Effect of 60Co-gamma radiation on the properties of furs

Radiat. Phys. Chem. Vol. 36, No. 3, pp. 313-315, 1990 Int. J. Radiat. Appl. Instrum., Part C

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EFFECT OF 6°Co-GAMMA RADIATION ON THE PROPERTIES OF FURS R. K. RAINA, ! B. K. WALIl and A. M. WANI 2 tRegional Research Laboratory (Branch), Sanat Nagar, Srinagar 190 005 and 2N. R. L. Bhabha Atomic Research Centre, Zakura, Srinagar, India (Received 12 June 1989; in revised form l0 August 1989) Abstract--Furs pretanned with various combinations of vegetable tanning agents and retanned with alum have been irradiated with 6°Co 3,-radiation in the dose range 5.0-114.0 kGy. The physico-chemical modifications induced by the radiation have been assessed by measuring changes in tensile strength, absorption of water, elongation and shrinkage temperature. For investigations, samples have been taken from the same topographic region of the rabbit furs, belonging to the same age and sex. The results are discussed hereunder.

INTRODUCTION

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The effect of radiation grafting on the absorption and other properties of leather has been studied (Pietrucha, 1982a,b). The effect of v-rays in the tanning of hides on its shrinkage temperature and breaking strength has also been studied (Pastuska, 1969). A detailed investigation report on radiation processes for textiles has been brought out by Walsh and Bittencourt (1977). Chrome tanned furs are considered to be the best in quality so far as the properties like tensile strength, elongation, shrinkage temperature and absorption of water are considered. Because of the toxic value of chromium salts, efforts are being made to replace chrome with an equally good tanning material. The present investigations have been carried out to study the changes induced by the v-radiation on the use properties of furs tanned with a variety of tanning agents other than chromium sulphate.

1 2 3 4 5 6 7 8 9 10

Pre-tanning material used Wattle Myrab Pomegranate Rind Vernatan-OS Wattle: Myrab (50% each) Wattle:OS (50% each) Wattle:Pomegranate (50% each) Myrab: Pomegranate (50% each) Vernatan OS:Myrab (50% each) Vernatan OS:Pomegranate (50% each)

EXPERIMENTAL

Fur processing Raw rabbit pelts of Grey Giant breed, of same age and sex were obtained from Government Rabbit Farm, Wussan, Kashmir, India and were divided into 10 sets. They were all soaked, de-fleshed and pickled in the usual manner (Wali et al., 1980) and pretanned with the tanning combinations listed in Table 1 (each tanning combination shall be represented by its tanning code for further tables and graphs). Retanning of all the furs was done with 33% aluminium sulphate and fatliquored by Cenfat SS (developed by Central Leather Research Institute, Madras, India) and Verminon Liq. ASN (ColourChem. India Ltd). The furs were dried, staked and buffed. Figure 1 shows the sampling position on the rabbit pelt taken for investigation. The properties

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Fig. I. Sampling area. of the processed furs before radiation (hereafter referred to as control samples) have been introduced in graphs at "zero" v-ray dose. The properties are

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R.K. RA]~A et al.

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expressed as the average of the readings on left-hand and right-hand sides of the pelt. Radiation source

The samples taken from the similar topographic region of the fur were irradiated with increasing radiation doses of 6°Co v-rays in sealed polythene bags, in air atmosphere and at room temperature. The dose rate was constant and equal to 34 Gy min -1

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as determined by Fricke dosimeter. The irradiation was done at Nuclear Research Laboratory, BARC, Zakura, Srinagar, India, using 6°Co v-radiation source. The rabbit furs tanned with 10 different combinations of tanning codes (Table 1), were separately subjected to increasing irradiation doses of 5.0, 10.0, 20.0, 35.0, 61.6 and l l 4 . 0 k G y . The effect of the irradiation has been assessed by comparing the physico-chemical properties such as tensile strength, shrinkage temperature, absorption of water and percent elongation with the control samples of unirradiated furs. Tensile strength and percent elongation at break have been measured using a tensile tester supplied by M/s Kamal Metal Industries, Ahmedabad, India. The shrinkage temperature and percent water absorption have been estimated using method described earlier ( W a l i e t al., 1981). RESULTS AND DISCUSSION

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The results of all the four parameters, for the 10 different tanning combinations have been condensed in the form of graphs, wherein the changes in the properties of tensile strength, percent elongation, and absorption of water have been separately plotted against the doses of 6°Co-radiation. The effect of irradiation on tensile strength and percent elongation do not show a uniform pattern (Figs 2a,b and 3a,b). But beyond a radiation dose of ( O)

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Fig. 4. Effect of radiation on absorption. 60 kGy the values for both the properties fall below that of the control samples showing degradation of physical properties at higher doses of radiation. The absorption of water (Figs 4a and 4b) by furs decreases when irradiated with doses of 5.0-30 kGy. As degradation increases with the increase in radiation dose beyond 35 kGy, the absorption of water also increases significantly indicating the presence of more ionic groups and space between the fibres to hold more water by capillary or adhesion. In general, a raw pelt of rabbit shrinks at 52°C. With the introduction of tanning materials, the values for shrinkage temperature increase, depending upon the nature of tanning material used. The shrinkage temperature of control samples from 1 to 10 (without irradiation) are as 95, 95, 90, 95, 65, 87, 95, 82, 87 to 92°C. The shrinkage temperature of all the samples decreases with the increasing radiation dose to a value of near raw pelt (65°C), showing that the higher doses of radiation continuously damage the bonding between tanning material and collagen. From the available data of all the four parameters, viz. tensile strength, percent elongation, water absorption capacity and shrinkage temperature, it is evident that at l l4.0kGy the tanning material or their bonding with the collagen is loosened resulting in the production of more amino and acidic groups as a result of irradiation and the samples become more hydrophilic. This is confirmed by the increase

in the capacity of absorption of water with the increase in radiation dose, which is also supported by the fact that, with the increase in radiation dose, the shrinkage temperature of the fur skins continuously decreases. The graphs for tensile strength and percent elongation at break also show that major reorientation of bonds occurs in the range of 10-35kGy where after the value for the above parameters continuously decreases. On the perusal of all the graphs, the results of the investigations show that on y-irradiation a product with unwanted properties of low shrinkage temperature and tensile strength is obtained. The major changes in the bonding of collagen and reorientation reactions, perhaps as a result of ionisation effect, take place at a radiation dose of 10.0-30.3 kGy.

REFERENCES

Pastuska G. (1969) Proc. Symp. Utilization of Large Radiation Sources and Accelerators in Industrial Processing. Munich. Pietrucha K. (1982a) Radiat. Phys. Chem. 19, 219. Pietrucha K. (1982b) Radiat. Phys. Chem. 19, 227. Wali B. K., Raina R. K. and Sharma T. (1981) Leather Sci.

28, 317. Wali B. K., Singh C. and Razdan R. K. (1980) The Tanner June, 23. Walsh W. K. and Bittencourt E. (1977) Radiat. Phys. Chem. 9, 289.