Effects of ozone treatment on the properties of raw and degummed tassar silk fabrics

Abstract

Ozone is a powerful oxidizing agent and is widely used in various applications, which includes bleaching of cotton. Literature on the action of ozone on silk is almost not available. Therefore, an elaborate study was carried out to understand the effects of process parameters in the ozone treatment of raw and degummed tassar silk fabrics on their properties. The study was extended with a view to compare the ozone treatment with soap degumming and hydrogen peroxide treatment carried out on raw and degummed tassar silk fabrics, respectively. The treatment results in improvement in pliability of the fabric and reduction in color. Decrease in breaking strength, breaking elongation, and weight as well an increase in amino group content is also experienced by the material. The results obtained are substantiated with tyrosine content, scanning electron micrographs, and infrared spectroscopy of the treated materials. The effect of pH on the treatment is maximum upto pH 4 and then decreases. The treatment is more severe when the wet pickup used is 50% compared to 10 and 100%. With respect to treatment time, though the severity increases with time, it is maximum during the first 10 min of the treatment. Soap degumming of raw silk fabric results in little higher yellowness index and lesser loss in breaking strength and elongation and flexural rigidity compared to that of ozone-treated material. There is not much of difference between ozone and hydrogen peroxide treatments of degummed silk fabric, except for the lesser yellowness index obtained in the latter case.

Effect of the ozonation process on the dyeability of mohair fibres

“…These results can be explained by assuming that the rate of oxidation is accelerated by the hydration of the hydrophilic groups in the fibre and, above a critical level of moisture content (at which the fibre is completely hydrated), it is retarded by the water, which enters the intermicellar and interfibrillar space. In several previous studies, the importance of water during the ozonation process has been reported [13,16,20]. Prabaharan and Rao have suggested a model in order to explain this phenomenon [13].…”

“…This is because, in a basic solution, more hydroxide ions are present, which act as an initiator for the decay of ozone [20]. Moreover, it is reported that the dissolved ozone concentration in water decreases from 4.3 × 10 −4 mol/l at pH 4 to 1.53 × 10 −4 mol/l at pH 10 [16]. This fact also explains why the efficiency of the ozonation decreases in a basic medium.…”

“…The increase in the alkali solubility of the ozonated fibres may have been because of the surface oxidation of the mohair fibre by the effect of ozonation, creating polar groups and modifying or volatilising the surface lipids [16]. After oxidation, cysteic acid is formed as a result of the cleavage of the disulphide linkage.…”

“…14.6% solubility, but, by taking into consideration that the alkali solubility values are between 9% and 15% for undamaged wool [21], it can be concluded that fibre damage is not excessive. The increase in the alkali solubility of the ozonated fibres may have been because of the surface oxidation of the mohair fibre by the effect of ozonation, creating polar groups and modifying or volatilising the surface lipids [16]. After oxidation, cysteic acid is formed as a result of the cleavage of the disulphide linkage.…”

Tuning the Refractive Index and Optical Band Gap of Silk Fibroin Films by Electron Irradiation

“…Upon irradiation, the transparent silk fibroin film polymer became yellow and the degree of yellowness was found to be increased with increasing electron irradiation dose. Treatment of silk with radiations is reported to produce yellow colour due to oxidation of amino acid residues glycine, alanine, serine, and tyrosine [29,30] and especially formation of chromophore products [31,32].…”