**Eco-Friendly Pretreatment of Cellulosic Fabrics with Chitosan and Its Influence on Dyeing Efficiency**

Mohamed Abd el-moneim Ramadan, Samar Samy, Marwa abdulhady and Ali Ali Hebeish *Textile Research Division, National Research centre, Dokki, Giza Egypt* 

## **1. Introduction**

Wet processing of textiles uses large quantities of water, and electrical and thermal energy. Most of these processes involve the use of chemicals as assisting, accelerating or retarding their rates and are carried out at elevated temperatures to transfer mass from processing liquid medium across the surface of textile material in a reasonable time. So, we can use some natural materials and some physical tools to reduce the chemicals, water, energy and pollution. This tools and natural material can use also to improvement the fabrics surface via introduce new active groups on its. Improvement of the fabrics surface can increase the efficiency of bleaching, dyeing and finishing processes.

Chitin, a major component of the shell of crab and shrimp is one of the most abundant natural polysaccharides with a large unexplored commercial potential. Chitosan is partially or completely N-deacetylated chitin and mainly consists of B-(1,4)- linked 2- amino-2-deoxy-B-D-glucopyranose. In recent years, a number of investigations have been carried out to exploit the potential applicability of chitosan(1). Chitosan have many applications in the medical and textile fields.

Cellulose which has been known to have good physical properties has been widely used as construction material, paper and clothes. Cellulosic fabrics can be oxidized by several oxidizing agents such as hydrogen peroxide (H2O2), sodium persulphate (Na2S2O8) and potassium periodate (KIO3). Oxidation of cellulosic fabric using sodium metaperiodate (NaIO4) has been extensively investigated in the literature, since it leads to selective cleavage at the C2 and C3 vicinal hydroxyl groups to yield a product with 2,3-dialdehyde units along the polymer chain(2). The latter is an important functional polymer for further derivatisation to specialized products.

As a naturally deriving substances, chitosan and cellulose share several common beneficial properties such as being nontoxic and biodegradable. Structurally, chitosan is slightly different from cellulose as the monosaccharide in chitosan chain is 2-amino-2-dehydroxy-Dglucose instead of D-glucose. The presence of amino group is responsible for the complete solubility of chitosan in a diluted aqueous acidic solution as a polycationic polymer whereas cellulose is totally insoluble. This polycationic nature makes chitosan very appealing as a surface treating agent for cellulose fabrics to improve its dyeability to reactive and acid dyes. Chitosan used for surface modification of cellulose fabrics. Direct padding or

Eco-Friendly Pretreatment of

**Dyeing with reactive dye** 

**Dyeing with acid dye** 

**2.2.5 Testing and analysis** 

reported method (6).

according to ASTM (7)

**3. Results and discussion** 

elsewhere (8). - FT-IR spectroscopy

**2.2.4 Dyeing** 

Cellulosic Fabrics with Chitosan and Its Influence on Dyeing Efficiency 5

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

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.




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,

Complexation of chitosan with cotton cellulose to produce cotton –based new textiles is of paramount concern. To render these new cotton textiles more durable and stable for subsequent treatments such as dyeing and finishing, it is a must to induce strong interactions between chitosan and cotton. One of the approaches to achieve this is to create aldehyde groups in the molecular structure of cotton cellulose. These aldehyde groups undergo coupling with the amino groups of chitosan to form iminic bonds (1) whereby

chitosan is fixed to cotton surface through a series of reactions as shown under:

with hot water followed by cold water and finally dried at ambient conditions


USA, in the spectra range 4000-400 cm-1 using the KBr disc technique.

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, dyeability, strength properties and IR spectra.
