Name: fasika mengesha
Message: please try to tell me briefley about,fault in reactive dyeing due to dye hydrolysis and the improvement to be taken. please i need this information in brief.

I suspect that you are involved with the textile industry; I am not, and cannot claim to be any sort of expert on industrial techniques. My perspective is that of the individual artist who works with dye. If you need this information for a textiles class, my answer may not be sufficient.

Fiber reactive dye can react with a cellulosate anion, or with a hydroxide ion. When the latter occurs, the fiber reactive dye can no longer react with the fiber. It can still be used as an acid dye on wool, silk, or nylon, but it cannot be used as a reactive dye.

Fiber reactive dye can also react with the moisture in the air, which is why it goes bad with time even when unused. In solution, fiber reactive dyes such as the dichlorotriazines last longest in a neutral solution, and break down more quickly in an acid or alkaline environment. Bicarbonate may be used in the print paste, instead of carbonate, for a less basic pH which will slow the reaction of the dye, allowing it to last hours longer before hydrolysis. If the fabric is then heat-treated, bicarbonate is converted to carbonate, which increases the pH further for rapid reaction, if moisture is still present; urea is frequently added to maintain moisture.

For the reaction between a specific dichlorotriazine dye with cellulose, see the May 19, 2005 entry in my Dyes & Dyeing weblog, "Chemical reaction for a dichlorotriazine dye with cellulose". Simply substitute a hydroxide anion for the cellulosate anion to obtain the reaction for the hydrolysis of this dye.