Indian Journal of Fibre & Textile Research Vol. 25, December 2000, pp. 27 1 -276

Influence of y-irradiation on jute yarn

A K Saha Indian Jute Industries' Research Association, 17 Taratola Road, Calcutta 700 088, India

and P Rath & D Bhatta'

Department of Chemistry, Utkal University, Bhubaneswar 75 1 004, India

Received 6 August 1999; revised received and accepted 21 December 1999

Jute yarn has been irradiated with y-rays in air at ambient temperature using six different dose levels ranging from 0. 1 x 1 0-2 to 20 x l O-2 MGY and some important physical and chemical properties of the irradiated jute samples studied. It is observed that y-irradiation of jute yarn results in the formation of reducing groups and carboxyl groups, increased solubility in caustic alkal i , decreased tensile strength of the yarn, very small change in moisture regain and relatively unchanged crystallinity and IR absorption spectra. ESR spectra reveal that on irradiation, free radical sites are formed within the jute constituents. SEM study shows a distinct change in the morphology of irradiated fibre.

Keywords : Crystallinity, Gamma irradiation, Jute yarn, Tensile strength

1 Introduction Several researchers 1 -8 have studied the influence of

y-irradiation on cellulose, cellulose derivatives and synthetic fibres. Cobalt-60, the most commonly used radio isotope, is a commercial source of y-irradiation.

Gilfillan and Linden9 studied the tensile strength of y- irradiated cotton, viscose, nylon and acrylic yarn and found that y-irradiation weakens the cellulosic and nylon fibres remarkably but there is no effect on the strength of acrylic fibre. B louin and ArthurlO investigated the effect of y-irradiation on purified cotton and found that carbonyl and carboxyl groups are generated and the cleavage of cellulose chain takes place. Irradiation increases the solubilit/o of cotton fibre in water and dilute alkali but decreases the degree of polymerization and tensile strength. Arthur I I proposed the mechanism of the effects of high energy y-radiation on some of the properties of the purified cotton . Westberry and Hydenl2 studied the protective action of dyes against y-radiation . Teszler et al. 1 3 reported the dyeing characteristics of y-irradiated cotton cellulose and Demint and Arthurl4 reported the base exchange properties of y-irradiated cotton.

Jute, a lignocellulosic bast fibre, differs markedly from cotton in fine structure as well as physical and chemical

a To whom all the correspondence should be addressed. Phone : 0674-582734

properties. As the data on the effect of y-irradiation on jute are scanty, it was thought worthwhile to study the influence of y-irradiation on jute. The present paper reports effect of y-irradiation on some of lhe important physical and chemical properties of jute fibre.

2 Materials and Methods

2.1 Materials

Jute yarn (2232 denier), supplied by B irla Jute Ltd, was extracted with alcohol - benzene mixture ( I :2) by soxhlet extraction method to remove both the inherent and added lubricants. The yarn was then washed with demineralized water, air dried and used for the study as control sample.

2.2 Methods

2.2.1 Irradiation

Jute yarn sample was kept in thin walled glass tube and then irradiated in air at room temperature with cobalt-60 y-rays of different doses (O. I -20x l O-2 MGY) by adjusting the exposure time.

2.2.2 Measurement of Tensile Strength and Elongation-at break

The tensile strength and elongation-at-break of the jute yarn were measured according to BIS method 1 5 using Instron universal testing machine (Model 430 I ) .

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

2.2.3 Determination of Moisture Regain indicator. The moisture content of the fibre was The samples were equi l ibrated under Standard

condition (27°C and 65% RH), the equil ibrium being approached from the dry side, and the accurate weight of the sample was taken. The samples were then dried to a constant weight in a forced draft oven at 1 05-1 1 0°C and the moisture regain was calculated on the basis of oven dry weight.

2.2.4 Infrared Spectra

Infrared spectra of jute yarn were obtained by Nicolet FfIR (Model-Magna 550) using KBr pellet technique. The KBr pellets were prepared quantitatively by keeping the KBr:fibre (weight) ratio constant for all the samples.

2.2.5 Solubility in Sodium Hydroxide Solution

To measure the solubility of jute yarn sample in sodium hydroxide solution, the sample weighing 2.0 g was cut into small pieces and then put into a 500 ml conical flask, maintaining the l iquor-to-material ratio at 1 00 : I both at room temperature (27°C) and boiling water temperature for 1 h. The sample was boiled under reflux with desired concentration of alkali and the treatment at 27°C was carried out in the conditioned room. After the treatment, undissolved material was col lected on a sintered glass crucible (IG2), washed till free from alkali and the loss in weight was determined on dry weight basis .

2.2.6 Estimation of Carboxyl Content

The carboxyl value (m eq. COOH / 1 00 g) was estimated by the iodometric method according to the BIS procedure'6 .

2.2.7 Estimation of Copper Number

The copper number (g / 1 00 g fibre) was estimated according to the BIS procedure 1 7•

2.2.8 Iodine Sorption Test

The method reported by Hessler and Powerl 8 was used to measure the accessibility per cent. Jute yarn (0.3 g) was taken in a 250 rnl Earlenmayer flask and 2 ml of iodine solution (5 g iodine and 40 g potassium iodide in 50 ml deionized water) was added to it. Saturated sodium sulphate solution ( 1 00 ml) was then added into the flask containing iodine-soaked sample. After one hour, 50 ml of the aliquot was pi petted into a 250 ml Earlenmayer flask and titrated with 0.02 N sodium thiosulphate solution using starch as an

determined separately and the accessibility per cent was determined using the fol lowing equation:

Per cent accessible region (a - b) x 2.04 x 2.54 x 1 00 =

4 1 2 x c

where a i s the volume of sodium thiosulphate for blank experiment; b, the volume of sodium thiosulphate for sample; and c, the oven dry weight of the fibre.

2.2.9 Dyeing Procedure

0.4 % Methylene Blue (C.I.Basic B lue 9) solution was prepared with 0.2 N acetic acid and used as a stock solution. The dyeing was carried out at 90°C for 90 min so that the absorption of the dye by the fibre was almost be at equilibrium. The material-to-liquor ratio was maintained at 1 : 1 00 in all the experiments and the amount of dye absorbed by the fibre was estimated by measuring the optical density of the exhausted dye bath using uv/vis spectrophotometer.

2.2.10 ESR Spectra

The weighed sample of powdered jute was taken in open pyrex glass capillaries, placed in the cavity of an electron spin resonance spectrometer ( Varien, Model No E- I I 2 ) at room temperature and the s ignals were recorded.

2.2.1 1 SEM Studies

Jute samples, after being coated with gold­palladium alloy, were studied in a Hitachi scanning electron microscope ( Model S 340 ) at an operating voltage of 1 0-20 keV.

3 Results and Discussion Cotton cellulose undergoes 1 0, 1 9,20 oxidative

reactions whereby cleavage of cellulose chains takes place accompanied by the formation of carboxyl and carbonyl groups by the influence of high energy y­rays. Jute, being a l ignocellulosic fibre, may have simi lar type of structural changes when it is subjected to y-radiation. Table 1 shows that carboxyl and carbonyl groups of jute increase with the increase in radiation dose, suggesting that y-irradiation causes depolymerization, \eading to the oxidative degradation of chain molecules with the formation of reducing groups and carboxylic groups. Table I . also

SAHA et at. : INFLUENCE OF y-IRRADIATION ON JUTE YARN 273

Table 1- Effect of y-irradiation on physico-chemical properties of jute yarn

Dose X 1 0-2 Moisture Carboxyl content Copper number Tenacity Elongation Accessibility MGY regain. % m eql J OO g gil 00 g glden % %

0 1 2.46 1 1 .48

0. 1 1 2.43 1 3 .32

0.5 1 2.40 1 5 . 1 7

1 .0 1 2.38 1 5 .98

2.0 1 2.3 1 1 6.02

4.0 1 2.22 1 7 .38

5.0 1 2.07 1 7.42

1 0.0 1 1 .98 1 8 .39

20.0 1 1 .37 1 8.86

shows that the moisture regain values do not alter very much due to the exposure to high energy y-rays . When the untreated sample possesses a moisture content of 1 2.46 %, the sample exposed to 20 x 1 0 -2 MGY radiation shows moisture content of 1 1 .37%.

The results show that irradiated jute yarns suffer a decrease in tenacity from 1 .84 g/den for untreated sample to 0.82 g/den for the sample irradiated with 20 x lO-2 MGY. The elongation- at- break, however, decreases from 2.07% to 1 .43%. The tensile strength of many synthetic polymeric materials has been improved by gamma radiation21 at a particular dose . . But it is observed that the strength, in case of jute fibre, does not improve on irradiation . This may be attributed to the scission of chain which predominates over inter molecular crosslinking.

For the qualitative study of accessibility, iodine sorption test was carried out which suggests that the accessibil ity does not alter up to 4.0x 1 0-2 MGY radiation dose but it increases remarkably with the further increase in dose level (Table I ) . It appears from the results that accessibility of jute is improved by exposing it to high-energy y-rays. But the data obtained from infrared study suggest that no appreciable change in crystall inity of the irradiated jute is observed. However, Bikales and Segal22 found that accessibility is influenced by degree of polymerization of chain molecules. Moreover, irradiated jute possesses higher amount of functional groups (carboxyl and carbonyl) as compared to that of the unirradiated one. This apparent ' increase in accessibility may be attributed to the chemically­altered structure of the irradiated sample rather than an alteration of the crystalline structure.

The percentage loss in the weight of jute fibre in 1% and 5% sodium hydroxide solutions at room temperature and boiling condition (Fig. I ) indicates

2.45

2.56

3.22

3.29

4.39

4.89

5. 1 7

6.68

8 . 1 8

1 .84 2.07 29.27

1 .79 2.06 29.27

1 .67 2.03 29.27

1 .62 2.01 29.27

1 .54 1 .96 30.08

1 .40 1 .82 33.5 1

1 . 39 1 .79 32.24

1 . 14 1 .53 52.85

0.82 1 .43 59.4 1

70 d 60 c

... 50 '" 40 VI 0 ....l ..... 30 x � __ ---- b

UJ 20 � 10 -::=-__ ------- a

0 0 2 4 6 8 10 12 14 16 18 20 RADIATION DOSE X 1 0-�MGY )

Fig. I-Effect of y-irradiation on solubility of jute in sodium hydroxide solution [(a) I % NaOH at room temp. (b) 5 % NaOH at room temp. (c) I % NaOH at boiling condition. and (d) 5 % NaOH at boiling condition]

that irradiated samples are soluble in alkali to a greater extent than the unirradiated one and the solubility increases with the increase in irradiation dose. It is also observed that solubility is increased to a considerable extent at higher temperature. The increased solubility of the irradiated sample in caustic alkali indicates that the average chain length of the irradiated jute is smaller than that of the unirradiated material and the degree of polymerization of chain molecules decreases as the irradiation dose increases. Moreover, the presence of carboxyl groups in irradiated samples greatly enhances their solubility in sodium hydroxide solution.

Fig. 2 shows that irradiated jute samples have all the absorption bands as observed in control jute. No additional peak is observed in irradiated samples except a more strong band at 1 735 - 1 740 cm-I due to C=O stretching for the whole range of dosages studied. Both the carboxyl and carbonyl groups show absorption at 1 735 - 1 740 cm-I Fig. 2 also shows that

274

38 38

34

32

30

28

28

24

22 Q) 0 ffi 20 � 'E 18 <J) c � 1& � 14

12

10

8

6

4

2 2000 1950 1900

INDIAN J. FIBRE TEXT. RES. , DECEMBER 2000

1850

i ( 8.005 ) II ( 5.842 )

1800 1750 1700 . -1 Wavenumber (em ) 1650 1600 1550

Fig. 2-lnfrared spectra of jute at 2000 - 1 500 em-I [(a) Control, (b) 0. 1 x 1 0-2 MGY, (c) 0.5 x 1 0-2 MGY, (d) Ix 1 0-2 MGY, (e) 2 x 1 0-2 MGY, (f) 4 X 1 0-2 MGY, (g) 5 x 10-2 MGY, (h) 10 x 1 0-2 MGY, and (i) 20 x 1 0-2 MGYj. Values in parentheses indicate intensity at 1 740 em-I

intensIties at 1 740 cm-I increase steadi ly with the increase in dose level .

Table 2- Effect or y-irradiation on the apparent crystallinity

To measure the crystall inity, the ratio of infrared absorbance at 1 372 cm-I to that at 2900 cm-I was calculated according to Nelson and O'connor23 . This ratio is the empirical crystall inity index (Table 2). It i s observed that the crystallinity of jute fibre remains unaffected on exposure to y-rays . Moreover, theory of sorption24 reminds that moisture regain increases with the decrease in crystaIlinity. The moisture regain data (Table 1 ) remain more or less same for both the irradiated and unirradiated jute and this further supports our observation In connection with crystal linity by IR study.

Because of the acidic nature25, jute fibre absorbs basic dyes. The results (Table 2) indicate that the basic dye absorption increases on exposure to gamma rays but the dye absorption bears no relation to carboxyl contents, as determined chemical ly.

index and dye absorption

Dose IR absoq�tion at Crystallinity Dye x 1 0-2 2900 1 375 index absorption MGY em- I em- I g/lOOg fibre

0 0.536 0.55 1 1 .028 1 .0743

0. 1 0.76 1 0.76 1 1 .000 1 .6752

0.5 0.688 0.797 1 . 1 58 1 .7795

1 .0 0.797 0.833 1 .045 1 .7862

2.0 0.933 0.869 1 .043 1 .8058

4.0 0.978 1 .050 1 .074 1 .7798

5.0 1 . 174 1 .262 1 .075 1 .7782

1 0.0 0.998 1 .086 1 .088 1 .7696

20.0 1 .355 1 .48 1 1 .093 1 .5638

3.1 ESR Study

y-Irradiation of jute fibre containing about 1 2 % moisture gives products contaInIng long-lived electron paramagnetic species (Fig 3) . This clearly

SAHA et at. : INFLUENCE OF 'Y-IRRADIATION ON JUTE YARN 275

(a)

•

( b)

200 GAU S S

MAGNETIC FIELD Fig. 3-ESR spectra of 'Y- irradiated jute [(a) 20 x 1 0-2 MGY and

(b) 10 x 1 0-2 MGYj

Fig. 4-Scanning electron micrographs of (a) unirradiated jute, and (b) jute irradiated at a dose of 20x I 0-2 MGY

shows an isotropic as well as broadened free radical signal centered at a g-value of about 2.003 . It is also evident from the spectra that the concentration of free radicals is directly related to the radiation dose. It can be concluded from the results that some of the radiation energy absorbed is localized to form free radicals on the cellulose and lignin molecules with depolymerization and loss of fibre strength .

3.2 SEM Study

The scanning electron micrographs (Fig. 4) of the unirridiated and irradiated jute fibres clearly show the multicellular structure of jute fibre with the distinct presence of an intercellular region between the neighbouring unit cel ls . No distinct change in surface morphology is observed at a dose level of 20xl O-2

MGY. Because of the presence of lignin and hemicellulose

in the outer layer of the fibre, l ittle information can be gained about the fine structure in its intact condition

Fig. 5-Scanning electron micrographs of a-r;ellulose col lected from (a) unirradiated jute, and (b) jute irradiated at a dose of 1 0 x 1 0-2 MGY

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

with the electron microscope. However, by chemical means it is possible to remove the non-cellulosic matters without degrading the cellulose.

Fig. 5 shows the scanning electron micrographs of a-cellulose obtained from unirridiated and irradiated jute fibres. Due to the complete removal of non­cellulosic part of the fibre ,the original multicellular fibre structure is lost and loose sheets of fibrils are formed as shown clearly in the figure. A remarkable decrease in length and width of the fibrils is clearly observed in the case of irradiated sample. This change in fibrillation pattern of the irradiated fibre is due to the excessive scission of cellulose molecule by y­irradiation.

4 Conclusions 4.1 The moisture regain of jute fibre decreases very

s lightly with the increase in irradiation dose. 4.2 The solubility of fibre in caustic alkali increases

enormously with the increase in irradiation dose. 4.3 Radiation-initiated depolymerization of the

cellulose molecule takes place with the formation of reducing groups and carboxyl groups and this results in the loss of yam strength.

4.4 Electron paramagnetic species are formed due to irradiation and the signal strength increases with the increase in irradiation dose.

4.5 IR study shows that y-i rradiation has practical ly no effect on the crystal l inity of jute fibre.

4.6 It seems to be highly probable that the basic dye uptake of jute fibre increases due to y-irradiation .

Acknowledgement One of the authors (AKS ) is grateful to Prof. K.

Jayachandran, Director, Indian Jute Industries'

Research Association, Calcutta, for his keen interest in the study.

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