**2. Experimental**

## **2.1 Materials**

A bleached cotton fabric was kindly supplied by Misr Company for Spinning and Weaving, Mehallah El-Kubra, Egypt. All chemicals used in current investigation were of analytical grade. Dyes used include acid dye which was of laboratory grade and, reactive dye, namely, Procion Turquoise® MXG which was of technical grade.

#### **2.2 Methods**

#### **2.2.1 Oxidation of cotton fabrics with sodium periodate**

Unless otherwise stated, bleached cotton fabric was immersed in an aqueous solution containing different concentrations of sodium periodate (30-80 mg/100ml). The solution was stirred for 1 hr at 60 ºC using a material to liquor ratio (M/L) 1:50 .The oxidized sample was washed several times with water to remove the oxidant .This oxidized sample was used for the next reaction without drying.

#### **2.2.2 Treatment with chitosan**

A chitosan solution was prepared by stirring a dispersion of chitosan (0.5-2%) in 1% (v/v) aqueous acetic acid solution. The aforementioned oxidized cotton fabric was immersed in the chitosan solution with constant shaking for different periods of time (30, 60, and 120 min.).The treatment process was performed at different temperatures (40, 60 and 80 ºC). A material to liquor ratio of 1:50 was used. The treated sample was washed several times with 1% (v/v) aqueous acetic acid solution followed by water and dried at 60 ºC.

#### **2.2.3 Oxidation of cotton fabrics and chitosan with sodium periodate in one bath**

An aqueous solution containing 2% chitosan, 50 mg/100ml sodium periodate was prepared. Fabric was impregnated in this aqueous solution at liquor ratio 1:50 for 1 hr at 60 ºC. The cotton fabric was then washed several times with 1% (v/v) aqueous acetic acid solution followed by water and dried at 60 ºC.

## **2.2.4 Dyeing**

4 Natural Dyes

exhausting chitosan solution onto cotton fiber was reported to show significant improvement in dyeability of the fiber with some reactive dyes (3). Oxidations of cotton fiber or fabric prior to the treatment of chitosan have been reported. Chitosan was applied after oxidation of cotton fabric by H2O2 show improved dyeability with reactive dyes (4). Potassium periodate is known to selectivity convert 1,2-dihydroxyl groups to a pair of aldehyde groups without significant side reaction and is widely used in structural analysis of carbohydrates(2). This oxidizing agent was used successfully for surface oxidation of cotton fiber prior to the treatment with chitosan to produce chitosan coated cotton fiber. We undertake this work with a view to establish appropriate conditions for synthesis of cotton fabric containing chitosan. We plan to incorporate chitosan in the molecular structure of cotton surface through strong interaction between chitosan molecules and cotton molecules. To achieve the goal, creation of functional groups such as aldehyde groups is effected by NaIO4 oxidation and thus obtained oxidized cotton is treated with chitosan. This is ratter a two-step process for producing cotton fabrics containing chitosan. A novel onestep process is also devised for preparation of the same modified fabrics; the fabric is treated in an aqueous solution containing the oxidant and chitosan. All modified fabrics are monitored for fixed amount of chitosan expressed as nitrogen content, carbonyl content,

A bleached cotton fabric was kindly supplied by Misr Company for Spinning and Weaving, Mehallah El-Kubra, Egypt. All chemicals used in current investigation were of analytical grade. Dyes used include acid dye which was of laboratory grade and, reactive dye, namely,

Unless otherwise stated, bleached cotton fabric was immersed in an aqueous solution containing different concentrations of sodium periodate (30-80 mg/100ml). The solution was stirred for 1 hr at 60 ºC using a material to liquor ratio (M/L) 1:50 .The oxidized sample was washed several times with water to remove the oxidant .This oxidized sample was used

A chitosan solution was prepared by stirring a dispersion of chitosan (0.5-2%) in 1% (v/v) aqueous acetic acid solution. The aforementioned oxidized cotton fabric was immersed in the chitosan solution with constant shaking for different periods of time (30, 60, and 120 min.).The treatment process was performed at different temperatures (40, 60 and 80 ºC). A material to liquor ratio of 1:50 was used. The treated sample was washed several times with

1% (v/v) aqueous acetic acid solution followed by water and dried at 60 ºC.

**2.2.3 Oxidation of cotton fabrics and chitosan with sodium periodate in one bath**  An aqueous solution containing 2% chitosan, 50 mg/100ml sodium periodate was prepared. Fabric was impregnated in this aqueous solution at liquor ratio 1:50 for 1 hr at 60 ºC. The cotton fabric was then washed several times with 1% (v/v) aqueous acetic acid solution

dyeability, strength properties and IR spectra.

for the next reaction without drying.

followed by water and dried at 60 ºC.

**2.2.2 Treatment with chitosan** 

Procion Turquoise® MXG which was of technical grade.

**2.2.1 Oxidation of cotton fabrics with sodium periodate** 

**2. Experimental** 

**2.1 Materials** 

**2.2 Methods** 

#### **Dyeing with reactive dye**

Cotton fabrics treated with solution periodate as described above were dyed using aqueous bath containing 1% of the reactive dye along with 5% sodium chloride and liquor ratio 1:50 at room temperature. The temperature of the dyeing bath was raised to 60 ºC for 45 minutes. The fabrics were then rinsed with water and treated with an aqueous solution containing 1% wetting agent at 60 ºC for 30 minutes at a liquor ratio 1:50. The dyed fabrics were rinsed with hot water followed by cold water and finally dried at ambient conditions

#### **Dyeing with acid dye**

After being treated with solution periodate, the cotton fabrics samples were dyed in an aqueous bath containing 1% of the acid dye together with 2% sodium sulphate using a liquor ratio 1:50 at pH, 5-6 and temperature 40 ºC. The latter was then raised to 100 ºC for 60 minutes. At this end, the fabrics were squeezed, washed with water and treated with an aqueous solution containing 2% wetting agent at 60 ºC for 30 minutes. The dyed fabrics so obtained were rinsed with hot water followed by cold water and finally dried at ambient conditions.

## **2.2.5 Testing and analysis**


The FT-IR spectra of cotton fabrics treated with NaIO4 and chitosan in two subsequent steps as well as concurrently were recorded on a Nexus 670 FT-IR spectrophotometer, Nicolet, USA, in the spectra range 4000-400 cm-1 using the KBr disc technique.
