**1.2.3 Plasma treatment**

306 Textile Dyeing

Where C is the dye absorbed after a short dyeing time, Co is constant, T is the dyeing temperature in 0K and E is the activation energy of diffusion. Plotting ln C versus 1/T, two straight lines may be drawn, one at high temperature and the other at lower temperature. The two lines intersect at a point with approximately constant value of 1n C (ln Ci) and 1/T is increasing for treated wool fabric. The slope of the straight line is -E/R from which the activation energy of diffusion (E) can be calculated where R is the universal gas constant. For the early stage of dyeing where the outer layers of the fibre are involved, a certain number of dye sites in the outer layer of the fibres saturate slowly; diffusion towards these sites presents high activation energy (E1) at dye concentration lower than Ci. Evaluation of E1 for untreated and pretreated wool fabric was 15.4 and 6.6 kJ/kg.mol.0K respectively. The enzymatic treatments led to first saturation at lower temperature, where it was 1020C for untreated wool sample and 720C for pretreated one. Diffusion towards the other sites follows the first saturation and a decrease in activation energy was observed at a second linear relationship (E2 at CCi), it was evaluated by 1.402 kJ/kg.mol.0K for treated wool fabric. The kinetic investigation of the dyeing process revealed a decrease in half dyeing time, an increase in the dye rate constant and diffusion coefficient and also a decrease in the

Type of Sample t1/2 min K' x10-5 (cm/sec)1/2 Dx10-7 cm2.sec-1 -Untreated 16 1.14 1.980

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

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,

exhaustion technique 7.5 2.08 3.803 Padding technique 7.5 2.08 3.803 Treatment: 2% (o.w.f.), 250C, 24h, Dyeing: 2% (o.w.f.) C.I. Reactive Red 21, 800C, pH 4.5, L.R. 1:50. Table 1.5. Time of half dyeing (t1/2), specific dyeing rate constant (K') and diffusion

activation energy of diffusion.

**1.2.1 Treatment with saccharin** 

coefficient (D) of pretreated wool fabric with lipase.


group of the fibres.

**1.2.2 Treatment with organic solvents** 

**1.2 Silk** 

Chemical modification of textile fabrics was early used as a tool for imparting new fibre properties and increasing its effective applications. However, these chemical methods are not always environmentally friendly and may also produce changes in the mechanical properties of the fabric which makes them less comfortable to wear. Nowadays, physical technologies can advantageously replace some of these chemical modifications as environmental friendly process. Plasma treatment is a rapid, innovative and environmentally amenable method which could replace wet chemical application to modify the surface properties of polymers and textile materials without significant effects in the bulk of fibres. Interest was directed to produce durable silk surface as well as use reactive dye for its printing. Plasma surface treatment of silk was carried out in atmospheric air at different discharge powers for different plasma exposure times. The effect of plasma treatment on the printability of silk fabric with reactive dye using conventional silk screen printing technique is investigated. The printability of silk was found to be markedly improved as well as its fastness properties. The whiteness of plasma treated silk increased by increasing the discharge power. The wettability of treated silk expressed as wetting time was found to depend upon the treatment time and discharge power (33).
