Compiled By M.Rezaul Karim Tutul

Achieving Higher Wet-rubbing Fastness with Reactive Dyestuffs: Following cares to be made regarding better wet-rubbing fastness:

01) Yarn: Combed yarn (ensuring minimum dead cotton %) to be used. 02) Pre-treatment with highest absorbency: To be checked with drop test

a) Scouring with increased wetting agent dosage b) Scouring with Caustic Soda(NaOH itself is a good wetting agent

03) Whiteness value: As whiteness value is not needed, Peroxide & Peroxide stabiliser dosage may be reduced & hence lower Peroxide Killer dosage.

04) Bio-polishing: Minimum Bio-polish Treatment ensuring maximum cellulosic dust removal. 05) Dyeing cycle: Dyeing Cycle to be fully completed may be with few minutes’ extension at

same temperature (60oC). 06) Soaping off: While soaping, a good dispersant along with soaping agent should be used for

maximum removal of unfixed dyes & other dye-complex sticking to fabric surface. 07) Finishing: Micro-emulsion/Semi Micro or Nano silicone Softener finish to be avoided.

Macro Emulsion can be used, if needed.

So, maintaining the above, good wet rubbing fastness can be achieved ----10min---------------50/60min---------- 60oC ---5min--------40min-------- 55oC Bath Drop Soda Ash (5g/l) for 25mins Caustic (36o Be) 1.5g/l for 25min Dyestuffs Salt Soaping:

a) Cold Rinse b) Neutralizing with Acetic Acid c)

Achieving High Light Fast Shades Light Fastness along with other related matters mostly depend on

a) Fabric surface-(Smoother Surface i. e Single Jersey gains better Light Fastness & rough surface i. e Pique, Rib etc gain lower Light Fastness) along with

b) Dyestuffs selection & c) Processing parameters.

Destruction of Chromophores group (Azo Group) resulting in affecting Light or Light Perspiration Fastness of Reactive Dyestuffs in following two ways:

01) Photo Oxidation

Singulet-O2 reacts with Hydrazone-tautomer of Azo Dye

02) Photo Reduction

Following cares to be made for processing High Light Fast Shades:

O

NN

H

OO

O

NN

OO

H

O

O

NN

+

OH

NN

NHN

.+ H - D o n o r NHN H

N H 2

N H 2•

Compiled By M.Rezaul Karim Tutul

01) Proper Scouring: Scouring is to be done with better bleaching effect, i.e. at least 75 White-ness Index is to be achieved, especially for light shades.

02) Proper Shading Component Selection-Higher Light Fast Shading components to be selec-tion, especially for dark shades.

03) Sequestrants has adverse affects on Shades: a) Grieg Fabric Demineralization is to be avoided as much as possible-Some Seques-

trants, left in fabrics after processes, enhance photo-oxidation or photo-reduction process of Chromophores, leading to deteriorations of light fastness of shades.

b) Avoid using Sequestrants in Dye-bath for their negative impacts on light fastness. 04) Cationic Finishing Agents have adverse affect on dye-chromophores-Any cationic finishing

agents assist in storing heat energy in fabrics which enhances decomposition of Chromo-phores leading to deteriorations of Light Fastness.