Clever Strategies: Salt Free Dyeing Design with Acidic (Neucleophilic Dyeing Method) and Alkaline (Electrophilic Dyeing Method) Process on Pure Cotton Fabric by Using Reactive Dye

The reactive dye produce a lot of effluent problems in terms of % AOX, BOD, COD, TDS etc. in spite of its capability of produce wide range of colours and varieties of gamut in hue. In addition the use of salt as electrolytes provides higher chances of eco-hazardous impact problems and end-users comfort related properties. The % dye fixation is being always a problem to reactive dyeing on cotton due to the higher degree of dye hydrolyzation inside the dye bath. In this current work we had tried to develop an unconventional reactive process in both like salt free acidic medium reactive dyeing and salt free alkaline dyeing on pure cotton fabric. Results of the current study shows that alkaline medium salt free reactive dyeing on cotton shows higher colour strength (K/S value), good mechanical properties-bending length modulus, flexural modulus, less generation of the % AOX etc. It also can be concluded that acidic medium salt free reactive dyeing is also better in terms of quality than the conventional reactive dyeing method in the industries. Clever Strategies: Salt Free Dyeing Design with Acidic (Neucleophilic Dyeing Method) and Alkaline (Electrophilic Dyeing Method) Process on Pure Cotton Fabric by Using Reactive Dye

To reduce the charge repulsion between the negatively charged cotton and the anionic dyes Salt ion

Dye Bath
Interboding between dye 100 A and fabric-dyeing completion   The normal cotton dyeing method with reactive dye has been shown as below (MLR=1:10) ( Table 1).

Color yield and fixation
Color strength (K/S) was measured using a Premier Colorscan Spectrophotometer SS 5100A (Premier Colorscan Instrument Pvt. Ltd.) with the specific arrangement of light source-Pulsed Xenon, dual beam, wavelength-10 nm, larger area view -25.4 mm diameter, smaller area view-12.0 mm diameter at the maximum absorption.
Where r=MLR, K=partition coefficient between the material and the dye liquor.

Color fastness
For color fastness testing, the dyed samples were soaped with 2 gpl nonionic detergent at boil for 30 min. After dyeing we had used Crockmeter (

Mechanical properties
Mechanical properties are improving in case of saltfree basic  medium reactive dyeing shows more mechanical properties than the standard commercial reactive dyeing process (n=6).

Conclusion
Salt free reactive dyed fabric in basic or alkaline medium provide the maximum mechanical properties in the fabric and also salt free alkaline medium reactive dyed fabric provides enhanced stiffness in the fabric than the salt free acidic medium reactive dyeing method or even superior than normal reactive dyeing on cotton. Rubbing fastness salt free alkaline medium reactive dyed fabric is higher than others categories of the dyeing process. In case of salt less acidic medium excessive acetic acid or for the case of salt less basic medium excess base sodium carbonate Na 2 CO 3 in dye bath will cause generation of nucleophiles (shifting of cell-O-charges due to bathochromic shift from the liquor to the substrates) and electrophiles respectively. In the subsequent step the nucleophiles will attach to cellulose molecule and electrophiles will attach to dye molecule [1]. Hence larger will be the interbonding and interfolding of dye segments (dye molecules) between cellulose (substrates) and the dye molecules will occurs in the dye bath liquor. As a results the ratio of the dye % in the fiber [Df] and dye in the liquor [DS] i.e. partition coefficient (k= [Df] / [DS] and k is equivalent to color strength, K found by the UV-visible spectrophometer instrument used here for the experiment) will always remain at a higher value which actually facilitates to the better dye penetration and dye absorption on to the fabric at a given thermodynamically plot. The other reason of these may be the cotton is more stable in the basic medium than the acidic medium due to the stability of the -CHO group inside the cotton in acidic medium (-CHO+H 2 -CH 2 -+[O]) and the dissociation will occurs due to the nascent oxygen but in basic medium the cotton will more stable (-CHO+[O]-COOH, and the -COOH group) is more dimer stable group in basic medium. As a consequence higher will be the color soaked, the effective mass-momentum inertia of the fabric also will increase and these will leads to results as higher stiffness and other properties like bending rigidity, flexural modulus etc [2].