

Tab lc 4- EITcct of dyes on UV protection factorJO·12.24_Col/ /(f

Fabric

Wool

Si lk

Polyester (s taple fibre)

Polyamide (stap le fibre)

Thickness mm

0.29

0.20

0.29

0.29

Porosity %

0.63

0.43

3.80

2.30

Sample

Contro l

Dyed (Pale grey)

Dyed (Black)

Cont ro l

Dyed (Pale grey)

Dyed (Black)

Control Dyed (Pale grey)

Dyed (Black)

Cont ro l Dyed (Pale grey)

Dyed (Black)

shade changes fro m a li ghter ye ll ow to a darker one . They have onl y reported that black, navy blue and dark green dyes s ignificantly improve fa bric UPFs whereas very pa le shades prov ide onl y small im­provement in UPF (Fig. 7). For example, a bl eached and merceri zed fa bric w ith 135 g/m2 weight , 0 .20 mm thickness, 3 .05 % poros ity and dyed with Ye l­low F-4G-Cibacron dyes with 1/10 standard depth resulted in the UPF of 7 ; the same dye with 1/1 standard depth showed the UPF of 23. However, for woo l fabric with a hi gh poros ity (4.07 %), even a bl ack shade cou ld not improve the UPF to a large ex tent (UPF=29). The poros ity imposes a limitati on here. Thi s was c lear when another woo l fabri c hav­ing a much less poros ity (0.63 %) was dyed with the same dye. The UPF achi eved was much hi gher th an 50 (Table 4). W ith Sil k fab ri cs, the improvement is very marg in a l w ith a pa le shade, while w ith bl ack shade, a hi gh UPF (250) can be achi eved when the poros ity is not too hi gh. Po lyester fabrics in gene ra l show a hi gh UPF. However, in case of stap le-fibre fabri c, due to the high poros ity, dye in g even with bl ack dyes even did not improve the UPF to a large extent. With polyamide, SPF was improved by dye­ing, but here a lso, limitati ons were imposed by the poros ity and thi ckness of the fabrics.

Dyes applied Method of application

UPF

15

Acid dye (Irgalan Grey GL, Exhaust or pad 25 Irgalan Bordeaux EL) batch Acid dye (Lanasel Black B) Exhaust or pad »50

batch 4

Ac id dye (Irgalan Grey GL,lrgalan Exhaust or pad 8 Bordeaux E L) batch Lanasel Black B Exhaust or pad >50

batch

Disperse dye (Teras il Yellow 4G, Ex haust 15

>22 Teras il Red R, Terasil Blue 3RL) Disperse dye (Terasil Black SPL) Exhaust »24

Exhaust Acid dye ( Tectil on Yell ow 3R, Exhaust

10 13

Tectil on Red 2B, Tect ilon Blue 4R) Acid dye (Erionyl Black MR, Exhaust 30 Lanasel Blue 5G)

6o,-----------------------------~~

50

~40 QJ U

Iii 30 :to

.~ 20 c ro ~ 10

uve

Bleached cation

Red dyeing

Yellow dyeing

Navy blue dyeing

UVB . UVA

~~0------~30=0--~------~3~50--------~400

Wavelength (nm)

Fig. 7- lnfluence of dye pick-up on UV transmittance (ref. 4)

In another study, the influence of dye ing on pro­tection factor has been reported by Bohringer et al. 8

A heavy lustrous viscose fabric weighing 152 g/nl was woven in Y2 twill weave and dyed in di fferent shades. The dyestu ffs se lected fo r thi s tes t series were Solophenyl dyes (Ciba Ge igy) used at a concentrati on of 3%. The fabrics were dyed at 120°C. It was found that fo r all shades, the transmi ss ion va lues were re­duced by at least 50% . C iba Geigy' 2, IJ has also d is­c losed a process of improv ing the sun protecti on fac­tor of cellulos ic fibre materi als by treating them wi th another suitable direct dye. Bleached tricot knitted cotton dyed with 0 .0 \-1.5 % (owf) of the direct dye

322 INDIAN 1. FIBRE TEXT. RES., DECEMBER 2000

(Structure l) exhibited sun protection factors of 110-1134 (determined by CIE D65) and 111-1100 (deter­mined by CIE S-Europe) while undyed samples ex­hibited sun protection factor of 4 (de te rmined by both method s).

Structure I

Suitable reactive dyes for increas ing the sun pro­tection factor of cellulosic fibres have also been tried l4

. The sun protection factor of cotton can be in­creased by react ion with the foll owing reactive dye (Structure TI).

Structure II

Vat dyes have also been used for increasing the sun protection factor of cellulosic fa brics. When ap­plied by dye ing or printing, these dyes act as sun­screen for ce llul os ics, espec ia lly for cotton. A 0 .2 mm thick cotton fabric treated with 2.4% of the vat dye (S truc ture III) showed solar protect ion factor o f 54 (determined by CIE D65) compared to 3 for untreated fabric 1 S.

o Structure III

4 Finishing with UV Absorbers UV absorbers are inorganic or organic substances

capable o f se lective ly absorbing short wave so lar ra­diation in the spectral region 280-400 nm and o f re­storing the absorbed energy intact to the environment. They are often used as UV screen agents. These UV screcners absorb part of the inc ident li ght and reduce the amount of li ght striking epide rmis o f the skin ,

. 16- 19 causmg sun burn .

Chemical compounds suitable for UV absorbers mu st meet the following criteria:

• It should absorb effectively th roughout the UV region (280-400 nm), but especially in 350-400 nm region.

• It must be UV stable itse lf .

• ]t must di ss ipate the absorbed e nergy in such a manner so as to cause no degradation or colour change in the medium it protects. The most im­portant chemical classes include: o-hydroxybenzo­phenone, o-hydroxyphenylbenzotriazole and o-hydroxyphenyltriazine. Of the inorganic substances with UV absorbing

properties, titanium dioxide (Ti02) deserves special mention. The improved UV protecti on is attributed to reflection and scattering of the UV rays20.

4.1 Application Methods Ciba Geigy offers a variety of UV absorbers that

can be applied on the fabric by e ither ex hau st or pad batch method :

. Cibatex UPF is a water soluble oxaldianilide with two reactive groups. It is appli ed by exhaust ( 1-4%) or pad batch ( 15-50 gil) method along with react ive or direct dyes. It is reported to have excell ent fastness properties .

Cibafast W is a monosulphonated benzotriazo le derivati ve. It is suitabl e for wool, s ilk , po lyamide and their blend s. It is applied under a id dye ing condi­tions, preferably by ex haust ( 1-3 % ) method .

Cibatex APS is an UV absorber used for polyester and its blends. It is a di spers ion of a benzotriazole derivative and is applied at 1-3 % by exhaustion with di sperse dyes. The effect of these UV absorbers on diffuse UV transmittance of diffe rent fabrics is shown in Figs 8-1 I.

Solartex CEL is recommended for dyeing/printing either by ex haust or cold pad batch technique. So­lartext CUT is recommended for fini shing with usual rec ipes with softeners and resins . Solartex UVP is used for combined protec tion again st sun burn and rai n. The applicati on concentrat ion of these products is 1-4%. They are applied e ither by ex hau st or co ld pad batch technique.

Reinert and Hil fiker2 1 described a process in which the sun protecti on of the fabric can be improved by treating with UV absorber UV A-I based on tri azine and UV A-2 based on hydroxytri azole. It may be seen from Fig. 12 that with UV A- I , the maximum SPF is only 25. This is due to the fact that UV A-I has an upper absorpti on limit of about 3 15 nm (Fig. 13) and

BAJAJ el {II: SOME INNOVATIONS IN UV PROTECTIVE CLOTHING 323

therefore it can never yield a very hi gh SPF. On the other hand, its extinction coeffi cient at 3 10 nm is very high and, therefore, the SPF increases steeply for very small UY A concentration. With UY A-2 however, due to a higher upper absorption limit at around 350 nm, the max imum SPF is much hi gher.

50

~ .- '- '- ' 40 .-IU .-u .---. C:: ·~~out . UVA 0 ..... +- 30 "E III c 0

20 ..= '" III OJ 10 -<0-

with UVA 0

0280 320 Wavelength (nmJ

Fig. 8-DilTuse transmi ttance spectra of cotton with and without UV absorber (2% Cibatex UPF) (ref. I I)

50.--------------------------,

~ 40 Sitk Crepe Satin Eabr';....;;. /~ _

? /' /./

~30 / X ~ 20 . //// 1/" WooL Fabric '" Wililout 'g UVA I

:;: 10 / o .".,/ with 1/'

.~/ UVA

0280 320 360 400 440 480 WaV!length (nm l

Fig. 9-Diffuse transmittance spectra of woo l and silk with and without UV absorber (2% Cibafast W) (ref. II )

~ 50[----:::: ~=- Fo brtc 40 ...- '

~ .

~ ./ ~~--- . E / .,,-;: -= 30 - . .-E I " j 20~ Without UVA /// ~I ~ 10

1 )~/~. I

a 0 -: ___ ~_:=-::_~ .W~h_=--~J 2'00 320 360 1.00 :,40 480

Wavele ngth (nm)

Fig. IO- Difl'use transmittance spectra of polyester with and wi thout UV absorber (2% Cibatex APS ) (ref. I I)

Triazinyl aminost ilbenes have been used as effec­tive ultraviolet absorbing agents to improve the sun protection factor as well as the whiteness of the tex­tile fibres22

. The invention provides a compound (Structure IV) which was treated with 3-dimethylamino-I-propylamine in an oil bath held at 90°C to produce Structure V. The latter compound improved the whiteness and UPF of the fabric .

70,-----------------------~

~ 60

~ 50 c: ,g E 40 With out UVA VI

c: 30 ,-~ 1)1 20 ::J

~ o

Wavele ngth (nm)

480

Fig. II - Diffuse transmittance spectra of polyamide with and without UV absorber (ref. I I)

100~------------------------~

--- UVA-1 -UVA-2

Cone , of UVA (Y. w/v 1

Fig. 12-Sun protection factor of cotton fabric treated with UV A-I & UV A-2 (ref. I)

3~------------------------~

./-, ,'" \ , ,

/ \ / \

I \ , \ ;' \

/ \

--- UVA- 1 -UVA-2

Q ~---'------'---"'" 280 300

Wavelength ( nm 1 400

Fig. 13-Absorbance spect ra as a functi on of UV absorber CO Il­

centration for UV A-I & UV A-2 (ref. I)

324 I DIAN J. FIBRE TEXT. RES. , DECEMBER 2000

Structure IV

Structure V

Another approach by Isharani ef at?' indicated the treatment of fabric to reduce the amount of light passing through it with 0. 1-6.0% (owf) UV absorber (Structure VI) in a neutral or an alkaline bath at about 90°C by pad thermofix or exhaust method . Treated fabrics provided protection against UV radiation for skin which is covered by the clothing, espec iall y li ght weight summer clothing.

A=Radical of the UV absorber B=Radical of the UV absorber or water solubili zing

group X=F or CI

The UV absorb ing groups A & B may be the same or different and are se lected from suitable radical s of any UV absorbing compound . If both A & Bare UV absorbing groups, at least one of them is advanta­geously subst ituted by at least one SO.,H, COOH or phenoli c OH or their salt.

Ciba Speciality Chemica l s23.2~ have developed an­other new product Tinofast CEL, which absorbs UV­A and UV -B rays and can be app l ied to cotton and cotton blends. This new product can be applied by padd ing on woven and knitted fabri cs to produce arti­cles having a sun protection fac tor of 40+ after 30 was hings. Dermatological tes ts al so showed no harm­ful effects on humans and no ecological problems are ex pected during app li cation or disposa l.

Clari ant has launched some UV absorbers for pro­tecti on of sk in under the trade name Rayosan. These

Rayosan products can be applied by any normal tex­tile finishing method on yarn , knitwear or woven fab­ric using the conventional textile fi nishing equ ipment. Two products have been introduced, viz. Rayosan C paste for cellulos ic fibres and polyamides, and Rayo­san P liquid for polyester fibres.

Rayosan C paste can be applied by exhaust or con­tinuous method, normally as a fin ishing process . It can be applied during dyeing on cellulosics together with Drimarene-K dyestuffs , and 011 polyamides to­gether with ac id dyes. It absorbs primarily in UV-C and UV-B regions, and very little in the UV-A region. Therefore, it has very little or no influence on f10urescent brightening agents. These products are very fast to washing and light.

Rayosan P liquid can be applied together with di s­perse dyes by exhaust method at high temperature or at the boil with carri ers, and by pad thermoso l con­tinuous processes. It exhibits a very hi gh absorbing effect in the whole UV region.

Palac in25 has also revealed an UV absorber composi­tion containing non-ionic sUlfactant for dyeing yarn an addition product of ethylene ox ide or propylene ox ide or both ethylene ox ide and propylene ox ide copolymer, and a mixture of fa tty alcohols, faul ty ac ids or fatty esters having preferably 14-1 8 carbon atoms or either tristyryl phenol or distyryl phenol. Such compositions have good storage stabili ty and shear stabili ty.

In another study, Clariant26.27 di sclosed the use of

a-hydroxybenzophenone derivati ves in aqueous di s­persions as UV absorber (Structure VII).

OH OH

ifo~ N°"©) OCH2CH(OH)CH20

Structure vn

BAJAJ el of: SOME INNOVATIONS IN UV PROTECTIVE CLOTHI NG 325

Thi s compound (Structure VII) is prepared by etheri ­fication of 2,4-dihydroxy-benzophenone with 1,3---di­chloro-2-propanol in EtOH. It was dispersed in water containing ethoxylated oleyl alcohol di spersant and the di spersion added to a dyeing bath to enhance the light fastness and UPF of a polyester tricot materi a l.

Thompson and Pailthorpe28 have described a proc­ess of inc reasi ng the SPF rating of a fibre or fabric by treating it w ith a UV absorber based on 2,4-difluoro-5-chloro-6-anilinopyrimidine at I % (on fibre we ight) to a cotton fabri c ( 145 g/m\ The SPF rat ing obtai ned

was 51 .3 ± 3 .2 . Ciba Specia lity C hemicals has a lso di sc losed a

method for increas ing the protection factor by trea ting texti les wi th non-reacti ve UV abso rbers (c .g. oxa lic anilides, hyd roxybenzophenones, tri azi ne compou nds or triazo le compounds, sa licy lic ac id esters, substituted ac rylonitrile, substituted arylaminoethylenes or nitril o­hydrazones), emul sifying agents, wate r and polysilox­anes. T hey observed that when a cotton fabric was padded with an aqueous so luti on contai ning 20 giL mixture of an UV absorber (S tructure Vlll) and non­ionic emul sifie r (Lutensol ON 60 & Arlecel C) with a

pickUp of 80% fo ll owed by drying and curing at 170°C for I min , the SPF of29.8 was obtained2

<) .

H~25 CC~ Me

Structure VIII

Reinert and Kaufmann 'o disc losed , in a patent , the treatment of fabrics with UV abso rbers for sk in pro tection aga inst sunli ght. The fa bri cs were treated with aqueous so luti on conta ining 2% o f Na salt of 2,4-d ichl oro-s- tri azine-6-yl-p-amino-o­

hydroxyphenyl sulphonic ac id for 30 min at 50°C , rinsed and dried to g ive fabrics with SPF > 25 . They have a lso shown that bl eached cotton tricot when treated with a liqu or conta ining hydroxybcnzotriazo lc

deri vative (Structure IX) at 60°C for 20 min in a j et

dye ing machine and then treated for another I h gave a highly UV-resistant fabric ' l.

Skehan:12 has di sc losed a chemical named Rayosun

for sunproof c lothing. Rayosun is a two-component molecul e, one part absorbs the UV rays while the second part reacts with the fabri c.

S Application of Resins Containing UV Absorber lpposha Oil Indu stri es" has developed a process of

coating the fabri cs with a homopo lymer or copolymer so lution (0. 1-7 wt% ) with a mo lecul ar we ight be­tween 10,000 and 800 ,000 wh ic h it c laims to impart pro longed li ght res istance and ultrav io le t sc reen ing actio n to fabrics than is normall y avai lab le . A number of monomers, inc luding 2-hydroxy-4-ac ryloy lox y benzophenone, a re suitab le for thi s, whil e ac ry lic ac id , methacryli c ac id and the ir es te rs a re best suited for copo lymerization with monoeth yle nica ll y unsatu­

rated monomers. In another coat ing technique, Toyota Res & Dev.

Lab34 has described a process in which the po lymers showing UV shie ld ing and ab ras ion res istance are manufactured by di spersing organi c a lkoxy sil anes, inorganic or organi c sa lts or a lkoxides of Ti , Mg, AI , Si , etc, and inorganic or organi c po lar so lvents fo l­lowed by mouldi ng.

Thus, 297.6 g 3-methacry loxypropy ltrimethoxy s il ane and 170.4 g titanium tetra isopropox ide were stirred in H20 to give 143 g powdered layered organo titanosilicate show ing good heat res istance, di s­pers ibility in organi c so lve nts, and good UV shi e ldi ng property .

Toray Industri es35 has a lso deve loped an immer­s ion tec hnique for making antibac ter ia l U V-bl ock ing fabrics. A pol yes te r fabric was immersed in ethano l

containing 3% fe ruli c acid, dri ed and hea ted at 190°C

to give a fabri c showing antibac te ri a l activity agai nst Staphylococcus aureus and UV absorpti on of 98 .5 and 94.9% in the UV-B (280-320 nm) and UV-A (320-400 nm) regions respecti ve ly.

Multifunc tional po lymeri c UV abso rbers for pho­tostabilization of wool have been studied by Riede l and Hocke,)6. The most effecti ve ones are deri vati ves

of 2-hydroxybenzophenone and hydroxyphenyl ben­zotriazole which show highest absorbance in the range of 290-360 nm . Photoye ll owing of wool can be reduced up to 50% when UV absorbers w ith polymethacrylate backbone are applied.

6 Application of Optical Brightening Agents Optical brightening agents (OSAs) are often ap-

326 INDIAN J. FIBRE TEXT. RES. , DECEMBER 2000

pli ed to enhance the whiteness of tex tiles by induc ing f lu orescence by UV excitat ion and visib le blue e mi s­s ion. This phenomenon of exc itation and emi ss ion is caused by the transition of e lect rons invol ving p-orb ita ls from ei ther conjugated or aromatic com­pounds. These optical br ightening agen ts are hi ghl y conj ugated deri va ti ves of sti lbene, benztriazo le or benzimidazo le wh ich have been de ri va ti zed to give them water so lubility or polar characteristi cs to be atrracted to the fabr ic substrate on which they will be used. Most OBAs have exc itation maxima in the very near UV or at the lower end of the vis ib le sca le in the range of 340-400 nm. Hence, OBAs can improve sun protection factor of textile mate rial. It has been shown that OBA used in laundering improve the UV blocking abi lity of cotton fabrics and cotton/polyester blend fa brics but not of the fabrics comprised e nti rely of polyester and nylon.

OBAs have the added benefit of increasing the UY absorption properties and hence, the su n protection facto,)7-4o. However, . the effect of OBAs can be

quenched s li ghtly to complete ly when UV absorbers a re appl ied dependi ng on the absorption properti es of the two prod ucts. As a result, ultraviol et spectropho­to meters used to measure spectra l transmittance can exh ibit systematic errors when fluoresce nt sampl es are introduced.

7 Development of UV-Resistant F ibres Du-pont41 has developed UY -res istant core-sheath

elas tomeri c monofilament wh ich comprises a po ly­et her este r, polyester ure th ane or polyeste r amide core and polyether ester, pol yester ure th ane or polyester

amide sheath havi ng me lting point at leas t 20 DC lower than the core and eac h containing about 1.8-3.0 weight % carbon to protect from U V rad iati on.

Duan and Zhang42 have described a process in which the composite fibres, compri s ing titanate­coupl ing agent treated BaS04 conta ining polypropyl­ene core and ti tanate-treated powdered AI or UV ab­sorber containing polypropylene sheath, were woven into fabr ics which showed good UV shie lding ability.

Kuraray Co. of Japan43 has developed UV-ray shieldi ng base fabric in wh ich the fibres, consi sting of a polyester and 10% Ti-ox ide, ZnO and/or alumina as a core and a polyester contai ning 2 mol% sul­foisopht ha lic acid units as the sheath were together melt spun at 45 :55 ratio, twisted, made into a woven taffeta and dyed to give a fabric with UV permeation of only 1.5%.

Teijin Ltd44 has also developed a core-sheath com­posite fibre. Po lyeste r containing 1.5% Ti02 parti c les as the sheath and po lyamide as core were me lt spun at core/sheath rati o 50:50 and drawn . This fibre showed

a hi gh UV protec tion.

Other innovations45-53 in produci ng UV-res istant fibres inc lude a new range of fabrics called ENKA

SUN, developed by Azko Nobel in co llaborat ion w ith Lenzing, to provide the wearer with a sun protection factor of 30+. The product E nka Sun is produced by the add iti on of a non-tox ic, c hem ica lly inert and wa­ter insoluble pig ment to continuous fil ament viscose yarns. These 'sun blockers' are not affected by wear­

ing, washi ng or dry c lean ing.

8 Designing of Innovative Sun-screen Fabrics Increasi ng awareness for sun protection has led to

the development of some innovative sun-screen fab­rics. A light reflecting sun-screen developed by Poly­sack Plastic Indus tri es54 comprises a ne t structure with equall y spaced th reads in the perpendicu lar di­rections. The threads are laminated strands in which a first laye r of mono-orien ted tran spare nt f ilm is cov­

e red by a second layer that essential ly compri ses alu­min ium, whi le a third (aga in transparent) layer pro­tects the intermediate (reflec ting) layer from deteri o­ration.

A composite tape and patch materia ls fo r app lying to human skin to block harmful sun ex posure have been developed. These compri se a printab le layer of nonwoven fab ri c mate ri al formed from po lyester, nylon or cellul osic fib res and their blends, and a thin adhes ive coati ng whic h is sk in compatibl e, non-tox ic, hypo-a lle rgenic and non-irritat i ng55 .

Wetmore Associates56.57 have described a ult ra­

vio let protective fa bric with a high weare r comfort. It compri ses multifila ment ny lon warp ya rns and multi­filament nyl on weft yarns. The fa br ic is undergone sanding only on one surface, drying and j et launder­ing fo llowed by air drying withou t tretching to pro­vide a fa bri c hav ing a sun protecti on factor of at least about 30, and pre fe rabl y about 70 or more . The pre­ferred warp yarn is at least 40/40 den ie r nylon , while the weft yarn count is pre fe rab ly 80/50.

With the dramatic ri se in sk in diseases, the hos iery market is also receiv ing attent ion as a means of UV protection. One such in novation is ' tights with sun protection '. One German Compan/ 8 has developed such 12 denier tights with a special coating to filter the sun rays. It is claimed that over 90% of UV-A,

BAJAJ el af: SOME IN OVATIONS IN UV PROTECTI VE CLOTHI NG 327

UV -8 and UV -C rays are thus kept away from the skin .

Kl opman International59 has reported a luminex high-visibility fabric which has been certified as ex­cellent when tested against UV-A's and UV-8 's as well as UV protection fac tor for safeguard aga inst sunli ght and ski n sensiti vity in accordance with AN­ZAC norm.

Backmann60 has described the screens made from warp-knitted nets fo!' protecti on from the sun for open spaces . Glass-fibre-solar screening fabrics have been reported by Stevens Co. Tnc.61

, whi ch prov ide ade­quate sun protection.

Crosb/ 2 has reported that fab rics containing mi ­cro-capsules of slow re lease substances can screen out harmful UV rays from the sun .

Screens with metalli zed polyester film , produced in a circul ar loom in the form of square-weave fab­rics, have also been reported to act as sun filters6

'.

Solar Fas hi on CO.64 has des igned bathing costumes made from SOLST AR, a net fabric which it claims to all ow onl y one third of the sun rays to reach the sk in .

Arnold et al.65 have reported the use of new ro ll er blinds or curtain-like so lar absorbers as low­temperature heaters having thermal insul ation effect. So, they have developed energy utili zing novel tex til e structures to regulate the incoming so lar energy on glassed-in-areas .

A new generati on of screens and techni cal nets is . 66 T' 1 • . ' I now emerging. eX ll10v I\Jllttec structures are spe-

cially engineered to fulfil spec ific requirements. Made of hi gh tenacity polyethylene, these are weather- and UV -res istant. Custom-made screens and nets have become an imperati ve necessity. Used as windbreak or sun shadowing fences, these al so pro­tect against hail frost, rain , snow, insects and birds.

Scienti sts at Quennsland Institute of Medical Re­search67 have ca lcul ated the rati o of the intensity of dangerous UV-B radi at ion in direct sunli ght with re­spect to the various shades used. For example, a hat gives reasonable protect ion ac ross the nose and eyes, but not on the rest of the face. House awnin gs too were twice as effecti ve when fac ing away from the sun, and beach umbrell as offe r littl e protecti on from UV-B scattered from the side.

9 Methods of Measuring UPF/SPF

Two methods, vi:. in vivo and ill vitro, are gener­al ly used to determi ne SPF or UPF. In the ill l'il'O

method, test subjects whose sk in is covered with the

textile in questi on are irradiated with li ght hav ing a spectrum, closely resembling that of sun , whil e in vitro method in vo lves measurement on human sub­ject, but the subjects are irradiated with monochro­matic light and the criti ca l amount required to cause skin reddening (erythema) is measured. From these results, the erythemal effecti veness, the reciproca l of critical dose of a given wave length , is determined. Thus, if the erythema acti on spectrum SeA) (a lso termed erythemal effectiveness) of UV radi ation, the spectrum of the li ght E (A) and the spectral transmit­tance of the sunscreen T(A) are known, the SPF can be calculated according to Eq ( I). It is assumed that no synergism or antagoni sm of effects due to UV lights of various wavelengths ex ists.

A poss ible major source of di screpancies between in vivo and in vitro SPF is the choice of illuminati on in in vivo tes ts. Since an arti ficial li ght source can never perfectly match the sunlight spectrum and a sli ght change of the spectrum can have a large effect on SPF, in vitro SPFs are actually more reli able than in vivo SPFs.

When the UV radi ation fall s on a textile material, a small portion of it passes through the materi al while a larger portion of it is scattered in the materi al. This scattered light is of course al so harmful to skin. So, it is important to measure the diffuse transmittance of textiles. This can be done by fixing the materi al over the entrance aperture of an integrating sphere, the internal surface of which is to be lined with a hi ghl y refl ective matt, for example barium sulphate p:li nt. Also, the beam of radi ati on of the spectrophotometer should be less than ±5° about the beam axis. How­ever, the results of UPF are very much in fluenced by the structure of fabric, fo r example, for a fancy weave, which is thick in one and thin in other places68

. Al so, fo r a multicoloured fabric, each co lour should be taken in turn and tes ted for UV transmis­sion for the whole of the fabric

UV IOOOF Ultrav iolet Transmittance Analyser is a special spectrometer developed fo r thi s purpose. It is compact, rugged and easy to use instrument for meas­uring the total transmittance i.e. the amount of UV rays that is direc tl y transmitted and diffu se ly scat­tered by the textiles. From the percentage transmit­tance in the UV region, the SPF is obtained through an automatic conversion.

Mesa69 has described an indirect screening test for UV protective fab rics . It is a simple and rap id tes t to determine the su n blocking effects of fabrics, and to

328 INDIAN 1. FIBRE TEXT RES ., DECEMBER 2000

evaluate the e ffec t that colourants and known UV abso rbing mate rials have on sun blocking ability. In one study, woo l fabri cs were dyed with 2 acid dyes o f

known poor light fastness ec. l. Acid Green 16 and c.r. Ac id Vi o let 17) and then ex posed to xenon arc radi at ion behind a range of fabrics o f different fibres, undyed and dyed , and treated with known UV ab­sorbers eC ibafast W ). Variati ons in fibre type, dyes and U V absorbe r affec ted the fadin g of th e dyed woo l fabrics. The two fabri cs had diffe rent responses to the va riables tested and thus, thi s seems to be potentia l method to assess a fabri c's UV protec ti on va lue.

It has been recogni zed that UPF measurement of text il es can resu lt in faulty UPF c lass ification if any

fIuoresence is present in the tex til e . Thus, not onl y the spectroph omete r hardware but also the appli cati ve know how of the instrument should be crit ica ll y ana­lysed.

Greenoak and Pailthorpe7o have indi ca ted the di s­crepanc ies between diffe rent testing methods found in Au stralian and US Standa rds Me lanoma & Skin Can­cer Research Institute.

Us ing the spectrophotometer of the Swiss Federa l Laboratory for T estin g Mate rial s and Research (EMPA), the meas urement va lues have been worked

out fo r assess ing the sun protec ti on of text i les. M eas­urements already carried out have served to define the testi ng scope of the ' Project Sun Protecti on' launched by EMPA, in w hi ch textiles are to be assessed for

. . ff ' 71 the ir sun protect ion e ect lveness . Seve ral in vesti gato rs72-75 have dea lt w ith the vari­

ous aspec ts of su n protective c lot hing and the ir test­IIlg.

10 Summary Various fac tors affecting the sun protection and the

effecti ve measures to improve the protection factor clearly indicate tha t the SPF or UPF of a fabric is de­pendent on a numbe r of factors including fibre type, fabric constructi on, nature of chemica l process ing and presence o f additives such as UV abso rbers or optica l bri ghteners:

• Natura l cellul os ic and li gnoce lloulosic fibres have a low to moderate UV absorpti on capacity over the entire UV region. Wool and s ilk have higher ab­sorpt ion than ce llulosics with wool having sub­stantial absorpt ion than any o ther natural fibres . Of the synthe tic fib res, acryl ic has the lowes t UV ab­sorpt ion in the UV-B reg ion . Pol yes ter and aro­matic polyamides have hi ghe r absorption in the

UV -B region , due to the presence of aromatic group, in comparison to aliphatic po lyamide.

• Moi sture/humidity has a dual ro le in affecting the UPF which depends on the f ibre type, chemical

nature of finishes applied, etc.

• Hi gh fabri c thickness and weight , close weave and high cover factor a lso inc rease the UPF or SPF.

• Bleac hing re moves some natura l U V abso rbers from the cellulosic and li gnoce llul os ic fib res, thus reduci ng the UV abso rpti on.

• Reac ti ve, direct or vat dyes can improve the UPF of cellul os ics and the ir bl ends s ignificant ly, spe­c ially at higher shade depth, a lthough the changes

are influenced by the chemical structure of dyes.

• UV absorbers spec iall y based on benztriazo!es, benzophenone, e tc. can reduce th total amount of radiati on affec tin g on the skin (UV cutting). OBAs, if present al ong with the UV absorber, can affec t the UPF rating o f fabrics depending on the ir absorption properties.

• The measurement of UPF on a c lothing mate rial can be done by measuring the diffuse spec tral

transmitt ance (ill vitro test method) or by measur­ing the increase in ex posure time requ ired to 1l1 -

duce e rythema or sun burn (ill I'i vo test method)

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BAJAJ el al: SOME INNOVATIONS I UV PROTECTIVE CLOTHING 329

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44 Fujii K & Taya K. Jap Pal 09,256,224 (to Teijin Ltd, Japan), 30 September 1997; Chelll Abslr, 127 ( 1997) 3 I 9990r.

45 Anon, Apparel/Ill , 28(2) ( 1997)5. 46 Hanke 0 , Hoffmann K , Altmeyer P, Sch indler G, Schon U,

Klotz M L & Bohringer B, Chelll Fibers /111 , 47(2) (1997 ) 130.

47 Anon, BeklidllllglWear, 22 ( 1996) 24. 48 Anon , BekleidllllgIWear, 22 ( 1996) 25. 49 Anon, BekleidllllglWear. 49 ( 1997) 34. 50 Anon, Chelll Fibres /11 1, 46(6) (1996) 386. 51 Azko nobel fibres, Melliand Texlilber, 78(6) ( 1997) 382. 52 Anon, Jap Texl Neil'S, ovember ( 1998) 23. 53 Anon, High Pe/fo rlll Texl. Apri l ( 1998) 7. 54 Anon, High Pe/fo rm Texl , October ( 1996) 5. 55 Seber B P, US Pal 47,45 ,9 16, 24 May 1988. 56 Hughes S N G, US Pal 54, 15,917 (to Wetmore Associate), 2

April! 996, Chem Abslr, 128 ( 1997) 872 1 g. 57 Hughes S N G. US Pal 54,14,9 13 (to Wetmore Associate),

16 M ay 1995; Chem Ahslr, 124 ( 1995) 253 16r. 58 Anon, High Pe/fo rm TexI, September ( 1996) 9. 59 Anon , Apparel /Ill , 29(5)( 1998) 45. 60 Backmann R, Kelle1l1l'irk Praxis, 28(2) ( 1994) 54, E-24. 6 1 JP Stevens ar,d Co. Inc., High Pelfonll TexI, 8(4) ( 1987) 14. 62 Croshy G, Call Apl)(Irel Mallllf , 20( I ) ( 1996) 24. 63 Verbeck P, EliI' Pal 00,89,422. 28 September 1983. 64 Anon, BekleidilnglWear, 22 ( 1996) 30 65 Arno ld R ~ Bani A M & Hufnagl E, Melliand /11 1, 4 ( 1995)

251. 66 Ducal J P, TUT Texliles-a Usages Techniql/es , 17 ( 1995 )

2 1. 67 Anon, New Sci, 158 (1998) 2 1. 68 Anon, Asiall TexI J, October ( 1998)41. 69 M esa Beatri z, Proc /11 1 CO Il/Exhib (AA TCC), 1997, 38. 70 Greenoak G E & Pailthorpe M T , AI/slralias Texl, 16 ( 1996)

6 1. 71 Camenzind M , TeXlil l'e redll/l1g, 29(9) ( 1994) 271 . 72 Perenich T A, Colol/rage AIIIII/al. ( 1998) 7 1. 73 Pailthorpe M T, AI/slralas TexI , 14(6) ( 1994) 54. 74 Garner J, Afr Tex!. October ( 1994) 16. 75 Anon, Asiall TexI .I, 7(3) ( 1998) 42.