**1.2 Silk**

#### **1.2.1 Treatment with saccharin**

Colouration of wool, silk and polyamide fibres are satisfactorily performed with acid dyestuffs. Energy saving as well as high fastness performance and reduction of costs can be reasonably gained by applying cationic dyes to the fibres used in carpet manufacture. An attempt has been directed to give evidence of the benefits of treatment of silk fibres with saccharin during dyeing (22, 25). Silk fabrics were treated with saccharin solutions (10 g/l); the treatment was carried out at 90°C for 1h. The effect of this treatment on the dyeing ability of silk fabrics with C. I. Basic Red 18 was studied. The pretreatment with saccharin had enhanced the colour intensity of the dyed fabrics, as compared to the untreated dyed one. The increase in colour intensity was found to be dependent on the temperature and the time of dyeing. The increased affinity of the saccharin treated fabric to the cationic dye can be attributed to the possibility of the breakdown of saccharin molecules liberating carboxylic acid groups. These groups have the ability to trap both cationic moiety as well as the NH2 group of the fibres.

#### **1.2.2 Treatment with organic solvents**

Some studies on the solvent effects on shrink proofing of silk fabrics were reported(31, 32). The shrink proofing was obtained by treatment with dimethylsulphoxide, dimethylformamide, dimethylacetamide, sulfolane, and ethylene glycol in a closed curing system. The treatments with hexa-amino-cyclotriphosphazene in dimethyl sulphoxide, ethylene glycol, glycerol and the mixtures of (dimethylsulphoxide, ethylene glycol), and (dimethylsulphoxide, glycerol) were more effective for shrink proofing even with small amounts of resin deposition. These results showed that the molecular orientation and cross linking in medium crystalline regions played the important role for shrink proofing of silk crepe. Dimethylsulphoxide was one of the best solvents for the shrink proofing by phosphoric amides. Some of the fundamentals governing the shrinkage of silk goods were explained based on the release of the strains imposed during manufacturing processes and the swelling produced on wetting. The mechanism of the swelling by organic solvents was explained in terms of the solubility parameter of the solvents and hydrogen bonding and dipolar interactions between silk and the solvents.
