**1.1.3 Treatment with chitosan**

Chitosan sorption on proteinic fibres is found to be due to ionic interaction between the negative charges of carboxylic groups in the polypeptide macromolecule and the protonated amino groups of chitosan, and possibly due to hydrogen bonding between the hydroxyl or amide groups of polypeptide chains and similar groups in chitosan. The application of chitosan onto wool reveals even dye uptake resulting in higher dye exhaustion with level and full penetration of dye molecules in wool fibres(16). The treatment of wool with chitosan permits the formation of an approximately uniform sheath on individual fibres. Chitosan treatment does not involve changes in colour fastness of the dyed wool to any extent, but may reveal some problems such as weak binding. Such problems are reported to be overcome upon applying chitosan onto wool with a nonionic surfactant (17, 18). The possibilities of improving the reactive dye affinity to wool fibres and their protection from damage by conducting chitosan treatments of wool before subjecting it to reactive dyeing were reported (10). Wool fabric was treated with chitosan and nonionic surfactant using diluted concentrations 0.1- 0.7 % (w/w) and then dyeing the pretreated wool with reactive dye at 80°C for 5-60 minutes. The pretreatment of wool with chitosan enhanced the colour

Pretreatment of Proteinic and Synthetic Fibres Prior to Dyeing 305

The possibility of obtaining various finishing effects on wool by the use of environmentally friendly treatments such as enzymes has been investigated. However the complexity of wool fibre makes it difficult to find the enzymes that are able to modify wool properties without excessive damaging its structure. Application of enzymes, particularly protease, to wool has been studied to achieve a non-felting fibre. The efficiency of shrink-resist protease treatment, the effect of treatment on the absorption of some reactive dyes, and the action of protease enzyme when added to the dyebath was reported to improve the dye absorption by wool fibres. The influence of pretreatment of wool fabrics with a lipase enzyme on its dyeability with reactive dyes was studied (28-30). The enzymatic treatments by exhaustion technique were performed in a bath of a liquor ratio, 1:40 for different intervals of time (10 min and 24h). The concentration of enzyme ranged between 0.2 - 2.0 % (o.w.f.). The pH of the treatment bath was adjusted to 10.7 using phosphate buffer. The enzyme treated fabric was then squeezed and air dried. Wool fabric was treated by padding technique after immersing in a 3 % enzyme solution buffered to pH 10.7. The fabric was padded and squeezed twice to have a pick up of 70 %. The padded fabric is then stored in an air tight polyethylene bag for 24 h. The treated fabric was then dried at room temperature before dyeing. The pretreatment of wool fabric with lipase enzyme has induced significant improvement on its dyeability with the reactive dyes (C.I. Reactive Blue 203 and C.I. Reactive Red 21). As the amount of the lipase increases, the rate of dye uptake increases. Lipase enzyme has been reported to remove the surface lipids of the fibre and thus enables improved penetration of solutions, including dyes, to the interior of wool fibres (28). The dye uptake of wool fabric is dependent on time of treatment. A complete exhaustion of C. I. Reactive Red 21 (1% o.w.f.) from the dyebath was achieved after about 10 min of dyeing of the enzyme pretreated wool at 800C compared to about 48% exhaustion for untreated one. Complete dye exhaustion has a positive impact on reduction of indoor pollution, cleaner production and energy saving. The half-dyeing time (t1/2), specific dyeing rate constant (K') as well as the diffusion coefficients (D) were calculated for untreated and pretreated wool

1/2 K 0.5 C (d t ) 1/2

<sup>2</sup> d 100 D=C /C <sup>t</sup> *<sup>t</sup>* 

Where C∞ is the % dye absorbed on the sample at equilibrium conditions between the sample and the dyebath divided by the weight of the sample, Ct is the dye uptake after 10 min and d is the fibre diameter in cm. Time of half dyeing (t1/2) of pretreated wool fabric is less than that of untreated one. This can be contributed to the higher dyeing rate and higher dye diffusion of the treated wool fabric (Table 1.5). Using exhaustion or padding technique in treatment process (for 24 h at room temperature) resulted in the same effect in enhancing the dyeability of wool and reducing the half-dyeing time. The quantity of dye absorbed after short dyeing time (10 min) can substitute the diffusion values, so a modified Arrhenius

> 0 <sup>E</sup> ln C=lnC

RT 

**1.1.5 Enzyme treatment** 

fabric with lipase according to the following equation:

relationship can be applied as follows :

intensity and the dye uptake as compared with the corresponding untreated one. The rate of dye fixation percentage of the dyed pretreated wool increased as compared with the corresponding untreated one. The rating of crocking and washing fastness was found to be higher than the corresponding untreated ones. Alkali solubility of wool and chitosan treated wool was 18.6 % compared to 15.6 % for untreated one, indicating that there is insignificant damage of treated wool. SEM micrograph of the chitosan treated wool is shown in Fig 1.4. Most of the scales have disappeared and wool attained a relatively smoother surface. Some holes were detected on the surface of treated wool.

Fig. 1.4. SEM of chitosan treated wool

#### **1.1.4 Treatment with epichlorohydrin and alkoxides**

Treatments of wool fabrics were performed using organic acids such as acetic, mono–, di –, trichloroacetic, propionic and butyric acids (19). Wool fabrics were treated with chitosan at different times and temperatures (17). The aforementioned treated fabrics were then dyed with reactive dye. The increase in the colour intensity and dye- uptake of the dyed fabrics was found to depend upon the type of the organic acid used in the pretreatment and the pKa values of the acids used (20, 21). The acquired colour intensity and dye uptake of the pretreated wool increased compared to those of the untreated one. The dyeability of the treated wool and wool/polyester with some alkoxides using methyl, ethyl, propyl and butyl alcohols is improved towards acid as well as disperse dyes. Treatment of wool with epichlorohydrin (22) was found to improve its dyeability in comparison with the untreated one. Wool fabrics were firstly immersed in sodium thiosulphate or sodium bicarbonate mixture then treated with epichlorohydrin solution (0.25 mol/l) at temperatures 60°C and 80°C for different time intervals 10- 20 min. The treated fabrics were then dyed with a reactive dye for one hour at 80°C and the corresponding dye uptake was determined. Upon increasing the time of wool treatment with epichlorohydrin, an increase in colour intensity and dye uptake were attained. It was reported (23) that serine, tyrosine, aspartic and glutamic acids, arginine, lysine, histidine and the amino end groups in wool macromolecule are possibly the reactive sites for the interactions with epoxides**.** Water is required to enhance the reaction of epoxide with wool. A wide variety of chemical treatments have been used for wool having the objective of controlling the degradation of the fibre surface, with the least amount of damage. One of the early approaches was the use of alkalies dissolved in aliphatic alcohol to reduce the fibre swelling and to confine the beneficial effects on the fibre surface (24- 27).

#### **1.1.5 Enzyme treatment**

304 Textile Dyeing

intensity and the dye uptake as compared with the corresponding untreated one. The rate of dye fixation percentage of the dyed pretreated wool increased as compared with the corresponding untreated one. The rating of crocking and washing fastness was found to be higher than the corresponding untreated ones. Alkali solubility of wool and chitosan treated wool was 18.6 % compared to 15.6 % for untreated one, indicating that there is insignificant damage of treated wool. SEM micrograph of the chitosan treated wool is shown in Fig 1.4. Most of the scales have disappeared and wool attained a relatively smoother surface. Some

Treatments of wool fabrics were performed using organic acids such as acetic, mono–, di –, trichloroacetic, propionic and butyric acids (19). Wool fabrics were treated with chitosan at different times and temperatures (17). The aforementioned treated fabrics were then dyed with reactive dye. The increase in the colour intensity and dye- uptake of the dyed fabrics was found to depend upon the type of the organic acid used in the pretreatment and the pKa values of the acids used (20, 21). The acquired colour intensity and dye uptake of the pretreated wool increased compared to those of the untreated one. The dyeability of the treated wool and wool/polyester with some alkoxides using methyl, ethyl, propyl and butyl alcohols is improved towards acid as well as disperse dyes. Treatment of wool with epichlorohydrin (22) was found to improve its dyeability in comparison with the untreated one. Wool fabrics were firstly immersed in sodium thiosulphate or sodium bicarbonate mixture then treated with epichlorohydrin solution (0.25 mol/l) at temperatures 60°C and 80°C for different time intervals 10- 20 min. The treated fabrics were then dyed with a reactive dye for one hour at 80°C and the corresponding dye uptake was determined. Upon increasing the time of wool treatment with epichlorohydrin, an increase in colour intensity and dye uptake were attained. It was reported (23) that serine, tyrosine, aspartic and glutamic acids, arginine, lysine, histidine and the amino end groups in wool macromolecule are possibly the reactive sites for the interactions with epoxides**.** Water is required to enhance the reaction of epoxide with wool. A wide variety of chemical treatments have been used for wool having the objective of controlling the degradation of the fibre surface, with the least amount of damage. One of the early approaches was the use of alkalies dissolved in aliphatic alcohol to reduce the fibre swelling and to confine the beneficial effects on the fibre

holes were detected on the surface of treated wool.

Fig. 1.4. SEM of chitosan treated wool

surface (24- 27).

**1.1.4 Treatment with epichlorohydrin and alkoxides** 

The possibility of obtaining various finishing effects on wool by the use of environmentally friendly treatments such as enzymes has been investigated. However the complexity of wool fibre makes it difficult to find the enzymes that are able to modify wool properties without excessive damaging its structure. Application of enzymes, particularly protease, to wool has been studied to achieve a non-felting fibre. The efficiency of shrink-resist protease treatment, the effect of treatment on the absorption of some reactive dyes, and the action of protease enzyme when added to the dyebath was reported to improve the dye absorption by wool fibres. The influence of pretreatment of wool fabrics with a lipase enzyme on its dyeability with reactive dyes was studied (28-30). The enzymatic treatments by exhaustion technique were performed in a bath of a liquor ratio, 1:40 for different intervals of time (10 min and 24h). The concentration of enzyme ranged between 0.2 - 2.0 % (o.w.f.). The pH of the treatment bath was adjusted to 10.7 using phosphate buffer. The enzyme treated fabric was then squeezed and air dried. Wool fabric was treated by padding technique after immersing in a 3 % enzyme solution buffered to pH 10.7. The fabric was padded and squeezed twice to have a pick up of 70 %. The padded fabric is then stored in an air tight polyethylene bag for 24 h. The treated fabric was then dried at room temperature before dyeing. The pretreatment of wool fabric with lipase enzyme has induced significant improvement on its dyeability with the reactive dyes (C.I. Reactive Blue 203 and C.I. Reactive Red 21). As the amount of the lipase increases, the rate of dye uptake increases. Lipase enzyme has been reported to remove the surface lipids of the fibre and thus enables improved penetration of solutions, including dyes, to the interior of wool fibres (28). The dye uptake of wool fabric is dependent on time of treatment. A complete exhaustion of C. I. Reactive Red 21 (1% o.w.f.) from the dyebath was achieved after about 10 min of dyeing of the enzyme pretreated wool at 800C compared to about 48% exhaustion for untreated one. Complete dye exhaustion has a positive impact on reduction of indoor pollution, cleaner production and energy saving. The half-dyeing time (t1/2), specific dyeing rate constant (K') as well as the diffusion coefficients (D) were calculated for untreated and pretreated wool fabric with lipase according to the following equation:

$$\begin{aligned} \mathsf{K}' &= 0.5 \cdot \mathsf{C}\_{\circ} \cdot (\mathsf{d}/\mathsf{t}\_{1/2})^{1/2} \\ \mathsf{D} &= \mathsf{C}\_{\circ} / \mathsf{C}\_{\circ} \cdot \frac{\mathsf{d}^2 \cdot 100}{\mathsf{t}} \end{aligned}$$

Where C∞ is the % dye absorbed on the sample at equilibrium conditions between the sample and the dyebath divided by the weight of the sample, Ct is the dye uptake after 10 min and d is the fibre diameter in cm. Time of half dyeing (t1/2) of pretreated wool fabric is less than that of untreated one. This can be contributed to the higher dyeing rate and higher dye diffusion of the treated wool fabric (Table 1.5). Using exhaustion or padding technique in treatment process (for 24 h at room temperature) resulted in the same effect in enhancing the dyeability of wool and reducing the half-dyeing time. The quantity of dye absorbed after short dyeing time (10 min) can substitute the diffusion values, so a modified Arrhenius relationship can be applied as follows :

$$
\ln \text{C=lnC}\_{\text{o}} \cdot \frac{-\text{E}}{\text{RT}}
$$

Pretreatment of Proteinic and Synthetic Fibres Prior to Dyeing 307

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

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

Polyester fibers have attained a major position in the textile and non-textile uses, although polyester fibers have several drawbacks vis. low moisture regain (0.4%), a tendency to accumulate static charges, pick up soil dirt during wearing, difficulty of cleaning during washing, pill formation, thus spoiling fabric appearance and flammability. Modifications of polyester fibers can have an effect to overcome these disadvantages and can promote its permeability, hydrophilicity, hand and thermal properties (1, 2). Modification of polyester fibers is carried out via its treatments with alkalies, combined thermal and alkali, mono or multifunctional amines, organic solvents and acids as well as enzymatic hydrolysis. Thermal treatment of polyester fibers is a well known and important method in modification of the polymeric structure of the fibers. The purposes have increased to concern and cover the specific physico-chemical changes of the fiber structure to induce a certain tendency of

was found to depend upon the treatment time and discharge power (33).

the solvents.

**1.2.3 Plasma treatment** 

**2. Man made fibres** 

crystallinity and orientation.

**2.1 Polyester** 

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 activation energy of diffusion.


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 coefficient (D) of pretreated wool fabric with lipase.
