engleski

Quantity Determination of Available Hydroxyl Groups with C.I. Reactive Blue 19

Cotton as a representative of cellulosic fibers, regarded from the chemical aspect behaves as a polyvalent alcohol. Functional cellulosic groups (hydroxyl -OH) may be engaged in reactions of chemical addition and substitution, which means establishing covalent chemical bonds in the processes of textile finishing and reactive dyeing. Within completely arranged structural elements of cotton fiber, a portion of free hydroxyl groups, on second, third and sixth atom of carbon is not equal and decreases in following order: second, sixth and then third COH. However, different pretreatment processes contribute to increase or decrease of free hydroxyl groups of cotton fiber, which directly affects its reactivity. In this paper dyestuff containing vinyl-sulphonic group (C.I. Reactive Blue 19), which establishes covalent chemical bond with hydroxyl group of cotton through a mechanism of nucleophilic addition, was used. Quantity of free hydroxyl groups and covalently bonded reactive dyestuff (mmol/g of material) is proportional, which was confirmed by dyeing differently pretreated cotton materials. This paper suggests an alternative method of defining free hydroxyl groups of cotton materials.

reactive dyeing; hyroxyl groups determination; mechanism of nucleophilic addition

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